[Federal Register Volume 88, Number 118 (Wednesday, June 21, 2023)]
[Rules and Regulations]
[Pages 40406-40494]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-11429]



[[Page 40405]]

Vol. 88

Wednesday,

No. 118

June 21, 2023

Part II





Department of Energy





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10 CFR Parts 429, 430, and 431





Energy Conservation Program: Test Procedure for Consumer Water Heaters 
and Residential-Duty Commercial Water Heaters; Final Rule

  Federal Register / Vol. 88, No. 118 / Wednesday, June 21, 2023 / 
Rules and Regulations  

[[Page 40406]]


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DEPARTMENT OF ENERGY

10 CFR Parts 429, 430, and 431

[EERE-2019-BT-TP-0032]
RIN 1904-AE77


Energy Conservation Program: Test Procedure for Consumer Water 
Heaters and Residential-Duty Commercial Water Heaters

AGENCY: Office of Energy Efficiency and Renewable Energy, Department of 
Energy.

ACTION: Final rule.

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SUMMARY: This final rule incorporates by reference the latest version 
of the industry testing standard for consumer water heaters and 
residential-duty commercial water heaters and adopts relevant portions 
of those standards into the Federal test procedure. In this final rule, 
the U.S. Department of Energy (DOE) is also expanding the scope of 
coverage of the test procedure to apply to certain consumer water 
heater designs (including circulating water heaters and low-temperature 
water heaters), adding definitions for certain specialty water heaters, 
updating test conditions and tolerance requirements to reduce burden, 
clarifying test set-up and installation methods, addressing the test 
conduct for products which can store water at temperatures above the 
delivery setpoint, establishing an effective volume calculation, and 
extending untested provisions to electric instantaneous water heaters.

DATES: The effective date of this rule is July 21, 2023. The final rule 
changes will be mandatory for consumer water heater testing starting 
December 18, 2023 and for residential-duty commercial water heater 
testing starting June 17, 2024. The incorporation by reference of 
certain material listed in this rule is approved by the Director of the 
Federal Register on July 21, 2023.

ADDRESSES: The docket, which includes Federal Register notices, public 
meeting attendee lists and transcripts, comments, and other supporting 
documents/materials, is available for review at www.regulations.gov. 
All documents in the docket are listed in the www.regulations.gov 
index. However, not all documents listed in the index may be publicly 
available, such as those containing information that is exempt from 
public disclosure.
    A link to the docket web page can be found at: www.regulations.gov/docket/EERE-2019-BT-TP-0032. The docket web page contains instructions 
on how to access all documents, including public comments, in the 
docket.
    For further information on how to review the docket, contact the 
Appliance and Equipment Standards Program staff at (202) 287-1445 or by 
email: [email protected].

FOR FURTHER INFORMATION CONTACT: 
    Ms. Julia Hegarty, U.S. Department of Energy, Office of Energy 
Efficiency and Renewable Energy, Building Technologies Office, EE-5B, 
1000 Independence Avenue SW, Washington, DC 20585-0121. Telephone: 
(202) 597-6737. Email: [email protected].
    Mr. Eric Stas, U.S. Department of Energy, Office of the General 
Counsel, GC-33, 1000 Independence Avenue SW, Washington, DC 20585-0121. 
Telephone: (202) 586-5827. Email: [email protected].

SUPPLEMENTARY INFORMATION: DOE incorporates by reference the following 
industry standards into part 430:
    ANSI/ASHRAE Standard 41.1-2020, ``Standard Methods for Temperature 
Measurement,'' ANSI-approved June 30, 2020 (``ASHRAE 41.1-2020'').
    ANSI/ASHRAE Standard 41.6-2014, ``Standard Method for Humidity 
Measurement,'' ANSI-approved July 3, 2014 (``ASHRAE 41.6-2014'').
    ANSI/ASHRAE Standard 118.2-2022, ``Method of Testing for Rating 
Residential Water Heaters and Residential-Duty Commercial Water 
Heaters,'' ANSI-approved March 1, 2022 (``ASHRAE 118.2-2022'').
    Copies of ASHRAE 41.1-2020, ASHRAE 41.6-2014, and ASHRAE 118.2-2022 
can be obtained from the American Society of Heating, Refrigerating, 
and Air-Conditioning Engineers, Inc., (ASHRAE), 180 Technology Parkway 
NW, Peachtree Corners, GA 30092, (800) 527-4723 or (404) 636-8400, or 
online at: www.ashrae.org.
    ASTM D2156-09 (Reapproved 2018) ``Standard Test Method for Smoke 
Density in Flue Gases from Burning Distillate Fuels,'' approved October 
1, 2018 (``ASTM D2156-09 (RA 2018)'').
    ASTM E97-82 (Reapproved 1987) ``Standard Test Methods for 
Directional Reflectance Factor, 45-Deg 0-Deg, of Opaque Specimens by 
Broad-Band Filter Reflectometry,'' approved October 29, 1982 and 
withdrawn 1991 (``ASTM E97-1987 (W1991)'').
    Copies of ASTM D2156-09 (RA 2018) can be obtained from ASTM 
International (ASTM), 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959 or online at: www.astm.org.
    Copies of ASTM E97-1987 (W1991) are reasonably available from 
standards resellers including GlobalSpec's Engineering 360 (https://standards.globalspec.com/std/3801495/astm-e97-82-1987) and IHS Markit 
(https://.global.ihs.com/
doc_detail.cfm?document_name=ASTM%20E97&item_s_key=00020483).
    See section IV.N of this document for a further discussion of these 
industry standards.

Table of Contents

I. Authority and Background
    A. Authority
    B. Background
II. Synopsis of the Final Rule
III. Discussion
    A. Scope of Applicability and Definitions
    1. Demand-Response Water Heaters
    2. Heat Pump Water Heaters
    3. Residential-Duty Commercial Water Heaters
    4. Specialty Water Heaters
    B. Updates to Industry Standards
    1. ASHRAE 41.1-2020
    2. ASHRAE 118.2-2022
    C. Test Conditions and Tolerances
    1. Supply Water Temperature Measurements
    2. Gas Pressure
    3. Input Rate
    4. Ambient Test Condition Tolerances
    5. Electrical Supply Voltage Tolerances
    6. Flow Rate Tolerances
    7. Optional Test Conditions for Heat Pump Water Heaters
    D. Test Set-Up and Installation
    1. Split-System Heat Pump Water Heaters
    2. Mixing Valves
    3. Flow Meter Location
    4. Separate Storage Tanks
    E. Test Conduct
    1. High Temperature Testing
    2. Very Small Draw Pattern Flow Rate
    3. Low-Temperature Water Heaters
    4. Delivery Temperature for Flow-Activated Water Heaters
    5. Heat Pump Water Heaters
    6. Draw Pattern for Commercial Applications
    7. Method for Determining Internal Tank Temperature for Certain 
Water Heaters
    8. Alternate Order 24-Hour Simulated-Use Test
    F. Computations
    1. Mass Calculations
    2. Effective Storage Volume
    G. Untested Provisions (Alternative Efficiency Determination 
Methods)
    1. Representations of First-Hour Ratings for Untested Basic 
Models
    2. Alternative Rating Method for Electric Instantaneous Water 
Heaters
    H. Corrections and Clarifications
    1. Flow-Activated Terminology
    2. Second Identical 24-Hour Simulated-Use Test
    3. Connected Products
    4. Heating Value of Gas
    I. Effective and Compliance Dates
    J. Test Procedure Costs
    1. Separate Storage Tanks
    2. Method for Determining Internal Tank Temperature for Certain 
Water Heaters

[[Page 40407]]

    3. High Temperature Testing
    4. Additional Amendments
IV. Procedural Issues and Regulatory Review
    A. Review Under Executive Orders 12866, 13563, and 14094
    B. Review Under the Regulatory Flexibility Act
    C. Review Under the Paperwork Reduction Act of 1995
    D. Review Under the National Environmental Policy Act of 1969
    E. Review Under Executive Order 13132
    F. Review Under Executive Order 12988
    G. Review Under the Unfunded Mandates Reform Act of 1995
    H. Review Under the Treasury and General Government 
Appropriations Act, 1999
    I. Review Under Executive Order 12630
    J. Review Under Treasury and General Government Appropriations 
Act, 2001
    K. Review Under Executive Order 13211
    L. Review Under Section 32 of the Federal Energy Administration 
Act of 1974
    M. Congressional Notification
    N. Description of Materials Incorporated by Reference
V. Approval of the Office of the Secretary

I. Authority and Background

    Consumer water heaters are included in the list of ``covered 
products'' for which DOE is authorized to establish and amend energy 
conservation standards and test procedures. (42 U.S.C. 6292(a)(4)) 
DOE's energy conservation standards and test procedures for consumer 
water heaters are currently prescribed respectively at title 10 of the 
Code of Federal Regulations (CFR), part 430, section 32(d), and 10 CFR 
part 430, subpart B, appendix E ((appendix E), Uniform Test Method for 
Measuring the Energy Consumption of Water Heaters. Residential-duty 
commercial water heaters, for which DOE is also authorized to establish 
and amend energy conservation standards and test procedures (42 U.S.C. 
6311(1)(K)), must also be tested according to appendix E. 10 CFR 
431.106(b)(1) (See 42 U.S.C. 6295(e)(5)(H)). DOE's energy conservation 
standards for residential-duty commercial water heaters are currently 
prescribed at 10 CFR 431.110(b)(1). The following sections discuss 
DOE's authority to establish and amend test procedures for consumer 
water heaters and residential-duty commercial water heaters, as well as 
relevant background information regarding DOE's consideration of test 
procedures for these products and equipment.

A. Authority

    The Energy Policy and Conservation Act, as amended (EPCA),\1\ 
authorizes DOE to regulate the energy efficiency of a number of 
consumer products and certain industrial equipment. (42 U.S.C. 6291-
6317, as codified) Title III, Part B \2\ of EPCA established the Energy 
Conservation Program for Consumer Products Other Than Automobiles, 
which sets forth a variety of provisions designed to improve energy 
efficiency. (42 U.S.C. 6291-6309, as codified) These products include 
consumer water heaters, one of the subjects of this document. (42 
U.S.C. 6292(a)(4)) Title III, Part C \3\ of EPCA, added by Public Law 
95-619, Title IV, section 441(a), established the Energy Conservation 
Program for Certain Industrial Equipment, which again sets forth a 
variety of provisions designed to improve energy efficiency. (42 U.S.C. 
6311-6317, as codified) This equipment includes residential-duty 
commercial water heaters, which are also the subject of this document. 
(42 U.S.C. 6311(1)(K))
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    \1\ All references to EPCA in this document refer to the statute 
as amended through the Energy Act of 2020, Public Law 116-260 (Dec. 
27, 2020), which reflect the last statutory amendments that impact 
Parts A and A-1 of EPCA.
    \2\ For editorial reasons, upon codification in the U.S. Code, 
Part B was redesignated Part A.
    \3\ For editorial reasons, upon codification in the U.S. Code, 
Part C was redesignated Part A-1.
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    The energy conservation program under EPCA consists essentially of 
four parts: (1) testing, (2) labeling, (3) Federal energy conservation 
standards, and (4) certification and enforcement procedures. Relevant 
provisions of EPCA specifically include definitions (42 U.S.C. 6291; 42 
U.S.C. 6311), test procedures (42 U.S.C. 6293; 42 U.S.C. 6314), 
labeling provisions (42 U.S.C. 6294; 42 U.S.C. 6315), energy 
conservation standards (42 U.S.C. 6295; 42 U.S.C. 6313), and the 
authority to require information and reports from manufacturers (42 
U.S.C. 6296; 42 U.S.C. 6316).
    The Federal testing requirements consist of test procedures that 
manufacturers of covered products and commercial equipment must use as 
the basis for: (1) certifying to DOE that their products/equipment 
comply with the applicable energy conservation standards adopted 
pursuant to EPCA (42 U.S.C. 6295(s); 42 U.S.C. 6296; 42 U.S.C. 6316(a)-
(b)), and (2) making other representations about the efficiency of 
those products/equipment (42 U.S.C. 6293(c); 42 U.S.C. 6314(d)). 
Similarly, DOE must use these test procedures to determine whether the 
products comply with any relevant standards promulgated under EPCA. (42 
U.S.C. 6295(s))
    Federal energy efficiency requirements for covered products and 
equipment established under EPCA generally supersede State laws and 
regulations concerning energy conservation testing, labeling, and 
standards. (42 U.S.C. 6297(a)-(c); 42 U.S.C. 6316(a)-(b)) DOE may, 
however, grant waivers of Federal preemption in limited circumstances 
for particular State laws or regulations, in accordance with the 
procedures and other provisions of EPCA. (42 U.S.C. 6297(d); 42 U.S.C. 
6316(a); 42 U.S.C. 6316(b)(2)(D))
    Under 42 U.S.C. 6293, EPCA sets forth the criteria and procedures 
DOE must follow when prescribing or amending test procedures for 
covered products. Specifically, EPCA requires that any test procedures 
prescribed or amended shall be reasonably designed to produce test 
results which measure energy efficiency, energy use, or estimated 
annual operating cost of a covered product during a representative 
average use cycle or period of use and not be unduly burdensome to 
conduct. (42 U.S.C. 6293(b)(3)) Under 42 U.S.C. 6314, the statute sets 
forth the criteria and procedures DOE must follow when prescribing or 
amending test procedures for covered equipment, reciting similar 
requirements at 42 U.S.C. 6314(a)(2).
    In addition, the Energy Independence and Security Act of 2007 
amended EPCA to require that DOE amend its test procedures for all 
covered consumer products to integrate measures of standby mode and off 
mode energy consumption. (42 U.S.C. 6295(gg)(2)(A)) Standby mode and 
off mode energy consumption must be incorporated into the overall 
energy efficiency, energy consumption, or other energy descriptor for 
each covered product, unless the current test procedure already 
accounts for and incorporates the standby mode and off mode energy 
consumption, or if such integration is technically infeasible. (42 
U.S.C. 6295(gg)(2)(A)(i)-(ii)) If an integrated test procedure is 
technically infeasible, DOE must prescribe separate standby mode and 
off mode energy use test procedures for the covered product, if a 
separate test is technically feasible. (42 U.S.C. 6295(gg)(2)(A)(ii))) 
Any such amendment must consider the most current versions of the 
International Electrotechnical Commission (IEC) Standard 62301 \4\ and 
IEC Standard 62087,\5\ as applicable. (42 U.S.C. 6295(gg)(2)(A))
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    \4\ IEC 62301, Household electrical appliances--Measurement of 
standby power (Edition 2.0, 2011-01).
    \5\ IEC 62087, Audio, video and related equipment--Methods of 
measurement for power consumption (Edition 1.0, Parts 1-6: 2015, 
Part 7: 2018).
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    The American Energy Manufacturing Technical Corrections Act 
(AEMTCA), Public Law 112-210, further amended

[[Page 40408]]

EPCA to require that DOE establish a uniform efficiency descriptor and 
accompanying test methods to replace the energy factor (EF) metric for 
covered consumer water heaters and the thermal efficiency (TE) and 
standby loss (SL) metrics for commercial water-heating equipment \6\ 
within one year of the enactment of AEMTCA. (42 U.S.C. 6295(e)(5)(B)-
(C)) The uniform efficiency descriptor and accompanying test method 
were required to apply, to the maximum extent practicable, to all 
water-heating technologies in use at the time and to future water-
heating technologies, but could exclude specific categories of covered 
water heaters that do not have residential uses, can be clearly 
described, and are effectively rated using the TE and SL descriptors. 
(42 U.S.C. 6295(e)(5)(F) and (H)) In addition, beginning one year after 
the date of publication of DOE's final rule establishing the uniform 
descriptor, the efficiency standards for covered water heaters were 
required to be denominated according to the uniform efficiency 
descriptor established in the final rule (42 U.S.C. 6295(e)(5)(D)); and 
for affected covered water heaters tested prior to the effective date 
of the test procedure final rule, DOE was required to develop a 
mathematical factor for converting the measurement of their energy 
efficiency from the EF, TE, and SL metrics to the new uniform energy 
descriptor. (42 U.S.C. 6295(e)(5)(E)(i)-(ii))
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    \6\ The initial thermal efficiency and standby loss test 
procedures for commercial water heating equipment (including 
residential-duty commercial water heaters) were added to EPCA by the 
Energy Policy Act of 1992 (EPACT 1992), Public Law 102-486, and 
corresponded to those referenced in the ASHRAE and Illuminating 
Engineering Society of North America (IESNA) Standard 90.1-1989 
(i.e., ASHRAE Standard 90.1-1989). (42 U.S.C. 6314(a)(4)(A)) DOE 
subsequently updated the commercial water heating equipment test 
procedures on two separate occasions--once in a direct final rule 
published on October 21, 2004, and again in a final rule published 
on May 16, 2012. These rules incorporated by reference certain 
sections of the latest versions of American National Standards 
Institute (ANSI) Standard Z21.10.3, Gas Water Heaters, Volume III, 
Storage Water Heaters with Input Ratings Above 75,000 Btu Per Hour, 
Circulating and Instantaneous, available at the time (i.e., ANSI 
Z21.10.3-1998 and ANSI Z21.10.3-2011, respectively). 69 FR 61974, 
61983 (Oct. 21, 2004) and 77 FR 28928, 28996 (May 16, 2012).
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    EPCA also requires that, at least once every seven years, DOE 
evaluate test procedures for each type of covered product and covered 
equipment, including consumer water heaters and residential-duty 
commercial water heaters, to determine whether amended test procedures 
would more accurately or fully comply with the requirements for the 
test procedures to not be unduly burdensome to conduct and be 
reasonably designed to produce test results that reflect energy 
efficiency, energy use, and estimated operating costs during a 
representative average use cycle (or additionally, period of use for 
consumer products). (42 U.S.C. 6293(b)(1)(A); 42 U.S.C. 6314(a)(1)(A))
    If the Secretary determines, on her own behalf or in response to a 
petition by any interested person, that a test procedure should be 
prescribed or amended, the Secretary shall promptly publish in the 
Federal Register proposed test procedures and afford interested persons 
an opportunity to present oral and written data, views, and arguments 
with respect to such procedures. (42 U.S.C. 6293(b)(2); 42 US.C. 
6314(b)) The comment period on a proposed rule to amend a test 
procedure shall be at least 60 days \7\ and may not exceed 270 days. 
(42 U.S.C. 6293(b)(2)) In prescribing or amending a test procedure, the 
Secretary shall take into account such information as the Secretary 
determines relevant to such procedure, including technological 
developments relating to energy use or energy efficiency of the type 
(or class) of covered products involved. (42 U.S.C. 6293(b)(2)) If DOE 
determines that test procedure revisions are not appropriate, DOE must 
publish in the Federal Register its determination not to amend the test 
procedures. (42 U.S.C. 6293(b)(1)(A)(ii); 42 U.S.C. 6314(a)(1)(A)(ii)) 
DOE is publishing this final rule in satisfaction of the 7-year review 
requirement specified in EPCA. (42 U.S.C. 6293(b)(1)(A) and 42 U.S.C. 
6314(a)(1)(A))
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    \7\ For covered equipment, if the Secretary determines that a 
test procedure amendment is warranted, the Secretary must publish 
proposed test procedures in the Federal Register and afford 
interested persons an opportunity (of not less than 45 days' 
duration) to present oral and written data, views, and arguments on 
the proposed test procedure. (42 U.S.C. 6314(b))
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B. Background

    The following discussion provides a brief history of the current 
rulemaking, which considers potential amendments to the test procedure 
for consumer water heaters and residential-duty commercial water 
heaters.\8\ On April 16, 2020, DOE published in the Federal Register a 
request for information (April 2020 RFI) seeking comments on the 
existing DOE test procedure for consumer water heaters and residential-
duty commercial water heaters. 85 FR 21104. The April 2020 RFI 
discussed a draft version of the American National Standards Institute 
(ANSI)/American Society of Heating, Refrigeration, and Air Conditioning 
Engineers (ASHRAE) Standard 118.2, ``Method of Testing for Rating 
Residential Water Heaters and Residential-Duty Commercial Water 
Heaters,'' published in March 2019 (March 2019 ASHRAE Draft 118.2), 
which is very similar to the existing DOE test procedure for consumer 
water heaters and residential-duty commercial water heaters. 85 FR 
21104, 21108-21110 (April 16, 2020).
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    \8\ For a more complete history of earlier rulemaking efforts to 
develop the energy conservation standards and test procedure for 
consumer water heaters and residential-duty commercial water 
heaters, please consult the January 11, 2022 NOPR. See 87 FR 1554, 
1556-1558.
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    In the April 2020 RFI, DOE requested comments, information, and 
data about a number of issues, including: (1) differences between the 
March 2019 ASHRAE Draft 118.2 and the existing DOE test procedure; (2) 
test tolerances for supply water temperature, ambient temperature, 
relative humidity, voltage, and gas pressure; (3) the location of the 
instrumentation that measures water volume or mass; and (4) how to test 
certain types of consumer water heaters that cannot be easily tested to 
the existing DOE test procedure (i.e., recirculating gas-fired 
instantaneous water heaters, water heaters that cannot deliver water at 
125 degrees Fahrenheit ([deg]F) 5 [deg]F, and water heaters 
with storage volumes greater than 2 gallons that cannot have their 
internal tank temperatures measured). Id. at 85 FR 21109-21114.
    DOE subsequently published in the Federal Register a notice of 
proposed rulemaking on January 11, 2022 (January 2022 NOPR) in which 
the Department proposed to update appendix E, and related sections of 
the CFR, as follows:
    (1) Incorporate by reference current versions of industry standards 
referenced by the current and proposed DOE test procedures: ASHRAE 
Standard 41.1,\9\ ASHRAE Standard 41.6,\10\ the pending update to 
ASHRAE Standard 118.2 \11\ (contingent on it being substantively the 
same as the draft which was under review), ASTM International (ASTM) 
Standard D2156,\12\ and ASTM Standard E97.\13\
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    \9\ ASHRAE Standard 41.1-2020, ``Standard Methods for 
Temperature Measurement,'' approved June 30, 2020.
    \10\ ASHRAE Standard 41.6-2014, ``Standard Method for Humidity 
Measurement,'' ANSI approved July 3, 2014.
    \11\ ASHRAE Standard 118.2-2022, ``Method of Testing for Rating 
Residential Water Heaters and Residential-Duty Commercial Water 
Heaters,'' ANSI approved March 1, 2022.
    \12\ ASTM Standard D2156-09 (RA 2018), ``Standard Test Method 
for Smoke Density in Flue Gases from Burning Distillate Fuels,'' 
reapproved October 1, 2018.
    \13\ ASTM Standard E97-1987 (W 1991), ``Standard Test Methods 
for Directional Reflectance Factor, 45-Deg 0-Deg, of Opaque 
Specimens by Broad-Band Filter Reflectometry,'' approved January 
1987, withdrawn 1991. Referenced by ASTM Standard D2156-09 (RA 
2018).

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[[Page 40409]]

    (2) Add definitions for ``circulating water heater,'' ``low 
temperature water heater,'' and ``tabletop water heater.''
    (3) Specify how a mixing valve should be installed when the water 
heater is designed to operate with one.
    (4) Modify flow rate requirements during the first-hour rating 
(FHR) test for water heaters with a rated storage volume less than 20 
gallons.
    (5) Modify timing of the first measurement in each draw of the 24-
hour simulated-use test.
    (6) Clarify the determination of the first recovery period.
    (7) Clarify the mass of water to be used to calculate recovery 
efficiency.
    (8) Modify the terminology throughout appendix E to explicitly 
state ``non-flow activated'' and ``flow-activated'' water heater, where 
appropriate.
    (9) Clarify the descriptions of defined measured values for the 
standby period measurements.
    (10) Modify the test condition specifications and tolerances, 
including electric supply voltage tolerance, ambient temperature, 
ambient dry-bulb temperature, ambient relative humidity, standard 
temperature and pressure definition, gas supply pressure, and manifold 
pressure.
    (11) Add provisions to address gas-fired water heaters with 
measured fuel input rates that deviate from the certified input rate.
    (12) Clarify provisions for calculating the volume or mass 
delivered.
    (13) Add specifications for testing for the newly defined ``low 
temperature water heaters.''
    (14) Clarify testing requirements for the heat pump part of a 
split-system heat pump water heater.
    (15) Define the use of a separate unfired hot water storage tank 
for testing water heaters designed to operate with a separately sold 
hot water storage tank.
    (16) Clarify that any connection to an external network or control 
be disconnected during testing.
    (17) Add procedures for estimating internal stored water 
temperature for water heater designs in which the internal tank 
temperature cannot be directly measured.
    (18) Modify the provisions for untested water heater basic models 
within 10 CFR 429.70(g) to include electric instantaneous water 
heaters.
    87 FR 1554, 1558.\14\
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    \14\ A correction was published in the Federal Register on 
January 19, 2022, to properly reflect the date of the public meeting 
to discuss the January 2022 NOPR. 87 FR 2731.
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    DOE held a public meeting related to the January 2022 NOPR on 
January 27, 2022 (hereinafter, the NOPR public meeting).
    On July 14, 2022, DOE published a supplemental notice of proposed 
rulemaking in the Federal Register (July 2022 SNOPR), that proposed to 
maintain the proposals from the January 2022 NOPR but with 
modifications discussed in the July 2022 SNOPR. 87 FR 42270. 
Specifically, the July 2022 SNOPR proposed to further update appendix E 
and related sections of the CFR by:
    (1) Additionally requiring that, for water heaters with rated 
storage volume less than 2 gallons and a rated maximum gallons per 
minute (Max GPM or maximum GPM) of less than 1 gallon per minute, the 
flow rate tolerance shall be 25 percent of the rated Max 
GPM.
    (2) Allowing optional efficiency representations at alternative 
test conditions for heat pump water heaters.
    (3) Adding a definition for ``split-system heat pump water 
heaters'' to distinguish these from circulating heat pump water heaters 
(i.e., ``heat pump-only'' water heaters).
    (4) Requiring gas-fired circulating water heaters to be tested 
using an unfired hot water storage tank (UFHWST) with a storage volume 
between 80 and 120 gallons and meets but does not exceed the minimum 
energy conservation standards (based on R-value) required at 10 CFR 
431.110(a), and that circulating heat pump water heaters be tested 
using a 40-gallon electric resistance water heater at the minimum UEF 
standard required at 10 CFR 430.32(d).
    (5) Requiring that water heaters (with the exception of demand-
response water heaters) with user-selectable modes to ``overheat'' the 
water stored in the tank to increase effective capacity be tested at 
the highest internal tank temperature that can be achieved while 
maintaining the outlet water temperature at 125 [deg]F 5 
[deg]F. (If no such overheated mode exists, the unit is to be tested in 
a default mode.)
    (6) Defining ``demand-response water heater'' based on the U.S. 
Environmental Protection Agency (EPA) ENERGY STAR Product Specification 
for Residential Water Heaters Version 5.0 (ENERGY STAR Water Heaters 
Specification v5.0) \15\ definition for ``connected water heating 
product,'' with the additional requirement that demand-response water 
heaters cannot overheat as a result of user-initiated operation.
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    \15\ EPA published the ENERGY STAR Water Heater Specification 
v5.0 on July 18, 2022. The ENERGY STAR Water Heater Specification 
v5.0 is available online at: www.energystar.gov/products/spec/residential_water_heaters_specification_version_5_0_pd (Last 
accessed on July 25, 2022).
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    (7) Establishing a metric and method for determining the effective 
storage volume.
    (8) Adopting a method of determining the internal storage tank 
temperature for certain water heaters which cannot be directly measured 
using draws at the beginning and end of the 24-hour simulated-use test. 
87 FR 42270, 42273-42274 (July 14, 2022).
    This final rule responds to comments received in response to the 
January 2022 NOPR that were not addressed in the July 2022 SNOPR and 
comments received in response to the July 2022 SNOPR. Table I.1 
presents the list of commenters who provided written submissions and/or 
oral statements at the NOPR public meeting which are addressed in this 
final rule.

               Table I.1--List of Commenters With Written Submissions Addressed in This Final Rule
----------------------------------------------------------------------------------------------------------------
                                       Reference in this final     Comment No. in the
             Commenter(s)                        rule                    docket               Commenter type
----------------------------------------------------------------------------------------------------------------
A.O. Smith Corporation...............  A.O. Smith.............  NOPR No. 37;             Manufacturer.
                                                                 Transcript*; SNOPR No.
                                                                 51*.
Air Conditioning, Heating, and         AHRI...................  NOPR No. 40;             Manufacturer Trade
 Refrigeration Institute.                                        Transcript; SNOPR No.    Association.
                                                                 55.
American Public Gas Association......  APGA...................  NOPR No. 38............  Utility Trade
                                                                                          Association.
Appliance Standards Awareness Project  ASAP...................  Transcript.............  Efficiency Advocacy
                                                                                          Organization.
Appliance Standards Awareness          ASAP, ACEEE, and NCLC..  NOPR No. 34............  Efficiency Advocacy
 Project, American Council for an                                                         Organizations.
 Energy-Efficient Economy, National
 Consumer Law Center (on behalf of
 its low-income clients).

[[Page 40410]]

 
Appliance Standards Awareness          ASAP, ACEEE, and NRDC..  SNOPR No. 54...........  Efficiency Advocacy
 Project, American Council for an                                                         Organizations.
 Energy-Efficient Economy, Natural
 Resources Defense Council.
Applied Energy Technology Company....  AET....................  NOPR No. 29............  Testing Laboratory.
Bradford White Corporation...........  BWC....................  NOPR No. 33; SNOPR No.   Manufacturer.
                                                                 48.
Edison Electric Institute............  EEI....................  Transcript.............  Utility Trade
                                                                                          Association.
GE Appliances........................  GEA....................  SNOPR No. 53...........  Manufacturer.
Jim Lutz.............................  Lutz...................  NOPR No. 35............  Individual.
Nathan Dyson.........................  Dyson..................  NOPR No. 28............  Individual.
New York State Energy Research and     NYSERDA................  NOPR No. 32; SNOPR No.   State Agency.
 Development Authority.                                          50.
Northwest Energy Efficiency Alliance.  NEEA...................  NOPR No. 30; SNOPR No.   Efficiency Advocacy
                                                                 56.                      Organization.
Nyle Water Heating Systems, LLC......  Nyle...................  SNOPR No. 57...........  Manufacturer.
Pacific Gas and Electric Company, San  CA IOUs................  NOPR No. 36; SNOPR No.   Utilities.
 Diego Gas and Electric, and Southern                            52.
 California Edison, collectively
 referred to as the ``California
 Investor-Owned Utilities''.
Rheem Manufacturing Company..........  Rheem..................  NOPR No. 31;             Manufacturer.
                                                                 Transcript; SNOPR No.
                                                                 47.
SEA Groups, Ltd......................  SEA....................  NOPR No. 24............  Manufacturer.
Stone Mountain Technologies, Inc.....  SMTI...................  SNOPR No. 49...........  Manufacturer.
----------------------------------------------------------------------------------------------------------------
* Note: The January 27, 2022 TP NOPR Pubic Meeting Transcript can be found in the docket for this rulemaking at
  www.regulations.gov under entry number EERE-2019-BT-TP-0032-0027. Comments arising from the public meeting
  will be cited as follows: (Commenter name, Jan. 27, 2022 Public Meeting Transcript, No. 27 at p. X).

    A parenthetical reference at the end of a comment quotation or 
paraphrase provides the location of the item in the public record.\16\ 
To the extent that interested parties have provided written comments 
that are substantively similar to any oral comments provided during the 
NOPR public meeting, DOE cites the written comments throughout this 
final rule. Any oral comments provided during the webinar that are 
substantively distinct from a submitter's written comments are 
summarized and cited separately throughout this final rule.
---------------------------------------------------------------------------

    \16\ The parenthetical reference provides a reference for 
information located in the docket of DOE's rulemaking to develop 
test procedures for consumer water heaters and residential-duty 
commercial water heaters. (Docket No. EERE-2019-BT-TP-0032, which is 
maintained at www.regulations.gov). The references are arranged as 
follows: (commenter name, comment docket ID number, page of that 
document).
---------------------------------------------------------------------------

    APGA commented that DOE should adopt changes to its rulemaking 
process as outlined in a report by National Academies of Sciences, 
Engineering, and Medicine (NASEM) for both test procedures and 
standards. (APGA, No. 38 at p. 2) In response, the Department notes 
that the rulemaking process for test procedures of covered products and 
equipment are outlined at appendix A to subpart C of 10 CFR part 430, 
and DOE periodically examines and revises these provisions in separate 
rulemaking proceedings.
    Section II of this document provides a synopsis of this final rule, 
and section III of this document discusses each amendment to the test 
procedure for consumer water heaters and residential-duty commercial 
water heaters in detail.

II. Synopsis of the Final Rule

    In this final rule, DOE amends appendix E and related sections of 
the CFR. In summary, the final rule:
    1. Incorporates by reference current versions of industry 
standards: ASHRAE 41.1, ASHRAE 41.6, ASHRAE 118.2, ASTM D2156, and ASTM 
E97.
    2. Adds definitions for ``circulating water heater, ``tabletop 
water heater, and ``low-temperature water heater.
    3. Harmonizes various aspects of the DOE test procedure with 
industry test procedures ASHRAE 118.2-2022 and NEEA Advanced Water 
Heating Specification v8.0.
    4. Modifies the test condition specifications and tolerances, 
including electric supply voltage tolerance, ambient conditions 
(ambient dry-bulb temperature and ambient relative humidity), standard 
temperature and pressure definition, gas supply pressure, manifold 
pressure, inlet water temperature, and flow rate tolerances, and adds 
optional test conditions for heat pump water heaters.
    5. Specifies and clarifies methods for mixing valve installation 
for affected water heaters, orifice modification, and calculation of 
volume or mass delivered.
    6. Defines the use of a separate unfired hot water storage tank or 
separate electric storage water heater for testing water heaters 
designed to operate with a separately sold tank.
    7. Adds procedures for estimating internal stored water temperature 
for water heater designs in which the internal tank temperature cannot 
be directly measured.
    8. Clarifies test procedures for water heaters with network 
connection capabilities.
    9. Clarifies test procedures for flow-activated water heaters and 
water heaters that are not flow-activated by aligning terminology.
    10. Includes additional testing provisions for electric resistance 
water heaters undergoing optional high temperature testing.
    11. Includes a calculation for determining the effective storage 
volume of a water heater.
    The adopted amendments are summarized in Table II.1 compared to the 
test procedure provision prior to the amendment, as well as the reason 
for the adopted change.

      Table II.1--Summary of Changes in the Amended Test Procedure
------------------------------------------------------------------------
   DOE test procedure prior to       Amended test
            amendment                  procedure          Attribution
------------------------------------------------------------------------
References the 1986 (Reaffirmed   References the      Industry TP Update
 2006) version of ASHRAE 41.1      updated 2020        to ASHRAE 41.1.
 for methods for temperature       version of ASHRAE
 measurement.                      41.1.
The 1982 version of ASHRAE 41.6   References the      Industry TP Update
 for methods for humidity          2014 version of     to ASHRAE 41.6.
 measurement is referenced         ASHRAE 41.6,
 within the 1986 version of        which is
 ASHRAE 41.1.                      referenced by
                                   ASHRAE 41.1-2020.

[[Page 40411]]

 
References the 2009 version of    References the      Industry TP Update
 ASTM D2156 for testing smoke      version of ASTM     to ASTM D2156.
 density in flue gases from        D2156 that was
 burning distillate fuels.         reaffirmed in
                                   2018.
The 1987 version of ASTM E97 for  References the      Industry TP Update
 testing directional reflectance   1987 version of     to ASTM E97.
 factor, 45-deg 0-deg, of opaque   ASTM E97, which
 specimens by broad-band filter    is referenced by
 reflectometry is referenced       ASTM D2156-09 (RA
 within ASTM D2156-09.             2018).
Does not define a ``circulating   Adds a definition   Allow for testing
 water heater'' as used in 10      for ``circulating   certain consumer
 CFR 430.2.                        water heater'' to   water heaters.
                                   10 CFR 430.2.
Does not define a ``tabletop      Adds a definition   Reinstate
 water heater'' as used as a       for ``tabletop      definition
 product class distinction at 10   water heater'' to   inadvertently
 CFR 430.32(d).                    10 CFR 430.2.       removed by
                                                       previous final
                                                       rule.
Interprets the upper limit for    Corrects the upper  Make consistent
 consumer electric heat pump       limit for           with statutory
 water heaters to be 12 kW of      consumer electric   definition.
 input, with ``commercial heat     heat pump water
 pump water heater'' defined at    heaters to 24
 10 CFR 431.102 as having rated    amperes at 250
 electric power input greater      volts of input
 than 12 kW.                       and amends the
                                   definition for
                                   ``commercial heat
                                   pump water
                                   heater''
                                   accordingly.
Does not address how to           Specifies how a     Method added by
 configure a water heater for      mixing valve        DOE to improve
 test when a mixing valve is       should be           repeatability.
 required for proper operation.    installed when
                                   the water heater
                                   is designed to
                                   operate with one.
Requires the flow rate during     Requires the flow   Harmonization with
 the FHR test to be 1.0  0.25 gpm (3.8  0.95 L/min) for water      1.5     2022.
 heaters with a rated storage      0.25 gpm (5.7
 volume less than 20 gallons.       0.95
                                   L/min) for water
                                   heaters with a
                                   rated storage
                                   volume less than
                                   20 gallons.
Does not address the situation    Clarifies that the  Harmonization with
 in which the first recovery       first recovery      industry TP
 ends during a draw when testing   period will         ASHRAE 118.2-
 to the 24-hour simulated-use      extend to the end   2022.
 test.                             of the draw in
                                   which the first
                                   recovery ended,
                                   and that if a
                                   second recovery
                                   initiates prior
                                   to the end of the
                                   draw, that the
                                   second recovery
                                   is part of the
                                   first recovery
                                   period as well.
The recovery efficiency equation  Clarifies that,     Harmonization with
 for storage-type water heaters    for the             industry TP
 refers to the mass of water       calculation of      ASHRAE 118.2-
 removed from the start of the     recovery            2022.
 test to the end of the first      efficiency, the
 recovery period.                  mass of water
                                   removed during
                                   the first
                                   recovery period
                                   includes water
                                   removed during
                                   all draws from
                                   the start of the
                                   test until the
                                   end of the first
                                   recovery period.
The procedures for the standby    Clarifies the       Harmonization with
 period after the last draw of     alternate           industry TP
 the 24-hour simulated-use test    approach to         ASHRAE 118.2-
 allow for a recovery to occur     determine the       2022.
 at the end of the 8-hour          energy consumed
 standby period, which indicates   during the 24-
 that the power to the main        hour simulated
 burner, heating element, or       use test if a
 compressor is not disabled.       standby period
                                   occurs after the
                                   final draw of the
                                   test.
Appendix E uses the phrases       Uses the terms      Clarification.
 ``storage-type'' and              ``non-flow
 ``instantaneous-type'' to refer   activated'' and
 to ``non-flow activated'' and     ``flow-
 ``flow-activated'' water          activated'' water
 heaters, respectively.            heater, where
                                   appropriate.
The descriptions for Qsu,0,       The descriptions    Clarification.
 Qsu,f, Tsu,0, Tsu,f,              for Qsu,0, Qsu,f,
 [tau]stby,1, Tt,stby,1, and       Tsu,0, Tsu,f,
 Ta,stby,1 only address when the   [tau]stby,1,
 standby period occurs between     Tt,stby,1, and
 draw clusters 1 and 2.            Ta,stby,1 are
                                   generalized to
                                   refer to the
                                   section where the
                                   standby period is
                                   determined.
Specifies that the first          Specifies that the  Method updated by
 required measurement for each     first required      DOE to reduce
 draw of the 24-hour simulated-    measurement for     burden.
 use test is 5 seconds after the   each draw of the
 draw is initiated.                24-hour simulated-
                                   use test is 15
                                   seconds after the
                                   draw is initiated.
Requires the electric supply      Requires the        Method updated by
 voltage to be within 1 percent of the rated      voltage to be       burden.
 voltage for the entire test.      within 2 percent
                                   of the rated
                                   voltage beginning
                                   5 seconds after
                                   the start of a
                                   recovery and
                                   ending 5 seconds
                                   before the end of
                                   a recovery.
Requires maintaining ambient      Requires            Method updated by
 temperature for non-heat pump     maintaining the     DOE to reduce
 water heaters within a range of   ambient             burden.
 67.5 [deg]F  2.5      temperature for
 [deg]F.                           non-heat pump
                                   water heaters
                                   within a range of
                                   67.5 [deg]F  5 [deg]F,
                                   and with an
                                   average of 67.5
                                   [deg]F  2.5 [deg]F.
Requires maintaining the dry-     Requires            Method updated by
 bulb temperature for heat pump    maintaining the     DOE to reduce
 water heaters within a range of   dry-bulb            burden.
 67.5 [deg]F  1        temperature for
 [deg]F.                           heat pump water
                                   heaters within a
                                   range of 67.5
                                   [deg]F  5 [deg]F,
                                   and with an
                                   average of 67.5
                                   [deg]F  1 [deg]F
                                   during recoveries
                                   and an average of
                                   67.5 [deg]F  2.5 [deg]F
                                   when not
                                   recovering.
Requires maintaining the          Requires            Method updated by
 relative humidity for heat pump   maintaining the     DOE to reduce
 water heaters within a range of   relative humidity   burden
 50 percent 2          for heat pump
 percent.                          water heaters
                                   within a range of
                                   50 percent 5 percent,
                                   and at an average
                                   of 50 percent
                                   2
                                   percent during
                                   recoveries.
Requires that the heating value   States that the     Harmonization with
 be corrected to a standard        standard            industry TP
 temperature and pressure, but     temperature is 60   ASHRAE 118.2-
 does not state what temperature   [deg]F (15.6        2022.
 and pressure is standard or how   [deg]C) and the
 to correct the heating value to   standard pressure
 the standard temperature and      is 30 inches of
 pressure.                         mercury column
                                   (101.6 kPa).
                                   Provides a method
                                   for converting
                                   heating value
                                   from the measured
                                   to the standard
                                   conditions via
                                   incorporation by
                                   reference of
                                   ASHRAE 118.2-2022.
Requires that the manifold        Clarifies that the  Method updated by
 pressure be within 10 percent of the           tolerance applies   burden.
 manufacturer recommended value.   only to water
                                   heaters with a
                                   pressure
                                   regulator that
                                   can be adjusted.
                                   Requires that the
                                   manifold pressure
                                   be within the
                                   greater of 10 percent
                                   of the
                                   manufacturer
                                   recommended value
                                   or 0.2 inches
                                   water column.
Does not specify the input rate   Specifies that the  Method added by
 at which the gas supply           gas supply          DOE to clarify
 pressure tolerance is             pressure            enforcement test
 determined.                       tolerance is to     procedure.
                                   be maintained
                                   when operating at
                                   the maximum input
                                   rate.
Does not contain procedures for   Adds provisions     Method added by
 modifying the orifice of a        regarding the       DOE to clarify
 water heater that is not          modification of     enforcement test
 operating at the manufacturer     the orifice.        procedure.
 specified input rate.
Does not specify how to           Specifies how to    Method added by
 calculate the mass removed from   calculate the       DOE to improve
 the water heater when mass is     mass of water       repeatability.
 calculated indirectly using       indirectly using
 density and volume measurements.  density and
                                   volume
                                   measurements.
Does not accommodate testing of   Adds a definition   Allow for testing
 ``low-temperature water           of ``low-           certain consumer
 heaters'' in appendix E.          temperature water   water heaters.
                                   heater'' in 10
                                   CFR 430.2 and
                                   requires low
                                   temperature water
                                   heaters to be
                                   tested to their
                                   maximum possible
                                   delivery
                                   temperature in
                                   appendix E.

[[Page 40412]]

 
Does not explicitly define the    Explicitly states   Method added by
 test conditions required for      that the heat       DOE to improve
 each part of a split-system       pump part of a      representativenes
 heat pump water heater.           split-system heat   s and
                                   pump water heater   repeatability.
                                   is tested at the
                                   dry-bulb
                                   temperature and
                                   relative humidity
                                   conditions
                                   required for heat
                                   pump water
                                   heaters, and that
                                   the storage tank
                                   is tested at the
                                   ambient
                                   temperature and
                                   relative humidity
                                   conditions
                                   required for non-
                                   heat pump water
                                   heaters.
Does not accommodate testing of   Requires that gas-  Allow for testing
 water heaters that require a      fired circulating   certain consumer
 separately-sold hot water         water heaters be    water heaters.
 storage tank to properly          tested using a
 operate.                          UFHWST with a
                                   storage volume
                                   between 80 and
                                   120 gallons and
                                   that meets but
                                   does not exceed
                                   the minimum
                                   energy
                                   conservation
                                   standards
                                   required
                                   according to 10
                                   CFR 431.110(a),
                                   and that heat
                                   pump circulating
                                   water heaters be
                                   tested using a 40-
                                   gallon electric
                                   storage water
                                   heater at the
                                   minimum UEF
                                   standard required
                                   at 10 CFR
                                   430.32(d).
Does not address water heaters    Explicitly states   Clarification.
 with network connection           that any
 capabilities.                     connection to an
                                   external network
                                   or control be
                                   disconnected
                                   during testing.
Does not accommodate certain      Establishes a       Allow for testing
 water heaters for which the       method of           certain consumer
 mean tank temperature cannot be   determining the     water heaters.
 directly measured.                internal storage
                                   tank temperature
                                   using draws at
                                   the beginning and
                                   end of the 24-
                                   hour simulated
                                   use test.
10 CFR 429.70(g) does not allow   Extends the         AEDM allowed by
 untested electric instantaneous   untested            DOE to reduce
 water heaters to be certified,    provisions within   burden.
 but does allow untested           10 CFR 429.70(g)
 electric storage water heaters    to include
 to be certified.                  electric
                                   instantaneous
                                   water heaters.
Does not specify flow rate        Specifies that      Method added by
 tolerance for water heaters       flow rates for      DOE to improve
 with rated storage volume less    all water heaters   repeatability and
 than 2 gallons.                   with rated          reproducibility.
                                   storage volume
                                   less than 2
                                   gallons must be
                                   maintained within
                                   a tolerance of
                                   0.25
                                   gallons per
                                   minute.
                                   Additionally
                                   proposes that for
                                   water heaters
                                   with rated
                                   storage volume
                                   less than 2
                                   gallons and a
                                   rated Max GPM of
                                   less than 1
                                   gallon per
                                   minute, the flow
                                   rate tolerance
                                   shall be 25 percent
                                   of the rated Max
                                   GPM.
Does not include optional         Allows for          Harmonization with
 efficiency representations at     optional            industry TP NEEA
 alternative test conditions for   efficiency          Advanced Water
 heat pump water heaters.          representations     Heating
                                   at alternative      Specification
                                   test conditions     v8.0.
                                   for heat pump
                                   water heaters.
Does not include a definition     Adds a definition   Harmonization with
 for ``split-system heat pump      for ``split-        industry TP NEEA
 water heater.''.                  system heat pump    Advanced Water
                                   water heater'' to   Heating
                                   distinguish these   Specification
                                   from heat pump-     v8.0.
                                   only water
                                   heaters.
Specifies that water heaters      Provides a test     Method added by
 with multiple modes of            method for          DOE to improve
 operation be tested in the        electric            representativenes
 ``default'' or other similarly    resistance water    s.
 named mode.                       heaters subject
                                   to high
                                   temperature
                                   testing (setting
                                   the water heater
                                   to the highest
                                   storage tank
                                   temperature and
                                   using a mixing
                                   valve to temper
                                   the delivery
                                   water to be
                                   within 125  5 [deg]F).
                                   Does not require
                                   the use of this
                                   type of testing
                                   for any water
                                   heaters, however,
                                   until compliance
                                   with amended
                                   standards is
                                   required.
Does not include any method to    Establishes a       Method added by
 determine effective storage       metric and method   DOE which adopts
 volume of storage-type water      for determining     a metric for
 heaters or circulating water      the effective       additional
 heaters.                          storage volume of   consumer
                                   storage-type        information.
                                   water heaters and
                                   circulating water
                                   heaters.
Does not include a definition     Adopts a            Harmonization with
 for ``thermal break.''.           definition for      industry TP
                                   ``thermal break''   ASHRAE 118.2-
                                   but does not        2022.
                                   mandate the use
                                   of this component
                                   in test set-up.
------------------------------------------------------------------------

    DOE has determined that the amendments described in section III and 
adopted in this document will not alter the measured efficiency of 
consumer water heaters and residential-duty commercial water heaters, 
or require retesting or recertification solely as a result of DOE's 
adoption of the amendments to the test procedures. Discussion of DOE's 
actions are addressed in detail in section III of this document.
    The effective date for the amended test procedures adopted in this 
final rule is 30 days after publication of this document in the Federal 
Register. Representations of energy use or energy efficiency must be 
based on testing in accordance with the amended test procedures 
beginning 180 days after the publication of this final rule for 
consumer water heaters and 360 after the publication of this final rule 
for residential-duty commercial water heaters.

III. Discussion

A. Scope of Applicability and Definitions

    This document covers those products that meet the definition of 
consumer ``water heaters,'' as defined in the statute at 42 U.S.C. 
6291(27), as codified at 10 CFR 430.2. This document also covers 
commercial water heating equipment with residential applications 
((i.e., those water heaters which meet the definition of ``residential-
duty commercial water heater'' at 10 CFR 431.102).
    In the context of covered consumer products, EPCA defines ``water 
heater'' as a product which utilizes oil, gas, or electricity to heat 
potable water for use outside the heater upon demand, including--
    (a) Storage type units which heat and store water at a 
thermostatically controlled temperature, including gas storage water 
heaters with an input of 75,000 Btu per hour or less, oil storage water 
heaters with an input of 105,000 Btu per hour or less, and electric 
storage water heaters with an input of 12 kilowatts or less;
    (b) Instantaneous type units which heat water but contain no more 
than one gallon of water per 4,000 Btu per hour of input, including gas 
instantaneous water heaters with an input of 200,000 Btu per hour or 
less, oil instantaneous water heaters with an input of 210,000 Btu per 
hour or less, and electric instantaneous water heaters with an input of 
12 kilowatts or less; and
    (c) Heat pump type units, with a maximum current rating of 24 
amperes at a voltage no greater than 250 volts, which are products 
designed to transfer thermal energy from one temperature level to a 
higher temperature level for the purpose of heating water, including 
all ancillary equipment such as fans, storage tanks, pumps, or controls

[[Page 40413]]

necessary for the device to perform its function.

(42 U.S.C. 6291(27); 10 CFR 430.2)
    In addition, at 10 CFR 430.2, DOE defines several specific 
categories of consumer water heaters, as follows:
    (1) ``Electric instantaneous water heater'' means a water heater 
that uses electricity as the energy source, has a nameplate input 
rating of 12 kW or less, and contains no more than one gallon of water 
per 4,000 Btu per hour of input.
    (2) ``Electric storage water heater'' means a water heater that 
uses electricity as the energy source, has a nameplate input rating of 
12 kW or less, and contains more than one gallon of water per 4,000 Btu 
per hour of input.
    (3) ``Gas-fired instantaneous water heater'' means a water heater 
that uses gas as the main energy source, has a nameplate input rating 
less than 200,000 Btu/h, and contains no more than one gallon of water 
per 4,000 Btu per hour of input.
    (4) ``Gas-fired storage water heater'' means a water heater that 
uses gas as the main energy source, has a nameplate input rating of 
75,000 Btu/h or less, and contains more than one gallon of water per 
4,000 Btu per hour of input.
    (5) ``Grid-enabled water heater'' means an electric resistance 
water heater that--
    (a) Has a rated storage tank volume of more than 75 gallons;
    (b) Is manufactured on or after April 16, 2015;
    (c) Is equipped at the point of manufacture with an activation lock 
and;
    (d) Bears a permanent label applied by the manufacturer that--
    (i) Is made of material not adversely affected by water;
    (ii) Is attached by means of non-water-soluble adhesive; and
    (iii) Advises purchasers and end-users of the intended and 
appropriate use of the product with the following notice printed in 
16.5 point Arial Narrow Bold font: ``IMPORTANT INFORMATION: This water 
heater is intended only for use as part of an electric thermal storage 
or demand response program. It will not provide adequate hot water 
unless enrolled in such a program and activated by your utility company 
or another program operator. Confirm the availability of a program in 
your local area before purchasing or installing this product.''
    (6) ``Oil-fired instantaneous water heater'' means a water heater 
that uses oil as the main energy source, has a nameplate input rating 
of 210,000 Btu/h or less, and contains no more than one gallon of water 
per 4,000 Btu per hour of input.
    (7) ``Oil-fired storage water heater'' means a water heater that 
uses oil as the main energy source, has a nameplate input rating of 
105,000 Btu/h or less, and contains more than one gallon of water per 
4,000 Btu per hour of input.
    The definition for ``grid-enabled water heater'' includes the term 
``activation lock,'' which is defined to mean a control mechanism 
(either by a physical device directly on the water heater or a control 
system integrated into the water heater) that is locked by default and 
contains a physical, software, or digital communication that must be 
activated with an activation key to enable the product to operate at 
its designed specifications and capabilities and without which the 
activation of the product will provide not greater than 50 percent of 
the rated first-hour delivery of hot water certified by the 
manufacturer. 10 CFR 430.2. As specified in this definition, the 
control mechanism must be physically incorporated into the water heater 
or, if a control system, integrated into the water heater to qualify as 
an activation lock. DOE is aware of certain State programs that 
encourage water heaters to be equipped with communication ports that 
allow for demand-response communication between the water heater and 
the utility.\17\ DOE notes that presence of such a communication port, 
in and of itself, would not qualify as an activation lock for the 
purpose of classifying a water heater as a grid-enabled water heater. 
Demand-response water heaters are discussed separately in section 
III.A.1 of this final rule.
---------------------------------------------------------------------------

    \17\ On May 7, 2019, the State of Washington signed House Bill 
1444 which amended the Revised Code of Washington (RCW) (i.e., the 
statutory code in the State of Washington), Title 19, Chapter 19.260 
(RCW 19.260). On January 6, 2020, the State of Washington amended 
the Washington Administrative Code (WAC) (i.e., the regulatory code 
in the State of Washington), Title 194, Chapter 194-24 (WAC 194-24) 
(Washington January 2020 Amendment) to align with RCW 19.260. 
Similarly, the State of Oregon published a final rule (Oregon August 
2020 final rule) on August 8, 2020, which amended the Oregon 
Administrative Rules (OAR), Chapter 330, Division 92 (OAR-330-092). 
The Washington House Bill 1444 and the Oregon August 2020 final rule 
established a definition for electric storage water heater (RCW 
19.260.020(14); OAR-330-092-0010(10)), an effective date of January 
1, 2021 in Washington and January 1, 2022 in Oregon (RCW 
19.260.080(1); OAR-330-092-0015(17)), a requirement that electric 
storage water heaters must have a modular demand response 
communications port compliant with the March 2018 version of the 
ANSI/CTA-2045-A communication interface standard, or a standard 
determined to be equivalent (RCW 19.260.080(1)(a)-(b); OAR-330-092-
0020(17)), and, in Oregon, must bear a label or marking on the 
products stating either ``DR-ready: CTA-2045-A'' or ``DR-ready: CTA-
2045-A and [equivalent DR system protocol]'' (OAR-330-092-0045(17)).
---------------------------------------------------------------------------

    Additionally, as discussed further in section III.A.3 of this 
document, the appendix E test procedure also applies to residential-
duty commercial water heaters. (See 10 CFR 431.106(b)(1)) DOE defines 
these equipment categories at 10 CFR 431.102 as any gas-fired storage, 
oil-fired storage, or electric instantaneous commercial water heater 
that meets the following conditions:
    (1) For models requiring electricity, uses single-phase external 
power supply;
    (2) Is not designed to provide outlet hot water at temperatures 
greater than 180 [deg]F; and
    (3) Does not meet any of the following criteria:

------------------------------------------------------------------------
       Water heater type        Indicator of non-residential application
------------------------------------------------------------------------
Gas-fired Storage.............  Rated input >105 kBtu/h; Rated storage
                                 volume >120 gallons.
Oil-fired Storage.............  Rated input >140 kBtu/h; Rated storage
                                 volume >120 gallons.
Electric Instantaneous........  Rated input >58.6 kW; Rated storage
                                 volume >2 gallons.
------------------------------------------------------------------------

    In the January 2022 NOPR, DOE discussed definitions and the scope 
of appendix E for heat pump water heaters (electric as well as gas-
fired), gas-fired instantaneous water heaters (specifically circulating 
gas-fired water heaters), tabletop water heaters, and residential-duty 
commercial water heaters. 87 FR 1554, 1560-1567 (Jan. 11, 2022). 
Additionally, DOE proposed a new definition for ``demand-response water 
heater'' in the July 2022 SNOPR. 87 FR 42270, 42280 (July 14, 2022).
    BWC generally agreed with DOE's determinations regarding product 
and equipment definitions and classifications. (BWC, No. 33 at p. 1) 
AET generally commented that DOE's test procedures should be 
appropriate for all consumer water heaters within the scope of 
standards, especially for electric instantaneous water heaters. (AET, 
No. 29 at pp. 11-12)

[[Page 40414]]

    As discussed throughout this rulemaking, it is DOE's intention to 
ensure that the appendix E test procedure amended by this final rule is 
appropriate and applicable to all consumer water heaters and 
residential-duty commercial water heaters. Sections III.A.1 through 
III.A.4 of this document address specific issues related to scope and 
definitions that either DOE requested comment on in the January 2022 
NOPR or July 2022 SNOPR, or that were identified by commenters in 
response to those documents.
1. Demand-Response Water Heaters
    Storage-type water heaters that have ``connected'' capability, 
often referred to as ``demand-response'' water heaters, can be remotely 
activated and/or deactivated by signals from a utility company or 
another program operator, and are able to serve as a thermal energy 
storage device. DOE considered whether specific testing requirements 
would be appropriate for demand-response water heaters (such as 
requiring measurement of the energy consumed by connected features, or 
providing a method for calculating the amount of thermal energy storage 
available); however, DOE had tentatively determined that additional 
test procedure provisions (such as the calculation of a thermal energy 
storage metric) are premature and unnecessary to specify at this time 
as the market continues to develop and evolve. DOE proposed only that a 
provision be added to the test procedure to require that if a water 
heater can connect to an external network or controller, that 
communication shall be disabled during testing. 87 FR 1554, 1585-1586 
(Jan. 11, 2022). Several stakeholders provided input on this tentative 
determination.
    NEEA encouraged DOE to adopt definitions and test methods for 
``connectable'' water heaters in the test procedure. The commenter 
pointed to the following existing and emerging standards as references: 
Consumer Technology Association (CTA) Standard 2045 (ANSI/CTA-2045)/
EcoPort,\18\ U.S. Environmental Protection Agency (EPA) ENERGY STAR 
connected device requirements, and AHRI 1430, Standard for Demand 
Response for Electric Water Heaters.\19\ NEEA stated that definitions 
of connectivity have already been adopted by the States of Washington, 
Oregon, and California as part of their water heating appliance 
standards. (NEEA, No. 30 at pp. 2-3) The CA IOUs recommended the 
adoption of a definition for the communication capability for grid-
enabled water heaters that is consistent with the Connected Product 
Criteria in the ENERGY STAR Product Specification for Residential Water 
Heaters.\20\ The CA IOUs also recommended that DOE incorporate the 
associated ENERGY STAR connected products test procedure into the 
appendix E test procedure. (CA IOUs, No. 36 at pp. 2-3)
---------------------------------------------------------------------------

    \18\ Available online at: shop.cta.tech/products/https-cdn-cta-
tech-cta-media-media-ansi-cta-2045-b-final-2022-pdf (Last accessed 
on Sept. 17, 2022).
    \19\ AHRI Standard 1430, ``Standard for Demand Response for 
Electric Water Heaters,'' was published in December 2022. It is an 
industry consensus standard developed by an AHRI Consensus Standards 
Project Committee that includes definitions, test requirements, 
operating and physical requirements, minimum data requirements for 
published ratings, marking and nameplate, and data and conformance 
conditions for demand-response electric water heaters. For more 
information, see www.ahrinet.org/search-standards/ahri-1430-demand-flexible-electric-storage-water-heaters (Last accessed on Feb. 17, 
2023).
    \20\ According to version 5.0 of the ENERGY STAR Program 
Requirements for Residential Water Heaters Eligibility Criteria, a 
``connected water heater product (CWHP)'' includes the ENERGY STAR 
certified water heater, integrated or separate communications 
hardware, and additional hardware and software required to enable 
connected functionality. ``Demand Response'' is also defined by that 
source to mean changes in electric or gas usage by end-use customers 
from their normal consumption patterns in response to changes in the 
price of electricity or gas over time, or to incentive payments 
designed to induce lower electricity or gas use at times of high 
wholesale market prices or when system reliability is jeopardized. 
Version 5.0 of the ENERGY STAR specification is available online at: 
www.energystar.gov/products/spec/residential_water_heaters_specification_version_5_0_pd (Last 
accessed on July 25, 2022).
---------------------------------------------------------------------------

    In response, DOE considered these comments and also assessed the 
operation of demand-response water heaters as grid thermal energy 
storage devices using specific communication protocols in order to 
determine how to distinguish these products from other water heaters 
capable of storage tank overheating. On July 18, 2022, EPA published an 
ENERGY STAR Version 5.0 Residential Water Heater Specification, which 
included definitions for ``connected water heater product'' and 
``demand response.'' These definitions included references to Consumer 
Technology Association (CTA) Standard 2045 (ANSI/CTA-2045),\21\ a 
design standard for a communications module that allows a water heater 
to receive signals from a utility company (e.g., a curtailment 
request). As indicated by NEEA and the CA IOUs, the presence of a CTA-
2045 port uniquely enables a water heater to be able to participate in 
any demand-response program, and DOE has additionally determined that 
products with these features are increasing in number.
---------------------------------------------------------------------------

    \21\ See section 4.D.a of the ENERGY STAR Version 5.0 
specification.
---------------------------------------------------------------------------

    In the July 2022 SNOPR, DOE noted that certain new water heaters 
were available on the market that are shipped from the point of 
manufacture with a mixing valve installed and intentionally 
``overheat'' \22\ the water to a stored temperature that is higher than 
the delivery temperature setpoint to provide additional capacity.\23\ 
87 FR 42270, 42279-42280 (July 14, 2022). DOE proposed specific test 
requirements for such products (see section III.E.1 of this document 
for discussion). DOE also noted that water heaters with demand-response 
capabilities may undergo utility-initiated overheating during certain 
periods to store additional energy in the water heater during peak 
demand periods, and tentatively determined that the test provisions 
proposed for water heaters that overheat may not be appropriate for 
demand-response water heaters that overheat. Id. To distinguish demand-
response water heaters from other types capable of overheating, DOE 
proposed to define a ``demand-response water heater'' as follows:
---------------------------------------------------------------------------

    \22\ The term ``overheating'' refers to raising the tank 
temperature above the outlet water setpoint and does not denote 
performance outside of the normal operating range of the water 
heater.
    \23\ While typical water heaters do not store water warmer than 
the outlet temperature setpoint (which is, on average, 125  5 [deg]F), water heaters designed to increase energy storage 
capacity may overheat the tank to temperatures such as 140-150 
[deg]F and use a mixing valve to temper the outlet water down to the 
setpoint condition. The energy storage capacity is proportional to 
both the size of the tank and the temperature of the water within.
---------------------------------------------------------------------------

    Demand-response water heater means a storage-type water heater 
that--
    1. Has integrated communications hardware and additional hardware 
and software required to enable connected functionality with a utility 
or third party, that dispatches signals with demand response 
instructions and/or price signals to the product and receives messages 
from the demand-response water heater;
    2. Meets the communication and equipment standards for Consumer 
Technology Association (CTA) Standard 2045-B (ANSI/CTA-2045-B); \24\
---------------------------------------------------------------------------

    \24\ ANSI/CTA-2045-B, ``Modular Communications Interface for 
Energy Management,'' published February 2021. (Available at: 
shop.cta.tech/products/https-cdn-cta-tech-cta-media-media-ansi-cta-
2045-b-final-2022-pdf) (Last accessed Sept. 17, 2022).
---------------------------------------------------------------------------

    3. Automatically heats the stored water above the delivery 
temperature setpoint only in response to instructions received from a 
utility or third party.

87 FR 42270, 42280 (July 14, 2022). DOE sought comment on this proposed 
definition. Id.

[[Page 40415]]

    In response to the July 2022 SNOPR, AHRI, A.O. Smith, BWC, and 
Rheem recommended that DOE change its definition of ``demand-response 
water heater'' to be consistent with ENERGY STAR and AHRI Standard 
1430.\25\ (AHRI, No. 55 at p. 7; A.O. Smith, No. 51 at pp. 6-7; BWC, 
No. 48 at p. 2; Rheem, No. 47 at p. 6) Specifically, AHRI and A.O. 
Smith requested that DOE define ``demand-flexible water heater'' as 
``an electric resistance storage water heater or heat pump water heater 
with the capability to reduce, shed, shift, load up, and modulate 
energy consumption in response to a command or instructions received 
from a utility or third party.'' (AHRI, No. 55 at p. 7; A.O. Smith, No. 
51 at pp. 6-7) BWC requested that DOE use the ENERGY STAR and AHRI 
Standard 1430 definitions of ``demand-response'' to avoid manufacturer 
burden and allow for easier future development of these products. (BWC, 
No. 48 at p. 2) Rheem further recommended that DOE seek direct feedback 
from EPA's ENERGY STAR program. (Rheem, No. 47 at p. 6)
---------------------------------------------------------------------------

    \25\ AHRI Standard 1430-2022 (I-P), ``2022 Standard for Demand 
Flexible Water Heaters,'' published December 2022. (Available at: 
https://www.ahrinet.org/search-standards/ahri-1430-demand-flexible-electric-storage-water-heaters.) (Last accessed Feb. 17, 2023)
---------------------------------------------------------------------------

    NYSERDA pointed out that DOE's proposed definition for ``demand-
response water heater,'' which states that it cannot overheat as a 
result of user-initiated operation, is an additional requirement beyond 
ENERGY STAR's definitions. Accordingly, NYSERDA urged DOE to define 
``overheating test exempt water heaters'' so as to avoid creating 
market confusion, and the commenter recommended that DOE consider the 
power usage for connectedness as included in the ENERGY STAR water 
heater specification, as it would allow utilities to plan more 
effectively, encourage the additional load to be minimal, and inform 
consumers regarding anticipated operating costs. (NYSERDA, No. 50 at p. 
2)
    NEEA indicated support for DOE's proposed definition of ``demand-
response water heater'' and the proposal for demand-response water 
heaters to meet the communication and equipment standards for ANSI/CTA-
2045. (NEEA, No. 56 at pp. 2-3) AHRI, however, indicated that DOE's 
definition would require compliance with the demand-response program 
the water heater is enrolled in, whereas other, non-DOE definitions 
allow consumers to opt out. (AHRI, No. 55 at p. 7) BWC and Rheem 
requested that DOE remove the requirement to comply with CTA-2045. 
(BWC, No. 48 at pp. 1-2, Rheem, No. 47 at p. 6) BWC stated that 
requiring compliance with CTA-2045 may prevent manufacturers from 
designing their products around separate and future protocols. (BWC, 
No. 48 at pp. 1-2)
    Rheem recommended that DOE's definition acknowledge the fact that 
many water heaters with demand-response capability are currently 
shipped without all necessary hardware to participate in a demand-
response program. Rheem also suggested that DOE's definition does not 
cover most demand-response water heaters because it excludes water 
heaters without the ability to heat water above the setpoint. (Rheem, 
No. 47 at p. 6)
    After reviewing these comments from stakeholders, DOE understands 
that, for the purpose of demand-response programs, utilities and 
manufacturers would benefit from a standardized definition of ``demand-
response water heater,'' specifically one that requires certain 
communications protocols to be present in order to be compatible with 
the demand-response signals from the utility or third-party. 
Stakeholders have indicated that, in order to be deemed a ``demand-
response water heater,'' a product must demonstrate that it is capable 
of executing the commands from the demand-response signals (i.e., pass 
the verification tests in the ENERGY STAR Test Method to Validate 
Demand Response or in AHRI Standard 1430). However, DOE proposed a more 
limited definition for ``demand-response water heater'' in the July 
2022 SNOPR, seeking only to describe the types of water heaters that 
could temporarily increase the storage tank temperature as a means to 
perform a load up \26\ such that this particular operation would not be 
considered ``overheating'' in the appendix E test procedure (see 87 FR 
42270, 42280 (July 14, 2022)). This led DOE to revisit its proposed 
definition and to reassess its planned approach.
---------------------------------------------------------------------------

    \26\ According to the ENERGY STAR Test Method to Validate Demand 
Response v1.2, a connected water heating product is required to use 
and/or store additional thermal energy that the device otherwise 
would not have used/stored under normal operation in response to a 
load up request. This allows the stored thermal energy to increase 
within the safety parameters determined by the manufacturer, and, 
for installations with a mixing valve, the device may exceed the 
user set point temperature.
---------------------------------------------------------------------------

    As a result, in this final rule, DOE has decided not to establish a 
definition for ``demand-response water heater.'' DOE has considered the 
various requirements which stakeholders suggested should be criteria 
for a product to be called a ``demand-response water heater'' and has 
determined that, while standardization of these requirements may be 
beneficial to utilities and industry, it is unnecessary at this time 
because DOE can instead describe the types of water heaters that can 
temporarily increase the storage tank temperature only in response to 
instructions from a utility or third-party demand response program 
without defining ``demand-response water heater''. Additionally, as 
discussed in section III.E.1.b of this document, this final rule only 
amends the test procedure to provide a means for testing water heaters 
in the highest tank temperature setting, and DOE is adopting it as a 
voluntary measure in this test procedure for certain electric storage 
water heaters. As such, it is no longer necessary to establish a 
definition for ``demand-response water heater'' in this test procedure 
rulemaking.
2. Heat Pump Water Heaters
    As discussed in section III.A of this document, EPCA defines 
``water heater'' to include, in relevant part, (A) storage type units 
which heat and store water at a thermostatically controlled 
temperature, including . . . electric storage water heaters with an 
input of 12 kilowatts or less; (B) instantaneous type units which heat 
water but contain no more than one gallon of water per 4,000 Btu per 
hour of input, including . . . electric instantaneous water heaters 
with an input of 12 kilowatts or less; and (C) heat pump type units, 
with a maximum current rating of 24 amperes at a voltage no greater 
than 250 volts, which are products designed to transfer thermal energy 
from one temperature level to a higher temperature level for the 
purpose of heating water, including all ancillary equipment such as 
fans, storage tanks, pumps, or controls necessary for the device to 
perform its function. (42 U.S.C. 6291(27))
    Because the maximum current and voltage ratings for consumer heat 
pump type units are 24 amperes at no more than 250 volts, the maximum 
electrical input for this type of product is determined to be 6 
kilowatts.\27\ In this final rule, DOE is providing clarifications on 
how these definitions apply to electric and gas-fired heat pump storage 
water heaters.
---------------------------------------------------------------------------

    \27\ Power equals current times voltage, so the definition of 
consumer heat pump type unit corresponds to a maximum power rating 
of 6,000 W, or 6 kW (i.e., 24 A times 250 V equals 6,000 W).
---------------------------------------------------------------------------

a. Electric Heat Pump Storage Water Heaters
    EPCA is not explicit as to whether heat pump type units are 
considered a subcategory of storage type units and

[[Page 40416]]

instantaneous type units. ``Storage type units'' and ``instantaneous 
type units'' are not exclusive of ``heat pump type units.'' Based on 
the statute's ``water heater'' definition, an electric heat pump type 
unit could be covered under the ``water heater'' definition's 
description of storage type units (if it heats and stores water at a 
thermostatically controlled temperature with an input of 12 kilowatts 
or less) or instantaneous type unit (if it heats water and contains no 
more than one gallon of water per 4,000 Btu per hour of input and has 
an input of 12 kilowatts or less).
    On November 10, 2016, DOE published a final rule in the Federal 
Register (the November 2016 Final Rule) that treated heat pump-type 
units as a subcategory of the other two types of units listed in the 
definition of water heater. Specifically, DOE stated in the November 
2016 final rule that a heat pump water heater with a total rated input 
of less than 12 kilowatts would be a consumer water heater because EPCA 
classifies electric water heaters with less than 12 kilowatts rated 
electrical input as consumer water heaters. 81 FR 79261, 79301-79302. 
In the January 2022 NOPR, DOE responded to comments requesting 
clarification on whether electric heat pump water heaters between 6 
kilowatts and 12 kilowatts of input should be classified as consumer 
water heaters or commercial water heaters. 87 FR 1554, 1561-1563 (Jan. 
11, 2022). Upon further review of EPCA and the water heater market, DOE 
initially determined in the January 2022 NOPR that the interpretation 
presented in the November 2016 Final Rule was not the best reading of 
EPCA. Id.
    In the January 2022 NOPR, DOE explained that the structure of the 
statutory definition of ``water heater'' in the Energy Conservation 
Program for Consumer Products in Part A of EPCA lists each type of 
water heater at equal subparagraph designations. Therefore, when 
defining ``water heater'' for the purpose of determining whether a 
water heater is a consumer water heater, the energy use criteria 
specified for heat pump-type units is to be applied separately and 
distinctly from the criteria specified for the categorizations of 
storage-type units and instantaneous-type units. Therefore, DOE had 
tentatively determined that heat pump water heaters, which operate with 
a maximum current rating greater than 24 amperes or at a voltage 
greater than 250 volts, are more appropriately covered as commercial 
water heaters than consumer water heaters. 87 FR 1554, 1561-1562 (Jan. 
11, 2022).
    As explained in the January 2022 NOPR, there are three other 
reasons why DOE tentatively concluded that the revised interpretation 
would be more applicable to the residential water heater market.
    First, heat pump technology is capable of providing heat output 
which exceeds the energy input. A heat pump type unit with an input 
rate of 12 kilowatts could have a heating capacity (i.e., output 
capacity) of approximately 42 kilowatts, which is 3.6 times the output 
heating capacity provided by the largest possible consumer electric 
storage type water heater (i.e., 11.8 kilowatts).\28\ While a heat 
pump-type unit with a 12 kilowatt input capacity could theoretically be 
designed and installed in a residential application, its water heating 
capacity (i.e., output capacity) would far exceed the water heating 
demand of any residential installation. 87 FR 1554, 1562 (Jan. 11, 
2022).
---------------------------------------------------------------------------

    \28\ A 12-kW electric resistance water heater with an assumed 
recovery efficiency of 98 percent would have an output heating 
capacity of 11.8 kW (12 kW x 0.98 = 11.8 kW). An electric heat pump-
type water heater with a 12-kW input capacity, with an assumed 
recovery efficiency of 350 percent, would have an output heating 
capacity of 42 kW (12 kW x 3.5 = 42 kW), which is 3.6 times greater 
than the 11.8 kW output heating capacity of an electric resistance 
water heater with equivalent input capacity.
---------------------------------------------------------------------------

    Second, the DOE test procedure for consumer water heaters at the 
time of the November 2016 Final Rule only covered heat pump water 
heaters which have ``a maximum current rating of 24 amperes (including 
the compressor and all auxiliary equipment such as fans, pumps, 
controls, and, if on the same circuit, any resistive elements) for an 
input voltage of 250 volts or less,'' and, therefore, electric heat 
pump water heaters with greater than 24 amperes at 250 volts were not 
considered at the time when the current energy conservation standards 
for consumer water heaters were established (April 2010). As a result, 
these current standards do not reflect energy usage for heat pump water 
heaters between 6 kilowatts and 12 kilowatts, and such products are 
more appropriately rated to the commercial water heater test procedure 
(10 CFR 431.106) and evaluated against the maximum standby loss 
standards for this equipment (10 CFR 431.110(a)). 87 FR 1554, 1562 
(Jan. 11, 2022).
    Third, based on its review of the market, DOE is aware of 
integrated heat pump water heaters, split-system heat pump water 
heaters, and heat pump-only water heaters (i.e., circulating heat pump 
water heaters) which are designed for use in residential applications, 
and all such products are rated at or below 24 A/250 V of input. 
Integrated heat pump water heaters, which consist of an air-source heat 
pump in one assembly with a storage tank, typically operate with 240-
volt input. Although integrated heat pump water heaters usually have 
backup 4.5-kilowatt electric resistance heating elements, the elements 
do not operate simultaneously, which ensures that these products do not 
surpass 6 kilowatts of input or 24 A/250 V at any given time. Some 
integrated heat pump water heaters are designed to operate at only 120 
volts of input (i.e., ``retrofit-ready,'' ``plug-in,'' or ``120-volt'' 
heat pump water heaters). Split-system heat pump water heaters, which 
consist of a separate heat pump and storage tank that are sold together 
(where the heat pump components are usually situated outdoors), are 
also covered by the currently applicable appendix E test procedure and 
have electrical input ratings which do not exceed 24 A/250 V. 
Circulating heat pump water heaters (or ``heat pump-only'' water 
heaters), which consist of only a heat pump module and must be 
installed with a separate storage tank, similarly do not exceed this 
limit, and there are models of circulating heat pump water heaters 
which are intended to operate on 120 volts of input. Alternative source 
heat pump water heaters (e.g., ground-source or water-source), were not 
considered in this rulemaking due to their predominant use as 
commercial products. 87 FR 1554, 1563 (Jan. 11, 2022).
    In this final rule, DOE maintains the revised interpretation as 
discussed in the January 2022 NOPR. To clarify this interpretation in 
the regulatory definitions, DOE is amending the definition of 
``commercial heat pump water heater'' at 10 CFR 431.102 to reflect this 
revised interpretation. The revised definition reads: ``Commercial heat 
pump water heater (CHPWH) means a water heater (including all ancillary 
equipment such as fans, blowers, pumps, storage tanks, piping, and 
controls, as applicable) that uses a refrigeration cycle, such as vapor 
compression, to transfer heat from a low-temperature source to a 
higher-temperature sink for the purpose of heating potable water, and 
operates with a current rating greater than 24 amperes or a voltage 
greater than 250 volts. Such equipment includes, but is not limited to, 
air-source heat pump water heaters, water-source heat pump water 
heaters, and direct geo-exchange heat pump water heaters.''
    In the April 2020 RFI, DOE requested feedback on the need for 
creating a separate definition for ``electric heat pump storage water 
heater,'' similar to the definition in the March 2019

[[Page 40417]]

ASHRAE Draft 118.2, or whether the current DOE definitions in 10 CFR 
430.2 for ``electric storage water heater'' and ``water heater,'' which 
include ``heat pump type units,'' would adequately cover such products 
for the purpose of performing the DOE test procedure. 85 FR 21104, 
21110 (April 16, 2020). The Department's tentative determination in the 
January 2022 NOPR was that a separate definition would not be needed 
because the current definitions were sufficient to describe these 
products. 87 FR 1554, 1563-1564 (Jan. 11, 2022). In response to the 
January 2022 NOPR, Rheem requested that the product class-specific 
definitions include or refer to the ``heat pump type'' requirements in 
EPCA. (Rheem, No. 31 at p. 2) BWC agreed with DOE's assessment that 
consumer heat pump water heaters operate at no greater than 24 amperes 
at 250 volts. (BWC, No. 33 at pp. 1-2)
    Additionally, DOE received several comments on the January 2022 
NOPR regarding definitions for specific types of heat pump water 
heaters used in residential applications.
    The CA IOUs recommended that DOE should supplement its test 
procedure definitions to address heat pump water heaters rated to 
operate at 120 volts of input. More specifically, the CA IOUs 
recommended that DOE develop a separate definition for 120-volt heat 
pump water heaters in the test procedure and consider any 
distinguishing characteristics that might require changes to the test 
procedure to represent their real-world performance accurately. These 
commenters argued that a separate definition would allow for the 
possibility of separate energy conservation standards for these 
products. The CA IOUs stated that they expect the first 120-volt heat 
pump water heaters to appear on the retail market in 2022 and noted 
that the California Energy Commission recently adopted a goal to 
install six million heat pumps (for space and water heating) by 2030, 
many of which they anticipate will be 120-volt heat pump water heaters. 
(CA IOUs, No. 36 at p. 4)
    AET expressed support for the inclusion of heat pump-only water 
heaters within the scope of the DOE test procedure but suggested 
revising the terminology so as to differentiate a ``heat pump water 
heater without a tank'' from a ``heat pump water heater with a tank.'' 
(AET, No. 29 at p. 2) On this point, DOE notes that there is not yet a 
particular term for these products defined at 10 CFR 430.2 or in 
appendix E. These products may be referred to using any of the terms 
mentioned by AET, but the clearest description of these products is 
``circulating heat pump water heaters.'' Circulating water heaters are 
discussed further in section III.A.4.a of this document. DOE is 
adopting a definition for ``circulating water heater'' in this final 
rule, which will include these products.
    Rheem recommended that DOE include split-system heat pump water 
heaters in the ``water heaters requiring a storage tank'' definition 
proposed in the January 2022 NOPR and that DOE define ``integrated heat 
pump water heater'' to distinguish them from split-system water 
heaters. (Rheem, No. 47 at p. 4) AHRI stated that a definition of 
``split-system water heater'' is not required if DOE does not include 
the proposed optional additional test conditions in this rulemaking. 
(AHRI, No. 55 at p. 5)
    In response to Rheem's comments, a split-system water heater is not 
necessarily a ``water heater requiring a storage tank,'' as proposed in 
the January 2022 NOPR, because for a water heater to meet the proposed 
definition of ``water heater requiring a storage tank'' would mean 
there is no storage tank specified or supplied by the manufacturer but 
that it requires one for testing and operation. A split-system water 
heater, however, may have a manufacturer supplied or specified tank 
and, as such, would not necessarily fall under the definition of a 
``water heater requiring a storage tank.'' When the tank is specified 
or supplied by the manufacturer, that tank should be used for testing, 
rather than a water heater or storage tank that meets the default 
conditions that were proposed to be added in section 4.10 of appendix 
E. Additionally, in response to the suggestion that DOE define 
``integrated heat pump water heater,'' DOE notes that, as discussed 
later in this section, it is modifying the definition of a ``split-
system water heater'' based on comments to mean a heat pump-type water 
heater in which at least the compressor, which may be installed 
outdoors, is separate from the storage tank. Therefore, heat pump water 
heaters that do not fall under the definition of ``split-system water 
heater'' adopted in this final rule would be integrated heat pump water 
heaters, as the refrigeration components would be integrated with the 
tank. Thus, it is unnecessary to separately define ``integrated heat 
pump water heaters,'' and the term would not be used in the test 
method. Creating additional definitions for this configuration may lead 
to confusion. In response to AHRI's comment, as discussed and for the 
reasons explained in section III.C.7 of this document, DOE has decided 
to include the proposed optional additional test conditions in this 
rulemaking, and, thus, the Department has defined the term ``split-
system water heater.''
    A.O. Smith requested that DOE clearly define ``heat pump-only water 
heater'' and elucidate how appendix E applies to them. (A.O. Smith, No. 
51 at p. 5) BWC requested that DOE clarify in its definitions the 
difference between split-system and heat pump-only water heaters. (BWC, 
No. 48 at p. 1)
    In response, a heat pump-only water heater is considered a 
circulating water heater, which is a type of heat pump water heater, 
falls under the circulating water heater product classes, and is 
covered under the associated provisions of appendix E. Such 
distinctions were previously discussed in the January 2022 NOPR. 87 FR 
1554, 1565 (Jan. 11, 2022). These units have an input greater than or 
equal to 4,000 Btu per hour per gallon, and accordingly, they are 
considered instantaneous water heaters. In contrast, split-system heat 
pump water heaters (which, unlike heat pump-only units, are distributed 
with a storage tank) are considered storage water heaters.
    After considering these comments, DOE has decided to affirm 
coverage in this test procedure final rule for all of the 
aforementioned types of consumer heat pump water heaters. In 
particular, DOE has determined that the current definitions of ``heat 
pump-type'' and ``electric storage water heater'' adequately cover the 
electric heat pump water heaters on the market that are representative 
of residential use (including, but not limited to, integrated 240-volt 
and 120-volt heat pump water heaters, split-system heat pump water 
heaters, and circulating heat pump water heaters), and that a separate 
definition for ``electric heat pump water heaters'' is not needed in 
order to appropriately characterize the test procedure for consumer 
water heaters and residential-duty commercial water heaters.
    At the time of this final rule, DOE is only aware of a small number 
of 120-volt integrated heat pump water heaters and circulating heat 
pump water heaters on the market. Therefore, DOE has limited 
information to determine whether there are any distinguishing 
characteristics of these products which would necessitate tailored test 
procedure requirements in order to produce ratings that are 
representative, reproducible, and repeatable. One manufacturer has 
publicly certified

[[Page 40418]]

ratings \29\ for 120-volt electric storage heat pump models using the 
currently applicable appendix E test procedure (without the use of a 
test procedure waiver), so DOE, therefore, concludes that the appendix 
E test procedure is appropriate and representative for these models. 
DOE is aware, however, that default mode operation of 120-volt electric 
storage heat pump water heaters may require raising the tank 
temperature above the delivery setpoint in order to meet consumer 
expectations of first hour rating (FHR), and further discussion of 
potential impacts of storage tank overheating on ratings for 120-volt 
electric storage heat pump water heaters as a result of this final 
rule's action can be found in section III.E.1 and III.J.3 of this 
document.
---------------------------------------------------------------------------

    \29\ DOE reviewed public certification data in its Compliance 
Certification Management System (CCMS) database, found online at 
www.regulations.doe.gov/certification-data/#q=Product_Group_s%3A*.
---------------------------------------------------------------------------

    In response to the July 2022 SNOPR, which proposed optional ambient 
test conditions and new definitions for ``split-system water heaters,'' 
AHRI and A.O. Smith requested that DOE change its definition of 
``split-system water heater'' to the definition used by ENERGY STAR, 
which specifies that the compressor, evaporator, and/or condenser are 
separated from a storage tank that is specified by the manufacturer and 
rated as a single system. (AHRI, No. 55 at p. 5; A.O. Smith, No. 51 at 
p. 4) A.O. Smith offered an alternative definition to DOE's earlier 
definition of ``split-system heat pump water heater'' which specified 
the heat pump as being an outdoor component. (A.O. Smith, No. 51 at pp. 
4-5)
    A.O. Smith, NEEA, and the CA IOUs stated that it is unnecessary for 
the definition of ``split-system water heater'' to specify the location 
of specific components and requested that DOE eliminate the distinction 
between indoor and outdoor components. (A.O. Smith, No. 51 at p. 5; CA 
IOUs, No. 52 at pp. 4-5; NEEA, No. 56 at p. 2) The CA IOUs stated that 
the compressor should be specified as the component separate from the 
storage tank, rather than the heat pump, to more generally reflect 
split-system water heaters. (CA IOUs, No. 52 at pp. 4-5)
    NEEA additionally recommended that DOE should not include 
references to ``indoor'' or ``outdoor'' in its proposed definition of 
``split-system heat pump water heater,'' as outdoor installation of the 
heat pump component does not necessarily follow the splitting of 
heating and storage functions into separate components, and an all-
indoor split-system HPWH has the potential to provide significant 
benefits to consumers. NEEA added that adopting a split-system 
definition that excludes such products could hinder manufacturers in 
bringing them to market. (NEEA, No. 56 at p. 2) Similarly, Nyle 
commented that the proposed definition is problematic because not all 
split-system heat pump water heaters contain an outdoor component, 
noting that it manufactures a 120-volt heat pump water heater for 
indoor use only. Nyle suggested revising the definition to indicate 
that a split-system heat pump water heater means a heat pump-type water 
heater where the storage unit and heat pump components are independent 
from one another but must be connected to operate (i.e., through 
refrigerant lines, water piping, or via a thermal storage device). 
(Nyle, No. 57 at p. 1)
    In order to address the need for separate test conditions for 
split-system water heaters (see section III.C.7 of this document for a 
discussion on optional test conditions, which simulate different indoor 
and outdoor air conditions for the different components of a split-
system water heater), DOE is adopting a definition for this subset of 
heat pump water heaters at 10 CFR part 430, subpart B, appendix E, 
section 1.14.
    In response to these comments, DOE acknowledges that it is not 
necessary to specify the location of the components and/or the storage 
tank in the definition of ``split-system heat pump water heater'' as 
long as they are separate. Therefore, DOE has changed the definition of 
``split-system heat pump water heater'' to mean a heat pump-type water 
heater in which at least the compressor, which may be installed 
outdoors, is separate from the storage tank. This definition still 
reflects that which is used in NEEA's Advanced Water Heating 
Specification (AWHS) version 8.0 (AWHS v8.0),\30\ with minor 
modifications.
---------------------------------------------------------------------------

    \30\ AWHS v8.0 was published by NEEA on March 1, 2022. Although 
early editions of the AWHS focused primarily on providing more 
representative performance metrics for heat pump water heaters in 
cold climates, the latest editions are now more broadly focused on 
providing representative performance metrics for heat pump water 
heaters across all climates. AWHS v8.0 includes separate test 
condition requirements for integrated and split-system heat pump 
water heaters. These test conditions are discussed further in detail 
in section III.C.1 of this final rule. (Available at: neea.org/resources/advanced-water-heating-specification-v8.0) (Last accessed 
on Sept. 19, 2022).
---------------------------------------------------------------------------

    Additionally, a new definition for ``circulating water heater'' is 
being established in this final rule at 10 CFR 430.2, as discussed in 
section III.A.4.a of this document. This product category includes heat 
pump-only water heaters, which is also discussed in section III.A.4.a 
of this document. Specific testing provisions for circulating water 
heaters are being newly established in this final rule, as discussed in 
section III.D.4 of this document.
b. Gas-Fired Heat Pump Storage Water Heaters
    The statutory definition for a ``heat pump type'' water heater (see 
42 U.S.C. 6291(27)(C)) is not specific to electric heat pump type water 
heaters. Gas-fired heat pump storage water heaters typically use an 
absorption or adsorption refrigeration cycle, driven by a gas burner, 
to transfer heat from the surrounding air to the water inside the water 
heater.
    In the July 2014 Final Rule, DOE codified a definition for ``gas-
fired heat pump water heater'' as follows:
    Gas-fired heat pump water heater means a water heater that uses gas 
as the main energy source, has a nameplate input rating of 75,000 Btu/h 
(79 MJ/h) or less, has a maximum current rating of 24 amperes 
(including all auxiliary equipment such as fans, pumps, controls, and, 
if on the same circuit, any resistive elements) at an input voltage of 
no greater than 250 volts, has a rated storage volume not more than 120 
gallons (450 liters), and is designed to transfer thermal energy from 
one temperature level to a higher temperature level to deliver water at 
a thermostatically controlled temperature less than or equal to 180 
[deg]F (82 [deg]C). 79 FR 40542, 40567 (July 11, 2014).
    Then, in the November 2016 Final Rule, DOE reasoned that even 
though gas-fired heat pump water heaters were covered by the existing 
test procedure, this definition was extraneous because it is not 
specifically referenced in any part of DOE's test procedures or energy 
conservation standards for consumer water heaters. 81 FR 79261, 79261, 
79287 (Nov. 10, 2016). The definition for ``gas-fired heat pump water 
heater'' was deleted, and the current definition for ``gas-fired 
storage water heater'' was added instead. Id. at 81 FR 79320-79321.
    Since the deletion of the definition in the November 2016 Final 
Rule, ASHRAE published an updated version of the test standard 118.2, 
``Method of Testing for Rating Residential Water Heaters and 
Residential-Duty Commercial Water Heaters,'' in January 2022 (ASHRAE 
118.2-2022) (see section III.B.2 for further discussion of this 
standard). The January 2022 NOPR issued prior to publication of ASHRAE 
118.2-2022 and assessed public review drafts of ASHRAE 118.2-2022--all 
of which still included a definition for

[[Page 40419]]

``gas-fired heat pump storage water heater.'' The definition for ``gas-
fired heat pump storage water heaters'' in the public review drafts of 
ASHRAE 118.2-2022 was adopted in section 2.4 of the final published 
version, which defines the term as follows:
    (a) Use gas as the main energy source,
    (b) Have a nameplate input rating of 20,000 Btu/h (26.4 MJ/h) or 
less,
    (c) Have a maximum current rating of 24 amp (including all 
auxiliary equipment, such as fans, pumps, controls, and, if on the same 
circuit, any resistive elements) at an input voltage of no greater than 
250 V,
    (d) Have a rated storage volume not more than 120 gal (450 L), and
    (e) Are designed to transfer thermal energy from one temperature 
level to a higher temperature level to deliver water at a 
thermostatically controlled temperature less than or equal to 180 
[deg]F (82 [deg]C).
    In the January 2022 NOPR, DOE stated that, currently, a water 
heater that uses gas as the main energy source, has a nameplate input 
rating of 75,000 Btu/h or less, and contains more than one gallon of 
water per 4,000 Btu per hour of input is a gas-fired storage water 
heater. (10 CFR 430.2) If the gas-fired storage water heater also has a 
heat pump with a maximum current rating of 24 amperes at a voltage no 
greater than 250 volts, is designed to transfer thermal energy from one 
temperature level to a higher temperature level for the purpose of 
heating water, including all ancillary equipment such as fans, storage 
tanks, pumps, or controls necessary for the device to perform its 
function, it would be a heat pump type unit (see 10 CFR 430.2). 87 FR 
1554, 1564 (Jan. 11, 2022).
    DOE also noted in the January 2022 NOPR that this industry 
definition establishes the scope of coverage for these products more 
narrowly than the current definitions for ``gas-fired storage water 
heater'' and ``heat pump type'' water heater together. Specifically, 
the ASHRAE 118.2-2022 definition limits the input rate at 20,000 Btu/
h--presumably because the input rates of models currently in 
development for residential applications are less than 20,000 Btu/h--
whereas the current definitions at 10 CFR 430.2 accommodate potential 
future products up to 75,000 Btu/h. In recognition of the developing 
market for gas-fired heat pump water heaters, DOE had tentatively 
determined not to limit scope of coverage to only 20,000 Btu/h. 87 FR 
1554, 1564 (Jan. 11, 2022).
    In response to the January 2022 NOPR, BWC suggested DOE re-evaluate 
whether current consumer water heater definitions adequately cover gas-
fired heat pump water heaters (as defined by ASHRAE) in light of 
questions as to whether features related to these products depart from 
the current consumer water heater definitions. (BWC, No. 33 at p. 2) 
However, the commenter did not provide further details.
    DOE did not receive any additional comments elucidating which 
features may be of concern, and as a result, DOE is not able to 
identify reasons to justify redefining gas-fired heat pump storage 
water heaters in a way that departs from the current definitions. At 
the time of this final rule, such products are still mostly in the 
field trial stage in the United States, and, thus, they are not mass-
produced, nor are they widely distributed in the commercial market. 
However, DOE is aware that products currently under development consist 
of a modulating gas-fired burner that powers an absorption cycle using 
a design which would meet the definition for a ``split-system heat pump 
water heater'' (discussed in section III.A.2.a of this document). 
Nonetheless, because the current definitions for ``gas-fired storage 
water heater'' and ``heat pump type'' water heater are sufficiently 
broad, such products would remain appropriately encompassed within the 
current scope of coverage. Should more designs of gas-fired heat pump 
water heaters (either storage type or instantaneous type) emerge into 
the water heaters market, DOE would evaluate the definitions and 
appropriateness of its test methods for gas-fired and heat pump 
products as they would apply to this novel technology.
    Moreover, while ASHRAE 118.2-2022 does define gas-fired heat pump 
storage water heaters, there are no unique test methods for these 
products outlined in the industry test standards. Similar to the 
determination in the November 2016 Final Rule, DOE has concluded that 
the definition in ASHRAE 118.2-2022 is extraneous. Furthermore, given 
that no concrete concerns regarding the applicability of the current 
methods to gas-fired heat pump water heaters have been identified, DOE 
has determined not to adopt any specific provisions for these in its 
amended appendix E test procedure at this time.
3. Residential-Duty Commercial Water Heaters
    In this rulemaking, DOE has sought comment on the definition for 
``residential-duty commercial water heater,'' which defines a category 
of commercial water heaters that are subject to the appendix E test 
procedure due to their residential applications. 85 FR 21104, 21108 
(April 16, 2020).
    In the January 2022 NOPR, DOE acknowledged that some water heaters 
intended for commercial use are covered by the residential-duty 
commercial water heater definition and tested and rated to the appendix 
E test procedure and residential-duty commercial water heater energy 
conservation standards in terms of UEF. DOE explained that these water 
heaters have characteristics that are similar to water heaters with 
residential applications and, as such, under 42 U.S.C. 6295(e)(5)(F), 
cannot be excluded from being tested and rated using the consumer water 
heaters test procedure and residential-duty commercial water heater 
energy conservation standards. Thus, DOE did not propose amendments to 
this definition. 87 FR 1554, 1566 (Jan. 11, 2022).
    DOE has determined that whether a product is marketed as commercial 
or residential may not always be indicative of the intended 
installation location. The January 2022 NOPR provided the example of 
water heaters that are intended for residential use but sometimes 
marketed as ``commercial-grade'' as a means to convey an expectation of 
reliability. 87 FR 1554, 1566-1567 (Jan. 11, 2022).
    In commenting on the January 2022 NOPR, with regards to 
residential-duty commercial water heaters, AET commented that the 
method used to evaluate consumer electric instantaneous and 
residential-duty commercial electric instantaneous water heaters in the 
December 2016 Conversion Factor Final Rule was not approved for these 
products, and the energy conservation standards DOE issued for consumer 
water heaters could not be met by them. AET argued that the energy 
conservation standards for residential-duty commercial electric 
instantaneous water heaters were based on performance for fossil fuel-
fired commercial tankless water heaters as opposed to actual product 
testing, and, therefore, the commenter asserted that the minimum 
efficiency requirements for residential-duty commercial electric 
instantaneous water heaters are too low and should be updated. (AET, 
No. 29 at pp. 14-15)
    DOE understands that the commenter's discussion of the ``method 
used to evaluate consumer electric instantaneous and residential-duty 
commercial electric instantaneous water heaters'' refers to the 
analytical approach in 2016 that was used to predict the UEF values of 
these water heaters from existing representations of maximum GPM (see 
81 FR 96204,

[[Page 40420]]

92616-92617 (Dec. 29, 2016)) and thermal efficiency (see 81 FR 96204, 
96218 (Dec. 29, 2016)). At this time, however, the current appendix E 
test procedure does provide a method to test and rate these water 
heaters.\31\ DOE notes that there are currently consumer and 
residential-duty commercial electric instantaneous water heaters 
certified to meet the applicable energy conservation standards.
---------------------------------------------------------------------------

    \31\ Section 5.3.2 of appendix E details the Max GPM rating test 
for flow-activated water heaters, Table II in section 5.4.1 of 
appendix E details how to select draw pattern based on Max GPM 
rating, and sections 5.4.2 and 5.4.3 of appendix E detail the test 
sequence.
---------------------------------------------------------------------------

    Otherwise, DOE did not receive any comments specifically pertaining 
to the definition for residential-duty commercial water heaters. 
Therefore, DOE is not amending the definition for ``residential-duty 
commercial water heater'' in this final rule for the reasons previously 
discussed. DOE may consider potential amended standards for 
residential-duty commercial electric instantaneous water heaters in a 
separate rulemaking addressing the energy conservation standards for 
commercial water heaters.\32\
---------------------------------------------------------------------------

    \32\ DOE is concurrently evaluating energy conservation 
standards for commercial water heaters in Docket No. EERE-2021-BT-
STD-0027.
---------------------------------------------------------------------------

4. Specialty Water Heaters
    As first proposed in the January 2022 NOPR, this final rule expands 
the scope of coverage of the appendix E test procedure to include low-
temperature water heaters and circulating water heaters, which both 
fall under the statutory definition of consumer ``water heater'' but 
did not previously have test methods appropriate for their unique 
operation. DOE is also re-instating an inadvertently omitted definition 
for ``tabletop water heater'' at 10 CFR 430.2. In addition, DOE has 
considered whether to address solar water heaters in the consumer water 
heaters test procedure, but the Department has determined not to expand 
the scope of coverage of the appendix E to these products at this time. 
DOE may further consider solar water heaters in a separate rulemaking 
in the future. Each of these categories of water heaters is discussed 
in the following subsections.
    Dyson generally commented that indirect circulation systems 
especially have an extraordinarily flexible use case and can be 
implemented in both warm and cool regions. (Dyson, No. 28 at p. 1) DOE 
understands this comment to refer to systems which use a separate 
boiler to provide the heat source for domestic water heating. However, 
consumer boilers are not within the scope of this rulemaking.
a. Circulating Water Heaters
    As discussed in section III.A of this document, a gas-fired 
instantaneous water heater is a water heater that uses gas as the main 
energy source, has a nameplate input rating less than 200,000 Btu per 
hour, and contains no more than one gallon of water per 4,000 Btu per 
hour of input. 10 CFR 430.2.
    In the April 2020 RFI, DOE requested feedback on the typical 
application of a specific configuration of gas-fired instantaneous 
water heaters, commonly referred to as ``circulating gas-fired 
instantaneous water heaters.'' 85 FR 21104, 21113 (April 16, 2020). As 
explained in the April 2020 RFI, DOE has found that several 
manufacturers produce consumer gas-fired instantaneous water heaters 
that are designed to be used with a volume of stored water (usually in 
a tank, but sometimes in a recirculating hot water system of sufficient 
volume, such as a hydronic space heating or designated hot water 
system) in which the water heater does not provide hot water directly 
to fixtures, such as a faucet or shower head, but rather replenishes 
heat lost from the tank or system through hot water draws or standby 
losses by circulating water to and from the tank or other system. These 
circulating gas-fired instantaneous water heaters are typically 
activated by an aquastat \33\ installed in a storage tank that is sold 
separately or by an inlet water temperature sensor. DOE further stated 
that while the products identified by DOE are within the statutory and 
regulatory definition of a consumer ``water heater'' and, therefore, a 
covered product, the design and application of circulating gas-fired 
instantaneous water heaters make testing to the currently applicable 
Federal test procedure for consumer water heaters difficult, if not 
impossible, as these products are not capable of delivering water at 
the temperatures and flow rates specified in the UEF test method 
contained therein. Id. As a result, the currently applicable appendix E 
test procedure does not sufficiently cover circulating water heaters.
---------------------------------------------------------------------------

    \33\ An ``aquastat'' is a temperature measuring device typically 
used to control the water temperature in a separate hot water 
storage tank.
---------------------------------------------------------------------------

    DOE received several comments on the April 2020 RFI recommending 
generally that DOE amend the regulatory definitions of gas-fired 
instantaneous water heaters to exclude models designed exclusively for 
commercial use even though they have input rates below the consumer 
water heater input rate limit (i.e., <=200,000 Btu/h). AHRI and 
individual manufacturers commented that these products are used in 
commercial applications even though they may in certain cases meet the 
statutory definition for a consumer water heater, and that the 
residential draw pattern profiles may not be applicable. These comments 
are discussed in detail in the January 2022 NOPR. 87 FR 1554, 1565 
(Jan. 11, 2022).
    In the January 2022 NOPR, DOE noted that 42 U.S.C. 6291(1) states 
that a ``consumer product'' means any article of a type which, to any 
significant extent, is distributed in commerce for personal use or 
consumption by individuals. DOE also stated that its examination of 
product literature has found that circulating water heaters are 
predominately marketed for commercial applications. However, the input 
rates of many of the available models are below the maximum input rate 
of a consumer water heater and can, therefore, be suitable for 
residential applications. DOE noted that there exist circulating heat 
pump water heaters (heat pump-only water heaters) which operate in the 
same manner as gas-fired circulating water heaters but are clearly 
marketed for residential applications. Consequently, it is foreseeable 
that there could be the potential for product substitution into the 
consumer market. For these reasons, DOE tentatively determined that 
circulating water heaters are covered ``consumer products.'' 87 FR 
1554, 1565 (Jan. 11, 2022).
    In the January 2022 NOPR, DOE proposed to include the following 
definition at 10 CFR 430.2: ``Circulating water heater means an 
instantaneous or heat pump-type water heater that does not have an 
operational scheme in which the burner, heating element, or compressor 
initiates and/or terminates heating based on sensing flow; has a water 
temperature sensor located at the inlet of the water heater or in a 
separate storage tank that is the primary means of initiating and 
terminating heating; and must be used in combination with a 
recirculating pump and either a separate storage tank or water 
circulation loop in order to achieve the water flow and temperature 
conditions recommended in the manufacturer's installation and operation 
instructions.'' 87 FR 1554, 1565 (Jan. 11, 2022).
    Commenters had varying viewpoints on this topic. AET expressed 
general agreement with DOE's proposal to add a new definition and 
product category for circulating water heaters. (AET, No. 29 at p. 1)

[[Page 40421]]

    Rheem supported the addition of a definition for ``circulating 
water heater'' to 10 CFR 430.2 and accompanying test procedures within 
appendix E for such products that have residential applications, but 
the commenter emphasized that the division between consumer and 
commercial water heaters should be appropriately set. Rheem argued that 
because a ``circulating water heater'' must use a separate storage 
tank, circulating water heater product classes should be defined using 
the storage-type unit input rate criteria (e.g., a gas-fired 
circulating water heater with an input rate at or below 75,000 Btu/h is 
a consumer water heater and greater than 75,000 Btu/h is a commercial 
water heater). Rheem also recommended further investigation as to 
whether certain capacities of storage-type water heaters could be 
covered by the ``circulating water heater'' definition. Rheem added 
that the ``circulating water heater'' definition should be amended to 
allow a water temperature sensor at the outlet of the water heater. 
(Rheem, No. 31 at p. 2)
    BWC generally disagreed with DOE's proposal that circulating water 
heaters should be covered as consumer products, arguing that these 
products are exclusively installed in commercial applications as either 
part of a recirculation loop or coupled to an unfired hot water storage 
tank. BWC also noted that circulating water heaters heat water to 
higher temperatures than consumer instantaneous water heaters do. BWC 
argued that classifying circulating water heaters as consumer products 
would provide little to no benefit to consumers, place additional 
burden on manufacturers, and cause market confusion as to how these 
products are specified and designed for field applications. (BWC, No. 
33 at pp. 1-2)
    AHRI expressed concerns about including circulating water heaters 
in a residential water heaters test procedure because they are mostly 
used in commercial applications, even with input rates below 200,000 
Btu/h. In lieu of a solution in the test procedure, AHRI requested that 
DOE reinstate the enforcement policy on circulating water heaters.\34\ 
(AHRI, No. 40 at p. 5) A.O. Smith provided similar comments, suggesting 
that DOE should reissue the September 5, 2019 enforcement policy for 
gas-fired circulating water heaters, or alternatively identify them in 
the test procedure as ``historically regulated as commercial water 
heating equipment'' that ``can be tested via the thermal efficiency 
energy metrics; and . . . therefore should not be subjected to UEF 
requirements.'' (A.O. Smith, No. 37 at pp. 2-3) Like AHRI and A.O. 
Smith, BWC recommended reinstating the September 2019 enforcement 
policy to allow industry to determine the proper test procedure. (BWC, 
No. 33 at pp. 1-2)
---------------------------------------------------------------------------

    \34\ DOE had issued an enforcement policy for circulating water 
heaters that expired on December 31, 2021.
---------------------------------------------------------------------------

    EEI requested more information on the size of the existing stock 
and current sales volumes of circulating water heaters. (EEI, Jan. 27, 
2022 Public Meeting Transcript, No. 27 at pp. 46-47)
    In response, the Department reiterates that EPCA directed DOE to 
develop a test procedure that applies, to the maximum extent 
practicable, to all water heating technologies in use and to future 
water heating technologies. (42 U.S.C. 6295(e)(5)(H)) As a circulating 
water heater could be designed to operate in a similar manner to other 
consumer water heaters (i.e., ``heat pump-only'' water heaters) and at 
conditions appropriate for residential applications, DOE is required to 
address these products in appendix E with other classes of consumer 
water heaters. Furthermore, the definition for ``consumer product'' 
states that it is an article ``of a type'' that is distributed for 
personal use or consumption by individuals ``without regard to whether 
such article of such type is in fact distributed in commerce for 
personal use or consumption by an individual.'' (42 U.S.C. 6291(1))
    In response to Rheem's comment, circulating water heaters have high 
input rate to storage volume ratios, which classify these products as 
instantaneous-type water heaters (see 10 CFR 430.2 and 42 U.S.C. 
6291(27)(B)). As such, the statutory definition of a storage-type water 
heater (found at 42 U.S.C. 6291(27)(A)) does not cover circulating 
water heaters because circulating water heaters have no more than one 
gallon of water per 4,000 Btu/h of input. As a result, the 75,000 Btu/h 
upper limit on the input rate for gas-fired storage-type water heaters 
would not apply and will not be included in the scope of the definition 
of ``circulating water heater.''
    In response to BWC's comments, DOE notes that hot water delivery 
temperature is not related to the statutory definition of coverage. 
Rather, EPCA defines whether a water heater is covered as a consumer 
product primarily according to its input rating, without regard to its 
maximum hot water delivery temperature. DOE also concludes that 
classifying circulating water heaters (that meet the input rating 
requirements) as consumer products would provide a benefit to consumers 
by allowing them to compare circulating water heaters alongside other 
consumer water heaters with a UEF rating. Under 42 U.S.C. 6293(b), EPCA 
requires that DOE test procedure not place undue burden on 
manufacturers. In this instance, although test burden would increase 
for manufacturers of circulating water heaters, it would not be 
considered an undue burden, because these water heaters are consumer 
products (by definition) and, therefore, should be subject to consumer 
water heater test procedures. Contrary to BWC's assertion, DOE 
concludes that covering circulating water heaters as consumer products 
would reduce or resolve market confusion surrounding these products; 
since they can be used in residential applications, they should be 
rated accordingly.
    In response to A.O. Smith's comment requesting DOE to consider 
circulating gas-fired water heaters as historically regulated as 
commercial water heaters and sufficiently described by the commercial 
water heater metrics, DOE is not expanding the scope to products which 
are ``historically regulated as commercial water heating equipment'' 
because DOE is only considering circulating gas-fired water heaters 
with input rates less than or equal to 200,000 Btu/h, which meet the 
existing statutory definition for consumer water heaters (and, thus, do 
not meet the definition for gas-fired instantaneous commercial water 
heaters). Furthermore, DOE clarifies that the Department is not 
considering these gas-fired circulating water heaters (ones which meet 
the existing statutory definition for consumer water heaters) to be 
residential-duty commercial water heaters.
    In response to the July 2022 SNOPR, BWC and AHRI once again 
reiterated their understanding that circulating water waters are used 
almost exclusively in commercial applications. (BWC, No. 48 at p.4; 
AHRI, No. 55 at p. 5) BWC requested that DOE exercise authority granted 
under the American Manufacturing Technical Corrections Act (AEMTCA) (42 
U.S.C. 6295(e)(5)(F)) to regulate circulating water heaters as 
commercial products even though they meet residential definitions, or 
clearly demonstrate residential use. (BWC, No. 48 at p. 4) AHRI 
suggested that addressing circulating water heaters in a consumer 
rulemaking would cause confusion because their efficiency metric is 
different from conventional consumer water heaters. (AHRI, No. 55 at p. 
5)
    In response, EPCA allows DOE to provide an exclusion from the 
uniform

[[Page 40422]]

efficiency descriptor for specific categories of otherwise covered 
water heaters that do not have residential uses, that can be clearly 
described, and that are effectively rated using the current thermal 
efficiency and standby loss descriptors. (42 U.S.C. 6295(e)(5)(F)(i)) 
\35\ However, DOE reads this statutory provision as only permitting 
exclusion of water heaters that were categories of covered commercial 
water heaters under section 342(a)(5) of EPCA [42 U.S.C. 6313(a)(5)]. 
It does not grant DOE authority to exclude consumer water heaters from 
the ambit of the uniform test procedure, nor to somehow convert 
consumer water heaters to commercial water heaters and to subject them 
to energy conservation standards applicable to commercial water 
heaters. In the present case, it is clear that the circulating water 
heaters in question are consumer water heaters, given that they have 
input rates below 200,000 Btu/h, and they otherwise meet the 
definitional criteria of the statute for an instantaneous-type water 
heater (see 42 U.S.C. 6291(27)(B)). Moreover, circulating water heaters 
have the demonstrated ability to perform tank loading or recirculating 
loop operation, as would indicate that these products do have clearly 
described residential uses. Consequently, in response to these 
comments, DOE notes that because both heat pump-only and gas-fired 
circulating water heaters meet the requirements to be classified as 
consumer products under EPCA, the statute requires that such water 
heaters must be tested according to DOE test procedure at appendix E.
---------------------------------------------------------------------------

    \35\ DOE acted in accordance with EPCA provisions as specified 
at 6295(e)(5)(F)(i) when establishing product classes for 
residential-duty commercial water heaters. In a July 2014 Final Rule 
establishing the UEF test procedure, DOE determined that covered 
commercial water heating equipment that did not meet the definition 
of a ``residential-duty commercial water heater'' met the criteria 
in EPCA for exclusion from the uniform efficiency descriptor. 79 FR 
40542, 40545-40547 (July 11, 2014).
---------------------------------------------------------------------------

    This final rule establishes a test method to determine the UEF of 
consumer circulating water heaters. Effective and compliance dates are 
discussed further in section III.I of this document.
    In development of this final rule, DOE was not able to discern 
rates of shipments and amount of stock for consumer circulating water 
heaters as EEI had requested. However, DOE did identify circulating 
water heater models currently on the market that are consumer water 
heaters. DOE has determined that circulating water heaters may have a 
water temperature sensor at the inlet or at the outlet of the water 
heater--as suggested by Rheem-- and, therefore, the Department agrees 
with Rheem and is adopting the following definition for ``circulating 
water heater'' at 10 CFR 430.2:
    Circulating water heater means an instantaneous or heat pump-type 
water heater that does not have an operational scheme in which the 
burner, heating element, or compressor initiates and/or terminates 
heating based on sensing flow; has a water temperature sensor located 
at the inlet or at the outlet of the water heater or in a separate 
storage tank that is the primary means of initiating and terminating 
heating; and must be used in combination with a recirculating pump and 
either a separate storage tank or water circulation loop in order to 
achieve the water flow and temperature conditions recommended in the 
manufacturer's installation and operation instructions.
b. Low-Temperature Water Heaters
    DOE has identified certain flow-activated water heaters that are 
designed to deliver water at temperatures below the set point 
temperature of 125 [deg]F 5 [deg]F (51.7 [deg]C 2.8 [deg]C) that is required by section 2.5 of the currently 
applicable appendix E (hereinafter referred to as ``low-temperature'' 
water heaters). These low-temperature water heaters (often referred to 
as ``handwashing'' or ``point-of-use'' water heaters in marketing 
literature) typically have low heating rates, which requires the 
testing agency to reduce the flow rate in order to be able to achieve 
the outlet temperature within the set point temperature range. However, 
these units also have a minimum activation flow rate below which the 
unit shuts off. To the extent that a unit would stop heating water when 
the flow rate is too low, there may be no flow rate at which the unit 
would operate and deliver water at the outlet temperature required 
under section 2.5 of appendix E. Further, the definition of water 
heater or electric instantaneous water heater does not include a 
minimum water delivery temperature. To the extent that a low-
temperature water heater uses electricity as the energy source, has a 
nameplate input rating of 12 kilowatts or less, and contains no more 
than one gallon of water per 4,000 Btu per hour of input, it would be 
an electric instantaneous water heater. 10 CFR 430.2. Therefore, 
because such products are within the scope of consumer water heater 
coverage under EPCA, the appendix E test procedure should address them; 
however, the currently applicable appendix E does not address them.
    DOE requested information in the April 2020 RFI on testing these 
products at a lower set point temperature and other potential changes 
which may be necessary to accommodate these types of models. 85 FR 
21104, 21113 (April 16, 2020). Several commenters on the April 2020 RFI 
recommended that the test procedure be modified to indicate a lower set 
point temperature for testing, such as the maximum water temperature 
delivery that the model is capable of delivering (see NOPR discussion 
for complete details). 87 FR 1554, 1582 (Jan. 11, 2022).
    In the January 2022 NOPR, DOE proposed to define a ``low-
temperature water heater'' as an electric instantaneous water heater 
that is not a circulating water heater and cannot deliver water at a 
temperature greater than or equal to the set point temperature 
specified in section 2.5 of appendix E to subpart B of this part when 
supplied with water at the supply water temperature specified in 
section 2.3 of appendix E to subpart B of this part. DOE also 
tentatively determined that lowering the set point temperature for low-
temperature water heaters to their maximum possible delivery 
temperature would allow these water heaters to be tested appropriately 
and in a representative manner. As such, DOE proposed to require low-
temperature water heaters to be tested to their maximum possible 
delivery temperature. 87 FR 1554, 1583 (Jan. 11, 2022).
    AET agreed with DOE's proposal to add a new definition and product 
category for low-temperature water heaters. (AET, No. 29 at p. 2) EEI 
requested more information on the size of the existing stock, as well 
as the current sales volumes of low-temperature water heaters. (EEI, 
Jan, 27, 2022 Public Meeting Transcript, No. 27 at pp. 46-47) As with 
circulating water heaters, DOE does not currently have this information 
available but will continue to gather this data to the extent possible.
    Rheem commented that the proposed definition for ``low-temperature 
water heater'' should include water heaters with less than 10 gallons 
of storage and clarify how it is different from other electric water 
heaters. Rheem suggested that the installation and operation (I&O) 
manual could be referenced to determine delivery temperature limits, 
but alternatively, manufacturers could certify supplemental testing 
instructions to DOE (i.e., when testing an electric instantaneous water 
heater set according to the I&O manual and cannot meet the required 
delivery temperature, the unit should be tested according to the

[[Page 40423]]

maximum delivery temperature). (Rheem, No. 31 at p. 3)
    In response to the comments from Rheem, DOE notes that the 
inability to deliver water at the specified outlet water temperatures 
in appendix E is independent of the storage volume of the water heater. 
Hence, restricting this product type definition to only those water 
heaters that have less than 10 gallons of storage volume may 
unintentionally leave larger low-temperature water heaters without 
adequate test provisions in appendix E. This inability to deliver water 
at 125 [deg]F 5 [deg]F--specifically at the appendix E flow 
rate--serves as the key distinguishing factor between low-temperature 
water heaters and other electric instantaneous water heaters. While the 
maximum delivery temperatures may be noted in an I&O manual, as Rheem 
suggested, this must be verified under the test conditions (most 
notably the supply water temperatures) specified in appendix E. Section 
5.2.2 of the amended appendix E includes instructions for setting the 
outlet discharge temperature. Should the flow rate need to be reduced 
in order to meet the outlet temperature requirements, then the product 
would meet the criterion for a low-temperature water heater.
    In this final rule, DOE is adopting a slightly modified definition 
for ``low-temperature water heater,'' taking into account the comments 
provided by Rheem. Accordingly, DOE is defining ``low-temperature water 
heater'' as an electric instantaneous water heater that is not a 
circulating water heater and cannot deliver water at a temperature 
greater than or equal to the set point temperature specified in section 
2.5 of appendix E when supplied with water at the supply water 
temperature specified in section 2.3 of appendix E at the flow rate 
specified in section 5.2.2.1 of appendix E. (DOE is including language 
which specifies that the delivery temperature is that which results 
from the appendix E flow rate.)
c. Tabletop Water Heaters
    As discussed in the January 2022 NOPR, the definition for 
``tabletop water heater'' was removed from appendix E as part of the 
July 2014 Final Rule but was inadvertently not added to 10 CFR 430.2 
(79 FR 40542, 40567-40568 (July 14, 2014)). 87 FR 1554, 1566 (Jan. 11, 
2022). Up until then, ``tabletop water heater'' was defined as a water 
heater in a rectangular box enclosure designed to slide into a kitchen 
countertop space with typical dimensions of 36 inches high, 25 inches 
deep, and 24 inches wide. 66 FR 4474, 4497 (Jan. 17, 2001). In the 
January 2022 NOPR, after considering comments on the April 2020 RFI, 
DOE proposed to add the definition of tabletop water heater 10 CFR 
430.2, as it read prior to being removed from appendix E. 87 FR 1554, 
1556.
    In response to the January 2022 NOPR, AET agreed with re-instating 
the definition for tabletop water heater at 10 CFR 430.2. (AET, No. 29 
at p. 2)
    DOE did not receive any other comment relating to this proposal, so 
the Department is re-instating the definition for ``tabletop water 
heater'' at 10 CFR 430.2, as proposed.
d. Solar Water Heaters
    In response to an RFI published on May 21, 2020 (May 2020 RFI), 
regarding the energy conservation standards for consumer water heaters 
(85 FR 30853), the Solar Rating & Certification Corporation (SRCC) 
recommended that solar water heating technologies be considered for 
inclusion in the energy conservation standards and test procedures for 
consumer water heaters. SRCC stated that without the involvement of 
DOE, the industry metrics struggle to gain acceptance with policymakers 
and consumers. SRCC also stated that DOE rulemakings to include solar-
equipped water heaters in regulations would serve to establish a single 
performance metric and signal the legitimacy of solar water heating 
technologies. (Docket: EERE-2017-BT-STD-0019, SRCC, No. 11 at pp. 3-4)
    Subsequently, on October 7, 2020, SRCC published a draft test 
procedure titled, ``Solar Uniform Energy Factor Procedure for Solar 
Water Heating Systems'' (SUEF test method).\36\ The draft SRCC test 
procedure addresses methods to test different types of solar water 
heaters.
---------------------------------------------------------------------------

    \36\ SRCC's draft Solar Uniform Energy Factor Procedure for 
Solar Water Heating Systems is available at: www.iccsafe.org/wp-content/uploads/is_stsc/Solar-UEF-Specification-for-Rating-Solar-Water-Heating-Systems-20201012.pdf (Last accessed on July 13, 2022).
---------------------------------------------------------------------------

    In the January 2022 NOPR, DOE responded to SRCC's comment on the 
May 2020 RFI, by noting that on April 8, 2015, DOE published an energy 
conservation standards NOPR (the April 2015 NOPR) addressing 
definitions for consumer water heaters (80 FR 18784). 87 FR 1554, 1585 
(Jan. 11, 2022). DOE further noted that the April 2015 NOPR proposed 
definitions for ``solar-assisted fossil fuel storage water heater'' and 
``solar-assisted electric storage water heater'' and clarified that 
water heaters meeting these definitions are not subject to the amended 
energy conservation standards for consumer water heaters established by 
the April 2010 final rule. Id. DOE stated its intention to address 
solar water heaters in a separate rulemaking. Id. In response to the 
January 2022 NOPR, SEA commented that DOE should account for solar 
water heaters in its test procedure and energy conservation standards. 
(SEA, No. 24 at p. 1)
    In response, DOE notes that ``solar water heater,'' as defined in 
section 5.1 of SRCC's SUEF test method, include a solar collector or 
module that is directly exposed to solar radiation outdoors and is 
often separated from a storage tank and/or back-up water heater located 
indoors. Therefore, appendix E does not currently accommodate these 
products, and an in-depth evaluation of the modifications to appendix E 
necessary to accommodate the testing of these products is required. 
Given the lack of available test data utilizing the SUEF test method, 
DOE is not amending the scope of the appendix E test procedure in this 
rulemaking to explicitly include solar water heaters at this time. 
However, DOE will continue to consider these solar water heater 
products further, and depending upon the conclusions reached, the 
Department may address them in a separate future rulemaking, as 
appropriate.

B. Updates to Industry Standards

    Prior to the effective date of this final rule, the applicable DOE 
test procedure in appendix E referenced the following industry 
standards:
     ASHRAE 41.1-1986 (Reaffirmed 2006), Standard Method for 
Temperature Measurement (ASHRAE 41.1-1986 (RA 2006)); and
     ASTM D2156-09, (ASTM D2156-09), Standard Test Method for 
Smoke Density in Flue Gases from Burning Distillate Fuels.
    ASHRAE 41.1-1986 (RA 2006) was superseded by ASHRAE 41.1-2013 on 
January 30, 2013 (ASHRAE 41.1-2013). ASHRAE 41.1-2013 was superseded by 
ASHRAE 41.1-2020 on June 30, 2020. Updates to ASHRAE 41.1 are discussed 
in section III.B.1 of this document.
    ASTM D2156-09 was reapproved without modification in 2018 (ASTM 
D2156-09 (RA 2018)). In the January 2022 NOPR, DOE proposed to update 
appendix E to reference the most recent version of ASTM D2156 (i.e., 
ASTM D2156-09 (RA 2018)). 87 FR 1554, 1567 (Jan. 11, 2022). DOE did not 
receive any comments in response to its proposal. Therefore, DOE is 
updating the reference of ASTM D2156-09 to the most recent industry 
standard (i.e., ASTM D2156-09 (RA 2018)). DOE is also incorporating by 
reference ASTM E97-1987 (W1991) because it is

[[Page 40424]]

necessary to perform procedures within ASTM D2156-09 and ASTM D2156-09 
(RA 2018).\37\
---------------------------------------------------------------------------

    \37\ Certain methods provided as part of ASTM E97-1987 (W1991) 
are directly referenced by ASTM D2156-09 and ASTM D2156-09 (RA 
2018). Copies of ASTM E97-1987 (W1991) are readily available from 
ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959 or online at: www.astm.org. (Last 
accessed on Sept. 20, 2022.)
---------------------------------------------------------------------------

    As discussed previously in this document, ASHRAE maintains a water 
heater test procedure, ANSI/ASHRAE Standard 118.2, ``Method of Testing 
for Rating Residential Water Heaters.'' The test procedure specified in 
ANSI/ASHRAE 118.2-2006 (RA 2015) is similar to the DOE test procedure 
that was in effect prior to the July 2014 final rule, although neither 
the previous DOE consumer water heater test procedure nor the version 
in place prior to this final rule reference ANSI/ASHRAE Standard 118.2-
2006 (RA 2015). In March 2019, ASHRAE published the March 2019 ASHRAE 
Draft 118.2, the second public review draft of Board of Standards 
Review (BSR) ANSI/ASHRAE Standard 118.2-2006R, ``Method of Testing for 
Rating Residential Water Heaters and Residential-Duty Commercial Water 
Heaters,'' which DOE referenced in the April 2020 RFI. 85 FR 21104, 
21109-21111 (April 16, 2020). In April 2021, ASHRAE published 
substantive changes to a previous public review draft \38\ of BSR ANSI/
ASHRAE Standard 118.2-2006R, ``Method of Testing for Rating Residential 
Water Heaters and Residential-Duty Commercial Water Heaters'' (April 
2021 ASHRAE Draft 118.2). The January 2022 NOPR examined these public 
review drafts and discussed the differences between them and the DOE 
test procedure. 87 FR 1554, 1567 (Jan. 11, 2022).
---------------------------------------------------------------------------

    \38\ The April 2021 ASHRAE Draft 118.2 shows only the proposed 
substantive changes to the March 2019 ASHRAE Draft 118.2. All 
sections not included in the April 2021 ASHRAE Draft 118.2 are as 
proposed in the March 2019 ASHRAE Draft 118.2 or have not been 
changed in a way that their content affects the results of the test 
procedure proposed in the March 2019 ASHRAE Draft 118.2.
---------------------------------------------------------------------------

    On January 24, 2022, ASHRAE published a revised edition of the 
118.2 standard, ``Method of Testing for Rating Residential Water 
Heaters and Residential-Duty Commercial Water Heaters,'' ASHRAE 118.2-
2022. The published edition finalized revisions shown in the March 2019 
and April 2021 public review drafts.
    In comments responding to the January 2022 NOPR, Lutz encouraged 
DOE to incorporate by reference the industry test standard ASHRAE 
118.2-2022. Lutz also recommended DOE review the test procedures in use 
in Europe and Japan. (Lutz, No. 35 at p. 1) BWC supported DOE's 
proposal to incorporate by reference the latest industry test 
standards. (BWC, No. 33 at p. 2)
    As discussed previously in this document, DOE will adopt industry 
test standards as DOE test procedures for covered products and 
equipment, unless such methodology would be unduly burdensome to 
conduct or would not produce test results that reflect the energy 
efficiency, energy use, water use (as specified in EPCA) or estimated 
operating costs of that equipment during a representative average use 
cycle. (10 CFR part 430, subpart C, appendix A, section 8(c)) In this 
final rule, DOE is harmonizing provisions in appendix E to align with 
certain updates in ASHRAE 118.2-2022 rather than incorporate the entire 
industry test standard. DOE has concluded that certain updates in 
ASHRAE 118.2-2022 do not meet the EPCA criteria outlined in this 
paragraph and has, thus, determined that those updates should not be 
incorporated into the DOE test procedure at appendix E. DOE's 
assessment of ASHRAE 118.2-2022 is laid out in detail in section 
III.B.2 of this document.
    Finally, as discussed in the July 2022 SNOPR, DOE has reviewed 
NEEA's Advanced Water Heating Specifications in order to assess 
optional rating conditions and methods for heat pump water heaters. 
This test procedure was identified by stakeholders in response to the 
January 2022 NOPR as becoming a widely used methodology to provide 
alternate ratings for heat pump water heaters at different climate 
conditions. 87 FR 42270, 42275-42276 (July 14, 2022). In the January 
2022 NOPR, DOE discussed comments previously received on the April 2020 
RFI suggesting that DOE explore the usage of NEEA's Advanced Water 
Heating Specification--which was at version 7.0 at the time--for 
voluntary climate-specific efficiency representations of heat pump 
water heaters. 87 FR 1554, 1580 (Jan. 11, 2022). In response to those 
comments, DOE stated that it did not have data to indicate what 
conditions would be representative for regional representations, and, 
thus, DOE tentatively determined not to allow optional representations 
of additional efficiency ratings at test conditions other than those 
found in the DOE test procedure (which are representative of the Nation 
as a whole), such as those made in accordance with NEEA's Advanced 
Water Heating Specification. Id. However, as discussed in the July 2022 
SNOPR, DOE has re-evaluated the benefits to consumers provided by 
optional representations. 87 FR 42270, 42275-42277 (July 14, 2022). In 
this final rule, DOE is including optional test conditions for heat 
pump water heaters aligning with version 8.0 (the latest version) of 
NEEA's Advanced Water Heating Specification. This matter is discussed 
in further detail in section III.C.7 of this document.
1. ASHRAE 41.1-2020
    As stated previously, ASHRAE 41.1-1986 (RA 2006) was superseded by 
ASHRAE 41.1-2013, and ASHRAE 41.1-2013 was superseded by ASHRAE 41.1-
2020. ASHRAE 41.1-2013 removed the aspirated wet-bulb psychrometer 
descriptions and stated they would be included in the next revision to 
ASHRAE 41.6, ``Standard Method for Humidity Measurement.'' ASHRAE 41.6 
was updated on July 3, 2014, and included the aspirated wet-bulb 
psychrometer descriptions that were removed in ASHRAE 41.1-2013. ASHRAE 
41.1-2013 also added uncertainty analysis for temperature measurements, 
information for thermistor-type devices, descriptions for thermopiles, 
and reorganized the standard to be consistent with other ASHRAE 
standards. ASHRAE 41.1-2020 added conditional steady-state test 
criteria and further updated the standard to meet ASHRAE's mandatory 
language requirements.
    As discussed in the January 2022 NOPR, section 3.2.1 of appendix E 
requires that temperature measurements be made in accordance with 
ASHRAE 41.1-1986 (RA 2006), and section 3.2.2 of appendix E provides 
accuracy and precision requirements for air dry-bulb, air wet-bulb, 
inlet and outlet water, and storage tank temperatures. Sections 5.2.2.1 
and 5.3.2 of appendix E effectively require steady-state operation in 
which the flow-activated water heater is operating at the maximum input 
rate, is supplied with water at a temperature of 58 [deg]F 2 [deg]F, and delivers water at a temperature of 125 [deg]F 
5 [deg]F. 87 FR 1554, 1567 (Jan. 11, 2022).
    In the development of this final rule, DOE reviewed ASHRAE 41.1-
1986 (RA 22006), ASHRAE 41.1-2013, and ASHRAE 41.1-2020 and found that 
the sections most relevant to appendix E are the temperature 
measurement sections (i.e., sections 5 through 11 of ASHRAE 41.1-1986 
(RA 2006), section 7 of ASHRAE 41.1-2013, and section 7 of ASHRAE 41.1-
2020) \39\ and the steady-state test criteria added in ASHRAE 41.1-
2020. The information in the

[[Page 40425]]

temperature measurement sections of the examined three versions of 
ASHRAE 41.1 does not vary significantly. The additional steady-state 
test criteria of ASHRAE 41.1-2020 varies significantly from and is more 
stringent than \40\ the criteria specified in sections 5.2.2.1 and 
5.3.2 of appendix E; however, the appendix E criteria supersede those 
in ASHRAE 41.1-2020.
---------------------------------------------------------------------------

    \39\ Sections 5 through 11 of ASHRAE 41.1-1986 (RA 2006) were 
combined into section 7 of ASHRAE 41.1-2013.
    \40\ Section 5.5.3 of ASHRAE 41.1-2020 would be used to 
determine steady-state operation within sections 5.2.2.1 and 5.3.2 
of appendix E. Using this criteria, a flow-activated water heater 
delivering water between 120 [deg]F and 121 [deg]F, which is within 
the current delivery temperature range of 125 [deg]F  5 
[deg]F, would not be considered in steady-state due to the 
difference in temperature between the average of the sample and the 
set point temperature.
---------------------------------------------------------------------------

    In the January 2022 NOPR, DOE tentatively determined that updating 
the reference of ASHRAE 41.1-1986 (RA 2006) to the most recent version 
of the industry standard (i.e., ASHRAE 41.1-2020) would not have a 
significant effect on the test results, as the content of the relevant 
sections of the ASHRAE 41.1 standards have not changed significantly 
and the new content published in ASHRAE 41.1-2020 is superseded by 
appendix E. As such, DOE proposed to update the reference of ASHRAE 
41.1-1986 (RA 2006) to ASHRAE 41.1-2020. ASHRAE 41.1-2020 references 
ASHRAE 41.6-2014 and requires its use when measuring the wet-bulb 
temperature. The wet-bulb temperature is required when testing heat 
pump water heaters to appendix E, and, therefore, DOE also proposed to 
incorporate by reference ASHRAE 41.6-2014. 87 FR 1554, 1567-1568 (Jan. 
11, 2022).
    DOE did not receive any comments in response to its proposals to 
incorporate by reference ASHRAE 41.1.-2020 and ASHRAE 41.6-2014; 
therefore, DOE is incorporating by reference both standards in this 
final rule for the reasons previously stated.
2. ASHRAE 118.2-2022
    ASHRAE 118.2-2022, published on January 24, 2022 and approved by 
ANSI on March 1, 2022, supersedes ASHRAE 118.2-2006. The foreword to 
ASHRAE 118.2-2022 states that it was derived from the DOE appendix E 
test procedure but also has several substantive changes. Specifically, 
it notes that a major change was to move the conditions of the test 
(air temperature, humidity, inlet and outlet water temperatures) and 
draw patterns to an Informative Appendix A, ``U.S. Values for Test 
Variables,'' indicating that this test standard has been revised such 
that it can easily be applied with other test conditions and draw 
patterns. Additionally, the foreword states that other changes include 
clarifying the timing of the standby period, clarifying the end of the 
recovery period, specifying that the density of water used in 
calculations be measured at the outlet, and adjusting the FHR flow rate 
for smaller tanks and defining a draw time limit if the water heater 
can keep up with the FHR flow rate. The following subsections of this 
final rule discuss the substantial differences between the updated 
ASHRAE 118.2-2022 test standard and DOE's existing appendix E test 
procedure. Based on a review of its own test data and stakeholder 
feedback, the Department is not adopting every update in ASHRAE 118.2-
2022 into the amended appendix E test procedure promulgated by this 
final rule. DOE has provided discussion of the amendments being made to 
harmonize with ASHRAE 118.2-2022 in section III.B.2.b of this document, 
whereas other updates in ASHRAE 118.2-2022 not being adopted are 
discussed in section III.B.2.c of this document.
    AET generally supported DOE's proposal to adopt most aspects of 
ASHRAE 118.2 but noted that the definition of ``UEF'' in ASHRAE 118.2 
is different from the definition of that term used by DOE. AET noted 
that a UEF rating per ASHRAE Standard 118.2 would not be comparable to 
a UEF rating per DOE's test procedure due to differences in test 
conditions. (AET, No. 29 at pp. 6-7) DOE agrees that there could be 
differences between the UEF test result from ASHRAE 118.2-2022 and the 
amended appendix E test procedure from this final rule. Where 
differences between these test procedures exist, the requirements at 10 
CFR 430.23 and appendix E control. As such, manufacturers must ensure 
that any representations of ``UEF'' are made in accordance with the 
applicable version of the DOE test procedure.
a. Scope
    Section 2 of ASHRAE 118.2-2022 states that the industry test 
standard applies to water heaters designed to be capable of providing 
outlet water at a controlled temperature of at least the nominal outlet 
water temperature under the conditions specified in the standard. As 
discussed in section III.A.4.b of this final rule, the January 2022 
NOPR proposed to expand the scope of the DOE test procedure to include 
low-temperature water heaters. 87 FR 1554, 1582-1583 (Jan. 11, 2022). 
As such, the scope of ASHRAE 118.2-2022 is narrower than the test 
procedure proposed in DOE's January 2022 NOPR and July 2022 SNOPR 
because it explicitly excludes low-temperature water heaters. In order 
to include low-temperature water heaters within the scope of the 
amended appendix E test procedure, DOE is including testing provisions 
which are not in ASHRAE 118.2-2022 to allow for the testing of low-
temperature water heaters. These test methods are discussed in section 
III.E.3 of this final rule.
    Additionally, the scope of ASHRAE 118.2-2022 differs significantly 
from the scope of products covered under the EPCA definition for 
consumer ``water heater'' and DOE's definition for ``residential-duty 
commercial water heater.'' For example, section 2 of ASHRAE 118.2-2022 
limits the storage volume for storage-type water heaters to 120 gallons 
or less and limits the maximum delivery temperature to 180 [deg]F (82 
[deg]C), whereas EPCA does not place limits on storage volume or 
maximum delivery temperature for consumer water heaters. (42 U.S.C. 
6291(27); 42 U.S.C. 6311(12)(A)-(B))) The scope of electric 
instantaneous water heaters covered by ASHRAE 118.2-2022 equates to the 
limit for residential-duty commercial electric instantaneous water 
heaters; however, section 2.2 of ASHRAE 118.2-2022 does not specify any 
limits on storage volume, and as a result, it covers certain commercial 
electric instantaneous water heaters--whereas the currently applicable 
appendix E test procedure does not. Section 2.1 of ASHRAE 118.2-2022 
has a definition for ``electric heat-pump storage water heater'' which 
explicitly limits the nameplate input rating to 12 kilowatts or less, 
which, as discussed in section III.A.2.a of this final rule, does not 
correspond to the statutory limit for heat pump-type units and would 
include commercial heat pump water heaters (which are outside of the 
scope of the appendix E test procedure). Finally, section 2.4 of ASHRAE 
118.2-2022 limits gas-fired heat pump storage water heaters to 
nameplate input ratings no greater than 20,000 Btu/h, which is 
significantly lower than the statutory limit of 75,000 Btu/h (see 42 
U.S.C. 6291(27)(A) and the discussion in section III.A.2.b of this 
document).
    In the January 2022 NOPR, DOE evaluated feedback from commenters 
indicating that most aspects of the test methods in ASHRAE 118.2-2022 
\41\ were still applicable outside of its formal scope of coverage. 87 
FR 1554, 1568 (Jan. 11, 2022). In the January 2022

[[Page 40426]]

NOPR, DOE stated that it has found through testing that models with 
rated storage volumes above 120 gallons or that can deliver water above 
180 [deg]F can be tested to DOE's appendix E test procedure, and, given 
the similarities between the currently applicable DOE test procedure 
and ASHRAE 118.2-2022, DOE tentatively determined that such models 
could also be tested using the methods in the ASHRAE test standard. Id. 
DOE did not receive any comments in response to this tentative 
conclusion in the January 2022 NOPR. Therefore, in evaluating the 
provisions within ASHRAE 118.2-2022, DOE has determined that its test 
methods remain applicable to all consumer water heaters and 
residential-duty commercial water heaters within the scope of appendix 
E (with the exception of low-temperature water heaters). As proposed in 
the January 2022 NOPR, this final rule makes several amendments to 
appendix E to harmonize with new provisions in ASHRAE 118.2-2022. 
Additionally, DOE determined that methods specified in annex B of 
ASHRAE 118.2 were applicable to the associated test procedures of this 
rulemaking, and, therefore, the Department has incorporated by 
reference ASHRAE 118.2-2022 for use in appendix E, with annex B being 
the directly applicable provision.
---------------------------------------------------------------------------

    \41\ ASHRAE 118.2-2022 was published on January 24, 2022, which 
was after the January 2022 NOPR was published in the Federal 
Register on January 11, 2022; thus, the NOPR only discusses public 
review drafts of ASHRAE 118.2-2022 which were available at the time.
---------------------------------------------------------------------------

b. Provisions in ASHRAE 118.2-2022 Being Addressed by DOE
Thermal Break
    ASHRAE 118.2-2022 specifies the use of a ``thermal break'' in the 
test set-ups shown for free-standing water heaters and water heaters 
supplied with a countertop enclosure (see Figures 1, 2, 3, 6, 7, 8, and 
9 of ASHRAE 118.2-2022). A thermal break is optional in the ASHRAE 
118.2-2022 test set-ups shown for wall-mounted water heaters (see 
Figures 4 and 5 of ASHRAE 118.2-2022).
    ASHRAE 118.2-2022 defines a ``thermal break'' in section 3 as a 
nipple made of material that has thermal insulation properties (e.g. 
plastics) to insulate the bypass loop from the inlet piping. It should 
be able to withstand a pressure of 150 psi (1.034 MPa), and a 
temperature greater than the maximum temperature the water heater is 
designed to produce. A thermal break is added to the test set-up to 
prevent heat from traveling up the inlet piping into a bypass line, if 
one is utilized. (ASHRAE 118.2-2022 requires a bypass line to be 
installed, whereas the existing appendix E test procedure does not.) 
When purging the inlet piping before a draw, any heat that is 
transferred from the water heater through the inlet piping to the 
bypass line section would be lost, as the bypass line is replenished 
with cold supply water. The thermal break helps to prevent this heat 
loss.
    In this rulemaking, DOE has sought feedback from stakeholders in 
the April 2020 RFI as to whether a thermal break should be required in 
the DOE test procedure regardless of whether a bypass line is used, and 
additionally, whether DOE should adopt a definition for this set-up 
component. 85 FR 21104, 21110 (April 16, 2020). The January 2022 NOPR 
discussed the mixed comments received on this topic. In summary, three 
commenters stated that a thermal break should be included in the test 
set-up regardless of whether there is a bypass or purge line; however, 
three others (including a testing standards organization, CSA Group) 
stated that a thermal break is not needed if no bypass or purge loop is 
present. Several commenters indicated that a standardized definition 
for a ``thermal break'' would be beneficial for repeatability of the 
test procedure. 87 FR 1554, 1569 (Jan. 11, 2022).
    In the January 2022 NOPR, DOE explained that a bypass line is a 
method that test laboratories use to ensure inlet water temperatures 
are within the bounds of the test procedure (i.e., within 58 [deg]F 
2 [deg]F by the first measurement of the draw), but its 
inclusion in the test set-up can create a condition whereby a constant 
low temperature can remove energy from the water heater at a higher 
rate than would be removed in the field. Because a bypass line is not 
the only approach to maintaining inlet conditions, DOE had tentatively 
determined that requiring a thermal break (and providing a definition 
for this component) would not be necessary. Id.
    BWC responded by indicating that it is not aware of any 
manufacturer or test laboratory omitting the use of a thermal break, 
and, therefore, DOE should adopt a definition for ``thermal break'' to 
ensure consistent results from laboratory to laboratory. The commenter 
recommended that a thermal break should be defined as ``a plastic and 
thermally non-conductive material that can withstand a minimum 
temperature of 150 [deg]F.'' BWC also stated that its testing indicated 
that when a bypass line (also known as a ``purge loop'') is used, all 
temperatures more consistently met the tolerance criteria in appendix 
E; furthermore, test results were more often out of tolerance when a 
bypass line was not used. BWC argued that as a result, use of a bypass 
line will remain common practice, and as such, thermal breaks will also 
continue to be used. (BWC, No. 33 at p. 3)
    DOE has considered the comments received on this topic throughout 
this rulemaking, and, although DOE maintains that a thermal break would 
not be needed in all set-up cases, the Department has concluded that 
there is overwhelming support for establishing a standardized 
definition for ``thermal break.'' In order to address concerns 
regarding the repeatability of the test procedure (i.e., various 
facilities maintaining a consistent set-up approach), DOE is adopting a 
definition for this component consistent with that in section 3 of 
ASHRAE 118.2-2022, but with minor modification. Specifically, DOE is 
defining ``thermal break'' as ``a thermally non-conductive material 
that can withstand a pressure of 150 psi (1.034 MPa) at a temperature 
greater than the maximum temperature the water heater is designed to 
produce and is utilized to insulate a bypass loop, if one is used in 
the test set-up, from the inlet piping.'' However, DOE is not requiring 
the use of a bypass loop or a thermal break in this final rule. DOE 
reasons that providing a definition for a thermal break will improve 
consistency in test set-ups when the testing agency opts to use a 
bypass loop with a thermal break.
FHR Test Flow Rates
    Section 7.3.3.1 of ASHRAE 118.2-2022 indicates that the flow rate 
for non-flow-activated water heaters with rated storage volumes less 
than 20 gallons would be 1.5  0.25 gallons per minute (gpm) 
(5.7  0.95 liters (L)/minute (min)) when conducting the FHR 
test. Section 5.3.3, ``First-Hour Rating Test,'' of appendix E requires 
that water heaters with a storage volume less than 20 gallons be tested 
at 1.0  0.25 gpm (3.8  0.95 L/min). These flow 
rates are lower than the 3.0  0.25 gpm (11.4  
0.95 L/min) required for water heaters with rated storage volumes 
greater than or equal to 20 gallons. Water heaters with low rated 
storage volumes (less than 20 gallons) and high input rates can 
potentially operate indefinitely (i.e., instantaneously) at even the 
3.0  0.25 gpm (11.4  0.95 L/min) flow rate. 
Therefore, when such products are tested as currently required by 
appendix E, the measured FHR is near the maximum possible value of 60 
gallons (227 L) \42\ and, as a result, these

[[Page 40427]]

products would be required to use the medium draw pattern according to 
Table I of appendix E. However, as discussed in the January 2022 NOPR, 
these models could be used in applications similar to water heaters 
that are required to test using the high draw pattern, and the existing 
method of testing these products may not best represent how they are 
used in the field. Instead, DOE finds that a flow rate of 1.5  0.25 gpm (5.7  0.95 L/min)--as introduced in ASHRAE 
118.2-2022--would be sufficient to allow these products to be tested 
and rated in the high draw pattern. 87 FR 1554, 1569-1570 (Jan. 11, 
2022).
---------------------------------------------------------------------------

    \42\ At 1.0 0.25 gallons per minute during the 60-
minute first-hour rating test, the maximum possible delivery 
capacity is 1.0 gallon per minute x 60 minutes = 60 gallons. At 1.5 
 0.25 gallons per minute during the 60-minute first-hour 
rating test, the maximum possible delivery capacity is 1.5 gallon 
per minute x 60 minutes = 90 gallons.
---------------------------------------------------------------------------

    In this rulemaking, DOE has sought information from commenters 
regarding the flow rate for the FHR test of non-flow-activated water 
heaters with rated storage volumes less than 20 gallons. DOE has also 
participated in the public review of ASHRAE 118.2 prior to the 2022 
edition being released, leading up to the establishment of the 1.5 
 0.25 gpm (5.7  0.95 L/min) flow rate criteria 
for these products during the FHR test. DOE also performed testing on 
three electric storage water heaters less than 20 gallons to both the 
then currently applicable appendix E and ASHRAE 118.2-2022 flow rates 
and provided these test data in the January 2022 NOPR. The results 
indicated that changing the flow rate during the FHR test for water 
heaters with a rated storage volume less than 20 gallons from 1.0 
 0.25 gpm (3.8  0.95L/min) to 1.5  
0.25 gpm (5.7  0.95 L/min) would have a relatively minimal 
impact on the FHR for water heaters with low input rates. For models 
with high input rates, the change in flow rate could significantly 
increase the FHR and result in some models being tested and rated for 
UEF using a higher draw pattern, which would provide ratings that are 
more representative of their actual use. Therefore, DOE proposed to 
adopt the higher flow rate of 1.5  0.25 gpm (5.7  0.95 L/min) for the FHR test of non-flow-activated water heaters 
with rated storage volumes less than 20 gallons. 87 FR 1554, 1570 (Jan. 
11, 2022).
    In response, AHRI indicated that the revised flow rate of 1.5 gpm 
may not be appropriate for models as small as 2 gallons, for which the 
proposed change could yield unrepresentative results for FHR. (AHRI, 
No. 40 at p. 4) AHRI also raised concerns about the accuracy of flow 
rates for smaller capacity water heaters. (AHRI, Jan. 27, 2022 Public 
Meeting Transcript, No. 27 at p. 41) Rheem generally supported DOE's 
proposal to align with ASHRAE 118.2-2022 on this issue. However, Rheem 
pointed out that the test data provided in the NOPR reflected consumer 
water heaters in only the very small draw pattern, so Rheem requested 
DOE to provide further test data and also to conduct testing on 
products near the division between the very small and low draw 
patterns. Rheem stated that a change in draw pattern will affect the 
UEF rating and will need to be taken into account. (Rheem, No. 31 at p. 
2)
    In response to the concerns raised by AHRI, DOE notes that its test 
data presented in the January 2022 NOPR were taken from samples in the 
very small draw pattern (see 87 FR 1554, 1570 (Jan. 11, 2022)). DOE has 
additionally provided the storage volumes of the products which were 
tested in Table III.1 of this final rule. The samples were all 
approximately 2 gallons in storage volume, and the 1.5 gpm flow rate 
was found to be sufficiently representative for these products (the 
absolute value of the largest percent difference was less than 5 
percent). Additionally, as stated in the January 2022 NOPR, the 
increase in flow rate did not cause any of these products to move from 
the very small draw pattern to the low draw pattern, which resolves a 
chief concern regarding the representativeness of the FHR results. Id. 
In response to Rheem's requests for additional data, DOE was not able 
to identify non-flow-activated water heaters less than 20 gallons 
closer to 18 gallons of FHR--the division between the very small and 
low draw patterns--in order to perform testing on such products. 
However, while the net average change may approximately be a 2-percent 
increase in FHR rating, DOE has determined that the increased flow rate 
will allow products to be rated in more representative draw patterns, 
as discussed earlier in this section.

               Table III.1--Average First-Hour Rating Based on a Flow Rate of 1.0 gpm and 1.5 gpm
----------------------------------------------------------------------------------------------------------------
                                       Measured
                                        storage      Average FHR * at 1.0   Average FHR * at 1.5
             Unit No.                   volume,        gpm (3.8 L/min),       gpm (5.7 L/min),       Change %
                                        gallons            gallons                gallons
----------------------------------------------------------------------------------------------------------------
1.................................             2.4  7.3 (Very Small).....  7.5 (Very Small).....            +3.4
2.................................             2.4  6.4 (Very Small).....  6.2 (Very Small).....            -2.2
3.................................             1.8  6.9 (Very Small).....  7.2 (Very Small).....            +4.7
    Net Average...................  ..............  .....................  +2.0.................
----------------------------------------------------------------------------------------------------------------
* FHR results are rounded to the nearest 0.1 gallon and reflect the arithmetic mean of four trials per water
  heater.

    In this final rule, DOE is amending section 5.3.3.1 of the appendix 
E test procedure to require a flow rate of 1.5  0.25 gpm 
(5.7  0.95 L/min) when conducting the FHR test on non-flow-
activated water heaters with rated storage volumes less than 20 
gallons.
24-Hour Simulated-Use Test First Recovery Period
    The first recovery period of the 24-hour simulated-use test is used 
in section 8.3.2 of ASHRAE 118.2-2022 and section 6.3.2 of appendix E 
to calculate recovery efficiency. Section 8.3.2 of ASHRAE 118.2-2022 
specifies that, when the first recovery of the 24-hour simulated-use 
test ends during a draw, the first recovery period extends until the 
end of that draw, whereas DOE's test procedure does not explicitly 
address how to calculate recovery efficiency if the first recovery 
period ends during a draw.
    A ``recovery period'' is defined in section 1 of appendix E as 
``the time when the main burner of a storage water heater is raising 
the temperature of the stored water.'' Each of the parameters in the 
current recovery efficiency equation in section 6.3.2 of appendix E is 
recorded from the ``beginning of the test to the end of the first 
recovery period following the first draw.'' The currently applicable 
appendix E test procedure does not explicitly state whether values are 
recorded at the end of the recovery period that ends after the 
initiation of the first draw, or at the end of a recovery period that 
occurs after the end of the first draw.
    In the January 2022 NOPR, DOE noted that the situation in which a 
recovery ends during a draw likely occurs during draws with a low 
enough flow rate that the water heater can heat water more

[[Page 40428]]

quickly than the draw is removing. 87 FR 1554, 1574 (Jan. 11, 2022). 
DOE also explained that the energy used for the recovery efficiency 
calculation includes energy used to heat water and auxiliary energy; 
therefore, the energy associated with the first recovery period should 
represent the entire draw to capture all energy use. Id.
    On January 31, 2020, DOE published in the Federal Register a Notice 
of Decision and Order \43\ (Decision and Order) by which a test 
procedure waiver for certain basic models was granted to address the 
issue of a second recovery initiating during the draw during which the 
first recovery ended. 85 FR 5648. The Decision and Order prescribes an 
alternate test procedure that extends the first recovery period to 
include both the first and second recoveries. Id. at 85 FR 5652. In the 
context of the Decision and Order, DOE determined that the 
consideration of delivered water mass and inlet and outlet temperatures 
until the end of the draw is appropriately representative, and, 
therefore, the entire energy used from both recoveries is included. Id. 
at 85 FR 5651-5652.
---------------------------------------------------------------------------

    \43\ Notice of Decision and Order in response to BWC petition 
for waiver is available at: www.regulations.gov/document?D=EERE-2019-BT-WAV-0020-0008.
---------------------------------------------------------------------------

    In the January 2022 NOPR, after considering comments received in 
response to the April 2020 RFI, DOE proposed to establish a new 
provision that states that when the first recovery ends during a draw, 
the first recovery period is extended to the end of the draw and the 
mean tank temperature measured immediately after cut-out is used as the 
maximum mean tank temperature value in the recovery efficiency 
calculation. 87 FR 1554, 1574 (Jan. 11, 2022). In addition, DOE 
proposed to update the recovery efficiency equation to specify 
accounting for the mass of water drawn for all draws initiated during 
the recovery period. DOE noted that such a change would be consistent 
with the published Notice of Decision and Order and was supported by 
commenters. Id.
    In response, BWC stated the proposed updates to the overall test 
procedure provide a more accurate calculation of recovery efficiency 
and eliminate situations where products would be disadvantaged for 
completing their recovery in the middle of a draw, thereby providing a 
more representative measurement of a product's overall energy 
efficiency. (BWC, No. 33 at pp. 5-6)
    DOE did not receive any other comments in response to these 
proposals. As such, DOE is amending appendix E to adopt the proposals 
from the January 2022 NOPR, which are consistent with the alternate 
test procedure in the Decision and Order and in ASHRAE 118.2-2022.
24-Hour Simulated-Use Test Final Hour
    Although not stated explicitly in section 5.4.2 of the currently 
applicable appendix E, in the case that the standby period is between 
the first and second draw clusters, power to the main burner, heating 
element, or compressor is disabled during the last hour of the 24-hour 
simulated-use test. In the case that the standby period is after the 
last draw of the 24-hour simulated-use test, power to the main burner, 
heating element, or compressor is not disabled. Section 5.4.2 of the 
currently applicable appendix E states that during the last hour of the 
24-hour simulated-use test, power to the main burner, heating element, 
or compressor shall be disabled; at 24 hours, record the reading given 
by the gas meter, oil meter, and/or the electrical energy meter as 
appropriate; and determine the fossil fuel and/or electrical energy 
consumed during the entire 24-hour simulated-use test and designate the 
quantity as Q. Section 5.4.2 of the currently applicable appendix E 
also provides that in the case that the standby period is after the 
last draw of the 24-hour simulated-use test, an 8-hour standby period 
is required, and this period may extend past hour 24. The procedures 
for the standby period after the last draw of the 24-hour simulated-use 
test allow for a recovery to occur at the end of the 8-hour standby 
period, which indicates that the power to the main burner, heating 
element, or compressor is not disabled. DOE's procedure, as described, 
may result in some confusion. Further, the method of determining the 
total energy use during the 24-hour simulated-use test, Q, and total 
test time are not explicitly stated for when a standby period occurs 
after the last draw of the 24-hour simulated-use test. As discussed in 
the following paragraphs, DOE is amending the procedures for the last 
hour of the 24-hour simulated-use test, consistent with its proposals 
in the January 2022 NOPR, to explain how to end the test for both 
standby period scenarios, and this amendment aligns with the updated 
approach in ASHRAE 118.2-2022.
    In ASHRAE 118.2-2022, power is not disabled when the standby period 
occurs after the last draw of the test. However, if a recovery occurs 
between an elapsed time of 23 hours following the start of the test 
(hour 23) and 24 hours following the start of the test (hour 24), the 
following alternate approach is applied to determine the energy 
consumed during the 24-hour simulated-use test: The time, total energy 
used, and mean tank temperature are recorded at 1 minute prior to the 
start of the recovery occurring between hour 23 and hour 24, along with 
the average ambient temperature from 1 minute prior to the start of the 
recovery occurring between hour 23 and hour 24 to hour 24 of the 24-
hour simulated-use test. These values are used to determine the total 
energy used by the water heater during the 24-hour simulated-use test. 
This alternate calculation combines the total energy used 1 minute 
prior to the start of the recovery occurring between hours 23 and 24 
and the standby loss experienced by the tank during the time between 
the minute prior to the recovery start and hour 24. This provision in 
section 7.4.3.2 of ASHRAE 118.2-2022 does not require the water heater 
to be de-energized during the standby period. Disabling power to the 
water heater is typically a manual operation that requires the presence 
of a technician. In cases where the technician does not disable power 
at the correct time, a retest of the 24-hour simulated-use test may be 
necessary. To the extent this provision would eliminate the need to 
ensure that a unit is switched off for the last hour of the 24-hour 
simulated-use test, it could reduce test burden.
    In the January 2022 NOPR, after considering comments on the April 
2020 RFI, DOE tentatively concluded that further evaluation of the 
alternate procedure presented in the March 2019 ASHRAE Draft 118.2 and 
April 2021 ASHRAE Draft 118.2 should be conducted before a 
determination is made on whether DOE should adopt such changes. 
However, DOE also tentatively determined that the procedure for the 
last hour of the 24-hour simulated-use test would benefit from further, 
more explicit instruction, and, thus, DOE proposed to explicitly state 
how to end the test depending on whether the standby period is between 
draw clusters 1 and 2 or after the last draw of the test. 87 FR 1554, 
1575 (Jan. 11, 2022).
    No comments or data were received on this topic in response to the 
January 2022 NOPR or July 2022 SNOPR.
    As such and for the reasons previously stated, DOE is finalizing 
its proposal from the January 2022 NOPR to clarify how to end the test 
depending on when the standby period occurs. DOE will continue to 
evaluate the impacts of fully adopting the ASHRAE 118.2-2022 method and 
may consider that in a future test procedure rulemaking for the subject 
water heaters.

[[Page 40429]]

    As discussed in section III.E.4 of this document, DOE is dividing 
section 5.4.2 of appendix E into two sections: section 5.4.2.1, ``Water 
Heaters that Can Have Internal Storage Tank Temperature Measured 
Directly,'' and section 5.4.2.2, ``Water Heaters that Cannot Have 
Internal Storage Tank Temperature Measured Directly.'' The new section 
5.4.2.1 of appendix E provides specific direction on the measurements 
to be taken if the standby period occurs at the end of the first 
recovery period after the last draw of the 24-hour simulated-use test. 
These revised instructions for the final hour of the 24-hour simulated-
use test also no longer require disabling the water heater for the 
standby mode, a change which harmonizes with the procedure in ASHRAE 
118.2-2022. DOE has determined that these provisions are appropriate 
only for water heaters that can have internal storage tank temperatures 
measured directly, because these steps require recording the mean tank 
temperature at various points during the final hour. For water heaters 
that cannot have internal storage tank temperatures measured directly, 
DOE is adopting an alternative method entirely (discussed in section 
III.E.7 of this document) which requires a standby period after the 
final draw and temperature measurements made via estimation.
c. Other Updates
Inlet Water Temperature Measurement Location
    In its review of the ASHRAE 118.2-2022 set-up figures, DOE 
determined that the placement of the inlet water temperature 
measurement probe differs between ASHRAE 118.2-2022 and the currently 
applicable appendix E. In ASHRAE 118.2-2022, the inlet water 
temperature is always measured on the upstream side of the heat trap 
formed by the U-bend in the required piping, whereas the figures in 
appendix E vary this location (i.e., either on the upstream side or on 
the downstream side of the U-bend) depending on the type of water 
heater being tested.
    DOE requested information about the potential impact of this 
measurement location on energy efficiency results in the January 2022 
NOPR. 87 FR 1554, 1569 (Jan. 11, 2022).
    On this topic, BWC stated there are inconsistencies in the 
placement of inlet thermocouples in the set-up figures currently shown 
in appendix E. BWC suggested adopting the figures in ASHRAE Standard 
118.2, as they are representative of most set-ups and illustrate 
placement of the inlet thermocouples on the upstream side of the U-bend 
in all instances. BWC also more generally urged DOE to adopt the water 
heater test set-up figures adopted in ASHRAE 118.2-2022, stating that 
it is not aware of any testing laboratory that does not utilize the 
set-ups depicted in these figures. (BWC, No. 33 at pp. 2-3) (DOE 
understands the ``inconsistencies'' mentioned by BWC as referring to 
the differences in temperature probe placement for different types of 
water heaters, as mentioned at the beginning of this subsection.)
    AET indicated that there may be problems with the location and 
orientation of the bypass (purge) line connection in the ASHRAE 118.2-
2022 test set-ups when testing small water heaters (i.e., electric 
instantaneous water heaters). The commenter claimed that without a 
bypass line installed at the water inlet, it is not possible to meet 
the test conditions and tolerances for the inlet water temperature 
during test draws when the measurement location is as specified in the 
current appendix E test procedure. AET explained that the location of 
the bypass line combined with the rest of the piping configuration for 
measuring inlet water temperature can induce a small amount of flow in 
the piping near the inlet to the water heater, even when a draw is not 
being conducted and there is no flow through the water heater. 
According to AET, flow-activated water heaters with especially 
sensitive flow sensors could initiate heating upon sensing this ``false 
flow,'' and this would in turn cause the energy consumption under test 
to increase in an unrepresentative manner. AET provided a detailed 
description of this phenomenon in its public comment and stated that 
its claims were substantiated by review of recent test data, though 
these data were not provided to DOE. AET suggested that one potential 
solution to the identified problem could be to move the connection 
point of the purge line and the inlet measurement location further from 
the water heater. In addition, AET suggested adjusting the various pipe 
T-junctions and their orientations such that the momentum of a cold-
water purge will be directed horizontally away from the pipe direction 
going to the water heater and not induce a false flow, with the 
commenter opining that this change could be implemented for all types 
of water heaters. (AET, No. 29 at pp. 6-9)
    As discussed in the January 2022 NOPR, maintaining the same inlet 
water temperature measurement location for all water heater types 
((i.e., harmonizing with ASHRAE 118.2-2022)) would simplify the test 
set-up as compared to the requirements of the currently applicable 
appendix E. However, DOE did not have sufficient information at the 
time to propose such harmonization. 87 FR 1554, 1568-1569 (Jan. 11, 
2022).
    In the January 2022 NOPR, DOE noted that use of a bypass loop is 
not the only possible test set-up for meeting the test conditions 
within appendix E. 87 FR 1554, 1569 (Jan. 11, 2022). However, based on 
the comment from BWC, DOE understands that many test facilities do use 
a bypass loop as a solution to having to stabilize the inlet water 
conditions. After considering the comments from AET and BWC, DOE has 
determined that laboratories are likely to continue to use bypass lines 
regardless of the placement of the inlet water temperature measurement, 
because a bypass line is simple to install and relatively low-cost. If 
this occurs, then there is a risk that UEF ratings for certain flow-
activated water heaters with highly sensitive sensors may be lower due 
to the additional energy consumption of the water heater when a false 
flow is sensed. DOE is not incorporating the updates found in the 
ASHRAE 118.2-2022 figures. Instead, DOE is maintaining the current set-
up directions for inlet water temperature measurement in appendix E 
and, which will allow for the continued use of a bypass line when 
necessary and appropriate. Regarding AET's concerns about the location 
of the bypass loop for certain electric instantaneous water heaters, 
DOE notes that it has not observed the issue in any of its testing. 
Further, DOE is not adopting the figures in ASHRAE 118.2-2022, so, 
therefore, the Department is not specifying the location of the bypass 
loop in its test set-up. Accordingly, during testing, there will be 
sufficient flexibility to locate the bypass line, when necessary, in a 
location that results in representative operation and performance of 
the unit under test.
FHR Test Initiation Criteria
    ASHRAE 118.2-2022 includes additional criteria defining the start 
of the FHR test as compared to DOE's test procedure at appendix E. 
These differences are briefly explained in the following paragraphs.
    Section 5.3.3.3 of the currently applicable appendix E states that 
prior to the start of the FHR test, if the water heater is not 
operating (i.e., heating water), initiate a draw until cut-in \44\

[[Page 40430]]

(i.e., when the water heater begins heating water). The draw is then 
terminated any time after cut-in, and the water heater is operated 
until cut-out.\45\ Once the maximum mean tank temperature is observed 
after cut-out, the initial draw of the FHR test begins.
---------------------------------------------------------------------------

    \44\ ``Cut-in'' is defined in section 1 of appendix E as ``the 
time when or water temperature at which a water heater control or 
thermostat acts to increase the energy or fuel input to the heating 
elements, compressor, or burner.''
    \45\ ``Cut-out'' is defined in section 1 of appendix E as ``the 
time when or water temperature at which a water heater control or 
thermostat acts to reduce to a minimum the energy or fuel input to 
the heating elements, compressor, or burner.''
---------------------------------------------------------------------------

    Section 7.3.3.3 of ASHRAE 118.2-2022 specifies that the draw 
preceding the initial draw of the FHR test must proceed until the 
outlet temperature drops 15 [deg]F below the maximum outlet temperature 
observed, or until a draw time limit \46\ is reached. If the draw time 
limit is reached before the outlet temperature drops 15 [deg]F below 
the maximum outlet temperature observed, then the main heating source 
of the water heater is shut off, and the draw is continued until the 
outlet temperature has dropped 15 [deg]F below the maximum outlet 
temperature. Requiring the outlet temperature to drop 15 [deg]F below 
the maximum outlet temperature may provide a more consistent starting 
condition for the FHR test compared to the pre-conditioning method 
specified in the currently applicable DOE test procedure because draws 
of varying lengths can create different internal tank temperature 
profiles.
---------------------------------------------------------------------------

    \46\ The draw time limit is the rated storage capacity divided 
by the flow rate times 1.2 (i.e., for a 75-gallon water heater the 
draw time limit would be 30 minutes, or 75 gallons divided by 3 gpm 
times 1.2).
---------------------------------------------------------------------------

    Thus, in the January 2022 NOPR, DOE tentatively determined that the 
additional requirement to tie the length of the initial draw to a 
specific outlet temperature (which in some cases would extend the draw 
length as compared to the currently applicable DOE test procedure) 
could increase the repeatability of the FHR test. 87 FR 1554, 1570-1571 
(Jan. 11, 2022). However, DOE also argued that, with both the ASHRAE 
118.2-2022 and appendix E initiation criteria, the water heater can be 
considered ``fully heated'' and to have similar internal energy content 
before beginning the FHR test, although differences may be present due 
to the internal water temperature gradient throughout the tank. DOE did 
not propose an amendment to include pre-FHR test conditioning, because 
it was unclear how these differences in internal tank temperature would 
affect the test results. 87 FR 1554, 1571 (Jan. 11, 2022).
    In response, A.O. Smith stated that the 15 [deg]F initiation 
criterion and the additional specificity on draw termination in ASHRAE 
118.2 would improve consistency and repeatability and would not 
conflict with the currently applicable DOE test procedure, and, 
therefore, those provisions should be adopted. (A.O. Smith, No. 37 at 
pp. 6-7) BWC also urged DOE to consider adopting the pre-FHR pre-
conditioning requirements specified in ASHRAE 118.2. BWC stated that 
the specifications in ASHRAE 118.2 only add parameters to achieve 
better testing consistency, and that the currently applicable test 
procedure may frequently yield inconsistencies from short pre-draws 
prior to the initiation of the FHR test, thereby causing storage water 
heaters to be unable to meet the test procedure's 125 [deg]F  5 [deg]F requirement. BWC stated that changes to the pre-FHR 
preconditioning requirements were agreed to by manufacturers during the 
development of ASHRAE 118.2, and that manufacturers are prepared to 
undertake the burden of any re-testing in favor of a more robust test 
method. (BWC, No. 33 at pp. 4-5)
    In response, DOE notes that commenters did not indicate the impact 
of this change on rated values of products nor did they provide any 
data in that regard. Additionally, DOE is not aware of storage water 
heaters which are not able to meet the 125 [deg]F  5 [deg]F 
outlet temperature requirement, but if this is demonstrated to be a 
problem, the Department would address the impacted products in a future 
rulemaking once more data are collected. Although the Department 
acknowledges the potential benefits to consistency and repeatability 
that may accompany a pre-FHR preconditioning requirement, without a 
clear understanding of the associated impact on ratings, DOE is not 
adopting this change to the Federal test procedure at this time.
    Additionally, DOE notes that the draw time limit in section 7.3.3.3 
of ASHRAE 118.2-2022 is a function of the ``nominal'' capacity of the 
water heater (in gallons or liters). Nominal capacity is typically not 
equal to the rated storage volume, and there is no standardized 
methodology in appendix E or in ASHRAE 118.2-2022 to determine nominal 
capacity; hence, there is a concern that the draw time limits could be 
different for two identical water heaters labeled at two different 
nominal capacities. If DOE were to adopt the essence of the initiation 
criteria in ASHRAE 118.2-2022, DOE would consider substituting 
``nominal capacity'' for ``rated storage volume'' (because rated 
storage volume is a standardized metric with a test method associated 
with it in section 5.2.1 of appendix E). This deviation could cause 
additional testing costs for manufacturers.
    For these reasons, DOE is maintaining the FHR test initiation 
criteria currently found in appendix E, which provide that the 
preconditioning draw can be terminated any time after cut-in, and the 
water heater is operated until cut-out. Once the maximum mean tank 
temperature is observed after cut-out, the initial draw of the FHR test 
begins.
24-Hour Simulated-Use Test Initiation Criteria
    Similar to the initiation criteria discussed in the previous 
section for the FHR test, section 7.4.2 of ASHRAE 118.2-2022 includes 
criteria for a pre-24-hour simulated-use test draw, which ends after 
either the outlet temperature drops by 15 [deg]F or the draw time limit 
is reached. Section 5.4.2 of the currently applicable appendix E 
requires that the water heater sit idle for 1 hour prior to the start 
of the 24-hour simulated-use test, during which time no water is drawn 
from the unit and no energy is input to the main heating elements, heat 
pump compressor, and/or burners. Appendix E provides no instruction on 
how to condition the tank prior to this one hour. However, as discussed 
in the previous section, it remains unclear how the outlet temperature 
drop criteria and the draw time limit will affect the internal tank 
temperature at the start of the 24-hour simulated-use test and how this 
difference in internal tank temperatures will affect the test results.
    In the January 2022 NOPR, DOE did not propose to amend appendix E 
to include the April 2021 ASHRAE Draft 118.2 24-hour simulated-use test 
initiation criteria (which was substantially the same as the 24-hour 
simulated-use test initiation criteria included in ASHRAE 118.2-2022) 
and invited comment and data that provide information on the impact of 
this update on UEF results. 87 FR 1554, 1573 (Jan. 11, 2022).
    On this topic, BWC argued that the initiation criteria in ASHRAE 
Standard 118.2 should also be adopted for the 24-hour simulated-use 
test so as to improve the repeatability and reproducibility of the test 
procedure. (BWC, No. 33 at pp. 4-5) DOE considered this comment, as 
well as those received regarding the FHR test initiation criteria, and 
has determined that it still lacks the necessary data that would 
provide a clear understanding of the impact that this update would have 
on ratings. Accordingly, for the same reasons stated in the previous 
section, DOE is not adopting this change in this final rule.

[[Page 40431]]

FHR Test Termination Temperature
    Section 7.3.3.4 of ASHRAE 118.2-2022 includes additional criteria 
regarding water draws during the FHR test, as compared to the current 
DOE test procedure. The FHR test required in section 5.3.3 of appendix 
E specifies a series of water draws over the course of one hour. After 
each water draw is initiated, the draw is terminated when the outlet 
water temperature decreases 15 [deg]F from the maximum outlet water 
temperature measured during the draw. For example, if after initiating 
a water draw, the outlet water temperature reaches a maximum 
temperature of 125 [deg]F, the water draw would continue until the 
outlet water temperature drops to 110 [deg]F, at which time the water 
draw would be terminated. Similar to the public review drafts of ASHRAE 
118.2, section 7.3.3.4 of ASHRAE 118.2-2022 specifies that water draws 
during the FHR test terminate if either: (1) The outlet water 
temperature decreases by the quantity of nominal delivery temperature 
minus 110 [deg]F from the maximum outlet water temperature \47\ or (2) 
the outlet water temperature decreases to 105 [deg]F, regardless of the 
maximum outlet water temperature measured during the draw. Setting a 
minimum temperature threshold of 105 [deg]F would reflect that, in 
practice, consumers would likely stop drawing water when it gets below 
105 [deg]F, as the water would no longer be considered ``hot.''
---------------------------------------------------------------------------

    \47\ The nominal delivery temperature in section 2.4 of the 
appendix E test procedure is 125 [deg]F, and 125 [deg]F-110 [deg]F = 
15 [deg]F. Thus, for a nominal delivery temperature of 125 [deg]F, 
ASHRAE 118.2-2022 and the DOE test procedure both use a 15 [deg]F 
drop to indicate when the draw must be terminated.
---------------------------------------------------------------------------

    A temperature of 105 [deg]F would be the FHR test termination 
temperature if the maximum outlet temperature were 120 [deg]F (a 15 
[deg]F difference) as per the current DOE test procedure. 120 [deg]F is 
the lower end of the outlet temperature tolerance band specified in 
section 5.2.2.2 of appendix E (i.e., 125 [deg]F  5 [deg]F). 
However, as discussed in section III.A.4.b of this document, there 
exist low-temperature water heaters that are not capable of maintaining 
these temperatures when tested to the flow rates required in section 
5.2.2.2 of appendix E, and this raises the question of whether a 
criterion for ending a draw when the outlet temperature reaches 105 
[deg]F would be representative for all consumer water heaters and 
residential-duty commercial water heaters.
    In this rulemaking, DOE sought information and feedback from 
stakeholders on the potential impacts and implications of setting an 
FHR test termination temperature such as 105 [deg]F. In particular, DOE 
was interested in data which would determine the representativeness of 
a 105 [deg]F minimum temperature based on consumer use and 
expectations. 85 FR 21104, 21109 (April 16, 2020). While several 
stakeholders generally supported the use of a termination temperature, 
two manufacturers indicated that more testing and investigation are 
necessary prior to adopting this. 87 FR 1554, 1571, 1572 (Jan. 11, 
2022). In commenting on the April 2020 RFI, Rheem suggested 100 [deg]F 
instead to account for low-temperature water heaters. (Rheem, No. 14 at 
p. 3) In the January 2022 NOPR, DOE tentatively determined that, based 
on a review of existing test data, the 105 [deg]F termination 
temperature criterion would affect only a small number of tests, if 
any. Additionally, DOE noted that Rheem's suggested 100 [deg]F 
termination temperature would most likely not be representative for all 
types of consumer water heaters and residential-duty commercial water 
heaters. Given the need for further evaluation of the specific 
termination temperature and its potential impacts, DOE did not propose 
to adopt a termination temperature for the FHR test in the January 2022 
NOPR. 87 FR 1554, 1572 (Jan. 11, 2022).
    In response to the January 2022 NOPR, BWC reiterated that DOE 
should include the 105 [deg]F termination temperature established in 
ASHRAE Standard 118.2 to provide additional clarity and reflect 
representative usage. (BWC, No. 33 at p. 4) However, commenters did not 
provide additional data or consumer usage information to indicate 
whether 105 [deg]F is representative of the minimum delivery 
temperature consumers generally expect. DOE was likewise unable to 
obtain widespread field use data on its own initiative.
    As of this final rule, there remains significant uncertainty 
regarding what the value of the termination temperature should be. As 
noted previously, Rheem indicated 100 [deg]F should be used to account 
for low-temperature water heaters. Section 7.3.3.4 of ASHRAE 118.2-2022 
uses a 105 [deg]F minimum termination temperature, which was 
recommended by several stakeholders. DOE did not receive, nor has DOE 
found, any additional data regarding the minimum delivery temperature 
consumers would generally expect. However, should the water heater 
provide a maximum delivery temperature during the test which is lower 
than 120 [deg]F (which may potentially occur even if the unit's 
controls are adjusted properly according to section 5.2.2 of appendix 
E), a 15 [deg]F temperature drop would result in termination below 105 
[deg]F. DOE expects this would impact a relatively small number of 
units, but at this time, there is inadequate test data to indicate how 
frequently this may occur, which types of products would be affected, 
and how they would be affected by a specific termination temperature.
    Given these considerations, DOE is not adopting a minimum 
termination temperature for the FHR test in this rulemaking.
FHR Test Final Draw Volume
    Section 5.3.3.3 of appendix E includes a provision for the FHR test 
requiring that if the final draw is not initiated prior to one hour 
from the start of the test, then a final draw is imposed at the elapsed 
time of one hour. In this situation, calculations presented in section 
6.1 of appendix E are used to determine the volume drawn during the 
final draw for purposes of calculating FHR. The volume of the final 
draw is ``scaled'' based on the temperature of the water delivered 
during the final draw as compared to the temperature of the water 
delivered during the previous draw to account for the water removed in 
the final draw being at a lower temperature than previous draws. The 
scaled final draw volume is added to the total volume drawn during the 
prior draws to determine the FHR. ASHRAE 118.2-2022 does not include a 
final draw volume scaling calculation for the case in which a draw is 
not in progress at one hour from the start of the test and a final draw 
is imposed at the elapsed time of one hour. Instead, the ASHRAE 118.2-
2022 method calculates FHR as the sum of the volume of hot water 
delivered giving full credit to the final draw.
    The methodology for conducting the FHR test, and in particular the 
issue of whether to scale the final draw, was considered by DOE in a 
final rule that was published in the Federal Register on May 11, 1998 
(the May 1998 Final Rule). 63 FR 25996. In the May 1998 Final Rule, DOE 
determined that scaling the final draw volume based on the outlet water 
temperature was appropriate and was included to adjust the volume of 
the last draw to account for the lower heat content of the last draw 
compared to the earlier draws with fully heated water. Id. at 63 FR 
25996, 26004-26005.
    In the January 2022 NOPR, after considering comments on the April 
2020 RFI, DOE proposed not to update the final draw volume provisions 
in the FHR test because DOE tentatively determined that scaling the 
final draw

[[Page 40432]]

volume based on outlet temperature is more representative of the actual 
use in the field. 87 FR 1554, 1573 (Jan. 11, 2022). As discussed in the 
January 2022 NOPR, AHRI and individual manufacturers recommended that 
DOE remove the scaling calculations to harmonize with ASHRAE 118.2-
2022, indicating that this change would have minimal impact on ratings. 
Id. at 87 FR 1572. CSA, however, raised concerns with that approach, 
because water is usually tempered by the end user, and the commenter 
argued that a water heater that delivers a volume of water at a higher 
temperature should not be credited the same as one that delivers 
roughly the same volume at a lower temperature. CSA also noted that 
removing the scaling of the final draw volume could possibly move water 
heaters to a higher draw pattern. Id.
    After considering these comments, DOE noted in the January 2022 
NOPR that the scaling of the final draw accounts for the possible lower 
heat content of the last draw as compared to earlier draws. DOE further 
explained that the test procedure specifies a constant flow rate 
throughout testing, and, as water is drawn from a typical non-flow-
activated water heater, the water temperature decreases. As the 
temperature of the water delivered by the water heater decreases, 
mixing valves at the point of use will reduce the amount of cold water 
being mixed with the hot water in order to maintain the same delivery 
temperature to the consumer. If the water from the water heater is at a 
lower temperature, more of this hot water will be required to reach the 
correct temperature at the fixture. Thus, DOE tentatively determined 
that scaling the final draw volume based on outlet temperature is more 
representative of the actual use in the field. 87 FR 1554, 1572-1573 
(Jan. 11, 2022). Furthermore, DOE also noted that if the scaling 
calculation were removed, many water heaters would have a different FHR 
than under the currently applicable appendix E, and some would change 
draw pattern bins, which would require retesting for UEF and thereby 
increase manufacturer burden. Id.
    In response, BWC strongly disagreed with DOE's position that 
scaling the final draw based on outlet temperature is representative of 
field use. BWC reiterated its earlier comments that scaling should not 
be necessary and would potentially lead to unrepeatable test results 
depending on the timing of the last draw (e.g., creating the 
possibility of two different FHR ratings for the same product). BWC 
instead recommended the procedure in ASHRAE Standard 118.2, where the 
sum of the volume of hot water delivered is used without scaling the 
final draw. BWC argued that this approach would more fairly account for 
water heated by the product. (BWC, No. 33 at pp. 4-5)
    After considering BWC's comment, DOE maintains that when the final 
draw is imposed at the end of the FHR test, scaling the volume of water 
drawn by temperature is representative and appropriate. Scaling the 
final draw allows FHR to capture the difference in hot water delivery 
capacity between water heaters that provide roughly the same amount of 
hot water in the final draw, but where one water heater provides water 
at a higher temperature than the other. This is appropriate because, as 
noted, the water temperature is usually tempered at the fixture to 
provide the end user with water at the target outlet temperature. If 
the hot water is at a lower temperature, more water is required to 
provide the user with water at the target temperature, while less water 
would be needed if the water is at a higher temperature. Therefore, DOE 
has concluded that it is appropriate for FHR to reflect this difference 
in capacity, which would not be accounted for if the scaling 
calculation is removed. DOE also notes that, at this time, there is 
limited information available to assess the potential impacts of 
removing the scaling calculation on UEF and FHR ratings, and as a 
result DOE is not amending the appendix E test procedure to include the 
full volume of the final draw.
24-Hour Simulated-Use Test Standby Period Duration
    Appendix E includes a standby \48\ loss measurement period between 
the first and second draw clusters \49\ of the 24-hour simulated use 
test. During this time, temperature data is recorded and used to 
calculate the standby heat loss coefficient. See section 5.4.2 of 
appendix E. Sections 7.4.3.1 and 7.4.3.2 of ASHRAE 118.2-2022 add a 
condition that the standby period data can be recorded between the 
first and second draw clusters only if the time between the observed 
maximum mean tank temperatures after cut-out following the first draw 
cluster to the start of the second draw cluster is greater than or 
equal to 6 hours. Otherwise, the standby period data would be recorded 
after the last draw of the test. This condition would provide a 
sufficiently long standby period to determine standby loss, which might 
make this calculation more repeatable and the results more 
representative of standby losses experienced in an average period of 
use. However, this might also cause the test to extend beyond a 24-hour 
duration.
---------------------------------------------------------------------------

    \48\ ``Standby'' is defined in section 1.12 of appendix E as 
``the time, in hours, during which water is not being withdrawn from 
the water heater.''
    \49\ A ``draw cluster'' is defined in section 1 of appendix E as 
``a collection of water draws initiated during the 24-hour 
simulated-use test during which no successive draws are separated by 
more than 2 hours.'' There are two draw clusters in the very small 
draw pattern and three draw clusters in the low, medium, and high 
draw patterns.
---------------------------------------------------------------------------

    The currently applicable DOE test procedure does not have a 6-hour 
minimum for a standby period between the first and second draw clusters 
of the 24-hour simulated use test. However, section 5.4.2 of appendix E 
states, ``In the event that the recovery period continues from the end 
of the last draw of the first draw cluster until the subsequent draw, 
the standby period will start after the end of the first recovery 
period after the last draw of the simulated-use test, when the 
temperature reaches the maximum average tank temperature, though no 
sooner than five minutes after the end of this recovery period. The 
standby period shall last eight hours, so testing will extend beyond 
the 24-hour duration of the simulated-use test.'' As such, DOE does 
currently have a minimum standby period duration, but only under the 
particular case that there is no opportunity to observe standby 
operation between the first draw cluster and the second draw cluster.
    In the April 2020 RFI, the Department requested comments on 
potentially adding a minimum standby period length of 6 hours and the 
associated data collection and calculations. 85 FR 21104, 21110 (April 
16, 2020). Commenters were split on the appropriateness of this 
amendment, with some stakeholders noting a key concern would be the 
extension of the total test period time to over 24 hours in many cases. 
87 FR 1554, 1574 (Jan. 11, 2022).
    The standby heat loss coefficient (i.e., UA) is the main result 
calculated from the data recorded during the standby period. DOE 
reviewed its available test data and found that, generally, the standby 
period duration has little effect on the UA value, and the UA value in 
turn has very little effect on UEF. As discussed in the January 2022 
NOPR, UA is used only to adjust the daily water heating energy 
consumption to the nominal ambient temperature of 67.5 [deg]F (19.7 
[deg]C); given that the ambient temperature range is relatively narrow 
(i.e., 65 [deg]F to 70 [deg]F (18.3 [deg]C to 21.1 [deg]C)), the 
adjustment has only a minimal impact on the daily water heating

[[Page 40433]]

energy consumption. 87 FR 1554, 1574 (Jan. 11, 2022).
    In commenting on the January 2022 NOPR, BWC generally disagreed 
with DOE's tentative determination that including a 6-hour standby 
period minimum would not significantly impact UEF ratings. BWC also 
mentioned that it has experienced difficulty having adequate time to 
calculate the standby loss coefficient after the first draw cluster. 
Thus, BWC reiterated its support for the methodology in ASHRAE 118.2-
2022 but stated that the company would like time to examine this matter 
before commenting further. (BWC, No. 33 at p. 6) BWC did not provide 
further comments or data on this topic in response to the July 2022 
SNOPR.
    Considering that DOE did not receive further comments demonstrating 
a quantifiable impact of the standby period length on the UEF, DOE 
concludes, as initially presented in the January 2022 NOPR, that based 
on its test data, the duration of the standby period does not 
significantly impact the UEF result. Therefore, in order to minimize 
burden (i.e., total test duration) on manufacturers and laboratories 
while still allowing results to be representative, repeatable, and 
reproducible, DOE is not amending the appendix E test procedure to 
require the standby period to be a minimum of 6 hours in duration.

C. Test Conditions and Tolerances

    In the January 2022 NOPR, DOE made a number of proposals to the 
test conditions and tolerances that were intended to improve 
representativeness, reduce testing burden, and/or harmonize with 
industry test methods. 87 1554, 1558-1559 (Jan. 11, 2022). These 
proposals included changes to the electric supply voltage tolerance, 
ambient condition tolerances, gas supply pressure and manifold pressure 
tolerances, and flow rate tolerances for certain water heaters. Id. In 
addition, in the July 2022 SNOPR, DOE made supplemental proposals 
regarding the tolerance on flow rate during the UEF test for models 
with rated storage volumes less than 2 gallons and max GPM less than 1 
gallon, and regarding optional test conditions for heat pump water 
heaters. 87 FR 42270, 42273 (July 14, 2022). These proposals were 
intended to improve repeatability and reproducibility and harmonize 
with industry testing practices, respectively. Id.
    In response to the January 2022 NOPR proposals, APGA provided 
general comments stressing the importance of ensuring accuracy, 
repeatability, and reproducibility in a test procedure that is not 
unduly burdensome to conduct. (APGA, No. 38 at pp. 1-2) AHRI indicated 
its support of DOE's proposals to reduce test burden; specifically, 
AHRI supported increasing test tolerances for ambient temperature and 
relative humidity, and extending untested provisions to include 
electric instantaneous water heaters. (AHRI, Jan. 27, 2022 Public 
Meeting Transcript, No. 27 at p. 40)
    As previously discussed in section I.A of this final rule, DOE's 
efforts are aligned with EPCA requirements to create test procedures 
that are representative of average use without being unduly burdensome 
to conduct. (42 U.S.C. 6293(b)(3)) Each of the proposed changes to test 
conditions and tolerances, along with specific stakeholder comments 
received and DOE's responses, are discussed further in the subsections 
that immediately follow.
1. Supply Water Temperature Measurements
    Section 2.3 of the currently applicable appendix E specifies 
maintaining the supply water temperature at 58 [deg]F  2 
[deg]F (14.4 [deg]C  1.1 [deg]C). During the 24-hour 
simulated-use test, maintaining the supply water temperature within 
this range can be difficult at the immediate start of a draw due to the 
short time between draw initiation and the first measurement at 5 
seconds (with subsequent measurements every 3 seconds thereafter), as 
required by sections 5.4.2 and 5.4.3 of appendix E. In some test 
configurations, particularly during the lower flow rate water draws, 
the inlet water and piping may retain heat from a previous draw, 
causing the water entering the unit during the initial measurements to 
be slightly outside of tolerance. Any supply water temperature reading 
outside of the test tolerances would invalidate a test. However, due to 
the small percentage of total water use that would be affected, supply 
water temperatures that are slightly out of tolerance for the first one 
or two data points would have a negligible effect on the overall test 
result.\50\ This issue is less evident during the FHR test, which 
specifies an initial temperature measurement 15 seconds after the start 
of the water draw. This is not an issue during the Max GPM test due to 
the system being in steady state during the entire test.
---------------------------------------------------------------------------

    \50\ For example, the first two temperature readings would 
reflect 8 seconds of water flow, in comparison to total water draw 
durations ranging from 1 minute to over 8 minutes, according to the 
water draw patterns defined in Tables III.1, III.2, III.3, and III.4 
of appendix E.
---------------------------------------------------------------------------

    In the April 2020 RFI, DOE requested feedback on whether one or two 
supply water temperature data points outside of the test tolerance at 
the beginning of a draw would have a measurable effect on the results 
of the test. 85 FR 21104, 21111 (April 16, 2020). DOE further requested 
feedback on whether it should consider relaxing the requirement for 
supply water temperature tolerances at the start of a draw, and if so, 
which methods are most appropriate for doing so while maintaining 
accuracy and repeatability. Id. at 85 FR 21111-21112. DOE received 
comments regarding these tolerances from stakeholders including AHRI, 
A.O. Smith, NEEA, Rheem, BWC, CSA, Rinnai, and SMTI. These comments are 
summarized and discussed in section III.C.3.a of the January 2022 NOPR. 
87 FR 1554, 1576-1577 (Jan. 11, 2022).
    In response to comments made on the April 2020 RFI, DOE proposed in 
the January 2022 NOPR to increase the time between initiating the draw 
and first measurement of supply water temperature from 5 seconds to 15 
seconds in sections 5.4.2 and 5.4.3 of appendix E, as recommended by 
the commenters. 87 FR 1554, 1577 (Jan. 11, 2022). DOE reasoned that the 
proposed change may, if adopted, reduce test burden by reducing the 
occurrence of a test being invalidated (which would require re-testing) 
due to the first one or two water temperature readings exceeding the 
defined temperature tolerance. Further, this proposed change would 
eliminate the need to amend the supply water temperature tolerances 
which, outside of the time period at the start of a draw, are 
relatively easy to maintain. Id.
    In response to the January 2022 NOPR, A.O. Smith reiterated its 
previous comment that there would be no measurable effect on test 
results by allowing one or two supply water temperature data points 
outside of the current test tolerance at the beginning of a draw. The 
commenter suggested that DOE should adopt the test set-up described in 
ASHRAE 118.2-2022, which includes a purge line designed by third-party 
laboratories to help achieve tolerances on supply water temperature. 
A.O. Smith also commented that widening tolerances in certain cases may 
ultimately cause variations in test results. (A.O. Smith, No. 37 at p. 
5) In contrast, BWC supported DOE's proposal to increase the span 
between the first draw initiation and the first temperature measurement 
from 5 seconds to 15 seconds because it would reduce testing burden; 
the 5-second

[[Page 40434]]

time interval requires significant and frequent purging which, if not 
conducted, may invalidate tests. (BWC, No. 33 at p. 7) In response to 
A.O. Smith, DOE reiterates its position, as previously stated in the 
January 2022 NOPR, that although one or two measurements outside the 
current tolerance may not have an effect on test results, DOE has 
chosen to alleviate the issue of potential test invalidation by instead 
increasing the time between initiating the draw and first measurement 
of supply water temperature. Id.
    After considering these comments, DOE has decided to adopt the 
proposal from the January 2022 NOPR to increase the time between 
initiating the draw and first measurement from 5 seconds to 15 seconds 
in sections 5.4.2 and 5.4.3 of appendix E. In response to A.O. Smith's 
suggestion that DOE adopt the test set-up in ASHRAE 118.2-2022, as 
discussed in detail in section III.B.2.c of this document, DOE is 
maintaining the current set-up directions for inlet water temperature 
measurement in appendix E and not incorporating the updates found in 
the ASHRAE 118.2-2022 figures because the addition of a bypass line and 
thermal break was determined to be optional. However, increasing the 
time of first recordation of the supply water temperature measurement 
after the start of a draw from being taken at 5 seconds to being taken 
at 15 seconds will allow units to reach a supply temperature within 
tolerance without need for modifications to the test set-up.
2. Gas Pressure
    For gas-fired water heaters, sections 2.7.2 and 2.7.3 of the 
currently applicable appendix E require maintaining the gas supply 
pressure in accordance with the manufacturer's specifications; or if 
the supply pressure is not specified, maintaining a supply pressure of 
7 to 10 inches of water column (1.7 to 2.5 kPa) for natural gas and 11 
to 13 inches of water column (2.7 to 3.2 kPa) for propane gas. In 
addition, for gas-fired water heaters with a pressure regulator, 
sections 2.7.2 and 2.7.3 of the currently applicable appendix E require 
the regulator outlet pressure to be within 10 percent of 
the manufacturer's specified manifold pressure.
    In the January 2022 NOPR, DOE noted that from a review of product 
literature, DOE found that many gas-fired water heaters with modulating 
input rate burners have a factory preset manifold pressure that is 
computer-controlled and cannot be adjusted directly. Further, the 
manufacturer-specified manifold pressure typically refers to when the 
water heater is operating at the maximum firing rate. As a result, and 
after considering comments on the April 2020 RFI, DOE proposed to 
remove the 10 percent manifold pressure tolerance for 
certain gas-fired water heaters, recognizing that some of these 
products do not provide the capability to adjust the manifold pressure. 
87 FR 1554, 1578-1579 (Jan. 11, 2022). DOE also proposed the addition 
of an absolute manifold pressure tolerance of 0.2 inches 
water column, which would be used for gas-fired water heaters with a 
zero-governor valve for which the 10 percent tolerance 
would be overly restrictive. Id. For example, applying the 10 percent to a manufacturer recommended gas pressure of 0.1 
inches water column would result in a tolerance of 0.01 
inches of water column, which is less than both the accuracy and 
precision tolerances required for gas pressure instrumentation within 
section 3.1 of the currently applicable appendix E. Further, DOE 
proposed that the required gas pressures within appendix E apply when 
operating at the manufacturer's specified input rate or, for modulating 
input rate water heaters, the maximum input rate. Id.
    DOE did not receive comments in response to the previously 
discussed amendments to sections 2.7.2 and 2.7.3 of appendix E proposed 
in the January 2022 NOPR concerning manifold pressure tolerance for 
gas-fired water heaters. Accordingly, DOE is adopting these amendments 
in this final rule for the reasons previously stated.
3. Input Rate
    In addition to the gas pressure requirements, section 5.2.3 of the 
currently applicable appendix E test procedure requires maintaining an 
hourly Btu rating (i.e., input rate) that is within 2 
percent of the value specified by the manufacturer (i.e., the nameplate 
value). DOE has observed during testing that an input rate cannot be 
achieved that is within 2 percent of the nameplate value 
while maintaining the gas supply pressure and manifold pressure within 
the required ranges for some gas-fired water heaters. In such 
instances, it is common practice for the testing laboratory to modify 
the size of the orifice that is shipped with the water heater; for 
example, the testing laboratory may enlarge the orifice to allow enough 
gas flow to achieve the nameplate input rating within the specified 
tolerance, if the input rate is too low with the orifice as supplied. 
For commercial water heating equipment, DOE addressed this issue by 
specifying in the product-specific enforcement provisions that, if the 
fuel input rate is still not within 2 percent of the rated 
input after adjusting the manifold and supply pressures to their 
specified limits, DOE will attempt to modify the gas inlet orifice. 10 
CFR 429.134(n)(ii).
    In the April 2020 RFI, DOE requested comment on whether provisions 
should be added to the test procedure at appendix E to address water 
heaters that cannot operate within 2 percent of the 
nameplate rated input as shipped from the factory and how this issue 
should be addressed. 85 FR 21104, 21112 (April 16, 2020). On this 
topic, DOE received comments from manufacturers and their 
representatives, including AHRI, Rheem, Rinnai, BWC, and CEC, 
suggesting various methods to achieve the 2 percent 
tolerance. These comments are summarized and discussed in the January 
2022 NOPR. 87 FR 1554, 1579 (Jan. 11, 2022).
    After considering these comments, DOE proposed in the January 2022 
NOPR to add provisions to appendix E to provide further direction for 
achieving an input rate that is 2 percent of the nameplate 
value specified by the manufacturer. 87 FR 1554, 1579 (Jan. 11, 2022). 
Specifically, DOE proposed to modify section 5.2.3 of appendix E to 
require that the following steps be taken to achieve an input rate that 
is 2 percent of the nameplate value specified by the 
manufacturer:
    (1) Attempt to increase or decrease the gas outlet pressure within 
10 percent of the value specified on the nameplate to 
achieve the nameplate input (within 2 percent).
    (2) If the fuel input rate is still not within 2 
percent of the nameplate input, increase or decrease the gas supply 
pressure within the range specified on the nameplate.
    (3) If the measured fuel input rate is still not within 2 percent of the certified rated input, modify the gas inlet 
orifice as required to achieve a fuel input rate that is 2 
percent of the nameplate input rate.

Id.
    Regarding commenters' suggestion to check for leaks as an 
additional step in the process, DOE noted that gas leak detection 
should be part of a test laboratory's normal operating procedures, and, 
therefore, detection does not require specification within DOE's test 
procedures. 87 FR 1554, 1579 (Jan. 11, 2022). DOE also explained that 
the purpose of adjusting the orifice during testing is to ensure that 
the performance of the water heater is representative of performance at 
the Btu rating specified by the manufacturer on the product's 
nameplate, which informs

[[Page 40435]]

the field installation conditions. Allowing for adjustment of the 
orifice reduces test burden and improves repeatability by providing 
test laboratories with a last resort to maintain the hourly Btu rating 
as specified by the manufacturer. Further, DOE noted that the proposal 
that the orifice be modified would occur only after other options have 
been exhausted. Lastly, DOE proposed that should a unit fail to achieve 
an input within the 2 percent tolerance, DOE would continue testing 
with the measured input value as opposed to the rated value (i.e., the 
fuel input rate found via testing would be used for the purpose of 
determining compliance). 87 FR 1554, 1579-1580 (Jan. 11, 2022).
    In response to DOE's proposals on this topic in the January 2022 
NOPR, AHRI agreed with the Department's proposal to first adjust the 
manifold pressure and then modify the orifice if an input rate within 2 
percent of the nameplate input rating is not achieved. (AHRI, No. 40 at 
pp. 1-2)
    Rheem, AHRI, and BWC commented that if the unit cannot reach input 
rates within 2 percent of the nameplate rate, the unit is 
likely faulty, and the test results should not be accepted. (Rheem, No. 
31 at pp. 2-3; AHRI, No. 40 at pp. 1-2; BWC, No. 33 at p. 8) AHRI 
suggested that if this occurs, the manufacturer should be contacted. 
AHRI also stated that laboratory testing should only be performed by 
qualified laboratory personnel, adding that the architecture of oil-
fired water heaters also introduces additional complexity for these 
products. (AHRI, No. 40 at p. 2) BWC also commented that last-resort 
orifice adjustments should only be performed by qualified laboratory 
personnel, and indicated that DOE may wish to reference language in 
Section A1.3.2.1.10 of the AHRI Residential Water Heater Operations 
Manual.\51\ (BWC, No. 33 at p. 7)
---------------------------------------------------------------------------

    \51\ AHRI maintains an Operations Manual for Residential Water 
Heater Certification Program (AHRI Residential Water Heaters 
Operations Manual), which addresses how testing will be done in the 
AHRI certification program. Section A1.3.2.1.10 of the January 2022 
edition of the AHRI Operations Manual for its Residential Water 
Heaters states: ``If adjusting the manifold pressure does not 
achieve the rated input, the operator shall re-orifice the unit 
using an alternate orifice supplied by the manufacturer. [Note: 
Manufacturers are to supply test facility with a selection of 
orifices for use at the test facility. When a test unit is re-
orificed, the test facility will notify the manufacturer of the 
alternate orifice used, and the manufacturer shall re-supply the 
test facility with a replacement orifice.'' See: www.ahrinet.org/Portals/OM/RWH_OM.pdf. (Last accessed July 21, 2022.)
---------------------------------------------------------------------------

    In response to these comments, DOE agrees with commenters that 
testing should generally be performed at accredited laboratory 
institutions by qualified personnel. In response to BWC's suggestion 
that DOE reference section A1.3.2.1.10 of the AHRI Residential Water 
Heater Operations Manual, DOE notes that the amendments to section 
5.2.3 of appendix E are consistent with the instructions in the AHRI 
Residential Water Heater Operations Manual in that they both require a 
modification to the orifice, with the AHRI Operations Manual requiring 
the testing laboratory to ``re-orifice'' the unit and the language DOE 
is adopting requiring the test agency to ``modify'' the orifice. The 
finalized amendment would provide a more flexible approach than the 
language of section A1.3.2.1.10 of the AHRI Residential Water Heater 
Operations Manual by not requiring involvement by the water heater 
manufacturer in any modifications to the orifice. DOE notes that a unit 
not achieving the nameplate input rate within 2 percent 
could represent a malfunctioning unit or a broader issue in the design 
of the model. Under the proposed test approach, such models would be 
tested and evaluated for compliance based on its actual performance.
    With regards to oil-fired water heaters, the amended section 5.2.3 
provisions to appendix E reference the fuel oil supply requirements in 
section 2.7.4 of appendix E, which provide adequate direction for the 
adjustment.
    After evaluating these comments, DOE is adopting modifications to 
appendix E and 10 CFR 429.134 concerning input rate provisions as 
proposed in the January 2022 NOPR and for the reasons previously 
stated.
4. Ambient Test Condition Tolerances
    Section 2.2 of appendix E specifies maintaining the ambient air 
temperature between 65.0 [deg]F and 70.0 [deg]F (18.3 [deg]C and 21.1 
[deg]C) on a continuous basis for all types of consumer water heaters 
(and residential-duty commercial water heaters) other than heat pump 
water heaters. For heat pump water heaters, the dry-bulb (ambient air) 
temperature must be maintained between 67.5 [deg]F 1 [deg]F 
(19.7 [deg]C 0.6 [deg]C), and the relative humidity must be 
maintained at 50 percent 2 percent throughout the test. 
Appendix E does not specify a relative humidity tolerance for non-heat 
pump water heaters. Similar to the supply water temperature discussed 
previously, a brief measurement of air temperature or relative humidity 
that is only minimally outside of the test tolerance would invalidate a 
test, but likely would have a negligible effect on the results of the 
test, as the total time out of tolerance would be insignificant 
compared to the total time of the test. In the April 2020 RFI, DOE 
requested feedback on whether the tolerances for ambient air 
temperature and relative humidity are difficult to maintain at the 
start of a draw, and if so, whether DOE should consider relaxing these 
requirements at the start of a draw and to what extent. 85 FR 21104, 
21112 (April 16, 2020).
    After considering comments received on the April 2020 RFI, DOE 
proposed in the January 2022 NOPR to change the ambient temperature 
requirement for non-heat pump water heaters to an average of 67.5 
[deg]F  2.5 [deg]F, with a maximum deviation of 67.5 [deg]F 
 5 [deg]F, as opposed to only a maximum deviation of 67.5 
[deg]F  2.5 [deg]F as currently specified in the test 
procedure. 87 FR 1554, 1578 (Jan. 11, 2022). DOE reasoned that such a 
change could, if adopted, reduce the need to re-run tests in instances 
in which the results of the invalid test and the valid test would not 
differ significantly, and, therefore, reduce test burden. Id. DOE also 
noted that through a review of its available test data, DOE found that 
short fluctuations in ambient temperature have little to no effect on 
the test results of non-heat pump water heaters. Id.
    For heat pump water heaters, DOE proposed in the January 2022 NOPR 
to change the dry-bulb temperature requirement for heat pump water 
heaters to an average of 67.5 [deg]F  1 [deg]F during 
recoveries and an average of 67.5 [deg]F  2.5 [deg]F when 
not recovering, with a maximum deviation of 67.5 [deg]F  5 
[deg]F, as opposed to only a maximum deviation of 67.5 [deg]F  1 [deg]F as currently specified in the test procedure. Id. DOE 
reasoned that this proposed change would maintain the stringency of the 
dry-bulb temperature requirement while allowing for short deviations 
from the targeted dry-bulb temperature range, which would reduce the 
need to re-run tests in instances in which the results of the invalid 
test and the valid test would not differ significantly, and, therefore, 
reduce test burden. Id.
    For heat pump water heaters, DOE also proposed in the January 2022 
NOPR to increase the absolute relative humidity tolerance from 2 percent to 5 percent across the entire test, with 
the average relative humidity between 50 percent 2 percent 
during recoveries. 87 FR 1554, 1578 (Jan. 11, 2022). DOE reasoned that 
this change, if adopted, would reduce test burden by reducing the need 
to re-run tests in instances in which the results of the invalid test 
and the valid test would not differ significantly. Id.
    As noted, the currently applicable appendix E does not specify a 
relative

[[Page 40436]]

humidity tolerance for non-heat pump water heaters. In the January 2022 
NOPR, DOE explained that (as initially described in the April 2020 
RFI), DOE conducted exploratory testing to investigate the effect of 
relative humidity on the measured UEF values of two consumer gas-fired 
instantaneous water heaters that are flow-activated and have less than 
2 gallons of storage volume, one using non-condensing technology and 
the other using condensing technology. 87 FR 1554, 1578 (Jan. 11, 
2022). For each model, testing was performed at a relative humidity of 
50 percent and at a relative humidity of 80 percent, and DOE found that 
increasing relative humidity from 50 percent to 80 percent resulted in 
a maximum change in UEF for the non-condensing and condensing models of 
0.011 and 0.015, respectively. DOE noted that UEF is reported to the 
nearest 0.01 (see 10 CFR 429.17(b)(2)), and, thus, a change in UEF on 
the order of 0.01 to 0.02 as suggested by DOE's test results could be 
considered as substantively impacting the test results. However, DOE 
did not propose to adopt a tolerance on relative humidity in the 
January 2022 NOPR, noting that it was still examining this issue. DOE 
requested further comment and test data on whether a relative humidity 
requirement should be added to appendix E for non-heat pump water 
heaters. Id.
    In response to the proposals made in the January 2022 NOPR 
concerning ambient air temperature and relative humidity tolerances, 
AHRI indicated its support of DOE's proposals to reduce test burden; 
specifically, AHRI supported increasing test tolerances for ambient 
temperature and relative humidity. (AHRI, Jan. 27, 2022 Public Meeting 
Transcript, No. 27 at p. 40) NEEA and CA IOUs suggested that DOE should 
specify a relative humidity level of 50 percent  5 percent 
for all water heater types as was proposed for heat pump water heaters 
in the January 2022 NOPR, which the commenters argued would reduce test 
burden and ensure that results are comparable, repeatable, and 
representative across all products and technologies. (NEEA, No. 30 at 
pp. 1-2; CA IOUs, No. 36 at pp. 3-4)
    BWC, however, anticipated difficulty maintaining even the proposed 
5 percent tolerance during compressor cycling for electric 
heat pump water heaters. BWC also argued that establishing a relative 
humidity tolerance when testing water heaters other than heat pump 
water heaters is unnecessary after observing low impact on UEF rating 
during its testing of a gas instantaneous water heater at both 20 
percent relative humidity and 100 percent relative humidity. (BWC, No. 
33 at p. 7) In response to BWC's comments, DOE notes that BWC has not 
provided, nor is DOE aware of, any data suggesting that a 5 
percent relative humidity tolerance would be difficult to maintain for 
heat pump water heaters.
    After considering comments on the January 2022 NOPR, DOE is 
adopting the changes to ambient air temperature and relative humidity 
tolerances as proposed. Regarding the recommendation that DOE specify a 
relative humidity level of 50 percent  5 percent for all 
water heater types, DOE finds that it does not have adequate test data 
to make such a change at this time, but DOE will continue to further 
investigate this issue.
5. Electrical Supply Voltage Tolerances
    For all water heaters, section 2.7.1 of the currently applicable 
appendix E specifies maintaining the electrical supply voltage within 
1 percent of the center of the voltage range specified by 
the manufacturer. In the April 2020 RFI, DOE requested feedback on 
whether the tolerances for electrical supply voltage are difficult to 
maintain at the start of a draw, and if so, whether DOE should consider 
relaxing these requirements at the start of a draw and to what extent. 
85 FR 21104, 21112 (April 16, 2020).
    In the January 2022 NOPR, after considering comments received in 
response to the April 2020 RFI, DOE proposed to increase the electrical 
supply voltage tolerance from 1 percent on a continuous 
basis to 2 percent on a continuous basis. 87 FR 1554, 1577 
(Jan. 11, 2022). DOE also proposed to add clarification that this 
tolerance is only applicable beginning 5 seconds after the start of a 
recovery to 5 seconds before the end of a recovery (i.e., only when the 
water heater is undergoing a recovery). Id. DOE reasoned that these 
proposed changes could reduce test burden by reducing the need to re-
run tests while maintaining the representativeness of the test 
procedure. Id.
    In response to these proposed changes, DOE received comment from 
BWC supporting the proposal to increase the tolerance for electric 
supply voltage. (BWC, No. 33 at p. 7)
    DOE has thus determined that the proposed changes to sections 2.7.1 
and 3.7 of appendix E concerning electric supply voltage tolerance are 
appropriate and is adopting them in this final rule for the reasons 
previously stated.
6. Flow Rate Tolerances
    Section 5.4.2 of appendix E, Test Sequence for Water Heaters with 
Rated Storage Volumes Greater Than or Equal to 2 Gallons, provides that 
all draws during the 24-hour simulated-use test must be made at the 
flow rates specified in the applicable draw pattern table in section 
5.5 of this appendix, within a tolerance of 0.25 gallons 
per minute (0.9 liters per minute). Section 5.4.3 of 
appendix E, Test Sequence for Water Heaters with Rated Storage Volume 
Less Than 2 Gallons, currently does not provide explicit instruction 
for the tolerance on the flow rate.
    Within the proposed amendments to the regulatory text provided in 
the January 2022 NOPR, DOE included a proposed amendment to section 
5.4.3 of appendix E to specify that flow rates for water heaters with 
rated storage volume less than 2 gallons must be maintained within a 
tolerance of 0.25 gallons per minute (0.9 
liters per minute). 87 FR 1554, 1603 (Jan. 11, 2022). Because this 
proposed change was not addressed explicitly in the preamble to the 
January 2022 NOPR, DOE raised this issue again in the July 2022 SNOPR. 
87 FR 42270, 42274 (July 14, 2022).
    However, as discussed in the July 2022 SNOPR, there are models with 
Max GPM delivery capacities at or below 1.0 gallon per minute, and for 
these products, the flow rate used during draws must be the Max GPM 
flow rate. A flow rate tolerance of 0.25 gallons per minute 
would be too wide for products with Max GPM flow rates as low as 0.20 
gallons per minute. Because the flow rate tolerance represents 25 
percent of the flow rate at 1.0 gallon per minute, DOE proposed another 
amendment to section 5.4.3 of appendix E in the July 2022 SNOR to 
specify that for water heaters with a rated Max GPM of less than 1 
gallon per minute, the flow rate tolerance shall be 25 
percent of the rated Max GPM. DOE reasoned that for such products, a 
flow rate tolerance 25 percent of the rated Max GPM would 
represent the same level of variation (on a percentage basis) as for 
products rated at 1.0 gallon per minute and subject to a tolerance of 
0.25 gallon per minute. DOE noted that third-party 
laboratories are currently technically capable of implementing this 
methodology based on DOE's own test data. 87 FR 42270, 42274 (July 14, 
2022).
    In response to the July 2022 SNOPR, ASAP, ACEEE, and NRDC expressed 
support for DOE's proposal to specify the flow rate tolerance 
requirements for water heaters with a rated storage volume under 2 
gallons. (ASAP, ACEEE, and NRDC, No. 54 at p. 1) BWC expressed they had 
not had adequate time to conduct testing in order to determine the 
impact of DOE's proposed

[[Page 40437]]

establishment of a 25 percent of maximum GPM threshold, and 
as a result, the company had no further comments on that proposal. 
(BWC, No. 48 at p. 2)
    AHRI, A.O. Smith, and Rheem offered a few potential revisions to 
the proposal. AHRI requested that DOE set a minimum tolerance of 0.1 gpm for the 24-hour simulated-use test for models with 
maximum flow rates less than 1 gpm because the proposed 25 
percent tolerance may be difficult to meet for some models. (AHRI, No. 
55 at p. 2) A.O. Smith stated that the proposed flow rate tolerances 
for the 24-hour simulated-use test for water heaters with a rated 
storage volume less than 2 gallons would require manufacturers to 
invest in more precise equipment and may also easily invalidate results 
for units with low Max GPM values. Accordingly, A.O. Smith requested 
that DOE adopt the proposed flow rate tolerance from the NOPR, rather 
than the SNOPR. (A.O. Smith, No. 51 at pp. 2-3) Rheem indicated that 
the proposed flow rate tolerance of 25 percent of Max GPM may be too 
low for water heaters with very low max GPM and recommended that DOE 
change the tolerance to the maximum between that value and 0.1 gpm. Rheem also recommended that all flow rate tolerances be 
calculated based on the average of the flow rate over the entire draw, 
so as to help reduce the number of invalid tests. (Rheem, No. 47 at p. 
2)
    As discussed previously, the lowest Max GPM certified to DOE is 
currently 0.2 gpm, and DOE's amended test procedure must provide a 
reproducible and repeatable method for testing products with such low 
flow rates. DOE has determined that a tolerance of 0.1 gpm 
could offer too much variability in test results for products rated 
with such low flow rates. Specifically, a tolerance this wide would 
represent 50 percent of the flow rate of this kind of water 
heater, and because the temperature rise through the water heater is 
inversely related to the flow rate when the water heater is constantly 
firing at its maximum input rate, this variation in flow rate can cause 
the temperature rise to potentially double. As stated, DOE is aware 
that third-party laboratories are equipped with instrumentation to 
measure flow rates within the tolerance level proposed in the July 2022 
SNOPR.
    DOE did not receive any test data in response to the July 2022 
SNOPR indicating that manufacturers or third party test laboratories 
would not be able to meet the tolerances proposed in the July 2022 
SNOPR. Furthermore, DOE has concluded that a 0.1 gpm tolerance is too 
large for the lowest flow rate models currently on the market (0.2 gpm) 
and would be even more problematic if models with flow rates below 0.2 
gpm are introduced in the future. As such, in this final rule, DOE is 
adopting the flow rate tolerance amendments to sections 5.4.2 and 5.4.3 
of appendix E, as proposed in the July 2022 SNOPR.
7. Optional Test Conditions for Heat Pump Water Heaters
    In the course of this rulemaking, DOE has received numerous 
comments from stakeholders requesting that DOE consider allowing 
manufacturers to optionally rate heat pump water heaters to test 
conditions other than those currently specified in appendix E, which 
are intended to be representative of national average water and air 
temperatures. Commenters noted that heat pump operation is dependent 
upon the surrounding ambient air temperatures,\52\ and that there would 
be significant value to providing consumers, installers, and utilities 
with efficiency representations that are closer to the conditions for 
particular climates. See 87 FR 1554, 1580 (Jan. 11, 2022) and 87 FR 
42270, 42275-42276 (July 14, 2022).
---------------------------------------------------------------------------

    \52\ Because heat pumps ``transfer thermal energy from one 
temperature level to a higher temperature level'' (see 42 U.S.C. 
6291(27)(C) and 10 CFR 430.2), the energy efficiency is dependent 
upon the difference between temperatures that must be overcome by 
the heat pump cycle. As discussed in section III.A.2 of this 
document, heat pump water heaters are typically air-source, i.e., 
these products source heat from surrounding air and transfer it to 
domestic hot water. Therefore, lower ambient air temperatures, such 
as those experienced in colder climates or due to seasonal 
differences, would result in lower efficiencies.
---------------------------------------------------------------------------

    For example, Lutz commented that a single inlet water temperature 
may not be representative for all cases because this may vary by 
geographical location, and, furthermore, that taking this into account 
is even more important for split-system heat pump water heaters with an 
outdoor unit. (Lutz, No. 35 at p. 1) NEEA argued that, because heat 
pump water heater performance can be affected by variations in ambient 
conditions, DOE should clarify what manufacturers can report about a 
unit's performance at conditions other than those required by the test 
procedure. NEEA added that information regarding delivery capacity and 
sizing guidance would be important for installers. (NEEA, No. 30 at p. 
3)
    In the January 2022 NOPR, DOE did not propose to allow for optional 
(voluntary) representations of heat pump water heater efficiencies at 
non-standard temperatures because there was not enough information at 
the time to identify the most representative alternate test conditions 
(e.g., regional conditions). 87 FR 1554, 1580 (Jan. 11, 2022). However, 
commenters on the July 2022 SNOPR identified the NEEA Advanced Water 
Heating Specification (currently at version 8.0, AWHS v8.0) provides 
multiple conditions which manufacturers are providing ratings at. 87 FR 
42270, 42775-42276 (July 14, 2022). Consequentially, DOE revisited the 
NEEA Advanced Water Heating Specification to determine how the test 
conditions specified in that document might be applied for optional 
representations in the DOE test procedure.
    Section 2.2 of appendix E currently specifies that the ambient air 
temperature shall be maintained between 65.0 [deg]F and 70.0 [deg]F 
(18.3 [deg]C and 21.1 [deg]C) on a continuous basis during the test. 
Additionally, for heat pump water heaters, that test procedure 
provision provides that the dry-bulb temperature shall be maintained at 
67.5 [deg]F  1 [deg]F (19.7 [deg]C  0.6 [deg]C) 
and that the relative humidity shall be maintained at 50 percent  2 percent throughout the test. EPCA requires that the DOE test 
procedure must be reasonably designed to produce test results which 
measure energy efficiency during a representative average use cycle or 
period of use. (42 U.S.C. 6293(b)(3)) While the test conditions in the 
current appendix E test procedure must remain representative for the 
nation as a whole, in the July 2022 SNOPR, DOE tentatively determined 
that comments from interested parties have demonstrated that allowing 
additional representations of efficiency at alternative ambient 
conditions could provide consumers with additional information about 
the expected performance of heat pump water heaters at conditions that 
are representative of their specific installation circumstances. For 
other types of covered products and equipment, DOE has adopted optional 
metrics for voluntary representations where it was determined that the 
primary efficiency metric would not be representative for certain 
installation conditions common for the product or equipment.\53\ As 
discussed in the July

[[Page 40438]]

2022 SNOPR, depending on the installation location (e.g., whether the 
water heater is installed in an unconditioned space such as a garage or 
attic), the ambient conditions may vary significantly from the 
conditions in the DOE test method, thereby resulting in significantly 
different performance for heat pump water heater products. Thus, DOE 
reversed its position and tentatively determined to allow for certain 
optional representations for additional ambient conditions. 87 FR 
42270, 42275-42276 (July 14, 2022).
---------------------------------------------------------------------------

    \53\ For example, on July 27, 2022, DOE published a final rule 
in the Federal Register pertaining to test procedures for direct-
expansion dedicated outdoor air systems, including provisions for 
optional representations of energy efficiency when the equipment is 
installed in applications where inlet water conditions are expected 
to deviate substantially from standard conditions. See 10 CFR part 
431, subpart F, appendix B, section 2.2.3(d) as established by that 
final rule. 87 FR 45164, 45201 (July 27, 2022).
---------------------------------------------------------------------------

    AWHS v8.0 was published by NEEA on March 1, 2022. Though early 
editions of the AWHS focused primarily on providing more representative 
performance metrics for heat pump water heaters in cold climates, the 
latest editions are now more broadly focused on providing 
representative performance metrics for heat pump water heaters across 
all climates. Performance metrics in the AWHS are generally calculated 
by measuring energy efficiency at multiple (two or more) ambient test 
conditions, linearly interpolating between the test results, and 
finally calculating an ambient temperature-weighted efficiency metric 
using temperature bin data. The metric is a cold climate efficiency 
(CCE) rating for integrated heat pump water heaters installed in semi-
conditioned spaces (i.e., garage, basement) and a seasonal coefficient 
of performance (SCOP) for split-system heat pump water heaters (where 
the heat pump is separated from the storage tank and located outdoors). 
DOE tentatively determined in the July 2022 SNOPR that adopting the 
test conditions in AWHS v8.0 would not significantly increase test 
burden for manufacturers who choose to provide these ratings, because 
manufacturers are already providing representations of CCE and SCOP to 
NEEA's Qualified Products List.\54\ The test conditions in AWHS v8.0 
differ from the standard conditions in appendix E in terms of inlet 
water temperature, ambient dry-bulb temperatures, and ambient relative 
humidity. A detailed discussion of these conditions was provided in the 
July 2022 SNOPR. 87 FR 42270, 42276 (July 14, 2022).
---------------------------------------------------------------------------

    \54\ Available at: neea.org/img/documents/residential-unitary-HPWH-qualified-products-list.pdf (Last accessed on May 11, 2022).
---------------------------------------------------------------------------

    In the July 2022 SNOPR, DOE proposed to allow voluntary 
representations of a new metric, EX, analogous to UEF, at 
optional test conditions for heat pump water heaters. The subscript 
``X'' would be used to denote the set of conditions being used, and 
these voluntary representations of EX would not be 
integrated together to form a seasonal efficiency metric--in contrast 
to the methodology in AWHS v8.0. DOE's proposal intended to eliminate 
any reduction in representativeness caused by assumptions in climate 
weighting factors. Without substantial additional data, DOE tentatively 
determined that it would not be able to evaluate whether or not the 
weighting factors in AWHS v8.0 (used to create a weighted average of 
the results at various test conditions together into one metric, CCE or 
SCOP) are representative of climates in the United States, and, thus, 
DOE proposed to allow for the use of standalone EX 
representations only in a way that it is clear to a consumer what test 
conditions were used in determining the rating. 87 FR 42270, 42276-
42277 (July 14, 2022).
    In response to the July 2022 SNOPR, ASAP, ACEEE, and NRDC expressed 
support for DOE's proposal to adopt optional test conditions needed for 
calculating climate-specific efficiencies. (ASAP, ACEEE, and NRDC, No. 
54 at p. 2) A.O. Smith acknowledged that optional efficiency ratings 
may have consumer utility and stated that additional measures of 
efficiency may assist with increasing market adoption of heat pump 
water heaters. (A.O. Smith, No. 51 at pp. 3-4) The CA IOUs supported 
DOE's tentative determination to allow optional efficiency 
representations at multiple test conditions for heat pump water 
heaters, stating that this change will help consumers choose the heat 
pump water heater that best suits their needs and will aid in the 
maturation and expansion of the heat pump water heater market. (CA 
IOUs, No. 52 at pp. 1-2)
    NEEA also supported DOE's proposal to allow for optional efficiency 
representations at alternative ambient conditions for heat pump water 
heaters but encouraged DOE not to limit condition representations based 
on the specific type of heat pump. NEEA stated that both split-system 
water heaters and heat pump-only water heaters can be designed for any 
combination of indoor, outdoor, and semi-conditioned space operation of 
the heat pump component. Therefore, NEEA suggested that DOE should not 
specify which metrics may be reported on the basis of heat pump type, 
as these additional representations would not add any burden to 
manufacturers because they are optional. (NEEA, No. 56 at pp. 1-2)
    A.O. Smith requested that DOE clarify whether manufacturers may 
represent optional metrics as consistent with appendix E. (A.O. Smith, 
No. 51 at pp. 3-4)
    In response to NEEA's comment, DOE acknowledges that split-system 
and heat pump-only water heaters may be installed in a variety of 
configurations which can vary the location of components. For example, 
a heat pump module (comprised of the compressor, evaporator, and 
expansion devices) could be installed either outdoors or in a separate 
room indoors. Therefore, DOE has updated the table of optional test 
conditions in section 2.8 of appendix E to reflect this fact by 
allowing split-system and heat pump-only water heaters to be tested at 
the conditions specified for any EX. In response to NEEA and 
A.O. Smith, DOE notes that manufacturers will be able to represent 
optional metrics as specified in the amended appendix E.
    Rheem stated that the Code of Federal Regulations only allows 
voluntary ratings for distribution transformers and commercial prerinse 
spray valves. Rheem also stated that the 24-hour simulated-use test for 
water heaters is more complex and very different from those specified 
for these other types of equipment which, according to Rheem, have test 
procedures that easily handle testing at alternate conditions. (Rheem, 
No. 47 at pp. 2-3)
    In response to Rheem's comment, DOE notes that optional additional 
test conditions are being adopted in appendix E because industry has 
already demonstrated its desire for them through testing at specific 
conditions in compliance with NEEA Advanced Water Heating Specification 
v8.0. By amending appendix E to include these conditions, DOE is simply 
standardizing current industry practices. Because ratings at such 
conditions are voluntary, DOE anticipates that there would be no undue 
burden associated with adoption of such provisions in this final rule.
    DOE also notes that water heaters are used in a variety of 
conditions and are expected to operate at all times despite them. This 
sets water heaters apart as compared to what is expected of other 
products (e.g., air conditioners), which are only active and operate in 
response to specific conditions. Test procedures for these products 
already include a range of conditions, and, therefore, they do not 
require optional representations of performance. For these other types 
of products, the range of conditions experienced would be narrower and 
more predictable than the range of conditions experienced by heat pump 
water heaters,\55\ and, therefore, it is not

[[Page 40439]]

unduly burdensome to require testing at multiple conditions for these 
other types of products. The narrower range of air conditions also 
ensures that the results of testing are highly representative of the 
product's average performance. This is not the case for heat pump water 
heaters because of the many different installation configurations which 
are applicable to heat pump water heaters--for instance, some are 
located indoors, and some are located outdoors. Allowing testing at 
these conditions to be optional avoids burdening manufacturers with 
test conditions that may not apply to their products. Using a different 
metric (EX) for these conditions also ensures that these 
representations are not read as being valid for all consumer 
applications; instead, the representation is specific to the condition 
at which the water heater is being tested.
---------------------------------------------------------------------------

    \55\ For example, Table 11 in section 3.6.1 of appendix M1 to 
subpart B of 10 CFR part 430 provides the heating mode test 
conditions for central (space-conditioning) heat pumps having a 
single-speed compressor and a fixed-speed indoor blower. The range 
of temperatures at which the outdoor evaporator coil can be tested 
is from 5 [deg]F at the lowest to 47 [deg]F at the highest. Because 
a heat pump water heater would also be active during the summer 
months, DOE has determined that the representative range of outdoor 
ambient temperatures for a split-system heat pump water heater's 
outdoor evaporator coil could be from 5 [deg]F at the lowest to 95 
[deg]F at the highest.
---------------------------------------------------------------------------

    AHRI, BWC, and Rheem suggested that allowing optional ambient test 
conditions may increase manufacturer burden, arguing that they may 
eventually be driven by the market to conduct such testing. (AHRI, No. 
55 at p. 3; BWC, No. 48 at p. 2; Rheem, No. 47 at p. 3) BWC also stated 
that not all manufacturers are currently conducting testing per NEEA 
Advanced Water Heating Specification v8.0, and that DOE allowing 
optional testing based on its test conditions would cause significant 
burden. (BWC, No. 48 at p. 2) Rheem requested that DOE either adopt the 
position from the last test procedure rulemaking that requiring 
additional testing at alternate conditions is unduly burdensome or 
provide justification for why it is not. (Rheem, No. 47 at p. 3) AHRI 
indicated that third-party laboratories may not be equipped to perform 
the optional tests at additional ambient conditions because of how the 
test set-up differs from that used in the standard test and that large 
capital burdens would need to be incurred in order to comply. AHRI also 
expressed concern that DOE did not adequately solicit manufacturer and 
laboratory feedback on increased test burden due to the proposed 
optional additional ambient test conditions. (AHRI, No. 55 at p. 4) 
Rheem also stated that optional tests currently performed by 
manufacturers are not necessarily done to be in accordance with AWHS 
and that NEEA, an entity which is not a manufacturer, distributor, 
retailer, or private labeler, was not restricted from making 
representations of products based on testing which did not use the DOE 
test procedure. (Rheem, No. 47 at pp. 2-3)
    In response to these comments, DOE disagrees that optional testing 
will increase manufacturer burden for a number of reasons. First, as 
previously discussed in the July 2022 SNOPR, DOE is currently aware of 
17 water heater brands represented in the Qualified Products List for 
AWHS v8.0. Participation in NEEA's program using Advanced Water Heating 
Specification v8.0 requires manufacturers to submit their own test 
results at the prescribed test conditions; NEEA does not appear to 
perform testing on behalf of manufacturers, per its own 
documentation.\56\ Most importantly, DOE reiterates that this testing 
is ultimately optional, so a manufacturer may decline to undertake any 
additional testing. Consequently, DOE has concluded that allowing 
optional additional testing conditions will not increase burden for 
manufacturers.
---------------------------------------------------------------------------

    \56\ Steps in the process flow for NEEA's AWHS Qualified 
Products List can be found online at: neea.org/img/documents/qualified-products-process-flow.pdf (Last accessed on Sept. 10, 
2022).
---------------------------------------------------------------------------

    BWC claimed that DOE is not authorized under EPCA to allow 
manufacturers to have additional optional representations of 
performance and requested that DOE clarify its statutory authority. 
(BWC, No. 48 at p. 2) Rheem claimed that justifications for other 
products allowing optional additional ratings do not apply to consumer 
water heaters and stated that EPCA \57\ can be interpreted as 
prohibiting optional additional test conditions that are not in the 
test procedure.
---------------------------------------------------------------------------

    \57\ The commenter cited 42 U.S.C. 6293(c), ``Restriction on 
Certain Representations,'' of which subsection (1) prohibits 
representations not made in accordance with the currently applicable 
test procedure and subsection (2) prohibits representations not made 
in accordance with a new or amended test procedure 180 days after 
the adoption of that test procedure.
---------------------------------------------------------------------------

    In response to these comments, DOE finds BWC's and Rheem's 
interpretations of 42 U.S.C. 6293(c) to be misguided. The statute 
requires appliance efficiency testing and representations to be done in 
accordance with the DOE test procedure. DOE routinely incorporates by 
reference private sector testing methods into Federal test procedures, 
and nothing in the statute would prohibit adoption of optional test 
conditions as these commenters suggest. DOE notes that the optional 
conditions at which manufacturers may choose to test their products are 
specified as part of the AWHS v8.0 test procedure and are not left up 
to manufacturers to determine individually. Precisely by including 
these optional conditions and metrics in the appendix E test procedure, 
DOE is permitting manufacturers and other parties to make such 
representations to the public in the manner which the statute 
contemplates. EPCA requires that a uniform efficiency metric (i.e., 
UEF) be used to rate all water heaters; however, the addition of 
optional representations does not prevent manufacturers from making its 
mandatory UEF rating under the required conditions. By virtue of the 
new heat pump water heater testing and metric being optional, DOE would 
not enforce the required energy conservation standard based upon 
results of testing at optional test conditions. Permitting testing 
under the specified optional conditions may also serve another purpose. 
In a future rulemaking considering further amendments to the appendix E 
test procedure, DOE may consider adopting multiple ambient test 
conditions for certain types of water heaters, if data from testing at 
these additional conditions proves that this methodology yields results 
more representative of energy consumption over an average use cycle. 
Hence, allowing manufacturers to test and rate these optional 
conditions would allow more data to be collected for potential future 
amendments.
    AHRI requested that DOE provide any data justifying the proposal to 
include optional ambient test conditions to stakeholders. (AHRI, No. 55 
at pp. 2-3) BWC requested that DOE readopt its position that there is 
insufficient data to support optional additional ambient test 
conditions and to provide the data that caused DOE to make this 
proposal in the SNOPR. (BWC, No. 48 at p. 2)
    In response, DOE notes that NEEA's Qualified Products List \58\ 
indicates the climate-weighted average performance of heat pump water 
heaters as tested by manufacturers to the various conditions in AWHS 
v8.0. (This performance metric, ``cool climate efficiency,'' is a 
result of testing under the optional conditions which DOE is adopting 
in this final rule.) From the data points in NEEA's Qualified Products 
List, manufacturers demonstrate that heat pump water heaters are less 
energy-efficient at these additional conditions. For example, Tier 4 
products, which

[[Page 40440]]

range in UEF from 3.45 to 4.02 at DOE's required test conditions, have 
cool climate efficiencies ranging from 3.1 to 3.5. These ratings have 
been provided to NEEA by manufacturers conducting their own testing. 
While DOE is not adopting the cool climate efficiency metric (because 
it requires testing at all of the additional ambient conditions, and 
that would significantly increase burden for a manufacturer wanting to 
provide consumers with additional ratings), these cool climate 
efficiency ratings are an objective indication of how performance can 
be impacted by varying climatic conditions. By adopting EX 
optional ratings in appendix E, DOE expects to facilitate manufacturer 
testing and the generation of relevant data related to water heater 
performance at these additional conditions. Again, the standardized 
voluntary ratings could be considered in a future rulemaking to 
determine the representativeness of the current mandatory ambient 
conditions in appendix E.
---------------------------------------------------------------------------

    \58\ Available at: www.neea.org/img/documents/residential-unitary-HPWH-qualified-products-list.pdf (Last accessed on Sept. 18, 
2022).
---------------------------------------------------------------------------

    AHRI also stated that DOE has not provided evidence that NEEA's 
AWHS test conditions ensure repeatability and reproducibility and 
suggested that these requirements still apply even if the procedure is 
optional. (AHRI, No. 55 at p. 4)
    Repeatability refers to the quality of a test method which allows a 
laboratory to achieve the same results when a product is tested on more 
than one occasion. Reproducibility refers to the quality of a test 
method which allows one laboratory to reproduce the results obtained by 
another laboratory. Test tolerances and set-up requirements are 
essential to these parameters. As proposed in the July 2022 SNOPR and 
adopted in this final rule, the optional test conditions would be 
tested per the same tolerances and set-up requirements as the current 
UEF test procedure--simply at different temperatures. Utilization of 
this Federal testing framework makes it possible for DOE to ensure that 
the voluntary ratings of EX are repeatable and reproducible.
    AHRI stated that DOE has not provided references to other occasions 
when it has adopted optional metrics for voluntary representations for 
other products or equipment. (AHRI, No. 55 at p. 4) AHRI requested that 
DOE remove the proposal concerning optional additional ambient test 
conditions from this rulemaking and instead address it in a subsequent 
rulemaking for these products. (AHRI, No. 55 at p. 4)
    In response and as discussed earlier in this section, DOE has 
previously adopted optional metrics for voluntary representations where 
there was a clear industry precedent for these metrics and a consumer 
utility for having the additional performance information. Most 
recently, this was done for dedicated outdoor air systems (DOASes). For 
heat pump water heaters, there is a clear indication that industry 
wishes to provide consumers with these additional ratings because 
numerous product representations have been submitted by several 
manufacturers to NEEA for its Qualified Products List. DOE's amendment 
to officially adopt these supplemental test conditions into the 
appendix E test procedure ensures that when these representations are 
provided, they are done so based on a consistent test method.
    Rheem stated that it has not had enough time to evaluate DOE's 
proposal to allow optional additional test conditions. (Rheem, No. 47 
at p. 2) Rheem requested that DOE clarify the sampling, certification, 
and enforcement provisions for heat pump water heaters with alternate 
representations. (Rheem, No. 47 at p. 3)
    In response, DOE notes that it provided a three-week comment period 
on the limited set of issues presented in the July 2022 SNOPR, and 
other commenters were able to assess DOE's latest proposal and provide 
substantive comments during the time allotted. By virtue of 
EX being an optional metric for voluntary representations, 
DOE will not require certification of EX representations. 
Manufacturers who opt to determine Ex must apply the sampling 
requirements for determining UEF in order to ensure consistency in 
values provided to consumers.
    Rheem recommended that DOE fully evaluate the alternate conditions 
specified in AWHS before adopting them. (Rheem, No. 47 at p. 4) Rheem 
stated that it has not had time to fully evaluate the alternate test 
conditions and questions whether they adequately represent the entire 
Nation, or only represent the Northwest, as these test conditions were 
developed by NEEA. (Rheem, No. 47 at p. 4)
    To clarify, by allowing manufacturers to make separate 
EX representations for each set of test conditions, the 
voluntary representations, individually, are not designed to be 
representative of the entire United States. To do so would require 
these test conditions to be averaged together based on prevalence of 
climate conditions at a given location, and this aspect of NEEA's AWHS 
v8.0 is not being used in the appendix E optional representations. 
Instead, it is DOE's mandatory testing scenario--the determination of 
UEF through the standard rating conditions--that is intended to reflect 
average conditions for the Nation as a whole. DOE has evaluated the 
full set of test conditions NEEA specifies in AWHS v8.0 and has 
determined that these conditions are meant to cover the full range of 
operating conditions (temperature and humidity) possible across the 
United States. They are not meant to only represent the range of 
conditions possible in the Northwestern United States. The purpose of 
EX representations, as employed by DOE at appendix E, is to 
indicate performance at individual rating points, which, along with 
UEF, will provide additional information to consumers. Manufacturers 
will be permitted to make voluntary representations at any of the 
optional test conditions specified in appendix E.
    BWC stated that DOE's proposal to allow optional additional test 
conditions would confuse consumers and installers because they may not 
have the means to sufficiently assess environmental conditions where 
they live. (BWC, No. 48 at p. 3) In addition, BWC commented that 
allowing optional additional test conditions may cause scarcity of 
testing resources, thereby significantly increasing manufacturer 
burden. (BWC, No. 48 at p. 3)
    DOE disagrees with BWC's presumption that consumers and installers 
cannot assess environmental conditions. These parties may easily access 
a variety of sources of freely available weather data, such as 
information generated by the National Oceanic and Atmospheric 
Administration (NOAA) and the National Weather Service (NWS).\59\ \60\ 
In addition, installers of central air conditioning, central heat pump, 
and cool-climate heat pump units already have sufficient access to 
local environmental data required to install them. These data are the 
same data required for the installation of water heaters. Although DOE 
understands BWC's concern regarding limited testing resources, DOE once 
again reiterates that this testing is ultimately optional; 
manufacturers are not obligated to make capital investments or dedicate 
testing resources if it is not feasible. To the extent that optional 
testing would

[[Page 40441]]

utilize resources that would otherwise be used for mandatory testing, 
DOE notes that manufacturers would have the option of foregoing or 
delaying optional testing to accommodate mandatory testing since DOE is 
not requiring use of any of the optional test conditions. Furthermore, 
as manufacturers have already provided ratings to NEEA at these 
alternate conditions, DOE does not believe that officially adopting 
these test conditions would change overall available laboratory 
capacity, especially as manufacturers may opt to test these optional 
conditions in-house.
---------------------------------------------------------------------------

    \59\ The National Weather Service (NWS) maintains a Climate page 
on their website which provides past weather records and climate 
information for regions of the United States and its territories. 
This page is available at: www.weather.gov/wrh/climate. (Last 
accessed Sept. 28, 2022)
    \60\ The National Centers for Environmental Information (NCEI) 
maintains a Past Weather page with past weather data from weather 
stations around the world. This data is available for download in 
various file formats. This page is available at: www.ncei.noaa.gov/access/past-weather/. (Last accessed Sept. 28, 2022)
---------------------------------------------------------------------------

    ASAP, ACEEE, and NRDC requested that DOE clarify which optional 
test conditions would apply to split-system water heaters with an 
indoor heat pump component. (ASAP, ACEEE, and NRDC, No. 54 at p. 2) In 
response, DOE notes that the included optional test conditions are 
intended to be used at the discretion of the manufacturer. 
Manufacturers are free to use the conditions specified by the test 
points they believe are most similar to what their product may 
experience during operation. For example, a manufacturer of a split-
system heat pump water heater whose compressor and storage tank are 
located outdoors and indoors, respectively, may decide it would be 
beneficial to evaluate the product's performance at an outdoor ambient 
temperature of 34.0 [deg]F. In this case, the manufacturer would test 
the product using the conditions specified by the E34 
metric: outdoor dry-bulb temperature and relative humidity of 34.0 
[deg]F and 72 percent, respectively, indoor dry-bulb temperature and 
relative humidity of 67.5 [deg]F and 50 percent, respectively, and 
supply water temperature of 47.0 [deg]F.
    Rheem requested that DOE evaluate wider tolerance ranges for the 
alternate test conditions. Rheem also asked that DOE clarify whether 
relative humidity control is required for storage tanks during split-
system water heater tests, in which case, the commenter argued that two 
psychrometric chambers would be required. (Rheem, No. 47 at pp. 3-4)
    In response, DOE notes that the amendments being adopted for 
ambient condition tolerances during UEF testing would also apply to 
EX testing, hence allowing a similarly wider tolerance range 
to apply at all conditions. When testing a split-system heat pump water 
heater or heat pump water heater requiring a separate storage tank, the 
heat pump portion of the system shall be tested at the relative 
humidity conditions specified, and the storage tank can be tested at 
either the same conditions or the conditions specified in section 2.2.1 
of appendix E. Thus, the relative humidity control is not required for 
the storage tank during split-system water heater tests. This is 
discussed further in section III.D.1 of this document.
    Rheem requested that DOE remove ``heat pump only'' from the table 
of alternate test conditions because they are the same as the outdoor 
portion of a split-system water heater. (Rheem, No. 47 at p. 4)
    In response, DOE wishes to make clear that circulating heat pump 
water heaters (heat pump-only water heaters) and split-system water 
heaters are not identical. Circulating heat pump water heaters are 
instantaneous-type units, whereas split-system heat pump water heaters 
have a storage tank and are, overall, storage-type units. Both types of 
products may have the heat pump module located remotely from the 
storage tank, but still indoors. In light of this comment, DOE has 
modified the table of alternate test conditions to explicitly allow 
split-system and circulating heat pump water heaters to be tested at 
any of the conditions specified.

D. Test Set-Up and Installation

1. Split-System Heat Pump Water Heaters
    In section III.A.2 of this document, DOE discussed a new definition 
for this subset of heat pump water heaters. As established by this 
final rule, a ``split-system heat pump water heater'' means a heat 
pump-type water heater with an indoor storage tank and outdoor heat 
pump component. In considering such products, DOE had found that in a 
split-system heat pump, the heat pump part of the system is typically 
installed outdoors and, as a result, does not use the indoor ambient 
air for water heating directly. In the current appendix E test 
procedure, different ambient conditions are specified in appendix E for 
heat pump water heaters and non-heat pump water heaters, but there are 
no specific conditions for split-system heat pump water heaters.
    In the January 2022 NOPR, DOE proposed to specify that the heat 
pump part of the system shall be tested using the heat pump water 
heater dry-bulb temperature and relative humidity requirements, while 
the storage tank part of the system shall be tested using the non-heat 
pump water heater ambient temperature and relative humidity 
requirements. DOE noted that the required non-heat pump water heater 
ambient conditions can be met by keeping the entire system within the 
dry-bulb temperature and relative humidity requirements for heat pump 
water heaters (i.e., both parts of the system can be tested in the same 
psychrometric chamber). 87 FR 1554, 1583 (Jan. 11, 2022).
    On this topic, AHRI requested that DOE clarify whether the proposed 
testing requirements for split-system heat pump water heaters would 
mean testing would have to be carried out with the heat pump and 
storage tank in separate rooms. (AHRI, Jan, 27, 2022 Public Meeting 
Transcript, No. 27 at p. 42) NYSERDA indicated that DOE should 
collaborate with manufacturers to ensure that test conditions and set-
up for split-system heat pump water heaters are consistent, repeatable, 
and not burdensome. (NYSERDA, No. 32 at p. 4) BWC suggested that DOE 
should permit manufacturers and testing laboratories as much 
flexibility as possible when determining the testing locations of 
separate system components and not prevent test set-ups that can meet 
the specified conditions for both systems in the same room or area, if 
a manufacturer or test laboratory so chooses. (BWC, No. 33 at p. 9) 
Rheem requested clarification that the storage tank can be tested at 
the heat pump test conditions and still meet the requirements of 
appendix E. (Rheem, No. 31 at p. 3)
    To reiterate DOE's explanation in the January 2022 NOPR, if a 
single room, chamber, or area is capable of meeting the dry-bulb 
temperature and relative humidity requirements for heat pump water 
heaters, then, like integrated heat pump water heaters, split-system 
heat pump water heaters can be tested with both indoor and outdoor 
components in the same space. In response to NYSERDA, by adopting this 
approach, DOE is aligning with the methodology used already by industry 
when testing heat pump water heater products for other representations 
(such as the Qualified Products List for NEEA's AWHS v8.0), so 
consequently, DOE expects the results generated to be consistent, 
repeatable, and not unduly burdensome.
2. Mixing Valves
    As discussed in section III.E.1 of this final rule, there are 
certain water heater designs which raise the temperature of water 
stored in the tank significantly above the outlet water temperature, 
and these products are meant to be used with a mixing valve (which may 
or may not be provided with or built-in to the unit) so that the hot 
stored water can be tempered down to a more typical delivery 
temperature. The January 2022 NOPR noted that the installation 
instructions in section 4 of appendix E do not address cases when a 
separate

[[Page 40442]]

mixing valve should be installed. 87 FR 1554, 1580 (Jan. 11, 2022).
    The January 2022 NOPR proposed to incorporate instructions for 
separate mixing valve installations based on those found in the ENERGY 
STAR Test Method to Validate Demand Response for Connected Residential 
Water Heaters (ENERGY STAR Connected Test Method) (published on April 
5, 2021). This set-up requires installing the mixing valve in 
accordance with the water heater and mixing valve manufacturer's 
instructions. Absent instruction from the water heater or mixing valve 
manufacturer, the mixing valve is to be installed in the outlet water 
line, upstream of the outlet water temperature measurement location, 
with the cold water supplied from a tee installed in the inlet water 
line, downstream of the inlet water temperature measurement location 
(i.e., the mixing valve and cold water tee are installed within the 
inlet and outlet water temperature measurement locations). Section 4.1 
of the ENERGY STAR Connected Test Method further clarifies that if the 
liquid flow rate and/or mass measuring instrumentation is installed on 
the outlet side of the water heater, that it shall be installed after 
the mixing valve. 87 FR 1554, 1580 (Jan. 11, 2022).
    On July 18, 2022, EPA published the ENERGY STAR Connected 
Residential Water Heaters Test Method to Validate Demand Response, 
Version 1.2.\61\ The updated test method retains the same instructions 
for setting up mixing valves in section 4.1.
---------------------------------------------------------------------------

    \61\ Available at: www.energystar.gov/products/spec/residential_water_heaters_specification_version_5_0_pd (Last 
accessed on July 25, 2022).
---------------------------------------------------------------------------

    In response to the January 2022 NOPR, ASAP, ACEEE, and NCLC; AET; 
A.O. Smith; and the CA IOUs supported DOE's proposal to include 
instructions for the installation of a mixing valve. (ASAP, ACEEE, and 
NCLC, No. 34 at pp. 1-2; AET, No. 29 at p. 2; A.O. Smith, No. 37 at p. 
4; CA IOUs, No. 36 at p. 4) A.O. Smith also commented that, depending 
on the design, there may be additional steps that are required (e.g., 
independently adjusting the tank thermostat and the mixing valve 
settings to remain in default mode per the manufacturer's 
instructions), and, therefore, DOE should clarify the details of this 
procedure. (A.O. Smith, No. 37 at p. 4)
    In this final rule, DOE is adopting the proposed installation 
instructions for mixing valves as discussed in the January 2022 NOPR. 
To the extent that there may be additional steps required to maintain 
normal operation with the mixing valve installed per the manufacturer's 
specifications, these instructions would be heeded in accordance with 
section 4.3 of the amended appendix E test procedure. As described in 
section III.E.1 of this document, DOE is also providing an optional 
test method for high storage tank temperature operation, and this test 
method involves the installation of mixing valves for products which do 
not come so equipped.
3. Flow Meter Location
    The current test procedure does not specify where in the flow path 
the flow volume and density of water must be measured, and this allows 
for laboratory test set-ups to perform these measurements either on the 
cold/inlet side of the water heater or on the hot/outlet side. As 
discussed in this rulemaking, water mass calculations can account for 
the difference in the density of water at the inlet vs. the outlet 
(colder water at the inlet has a higher density); however, there could 
be cases when a measurement based on the inlet location could result in 
inaccurate mass calculations. Specifically, some of the mass of inlet 
water could, after being heated, expand out of the water heater into 
the expansion tank and be purged prior to a draw. Any ``expanded'' 
volume of water that is lost through the bypass (purge) line could be 
included in a volume measurement taken at the inlet, but not be 
included in a volume measurement taken at the outlet. 87 FR 1554, 1581 
(Jan. 11, 2022). The Department requested information and data 
regarding the issue of flow meter location (inlet vs. outlet) in the 
April 2020 RFI and the January 2022 NOPR. 85 FR 21104, 21113 (April 16, 
2020); 87 FR 1554, 1581 (Jan. 11, 2022).
    In response to the April 2020 RFI, four commenters either disagreed 
with requiring the flow meter to be located at the outlet or requested 
that DOE continue to allow facilities to choose the location, whereas 
two commenters stated that the flow rate should be measured at the 
outlet of the water heater, expressing concern that measuring at the 
inlet may be inaccurate. 87 FR 1554, 1581 (Jan. 11, 2022). The January 
2022 NOPR presented DOE's exploratory test data evaluating the effect 
of flow meter location on the water mass measurement (see Table III.2 
of the January 2022 NOPR). DOE's testing using Coriolis flow meters on 
both the inlet and outlet water lines indicated that more accurate 
measurements of the mass of water delivered are obtained when the flow 
meter is located in the outlet water line than when located on the 
inlet line, when both results were compared to a mass scale.\62\ In 
particular, the error in the UEF resulting from a mass measurement from 
a flow meter at the outlet ranged between 0.002 and 0.016, whereas the 
error in the UEF resulting from a mass measurement from a flow meter at 
the inlet ranged between 0.023 and 0.029, depending on the type of 
water heater (with DOE testing both gas-fired storage and gas-fired 
instantaneous water heaters). DOE also acknowledged that third party 
laboratories typically install a flow meter on the inlet side. However, 
DOE did not propose a change based on this limited set of test results, 
which only included one gas-fired storage water heater sample and one 
gas-fired instantaneous water heater sample, and stated that more test 
data are required. Id. at 87 FR1581-1582.
---------------------------------------------------------------------------

    \62\ Mass of water drawn from the water heater can either be 
directly measured using a mass scale, or it can be calculated by 
using a flow meter to measure the volume of water moved (and 
converted to mass using the density of the water). The mass scale 
approach represents the actual value of the mass of water drawn, 
against which the flow meter results can be compared.
---------------------------------------------------------------------------

    In response to the NOPR's request for information on this issue, 
AHRI stated that having the flow meter at the inlet of the water heater 
avoids having debris damage the flow meters (e.g., Teflon tape debris 
from the test rig can end up in the flow meter and cause damage). In 
addition, AHRI commented that placing the flow meter at the outlet may 
cause water mass calculation problems, because the temperature 
variation is greater at the outlet, and flow meters may not be designed 
to withstand these higher outlet water temperatures. Therefore, AHRI 
indicated it would support the option of installing a flow meter at the 
inlet. (AHRI, No. 40 at p. 2) Rheem once again noted that major third-
party testing laboratories have flow meters installed at the inlet of 
the water heater and that it is likely that all certified models have 
been tested with such a set-up. (Rheem, No. 31 at pp. 4-5) BWC 
commented that manufacturers should still have the option to install 
flow meters at the inlet to ensure accurate results and longevity of 
testing equipment, as well as to avoid manufacturer burden. 
Specifically, BWC indicated that manufacturers may have sophisticated 
set-ups with flow meters installed at the inlet, and there could be 
substantial burden with overhauling these set-ups. (BWC, No. 33 at p. 
8)
    Based on these comments, DOE has determined that a requirement for 
flow meters to be installed at the outlet may not only require re-
testing a large number of basic models but also

[[Page 40443]]

potentially degrade the reliability of the testing rig due to debris 
flowing downstream. Because there is a generally consensus among 
stakeholders who commented on this issue that it is necessary to retain 
the ability to install the flow meter at the inlet side, DOE is not 
amending appendix E to require measurement at the outlet side. Instead, 
DOE is maintaining its current provisions in sections 3 and 4 of 
appendix E, which allow for the flow meter to be installed on either 
the inlet or outlet side.
4. Separate Storage Tanks
    Some water heaters on the market require a volume of water, 
typically contained in either a storage tank (or tanks) or in a piping 
distribution system of sufficient volume, to operate. These products 
operate by circulating water stored either in the piping system or from 
a separate tank (or multiple separate tanks) to the water heater to be 
heated then back to the piping system or tank until hot water is 
needed. As discussed in section III.A.4.a of this document, DOE is 
adopting a definition for these products, which are termed 
``circulating water heaters.'' In the January 2022 NOPR, DOE identified 
two types of circulating water heater products that require a volume of 
water to operate--heat pump-only water heaters that require 
installation with a separate storage tank and circulating gas-fired 
instantaneous water heaters that require installation with a separate 
storage tank or a piping system of sufficient volume. 87 FR 1554, 1583-
1585 (Jan. 11, 2022). Circulating gas-fired instantaneous water heaters 
are distinct from other types of gas-fired instantaneous water heaters 
in that they are not designed to operate independent of a storage tank 
or hot water system, as other gas-fired instantaneous water heaters 
are. This applies generally to circulating water heaters; however, DOE 
has determined that there are no electric resistance or oil-fired 
circulating water heaters on the market today.
    The currently applicable appendix E test procedure does not have 
procedures in place to appropriately test circulating water heaters. In 
the January 2022 NOPR, DOE proposed to require that circulating water 
heaters be tested using an 80 gallon (1 gallon) unfired hot 
water storage tank (UFHWST) that meets the energy conservation 
standards for an unfired hot water storage tank at 10 CFR 431.110(a). 
87 FR 1554, 1583-1585 (Jan. 11, 2022).
    In response to the January 2022 NOPR, DOE received a number of 
comments regarding the separate storage tank requirements, primarily 
related to the 1 gallon tolerance, the representativeness 
of an 80-gallon unfired hot water storage tank, and the lack of a 
specification of an upper bound on thermal insulation for the unfired 
hot water storage tank. These comments were discussed in detail and 
addressed in the July 2022 SNOPR. Some commenters specifically 
recommended that DOE specify electric storage water heaters to be 
paired with heat pump-only water heaters. Commenters also raised 
questions as to whether or not the separate tanks to be used during 
testing may have back-up heating. For gas-fired circulating water 
heaters, commenters urged DOE to consider allowing multiple tank sizes 
to be used for testing rather than just the 80-gallon tank proposed in 
the January 2022 NOPR. 87 FR 42270, 42281-42283 (July 14, 2022).
    After considering the issues raised by commenters responding to the 
January 2022 NOPR, in the July 2022 SNOPR, DOE proposed several updates 
to its earlier proposals (in section 4.10 of appendix E) for testing 
circulating water heaters as initially presented in the January 2022 
NOPR. 87 FR 42270, 42282-42283 (July 14, 2022). These proposed 
modifications to DOE's initial proposal are set forth in the paragraphs 
that follow.
    After re-evaluating the market for heat-pump-only water heaters, 
DOE tentatively determined that testing such products with a 
conventional electric storage water (i.e., an electric water heater 
that uses only electric resistance heating elements) would be more 
representative than testing with an UFHWST. Therefore, DOE proposed 
that heat-pump-only water heaters be tested in the medium draw pattern 
using a 40-gallon traditional electric storage tank (i.e., that 
provides heat only with electric resistance heating elements) that has 
a UEF rating at the minimum required at 10 CFR 430.32(d). DOE chose a 
40-gallon tank in the medium draw pattern because that size and draw 
pattern combination has the highest number of models currently 
available on the market.\63\ DOE also proposed that, for heat pump-only 
water heaters, the test be carried out using a tank that does not 
``over-heat'' the stored water (i.e., Tmax,1 (maximum 
measured mean tank temperature after cut-out following the first draw 
of the 24-hour simulated-use test) must be less than or equal to 
Tdel,2 (average outlet water temperature during the 2nd draw 
of the 24-hour simulated-use test); see section III.E.1 of this 
document for more discussion of water heater ``over-heating''). This 
would ensure that the electric storage tanks are not overheating during 
the test, thereby ensuring consistency across tests. 87 FR 42270, 42282 
(July 14, 2022).
---------------------------------------------------------------------------

    \63\ See Figure 3A.2.8 of the Preliminary Analysis Technical 
Support Document for consumer water heaters (Docket No. EERE-2017-
BT-STD-0019- 0018).
---------------------------------------------------------------------------

    By contrast, DOE maintained its earlier proposal that a UFHWST be 
used for testing of circulating gas-fired water heaters, as those 
products are more likely to be installed with a UFHWST in the field. 
Therefore, DOE tentatively concluded that testing with an UFHWST would 
be representative for such units. 87 FR 42270, 42282 (July 14, 2022).
    In response to the January 2022 NOPR, some commenters suggested 
that DOE allow manufacturers to specify the storage tank used for 
testing. DOE noted that this approach could lead to additional test 
burden for third-party testing laboratories, which may need to acquire 
more than one storage tank if they are performing tests for multiple 
manufacturers, each of whom may specify a different storage tank for 
testing. In order to avoid creating the potential for additional test 
burden, DOE tentatively determined not to allow manufacturers to 
specify the electric storage water heater or unfired hot water storage 
tank used respectively for testing the heat pump-only or gas-fired 
instantaneous circulating water heaters. Additionally, DOE stated it 
would consider relevant amendments to certification and reporting 
requirements in a separate rulemaking. 87 FR 42270, 42282 (July 14, 
2022).
    After considering the comments regarding the tolerance on the 
storage tank initially proposed in the January 2022 NOPR, DOE 
tentatively determined in the July 2022 SNOPR that a wider tolerance 
would reduce potential testing burden while still providing 
representative and reproducible results. Specifically, DOE tentatively 
concluded that a 10-percent tolerance would increase flexibility for 
manufacturers by increasing the number of tanks that could be used for 
testing, while not materially impacting the UEF test results. 
Therefore, consistent with the recommendations provided by commenters, 
DOE proposed to adopt a 10 percent tolerance (10 percent, 
allowing products with rated storage volumes between 36 gallons and 44 
gallons) for the electric storage water heater used for testing heat-
pump-only water heaters. 87 FR 42270, 42282 (July 14, 2022).
    Additionally, after further review of the market for circulating 
gas-fired instantaneous water heaters and unfired

[[Page 40444]]

hot water storage tanks, DOE proposed in the July 2022 SNOPR to allow 
testing with a tank at any storage volume between 80- and 120-gallons. 
Based on further analysis, DOE tentatively determined that variations 
in the tank size should not significantly impact the result of the 
test. During a water draw, the internal tank temperature decreases as 
hot water exits the tank and is replenished by colder water entering 
the tank. Generally, different tank sizes will result in different 
rates of internal temperature decrease during a water draw (e.g., 
during a specified water draw, a smaller tank will generally experience 
a faster decrease in temperature compared to a larger tank). During a 
test, any potential differences in the tank water temperature due to 
the use of different size tanks would be accompanied by a corresponding 
proportional difference in burner on-time, such that the impact on 
measured efficiency (i.e., the ratio of energy output to energy input) 
would be negligible. DOE noted its recognition that a larger tank would 
likely have more standby losses than a smaller tank; however, DOE 
tentatively determined that the impact this would have on measure 
efficiency would also not be significant. 87 FR 42270, 42282-42283 
(July 14, 2022).
    DOE noted that providing a range of allowable tank volumes would 
reduce potential burden by providing manufacturers with more tank 
options, thereby allowing them to pair their circulating gas-fired 
instantaneous water heaters with an existing UFHWST model. This 
approach is also likely to be more representative of how the units 
would be installed in the field as opposed to testing with a custom-
made tank for testing or a competitor's tank that meets a specific 
volume requirement. 87 FR 42270, 42283 (July 14, 2022).
    In addition, after considering comments in response to the January 
2022 NOPR, DOE tentatively determined in the July 2022 SNOPR that the 
lack of an upper bound on the thermal insulation value for the UFHWST 
could lead to differences in measured efficiency that reflect 
differences in tank performance, rather than reflecting differences in 
water heater performance. Therefore, DOE tentatively determined that 
more specific constraints on tank performance are warranted to ensure 
more comparable test results across the subject water heater models. 
DOE proposed to require that UFHWSTs used for testing circulating gas-
fired instantaneous water heaters exactly meet the baseline energy 
conservation standard for UFHWSTs.\64\ 87 FR 42270, 42283 (July 14, 
2022). However, DOE did not include commenters' suggested 
specifications for other tank characteristics (such as the inlet and 
outlet connection locations, internal tank baffling, and inlet tube 
designs) for the UFHWST because, as explained in the July 2022 SNOPR, 
DOE tentatively determined that over-specifying the design of the 
UFHWST--given the impacts on the UEF rating are minimal--could result 
in a very narrow range of UFHWST models which could be used for testing 
circulating water heaters, thereby potentially introducing significant 
barriers to testing these products at third-party laboratories. In 
addition, DOE tentatively concluded that it lacked sufficient 
information regarding these specifications to do so. 87 FR 42270, 42283 
(July 14, 2022).
---------------------------------------------------------------------------

    \64\ Currently, baseline energy conservation standards for 
UFHWSTs require a thermal insulation of R-12.5. 10 CFR 431.110(a).
---------------------------------------------------------------------------

    Similarly, DOE proposed that the electric storage water heater used 
for testing heat-pump-only water heaters have a rated UEF corresponding 
to the minimum standard found at 10 CFR 430.32(d), thereby helping to 
ensure more comparable results.
    In summary, in the July 2022 SNOPR, DOE proposed to further amend 
the separate storage tank requirements proposed in the January 2022 
NOPR for heat pump-only and gas-fired circulating water heaters. DOE 
proposed that heat pump-only water heaters be tested with a 40-gallon 
(4 gallons) electric storage water heater that has a UEF 
value corresponding to the minimum standard for such products and that 
does not ``over-heat''; and that gas-fired circulating water heaters be 
tested with an 80-gallon to 120-gallon unfired hot water storage tank 
that is rated equal to the energy conservation standard for such 
equipment.
    In response to the July 2022 SNOPR, NEEA indicated support for 
DOE's revisions to the proposed test procedure for circulating water 
heaters. (NEEA, No. 56 at p. 2) A.O. Smith and the CA IOUs supported 
DOE's proposal requiring gas[hyphen]fired circulating water heaters to 
be tested using a UFHWST with a storage volume between 80 and 120 
gallons and an R[hyphen]value exactly at the minimum R[hyphen]value 
required at 10 CFR 431.110(a). (A.O. Smith, No. 51 at p. 8; CA IOUs, 
No. 52 at p. 6) The CA IOUs also indicated support for the revision to 
require heat pump circulating water heaters to use a 40-gallon electric 
resistance water heater meeting the minimum UEF requirements. (CA IOUs, 
No. 52 at p. 6)
    AHRI stated that allowing manufacturers to specify the storage tank 
used for testing circulating water heaters would not increase test 
burden for third-party laboratories because manufacturers would provide 
both the water heater and the storage tank it was designed to be used 
with to the laboratories. (AHRI, No. 55 at pp. 5-6) BWC suggested that 
the capacity range of 80 to 120 gallons for UFHWSTs used to test 
circulating water heaters is too wide to ensure consistent results, so, 
therefore, the commenter requested that DOE complete further testing to 
validate it. (BWC, No. 48 at p. 4)
    After considering these comments, DOE has concluded that providing 
a range of allowable tank volumes for use with circulating gas-fired 
instantaneous water heaters as described in the July 2022 SNOPR would 
reduce potential burden by providing manufacturers with more tank 
options, thereby allowing them to pair their circulating gas-fired 
instantaneous water heaters with an existing UFHWST model. This 
approach balances manufacturer burden (by allowing flexibility in the 
tank size) with ensuring reproducibility of test results (by limiting 
the options to a fixed range of sizes). In response to AHRI's comments, 
DOE notes that it is not adopting changes to the certification 
requirements in this final rule, and whether or not manufacturers may 
specify a specific model of UFHWST is an issue out of the scope of this 
test procedure rulemaking and will be addressed in a future rulemaking 
addressing certification requirements for consumer water heaters.
    As such, in this final rule, DOE is adopting the separate storage 
tank requirements for circulating gas-fired instantaneous water heaters 
as proposed in the July 2022 SNOPR. In response to BWC's comment, DOE 
understands that the choice of tank size may result in slightly 
different ratings for these products, and BWC seeks to determine how 
much variability in results there would be if testing were to be 
conducted with an 80-gallon UFHWST versus a 120-gallon UFHWST. However, 
the Department's approach is instead to permit manufacturers some 
flexibility in testing options so as to be able to tailor the tank 
pairing to the design or application intent of the circulating water 
heater, and to then subsequently account for the variation in ratings 
when setting amended standards for circulating water heaters by having 
the required UEF be a function of the effective volume. As discussed in 
section III.I of this document, compliance with the separate storage 
tank test method will not be required

[[Page 40445]]

until compliance with amended energy conservation standards is 
mandatory, if such standards are adopted. Additionally, section 
III.F.2.b of this document describes the use of the effective storage 
volume metric to be able to associate efficiency ratings to the storage 
tank size for circulating water heaters. This matter is discussed 
further in this section in response to other comments. In taking these 
steps, DOE can, in the ongoing standards rulemaking for consumer water 
heaters, propose and request comment on new energy conservation 
standards for circulating water heaters that are functions of the 
effective storage volume.
    SMTI requested that DOE widen the accepted volume range for 
electric storage tanks used to test separate heat pump-only water 
heaters based on the performance requirements of each product instead 
of requiring that all products be tested with a 40-gallon tank. (SMTI, 
No. 49 at p. 1) SMTI suggested that heat pump-only water heaters be 
tested with manufacturer-specified storage tanks, which the 
manufacturer would provide to third-party laboratories, and that a 40-
gallon tank be used if a specific storage tank is not specified. (SMTI, 
No. 49 at p. 2) A.O. Smith stated that there is insufficient data to 
conclude that the 40-gallon electric resistance water heater should be 
used for testing heat-pump-only or split-system water heaters and that 
a 50-gallon electric resistance water heater may be more representative 
based on manufacturer data. (A.O. Smith, No. 51 at p. 9) However, A.O. 
Smith did not provide any manufacturer data to support its claim that a 
50-gallon electric resistance water heater would be more 
representative.
    As described in the July 2022 SNOPR, DOE selected a 40-gallon tank 
in the medium draw pattern because that size and draw pattern 
combination has the highest number of models currently available on the 
market as observed in models currently certified to DOE's Compliance 
Certification Database (see Figure 3A.2.8 of Preliminary Analysis TSD). 
87 FR 42270, 42282 (July 14, 2022). This finding has not changed since 
the publication of the July 2022 SNOPR, and on this basis (because 
additional data were not provided by stakeholders), DOE has concluded 
that this tank size and draw pattern are the most representative choice 
to be paired with a heat pump-only water heater. In response to SMTI's 
request to widen the volume range, DOE has determined to adopt a volume 
tolerance of 5 gallons, as opposed to 10% (4 
gallons) which was proposed in the July 2022 SNOPR. This change is 
based on further inspection of the rated storage volumes of electric 
storage water heaters which have a nominal capacity of ``40 gallons'' 
as observed in models certified to DOE's Compliance Certification 
Database. As such, DOE does not expect the difference to be substantial 
in impacting energy efficiency results for circulating heat pump water 
heaters because the volume range covers products of the same nominal 
volume. As previously stated in response to a comment made by AHRI, DOE 
is allowing manufacturers to specify an effective storage volume for 
the tank rather than a specific model because any characteristics of 
the tank that would affect the efficiency rating of the circulating 
water heater during a test are accounted for in the volume and 
efficiency rating (in this case, UEF) of the tank.
    AHRI and BWC indicated that DOE's primary TSD for energy 
conservation standards for consumer water heaters suggests that the 40-
gallon electric resistance water heaters used to test heat-pump-only 
water heaters may be phased out by future DOE regulations. (AHRI, No. 
55 at p. 5; BWC, No. 48 at pp. 4-5) Rheem supported AHRI's comment on 
this issue. (Rheem, No. 47 at p. 5)
    In response, DOE notes that the current energy conservation 
standards rulemaking for consumer water heaters is still ongoing, and 
any preliminary results published as part of that rulemaking are 
neither final nor binding in any way. Consequently, it is not confirmed 
that electric resistance storage water heaters will be phased out. 
Nevertheless, to ensure there will be no confusion in the event such 
regulatory changes were to occur, DOE is removing the requirement that 
the storage tank use only electric resistance heating elements. 
Accordingly, the associated portion of section 4.10 of appendix E has 
been updated to read as follows:
    ``When testing a heat pump circulating water heater, the tank to be 
used for testing shall be an electric storage water heater that has a 
measured volume of 40 gallons (5 gallons), has a First-Hour 
Rating greater than or equal to 51 gallons and less than 75 gallons 
resulting in classification under the medium draw pattern, and has a 
rated UEF equal to the minimum UEF standard specified at 10 CFR 
430.32(d), rounded to the nearest 0.01. The operational mode of the 
heat pump circulating water heater and storage water heater paired 
system shall be set in accordance with section 5.1.1 of this 
appendix.''
    In its comments on the July 2022 SNOPR, A.O. Smith supported 
ensuring that non[hyphen]unitary heat pump water heaters \65\ intended 
for use in a single[hyphen]family home or an individual dwelling unit 
that need to be paired with a separate storage tank are tested and 
certified to the Department consistent with appendix E. (A.O. Smith, 
No. 51 at pp. 8-9) A.O. Smith also requested that DOE clearly define 
the test apparatus for heat pump circulating water heaters. (A.O. 
Smith, No. 51 at p. 9)
---------------------------------------------------------------------------

    \65\ DOE understands ``non-unitary heat pump water heaters'' to 
refer to products which consist of a heat pump system to heat water 
but are not packaged with the rest of the components used in 
domestic hot water production (i.e., a hot water storage tank). 
These products are considered circulating heat pump water heaters in 
this rulemaking.
---------------------------------------------------------------------------

    In response to concern from certain stakeholders, DOE will allow 
manufacturers of gas-fired circulating water heaters to represent 
thermal efficiency test results measured according to the commercial 
water heaters test procedure outlined at 10 CFR part 431, subpart G, in 
addition to the required UEF test results. DOE also notes that this 
final rule clearly defines the test apparatus for circulating heat pump 
water heaters in section 4.10 of the amended appendix E.
    Rheem reiterated its request for clarification as to whether a 
system (i.e., a heat pump and storage tank designed to be used 
together) can be certified independent of the proposed method to use a 
specific storage tank or electric resistance water heater. (Rheem, No. 
47 at p. 5) Rheem also requested that DOE address whether a split-
system water heater, designed to be used with an 80-gallon tank, can 
have a storage tank with electric resistance elements and whether a 
replacement tank can be sold. (Rheem, No. 47 at p. 5)
    In response to Rheem, DOE would clarify that a product which 
consists of a heat pump and a storage tank designed to be used together 
and are sold together would constitute a ``split-system heat pump water 
heater.'' Such a system would be certified altogether as an electric 
storage water heater, and there would be no need to use the test 
procedure provisions for a separate storage tank. If the heat pump 
module were sold separately and independent of the tank, then it would 
constitute a ``circulating heat pump water heater,'' and the test 
procedure provisions for a 40-gallon 5 gallon separate 
storage water heater would then apply. In Rheem's example of a product 
with an 80-gallon storage tank, that configuration would constitute a 
``split-

[[Page 40446]]

system heat pump water heater''--an electric storage water heater with 
a storage volume of 80 gallons. The separate storage tank provisions do 
not apply to such a product. The 80-gallon storage tank component of 
the split-system heat pump water heater may have electric resistance 
back-up elements. Replacement storage tanks sold on a separate basis--
essentially an electric resistance water heater with a storage volume 
of 80-gallons--would not be permitted, because electric resistance 
heating elements would not be able to achieve the UEF energy 
conservation standard levels mandatory for electric storage water 
heaters greater than 55 gallons for which compliance is currently 
required (see 10 CFR 430.32(d)).
    In response to the January 2022 NOPR, A.O. Smith also commented 
that the energy from a circulating pump should be used in the UEF 
calculations and that the flow rates between the circulating heat pump 
water heater and the storage tank should be specified by the 
manufacturer. (A.O. Smith, No. 37 at p. 3) DOE agrees that including 
the energy use of the circulating pump is appropriate and consistent 
with the currently applicable appendix E test procedure, which requires 
measurement of power consumption of auxiliary electricity-using 
components. In this final rule, for water heaters which require 
separate storage tanks, the power consumption of the circulating pump 
shall be directly metered if the pump is integrated into the water 
heater. Section 4.10 of the amended appendix E test procedure will 
require that if the water heater is supplied with a separate, non-
integrated circulating pump, it is to be installed as per the 
manufacturer's installation instructions, and its power consumption 
will similarly be accounted for in the energy measurements to determine 
UEF.
    In conclusion, after considering comments received in response to 
the January 2022 NOPR and the July 2022 SNOPR, DOE is adopting the 
requirements for separate storage tanks as discussed in this final 
rule.
    DOE's previous proposals involving the use of separate storage 
tanks did not specify a test procedure by which the storage volume of 
unfired hot water storage tanks paired with circulating water heaters 
to determine efficiency is to be measured. It is important to obtain a 
precise measurement of the storage volume of the UFHWST because its 
physical size affects the measured efficiency of the water heater due 
to standby losses of heat from the stored water to the air surrounding 
the storage tank; these standby losses increase as the size of the tank 
increases.
    To ensure the accuracy and repeatability of test results, DOE is 
amending sections 4.10 and 5.2.1 of appendix E so that the method for 
determining storage tank volume specified in section 5.2.1 must also be 
conducted to verify the volume of unfired hot water storage tanks used 
to test circulating water heaters. In this method, storage volume is 
determined in gallons by subtracting the tare weight, measured while 
the tank is dry and empty, from the weight of the system when filled 
with water and dividing the resulting net weight of water by the 
density of water at the measured water temperature. This method is 
consistent with how the volume of unfired hot water storage tanks is 
currently rated. It is also the method specified for storage-type and 
storage-type instantaneous commercial water heaters under subpart G to 
10 CFR part 431.
    Additionally, as discussed in section III.F.2.b of this document, 
DOE is establishing that the effective storage volume of a circulating 
water heater is equivalent to the measured storage volume of the 
separate storage tank which was used during testing of the circulating 
water heater. This alleviates the manufacturers' concerns by ensuring 
that the standby losses reflected in the UEF rating of the circulating 
water heater can be mapped to the volume of the separate storage tank 
which was used during testing without having to specify a particular 
model of tank, for example. DOE would consider this tank volume in the 
development of energy conservation standards for circulating water 
heaters.

E. Test Conduct

    As discussed throughout this rulemaking, EPCA requires that any 
test procedures prescribed or amended under this section shall be 
reasonably designed to produce test results which measure energy 
efficiency, energy use, or estimated annual operating cost of a covered 
product during a representative average use cycle (as determined by the 
Secretary) or period of use and shall not be unduly burdensome to 
conduct. (42 U.S.C. 6293(b)(3)) The proposed changes to test conduct, 
along with specific stakeholder comments received and DOE's responses, 
are discussed further in the subsections that immediately follow.
1. High Temperature Testing
    Certain electric storage water heaters on the market are capable of 
raising the temperature of the stored water significantly above the 
outlet water temperature requirements specified in section 2.4 of 
appendix E, while still delivering water at a lower temperature that is 
at or near the temperature specified in appendix E. The storage tank is 
heated to a temperature which is still within the normal operating 
range of the water heater, but a mixing valve is typically installed 
with these products (either integrated into the water heater by the 
manufacturer at the factory, or added to the water heater in the field 
by the installer) to temper the outlet water to a more typical delivery 
temperature. (Set-up requirements for mixing valves that are to be used 
during testing are discussed in section III.D.2 of this final rule.) 
When the outlet water is tempered like this, a smaller amount of the 
hot water from the tank is required to meet demand (because the water 
in the tank is hotter than desired). Because less water needs to be 
removed from the tank, the effect of a mixing valve is to increase the 
amount of hot water that can be delivered overall by the water heater. 
In addition to determining the set-up considerations to test these 
products in a representative manner, DOE must consider the impact of 
raising the storage tank temperature significantly above the setpoint 
outlet temperature (i.e., ``storage tank overheating'') on the 
efficiency of a water heater since this represents how the water heater 
will be used in the field.
    As discussed in the July 2022 SNOPR, storage tank overheating 
increases the amount of hot water that a given size water heater can 
deliver. 87 FR 42270, 42277-42278 (July 14, 2022).
    Historically, it has not been uncommon for water heaters to come 
with the capability to adjust the settings to increase the temperature 
of the water being stored in the tank, although, it is DOE's 
understanding that in the past, consumers rarely modified the 
preconfigured settings on their storage tanks. However, DOE has 
recently become aware of products that are being marketed to consumers 
with ``capacity boosting'' capabilities so as to avoid the need to 
install a larger storage-type water heater. The products (that DOE 
addressed in the July 2022 SNOPR) are equipped with user-operable modes 
which set the water heater to boost the storage tank temperature and 
use a built-in mixing valve (or one installed at the point of 
manufacture) to automatically maintain the delivery temperature. For 
example, one manufacturer produces 30-, 40-, and 50-gallon water 
heaters with an ``X-High Setting'' claiming to provide the same amount 
of hot water (``Effective Capacity,'' as the manufacturer refers to

[[Page 40447]]

it) as significantly larger water heaters with a more typical storage 
tank temperature of 125 [deg]F--such as an 80-gallon capacity for the 
50-gallon model, 64-gallon capacity for the 40-gallon model, and 48-
gallon capacity for the 30-gallon model.\66\ DOE notes that the 40-
gallon model and the 50-gallon model are capable of providing effective 
capacities greater than 55 gallons, which, based on effective capacity, 
would put these models into a different product class. (see 10 CFR 
430.32(d)). Another manufacturer produces a 55-gallon water heater with 
a variety of settings allowing the user to get ``performance 
equivalency'' of a 65-, 80-, or 100-gallon tank, stating that the tank 
raises the temperature safely up to 170 [deg]F.\67\ Again, these 
increased capacities would put this model into a different product 
class.
---------------------------------------------------------------------------

    \66\ See, for example: www.geappliances.com/appliance/GE-Smart-50-Gallon-Electric-Water-Heater-with-Flexible-Capacity-GE50S10BMM 
(Last accessed April 14, 2023).
    \67\ For example, DOE's Compliance Certification Database 
includes a 107-gallon electric storage water heater with an FHR of 
94 gallons.
---------------------------------------------------------------------------

    As stated in the July 2022 SNOPR, consumers would be expected to 
use the over-heated mode as part of the regular operation of their 
water heater. Accordingly, for such products, DOE expects that a 
representative average use cycle would include some portion of time in 
over-heated mode. 87 FR 42270, 42279 (July 14, 2022). For these water 
heaters, DOE believes that a representative average use cycle in the 
test procedure must encompass the ''capacity boosting'' capability, as 
this is the mode that DOE believes the consumer will likely be using 
once installed in the field, because such purchases are likely 
predicated on this capacity-boosting capability.
    The operational mode selection instructions in section 5.1 of 
appendix E do not specifically address the situation when a water 
heater has this type of operational mode that boosts the capacity. In 
response to the January 2022 NOPR, several commenters requested that 
DOE consider amendments to the appendix E test procedure to provide 
more representative efficiency results (including ways to account for 
the increased effective capacity) for these products that ``overheat'' 
the stored water beyond the delivery temperature. After considering 
these comments in the July 2022 SNOPR, DOE proposed to establish 
additional requirements for the testing of water heaters which have 
these operational modes. 87 FR 42270, 42278 (July 14, 2022).
    In order to further examine the potential impacts of storing water 
at temperatures higher than the delivery temperature, DOE performed 
testing on one 50-gallon electric resistance storage water heater that 
includes a built-in mixing valve and multiple user-selectable modes to 
boost the delivery capacity through storage tank overheating. As 
described in the July 2022 SNOPR, DOE collected data at three different 
storage tank temperatures, each of which provided an outlet water 
temperature at 125 [deg]F 5 [deg]F through the use of the 
built-in mixing valve. DOE compared the maximum measured mean tank 
temperature after cut-out following the first draw of the 24-hour 
simulated-use test (Tmax,1) to the average outlet water 
temperature during the second draw (Tdel,2) as an indicator 
of the degree of ``overheating.'' DOE's test data is provided in Table 
III.3 of the July 2022 SNOPR. 87 FR 42270, 42278-42279 (July 14, 2022).
    The test results indicated that storage tank overheating clearly 
leads to an increase in the measured FHR value. The test configuration 
corresponding to the current DOE test procedure produced an FHR value 
of 77 gallons. The overheated configurations with mean tank 
temperatures of 144.5 and 159.6 produced FHR values of 81 and 95 
gallons, respectively. DOE notes that an FHR of 95 gallons is 
comparable to that of a 100-gallon electric storage water heater.\68\ 
However, increasing the temperature of the stored water can reduce 
energy efficiency because the hotter tank undergoes substantially 
higher standby energy losses. As shown in Table III.3 of the July 2022 
SNOPR, DOE's test data show that at a tank temperature of 124.3 [deg]F, 
the measured UEF is 0.94, which is compliant with the current 
standards. When the temperature is increased to 144.5 [deg]F, the UEF 
decreases to 0.90. Further increasing the temperature to 159.6 [deg]F 
decreases the UEF to 0.88. 87 FR 42270, 42279 (July 14, 2022).
---------------------------------------------------------------------------

    \68\ For example, DOE's Compliance Certification Database 
includes a 107-gallon electric storage water heater with an FHR of 
94 gallons.
---------------------------------------------------------------------------

    All of the tested temperatures correspond to normal operational 
modes for the water heater, and a review of publicly-available product 
literature indicates that products that utilize storage tank 
overheating generally offer user-selectable operational modes that 
result in stored water temperatures ranging from 100 [deg]F to 170 
[deg]F. Consumers who choose to use a high-capacity (i.e., 
``overheated'') mode will experience the water heater performing 
significantly worse in terms of its energy efficiency rating than if 
the rating were determined based on testing without storage tank 
overheating. In other words, the rated efficiency at the rated delivery 
capacity would not be representative of an average use cycle or period 
of use when operated in a high-capacity mode. 87 FR 42270, 42279 (July 
14, 2022).
    In the July 2022 SNOPR, DOE surmised that consumers who purchase a 
water heater that provides overheating capability would do so with the 
intent to use such capability; as such, these consumers would be 
expected to use the over-heated mode some portion of the time, ranging 
from occasional use (e.g., switching between the normal mode and the 
overheated mode depending on the hot water capacity needed at any 
particular time) to regular use. Accordingly, for such products, DOE 
expects that a representative average use cycle would include some 
portion of time in overheated mode. For this reason, DOE tentatively 
determined that testing storage-type water heaters that offer user-
selectable overheated modes in the overheated mode would provide a more 
representative result than testing in the default mode. Therefore, DOE 
proposed to amend section 5.1 of appendix E to require that for water 
heaters that offer a user-selected operational mode(s) in which the 
storage tank is maintained at a temperature higher than the delivery 
temperature, the operational mode shall be that which results in the 
highest mean tank temperature while maintaining an outlet temperature 
of 125 [deg]F 5 [deg]F. Because this amendment would change 
the measured energy efficiency, DOE proposed that compliance with this 
requirement would not be necessary until the compliance date for 
amended energy conservation standards. 87 FR 42270, 42279 (July 14, 
2022).
    As explained in the July 2022 SNOPR, demand-response water heaters 
with the capability to undergo utility-initiated overheating would not 
be expected to increase the capacity of the water heater over a typical 
average use cycle in the same way that a water heater with user-
initiated overheating would, so DOE had tentatively concluded that 
testing demand-response water heaters in the default/normal would be 
the most representative method for those products. Therefore, DOE 
proposed to define ``demand-response water heater'' (see section 
III.A.1 of this document) and exclude such products from the 
requirement to test in the operational mode that results in the highest 
mean tank temperature while maintaining an

[[Page 40448]]

outlet temperature of 125 [deg]F 5 [deg]F, even if they are 
capable of overheating the stored water. 87 FR 42270, 42280 (July 14, 
2022).
    In response to the July 2022 SNOPR, BWC stated that the phrase 
``storage tank overheating'' may be confusing to consumers and 
suggested that DOE find an alternate phrase to describe this concept 
(i.e., ``water heaters with high heat modes''). (BWC, No. 48 at p. 3) 
GEA also disagreed with DOE's use of the term ``over-heating'' to refer 
to water heaters that can deliver water at lower temperature than that 
at which it is stored, suggesting ``delivery-control'' as an 
alternative, given that these products heat in the manner intended. 
(GEA, No. 53 at p. 2) In response to these comments and acknowledging 
the sensitivity around the potentially negative connotation of the term 
``overheating,'' as noted earlier in this document, DOE's use of the 
term ``overheating'' does not denote performance outside of the normal 
operating range of the water heater, but rather refers to raising the 
tank temperature above the outlet water setpoint. To avoid any 
potential confusion, DOE will hereinafter refer to water heaters with 
overheating capability as water heaters with ``high heat modes.''
    The following subsections summarize the remaining comments received 
in response to the provisions proposed in the July 2022 SNOPR for water 
heaters with high heat modes and include DOE's additional assessments 
of the impact on UEF ratings, representativeness of the test method, 
and implications for compliance with standards associated with high 
temperature testing.\69\ As discussed in the following subsections, DOE 
has concluded that including test conduct provisions for determining 
the ratings of water heaters tested using the high temperature testing 
method would be justified. Therefore, in this final rule, DOE is 
establishing the methodology for determining ratings for electric 
resistance storage water heater using high temperature testing in 
appendix E, but DOE is allowing voluntary representations at this 
point. Specifically, manufacturers may opt to use the high temperature 
test method in addition to the regular temperature setting test method 
if they desire to make voluntary representations of the efficiency when 
tested in high temperature mode. DOE will consider establishing 
requirements for which electric resistance storage water heaters must 
be tested and represented according to the method for high temperature 
testing in its ongoing energy conservation standards rulemaking for 
consumer water heaters. Until such time, the regular test method is 
mandatory for compliance with the current Federal energy conservation 
standards.
---------------------------------------------------------------------------

    \69\ DOE is establishing a method for testing water heaters at 
an elevated tank temperature, including water heaters without ``high 
heat modes.'' Therefore, DOE refers to water heaters with a built-in 
mixing valve and operational mode for overheating the water in the 
tank as water heaters with ``high heat modes'' but refers to the 
testing of water heaters at elevated storage water temperatures as 
``high temperature testing.''
---------------------------------------------------------------------------

a. Impact on UEF Ratings
    In response to the July 2022 SNOPR, ASAP, ACEEE, and NRDC expressed 
support for DOE's proposal for addressing storage-type water heaters 
that heat the stored water beyond the delivery temperature. (ASAP, 
ACEEE, and NRDC, No. 54 at p. 2)
    NEEA supported DOE's proposal to test water heaters in a user-
selectable ``overheat'' mode when such a mode is available, as well as 
DOE's proposed methodology for identifying ``overheat'' modes. NEEA 
also indicated that it had performed testing on two 120-volt heat pump 
water heater models which had these modes available, and its test 
results showed a significant reduction in efficiency when the water 
heater was set to store water at an elevated temperature of 140 
[deg]F.\70\ Thus, NEEA stated that requiring testing in the 
``overheat'' mode would help realize the energy and cost savings 
intended with efficiency standards. (NEEA, No. 56 at p. 2)
---------------------------------------------------------------------------

    \70\ An August 30, 2022 report by NEEA containing test data for 
these water heaters can be found online at: neea.org/resources/plug-in-heat-pump-water-heaters-an-early-look-to-120-volt-products (Last 
accessed on Nov. 22, 2022).
---------------------------------------------------------------------------

    BWC disagreed that water heaters with high heat modes should have 
separate testing requirements and expressed concern that tests to 
examine the potential effects of heating stored water above the 
delivery temperature setpoint were conducted on a single 50-gallon 
electric resistance storage water heater. BWC urged DOE to conduct 
further testing before finalizing this proposal. (BWC, No. 48 at p. 3) 
In response, DOE notes that the UEF ratings of products which store 
water at higher temperatures will be lower due to the higher standby 
losses incurred as a result of this high temperature storage. DOE did, 
however, conduct additional testing (see section III.F.2 of this 
document) to determine that the method of determining effective storage 
volume from the high temperature testing will only affect products 
which significantly increase capacity by increasing storage 
temperature.
    Additionally, DOE reviewed the heat pump water heater test data 
referenced in NEEA's comment. NEEA tested two 50-gallon 120-volt heat 
pump water heaters at two storage setpoint temperatures (i.e., 125 
[deg]F and 140 [deg]F), with mixing valves installed to temper the 
delivery to 120 [deg]F. NEEA's report concludes that the recovery 
efficiency can decrease by a factor of 3 to 8 percent when the setpoint 
temperature is increased from 125 [deg]F to 140 [deg]F. The higher 
setpoint temperature resulted in an increase in FHR of approximately 13 
gallons. NEEA's report also states that at 67.5 [deg]F ambient air, an 
increase in the setpoint temperature could increase standby losses by 
25 percent, although NEEA stated that standby losses contribute less to 
the overall energy consumption of a heat pump water heater compared to 
recovery periods. DOE notes that NEEA did not conduct standby loss 
testing or present the UEF results of these water heaters in each mode. 
DOE expects that the standby loss from having a higher setpoint 
temperature would have a more significant impact on electric resistance 
water heaters because the recovery efficiency of electric resistance 
heating is not affected by the water temperature.\71\ However, in 
conjunction with DOE's own test data (which was obtained through full 
24-hour simulated use test measurements of an electric resistance 
storage water heater), DOE has determined that high temperature testing 
would result in significantly lower UEF results compared to setting the 
tank temperature close to the delivery setpoint of 125 [deg]F.
---------------------------------------------------------------------------

    \71\ Section 6.3.2 of the currently applicable appendix E test 
procedure (which will be re-located to section 6.3.3 upon the 
effective date of this final rule) states that the recovery 
efficiency for electric water heaters with immersed heating 
elements, not including heat pump water heaters with immersed 
heating elements, is assumed to be 98 percent.
---------------------------------------------------------------------------

    Given the significant difference in UEF performance that have been 
observed based on the temperature of the water stored in the tank, DOE 
has concluded it is appropriate to provide a method to conduct high 
temperature testing. Section III.E.1.d of this document describes how 
DOE is establishing the requirements for high temperature testing. Due 
to the expected impacts of high temperature testing on UEF, DOE will 
not require compliance with this test method until compliance with 
amended energy conservation standards accounting for such water heaters 
is also required.

[[Page 40449]]

b. Demand-Response Water Heaters
    As discussed previously, in the July 2022 SNOPR, DOE proposed to 
define ``demand-response water heater'' and exclude such products from 
the proposed requirement to test in the operational mode that results 
in the highest mean tank temperature while maintaining an outlet 
temperature of 125 [deg]F 5 [deg]F, even if they are 
capable of heating the stored water above the delivery temperature. 87 
FR 42270, 42280 (July 14, 2022).
    In response to the July 2022 SNOPR, NYSERDA indicated that water 
heaters with demand-response functionality should be excluded from 
testing at the highest tank temperature available. (NYSERDA, No. 50 at 
p. 3) A.O. Smith agreed with DOE's assessment that demand-response 
water heaters need the operational capability to ``over[hyphen]heat'' 
the stored water in the tank above the intended outlet water 
temperature in response to a signal or command from a utility or 
third[hyphen]party aggregator. The commenter stated that these load-up 
events are typically short in duration and do not keep the stored water 
in an over-heated state continuously or permanently. However, A.O. 
Smith raised concerns about the impact of this proposed amendment on 
the availability of the high heat mode feature on non-demand-response 
products. A.O. Smith urged DOE to continue to allow non-demand-response 
heat pump water heaters with selectable high heat modes to retain this 
functionality for customer utility. (A.O. Smith, No. 51 at pp. 5-6)
    In contrast, the CA IOUs suggested that demand-response capable 
water heaters should be subject to the same test procedure as other 
water heaters capable of operating in high heat modes. (CA IOUs, No. 52 
at p. 6)
    As noted in section III.A.1 of this document, DOE is not 
establishing a definition for ``demand-response water heater'' in this 
final rule in order to prevent potential industry confusion from 
arising due to any differences in the features requirements specified 
in such definition. However, DOE has found it appropriate to still 
consider factors which would help to determine whether it is most 
representative to require demand-response water heaters to test at the 
highest tank temperature setting.
    As described in the July 2022 SNOPR and discussed in section 
III.A.1 of this document, high-temperature water storage occurring in 
demand-response water heaters and initiated by the electric utility 
serves an important purpose for energy storage and grid flexibility. 87 
FR 44270, 42279-42280 (July 14, 2022). Additionally, DOE noted that 
demand-response water heaters do not perform this action to increase 
the overall daily capacity of the water heater. Instead, the capacity 
is only temporarily boosted to counteract the deactivation of the 
heating elements for extended periods of time when demand curtailment 
is occurring. As such, demand-response water heaters with the 
capability to undergo only utility-initiated high heat modes would not 
be expected to increase the capacity of the water heater over a typical 
average use cycle in the same way that a water heater with the ability 
to have the user increase the storage tank temperature would. Id.
    To reiterate, EPCA requires that any test procedures prescribed or 
amended shall be reasonably designed to product test results which 
measure energy efficiency, energy use, or estimated annual operating 
cost of a covered product or equipment during a representative average 
use cycle or period of use and not be unduly burdensome to conduct. (42 
U.S.C. 6293(b)(3); 42 U.S.C. 6314(a)(2)). Thus, DOE must determine 
whether testing at the highest tank temperature setting during the 
delivery capacity test and the 24-hour simulated-use test is 
representative of an average use cycle for a demand-response water 
heater. Based on information collected during this rulemaking, 
including the comment from NYSERDA, demand-response water heaters do 
not typically remain in a high-temperature storage state for the 
entirety of a 24-hour average use cycle. The additional energy used and 
stored when this type of water heater increases the tank temperature is 
offset by significant periods of low energy usage such that, over a 24-
hour average use cycle, the total energy stored and consumed by the 
water heater is similar to that for a product which maintains a normal 
storage tank temperature throughout the day.
    In response to A.O. Smith's concern about non-demand-response water 
heaters, as discussed in further detail in sections III.E.1.c and 
III.E.1.d of this document, DOE notes that the provisions finalized in 
this rulemaking do not require high temperature testing for any water 
heaters in particular at this time and, therefore, would not preclude 
the possibility of non-demand-response heat pump water heaters having 
user-selectable high heat modes. DOE will consider these concerns 
further at such time as it proposes to require high temperature testing 
for certain types of water heaters in a future rulemaking.
c. Representativeness of Field Use
    AHRI indicated that additional operational modes to heat water 
above 125 [deg]F are not meant to be the primary mode of operation and 
should not be used continuously. AHRI stated that the proposal in the 
July 2022 SNOPR to test water heaters with these modes at the settings 
providing the highest internal tank temperature does not reflect the 
purpose of these modes, and that proposal would require more test data 
than provided in the NOPR to understand its consequences. For these 
reasons, AHRI requested that DOE retract this proposal from the current 
rulemaking and address it at a later time. (AHRI, No. 55 at p. 6) 
Similarly, Rheem requested that DOE not consider water heaters with a 
temporary, non-default high heat mode as being water heaters with high 
heat modes and that DOE not include any changes related to high heat 
modes in the final rule. (Rheem, No. 47 at p. 6)
    GEA argued that the essential function of ``delivery-control'' 
water heaters is no different than a consumer who sets their standard 
storage water heater to a higher temperature and regulates water 
temperature at the tap by mixing in cold water. GEA added that 
``delivery-control'' water heaters provide practical energy savings 
benefits not captured by the consumer water heater test procedure, and 
that these energy savings benefits mitigate against requiring testing 
at the maximum tank storage temperature. Specifically, GEA described a 
use case where a consumer may use a ``delivery-control'' water heater 
in a high heat mode on occasion when more guests are in the home, which 
they suggested would, on balance, use less energy as compared to full 
time use of a water heater with an oversized storage capacity. (GEA, 
No. 53 at p. 3)
    GEA suggested that many consumers already set their storage water 
heater to temperatures above 140 [deg]F and that ``delivery-control'' 
water heaters simply allow consumers to do so in a safer way by 
premixing to a lower temperature, adding that such water heaters should 
not be penalized through efficiency ratings for providing a safety 
feature to prevent scalding. (GEA, No. 53 at p. 3)
    GEA stated that DOE has provided no evidence that setting 
``delivery-control'' water heaters at their maximum storage temperature 
is a ``representative average use cycle or period of use'' as required 
by EPCA at 42 U.S.C. 6293(b)(3). GEA also noted that many other 
products regulated under EPCA have modes that allow for increased or 
decreased energy consumption relative to their default

[[Page 40450]]

setting but that these modes are not included in their respective DOE 
test procedures because they have not been deemed representative of an 
average use cycle. (GEA, No. 53 at p. 4)
    NYSERDA recommended that all water heaters with the option to 
elevate the tank temperature, except those with demand-response 
functionality, should be tested at the highest tank temperature 
available, as thermostatic mixing valves are regularly installed in the 
field. (NYSERDA, No. 50 at p. 3) The CA IOUs also commented that 
external mixing valves are readily available to consumers, and in at 
least one State (Vermont), they are required for all residential water 
heater installations. Therefore, the CA IOUs urged DOE to consider 
changes to its regulations that would further incentivize installers 
and consumers to minimize installation costs at the expense of energy 
efficiency. (CA IOUs, No. 52 at p. 5) GEA stated that thermostatic 
mixing valves can be integrated into a product at the factory or added 
as an accessory at a consumer's home and suggested that if 
manufacturers are required to make ``inaccurate'' representations of 
energy consumption for mixing valves integrated at factories, more 
mixing valves will be sold as accessories, because consumer demand for 
flexibility and safety will not change. (GEA, No. 53 at p. 4)
    As previously discussed in the July 2022 SNOPR and in response to 
the comments of AHRI and Rheem, DOE expects that consumers who purchase 
a water heater with high heat modes intend to use it in order to meet 
hot water demands; therefore, testing these water heaters using only 
the default operational mode would not be representative of the 
product's energy consumption over an average use cycle. 87 FR 42270, 
42279 (July 14, 2022). From its review of product literature, DOE has 
found that manufacturers of water heaters with high heat modes market 
these products as smaller storage water heaters which provide the 
delivery capacities of larger storage water heaters, and consumers may 
opt to install a smaller water heater with high heat mode in lieu of a 
larger water heater as a result (e.g., if a larger water heater does 
not fit in the installation space). As such, in order to yield 
efficiency results that would be most representative of the product's 
enhanced delivery capabilities, DOE has concluded that it would be 
necessary to include a high temperature testing method.
    In light of these comments, DOE has determined that the ability to 
operate with an elevated tank temperature is not limited to products 
with built-in mixing valves and user-selectable capacity boosting 
settings. DOE agrees with commenters that a product with a field-
installed mixing valve and the storage tank manually set to a higher 
temperature could operate in much the same way, and that this practice 
may be prevalent given how readily available separate mixing valves are 
to consumers. As a result of these considerations, DOE concludes that 
it is possible such testing could be appropriate for models capable of 
heating and storing water above the delivery temperature specified in 
the test method while still delivering water at the setpoint 
temperature of 125  5 [deg]F. Thus, DOE is not limiting the 
high temperature testing method only to products with a specific 
capacity boosting mode. In other words, manufacturers may optionally 
apply the high temperature test method to electric resistance storage 
water heaters with the capability to heat and store water above the 
delivery setpoint temperature of 125  5 [deg]F, including 
products that would require a field-installed mixing valve to do so.
    The provisions for high temperature testing adopted by this final 
rule complement the existing operational mode selection requirements, 
which, generally, would require water heaters to be set to a ``normal'' 
storage tank temperature close to the delivery setpoint of 125 [deg]F 
(see section 5.2.1 of the currently applicable appendix E test 
procedure). Specifically, the high temperature testing provisions 
require setting the water heater to the highest storage tank 
temperature and installing a separate mixing valve to temper the 
delivery water to the outlet water requirements for products that do 
not already have a mixing valve installed. If the product is equipped 
with a built-in mixing valve, then the water heater's storage tank 
temperature shall be set to the highest temperature which allows the 
built-in mixing valve to deliver water in accordance with the outlet 
water requirements.
d. Use of High Temperature Testing
    In response to the July 2022 SNOPR, NEEA agreed with DOE's proposal 
to implement this testing requirement only upon adoption of new 
standards. (NEEA, No. 56 at p. 2) A.O. Smith supported the Department's 
position that the effective date of the proposed changes to the test 
procedure covering user[hyphen]selectable over-heat modes for 
non[hyphen]demand-response water heaters should coincide with the 
compliance date of any amendments to the energy conservation standards 
for consumer water heaters. (A.O. Smith, No. 51 at p. 6)
    Rheem stated that DOE's proposal to delay testing until amended 
standards are required may not align with EPCA at 42 U.S.C 6293(c)(2) 
\72\ and requested clarification on DOE's interpretation of this 
statutory provision. (Rheem, No. 47 at p. 5) Rheem also requested DOE's 
interpretation of the 42 U.S.C. 6293(e)(2) requirement to ``amend the 
applicable energy conservation standard during the rulemaking carried 
out with respect to such test procedure'' with respect to water heaters 
with high heat modes because the amended test procedure will alter 
their measured efficiency. (Rheem, No. 47 at p. 5)
---------------------------------------------------------------------------

    \72\ Under 42 U.S.C. 6293(c)(2), the statute provides that 
effective 180 days after an amended or new test procedure applicable 
to a covered product is prescribed or established under paragraph 
(b) of this section, no manufacturer, distributor, retailer, or 
private labeler may make any representation--(A) in writing 
(including a representation on a label); or (B) in any broadcast 
advertisement, with respect to energy use or efficiency or, in the 
case of showerheads, faucets, water closets, and urinals, water use 
of such product or cost of energy consumed by such product, unless 
such product has been tested in accordance with such amended or new 
test procedure and such representation fairly discloses the results 
of such testing.
---------------------------------------------------------------------------

    In response to Rheem's questions regarding the relevant statutory 
provisions at 42 U.S.C. 6293(c)(2) and (e)(2), DOE has concluded that 
the Department's approach comports with both of these EPCA provisions. 
To recap, as discussed in section III.I of this document, DOE is not 
requiring compliance with the high temperature testing provisions until 
compliance with amended energy conservation standards that address 
water heaters with such capabilities, if finalized, because DOE has 
determined that this change to the test procedure will impact the 
measured efficiency of such water heaters. Under 42 U.S.C. 6293(c)(2), 
effective 180 days after an amended or new test procedure is prescribed 
or established for a covered product, no regulated party (i.e., 
manufacturer, distributor, retailer, or private labeler) may make any 
representations about the energy use or efficiency of such product 
unless it has been tested according to the new or amended test 
procedure and such representations fairly disclose the results of such 
testing. In the present case, DOE is making clear that its test 
procedure provisions related to high temperature testing are not 
required to be used until the compliance date of any amended standards 
that address such water heaters.
    Under 42 U.S.C. 6293(e)(1), DOE must determine whether any test 
procedure amendments would alter the measured energy efficiency, energy 
use, or

[[Page 40451]]

measured water use of any covered products as determined under the 
existing test procedure. As explained elsewhere, DOE has determined 
that the provisions for high temperature testing would alter measured 
efficiency, so this statutory provision is likewise satisfied.
    Finally, under 42 U.S.C. 6293(e)(2), if DOE determines that its 
amended test procedure will alter the measured energy efficiency or 
energy use of a covered product, the Department shall amend the 
applicable energy conservation standard during the rulemaking carried 
out with respect to such test procedure. This provision applies to the 
currently applicable energy conservation standard. As noted previously, 
the high temperature testing provisions that would alter the measured 
energy efficiency of certain water heaters are not required for 
determining compliance with the currently applicable standard. These 
provisions would only be required on the compliance date of any amended 
standards that address such water heaters. As such, there is no need to 
amend the current standards under 42 U.S.C. 6293(e)(2).
    DOE has determined that the high temperature test method should 
apply to electric resistance storage water heaters for the reasons 
discussed in section III.E.1 of this document. Specifically, based on 
information from stakeholders regarding the operation of demand-
response water heaters (see section III.E.1.b of this document) and the 
Department's own testing and calculations (see section III.F.2.a of 
this document), DOE has determined that the high temperature test 
method would apply to electric resistance storage water heaters that 
are capable of raising their internal tank temperature significantly 
above their delivery temperature, without utility initiation, to boost 
hot water delivery capacity in order to meet daily household needs. 
Products which raise the internal tank temperature only as part of 
demand-response operation should not use this method.
    In this rulemaking, commenters have urged DOE to provide better 
clarity and specificity regarding which water heaters may be ``exempt'' 
from high temperature testing (for example, see NYSERDA's comments 
discussed in section III.A.1 of this document). In the concurrent the 
energy conservation standards rulemaking, DOE may consider and propose 
additional criteria to further specify the subset of water heaters 
which would have to comply with potential amended standards using the 
high temperature test method. This is because there could be specific 
cases when a water heater would reach a higher storage tank temperature 
in a way that does not necessarily increase the delivery capacity over 
the course of an average use cycle. For example, a user may choose to 
use an elevated setpoint for storage temperature, but with a delivery 
temperature equal to this setpoint. In such a case where a higher 
delivery temperature is actually desired, because no cold water mixing 
is occurring at the outlet, there is no increase in the volume of hot 
water that can be provided to the home. Therefore, in its accompanying 
energy conservation standards rulemaking for consumer water heaters, 
DOE will consider specifying what user-controllable tank temperature 
settings might actually constitute ``delivery capacity boosting.'' 
Additionally, DOE will also consider the length of time these settings 
may be in use to determine which types of temperature settings would 
result in capacity boosting over an average daily use cycle.
    Once again, because high temperature testing may cause ratings for 
certain electric resistance storage water heaters to decrease, DOE is 
not requiring the use of these test provisions until the compliance 
date of any new energy conservation standards addressing such water 
heaters (i.e., as part of the separate rulemakings for consumer water 
heaters). After the effective date of this final rule and before the 
compliance date of an amended standards final rule, manufacturers of 
certain electric resistance storage water heaters will be allowed to 
use the high temperature test method voluntarily to make additional 
representations of performance in high-temperature mode.
2. Very Small Draw Pattern Flow Rate
    Section 5.4.1 of appendix E states that if the Max GPM is less than 
1.7 gpm (6.4 L/min), then the very small draw pattern must be used 
during the 24-hour simulated-use test. Section 5.5 of appendix E states 
that, for the very small draw pattern, if the water heater has a Max 
GPM rating less than 1 gpm (3.8 L/min), then all draws shall be 
implemented at a flow rate equal to the rated Max GPM.
    As discussed in the January 2022 NOPR, DOE has identified flow-
activated water heaters that are designed to deliver water at the set 
point temperature of 125 [deg]F 5 [deg]F (51.7 [deg]C 
2.8 [deg]C) that is required by section 2.5 of appendix E 
at a flow rate well below 1 gpm (3.8 L/min). For these products, the 
second draw of the very small draw pattern requires 1 gallon to be 
removed at the rated Max GPM, and the pattern requires the third draw 
to start five minutes after the initiation of the second draw. However, 
any rated Max GPM less than or equal to 0.2 gpm (0.76 L/min) will 
result in the second draw lasting more than five minutes and past the 
start time of the third draw. To clarify the appropriate method of 
testing these products, DOE proposed to amend the very small draw 
pattern description to state that when a draw extends beyond the start 
time of a subsequent draw, that the subsequent draw will start after 
the required volume of the previous draw has been delivered. 87 FR 
1554, 1582 (Jan. 11, 2022).
    DOE did not receive any comments in response to this proposal, so, 
therefore, in this final rule, DOE is adopting the amendment to 
appendix E as proposed in the January 2022 NOPR for the reasons 
previously stated.
3. Low-Temperature Water Heaters
    Low-temperature water heaters (discussed further in section 
III.A.4.b of this document) are flow-activated products that do not 
deliver temperatures within the required set point temperature range of 
125 [deg]F 5 [deg]F when tested according to the supply 
water temperature and flow rate requirements of appendix E. These 
products are typically suited for point-of-use (POU) applications where 
the outlet water is minimally tempered prior to delivery through the 
faucet (typically marketed as ``handwashing'' or ``POU water 
heaters''). However, because these products cannot meet the outlet 
temperature requirements in appendix E, DOE is establishing new 
provisions to address these products.
    One primary concern identified in this rulemaking is that these 
units typically have low heating rates, which currently requires the 
testing agency to reduce the flow rate in order to be able to achieve 
the outlet temperature within the set point temperature range. However, 
these units have a minimum activation flow rate below which the unit 
shuts off. To the extent that a unit would stop heating water when the 
flow rate is too low, there may be no flow rate at which the unit would 
operate and deliver water at the outlet temperature required under 
section 2.5 of appendix E. In response to the April 2020 RFI, 
commenters generally indicated that DOE should adopt provisions to use 
a lower setpoint temperature for low-temperature water heaters. 87 FR 
1554, 1582 (Jan. 11, 2022).
    For the reasons explained in further detail in the January 2022 
NOPR, DOE proposed that low-temperature water heaters be tested at the 
maximum delivery temperature when using the flow rate requirements 
already

[[Page 40452]]

established in appendix E. Specifically, lowering the flow rate in 
order to establish a delivery temperature of 125 [deg]F may not be 
feasible for these products because the flow rate may be so low that 
the water heater does not activate. DOE tentatively determined that 
lowering the set point temperature for low-temperature water heaters to 
their maximum possible delivery temperature would permit these water 
heaters to be tested appropriately and in a manner that would produce 
representative test results. 87 FR 1554, 1582-1583 (Jan. 11, 2022).
    In commenting on this issue, BWC requested that DOE further assess 
differences in testing and ratings between electric instantaneous water 
heaters and low-temperature water heaters. (BWC, No. 33 at p. 8)
    In response, DOE will continue to assess the impact of the test 
procedure provision in section 5.2.2 of appendix E on ratings for low-
temperature water heaters as more of these products enter the market 
and are certified, but at this time, DOE is adopting these provisions 
in order to set forth a repeatable, representative approach to testing 
such products. Currently, there is no appendix E test method to test 
low-temperature water heaters, and, therefore, ratings for low-
temperature water heaters are not possible until the effective date of 
this final rule. DOE is distinguishing low-temperature water heaters 
from other electric instantaneous water heaters mainly on the inability 
to reach the standardized outlet water temperatures under the appendix 
E test procedure. DOE will consider potential impacts on UEF ratings in 
its concurrent energy conservation standards rulemaking (see Docket No. 
EERE-2017-BT-STD-0019).
4. Delivery Temperature for Flow-Activated Water Heaters
    In providing comments in response to the January 2022 NOPR, AET 
introduced a new topic for DOE to consider when amending the test 
procedure for consumer water heaters and residential-duty commercial 
water heaters. AET indicated that the test procedure needs to further 
clarify the process for setting the delivery temperature for flow-
activated water heaters. The commenter argued that such clarification 
is necessary because the DOE test procedure simply says to initiate 
normal operation of the water heater at the design power rating. AET 
stated that, when operating flow-activated water heaters at their 
maximum heating rate, outlet temperature can be controlled two 
different ways: (1) adjust some thermostat, and/or (2) adjust flow 
rate; since the instructions do not specify a flow rate at which to set 
the thermostat, it is theoretically possible to set the thermostat to a 
very high temperature, and then adjust the flow rate so that the unit 
only delivers the desired 125 [deg]F outlet temperature. AET claimed 
that this would allow the water heater to deliver much hotter 
temperatures when the flow rate is less than the flow rate needed to 
deliver 125 [deg]F when operating at maximum heating rate. AET 
recommended to amend the test procedure so as to provide instructions 
that the flow rate for draws should be 90 percent of the theoretically 
calculated maximum flow rate that could be achieved when operating at a 
full heating rate and delivering the required 125 [deg]F outlet 
temperature in order to ensure that this temperature is consistent. 
(AET, No. 29 at p. 11)
    On this issue, DOE notes that section 5.2.2.1 of appendix E, 
``Flow-Activated Water Heaters, including certain instantaneous water 
heaters and certain storage-type water heaters,'' instructs the test 
agency to first initiate normal operation of the water heater at the 
full input rating for electric water heaters and at the maximum firing 
rate specified by the manufacturer for gas or oil water heaters. 
Section 5.2.2.1 then states that the test agency must monitor the 
discharge water temperature and set to a value of 125 [deg]F 5 [deg]F (51.7 [deg]C 2.8 [deg]C) in accordance with 
the manufacturer's instructions. If the water heater is not capable of 
providing this discharge temperature when the flow rate is 1.7 gallons 
0.25 gallons per minute (6.4 liters 0.95 liters 
per minute), then the flow rate is adjusted as necessary to achieve the 
specified discharge water temperature. Once the proper temperature 
control setting is achieved, the setting must remain fixed for the 
duration of the maximum GPM test and the simulated-use test.
    In response to AET's comment, DOE notes that the current appendix E 
test instructions specify that the flow rate for setting the discharge 
water temperature is 1.7 gallons 0.25 gallons per minute 
(6.4 liters 0.95 liters per minute). If a discharge 
temperature of 125 [deg]F 5 [deg]F is not possible at that 
flow rate, the test method allows for the flow rate to be varied only 
to the extent necessary to achieve a discharge temperature of 125 
[deg]F 5 [deg]F. Therefore, DOE has determined that the 
current instruction is explicit enough for the delivery temperature 
setting to be conducted in a repeatable and reproducible manner.
5. Heat Pump Water Heaters
    In this rulemaking, DOE has sought to address multiple test 
procedure provisions related to heat pump water heaters. In section 
III.A.2 of this final rule, DOE discusses the scope of applicability of 
the appendix E test procedure to heat pump water heaters designed for 
residential applications. Section III.C.7 of this document describes 
the new optional test conditions being allowed for heat pump water 
heaters for voluntary representations of EX based on NEEA's 
Advanced Water Heating Specification. Additionally, DOE is amending 
ambient air condition tolerances for heat pump water heater testing 
because air-source heat pumps exchange latent and sensible heat \73\ 
with the surrounding air, and, thus, the water heater's normal 
operation will have a tangible impact on air temperature and moisture 
content (see section III.C.4 of this document). Furthermore, there are 
other requirements being established for the test set-up and 
installation of split-system heat pump water heaters and circulating 
heat pump water heaters (see sections III.D.1 and III.D.4 of this 
document).
---------------------------------------------------------------------------

    \73\ ``Sensible heat'' refers to heat that is exchanged with 
surrounding air that is detectable by measuring the change in 
temperature of the air, as it does not change the moisture content 
of the air. ``Latent heat'' refers to heat that is exchanged when 
moisture in the air is condensed into liquid water (i.e., at the 
evaporator of a heat pump water heater).
---------------------------------------------------------------------------

    In addition to these topics, DOE has evaluated the draw patterns 
for conducting the 24-hour simulated-use test on heat pump water 
heaters with back-up electric resistance heating elements. In the 
present market, consumer heat pump water heaters are typically 
``integrated,'' with the air-source heat pump and storage tank built 
together into one assembly. This ``typical'' consumer heat pump water 
heater uses electricity and has back-up electric resistance elements 
within the storage tank. Heating water with the heat pump components is 
more efficient than heating water with the back-up resistance elements. 
Therefore, water heaters with controls that prioritize heat pump water 
heating over resistance element water heating will operate more 
efficiently than water heaters that do not prioritize heat pump water 
heating or that do not prioritize heat pump water heating to the same 
extent.
    In response to the April 2020 RFI, the Joint Commenters suggested 
modifying the test procedure to reflect the effectiveness of controls 
in minimizing use of the resistance element in heat pump water heaters, 
stating this modification would improve the

[[Page 40453]]

representativeness of the test procedure and create new incentives for 
manufacturers to develop products that provide increased savings for 
consumers. As noted in the January 2022 NOPR, no suggestion was 
provided on how to better reflect the use of controls to minimize 
element usage. 87 FR 1554, 1583 (Jan. 11, 2022).
    In the January 2022 NOPR, DOE noted that its test data indicate 
that most (or possibly all) heat pump water heater models available on 
the market currently operate without activating the electric elements 
during the 24-hour simulated-use test under the current appendix E test 
procedure. DOE argued that although element usage during the test could 
be forced through a more aggressive draw pattern (i.e., longer or more 
frequent draws designed to deplete the water heater and require more 
hot water than the heat pump alone could keep up with), the draw 
patterns are required to be representative of actual use. Therefore, 
designing the draw pattern with the goal of forcing resistance element 
use would not be representative of typical use. 87 FR 1554, 1583 (Jan. 
11, 2022).
    In commenting on this issue in response to the January 2022 NOPR, 
the ASAP, ACEEE and NCLC once again encouraged DOE to evaluate whether 
current draw patterns are representative of real-world conditions for 
heat pump water heaters. The ASAP, ACEEE and NCLC noted that 
investigations conducted by NEEA \74\ indicate that electric resistance 
elements are activated more frequently in heat pump water heaters than 
DOE observed in its testing. Specifically, ASAP, ACEEE and NCLC pointed 
to the finding in the NEEA study that the average annual proportion of 
total input energy that was provided by resistance heat ranged from 4 
to 45 percent, depending on the water heater model and location of 
installation. (ASAP, ACEEE, and NCLC, No. 34 at p. 2) However, DOE did 
not receive any additional comments in this rulemaking providing any 
specific approach to testing heat pump water heaters with back-up 
electric resistance elements in a more representative manner.
---------------------------------------------------------------------------

    \74\ ASAP, ACEEE and NCLC cited NEEA's 2015 Heat Pump Water 
Heater Model Validation Study, (Report #E15-306), found online at: 
ecotopewebstorage.s3.amazonaws.com/2015_001_1_HPWHModelVal.pdf (Last 
accessed on Sept. 13, 2022).
---------------------------------------------------------------------------

    In response, DOE notes that the 2015 study by NEEA relies on data 
collected in a limited geographical area within the U.S.--namely, the 
Pacific Northwest--and the results may not be representative of 
installations across the U.S, which is the requisite benchmark for a 
Federal test procedure. For example, one condition for electric 
resistance back-up is when the ambient air temperature is below the 
low-temperature cut-out of the compressor (e.g., 45 [deg]F), and this 
is more likely to occur in northern climates than it is to occur across 
the country as a whole. Nevertheless, the study finding demonstrated a 
substantial range of electric resistance contribution, such that it 
remains unclear whether an amended draw pattern would be more 
representative.
    The CA IOUs did, however, suggest that DOE should consider any 
distinguishing characteristics of 120-volt heat pump water heaters that 
might require changes to the test procedure to represent their real-
world performance accurately. (CA IOUs, No. 36 at p. 4) In response to 
the CA IOUs, within the context of back-up element usage, early 
indications suggest that not all 120-volt heat pump water heaters will 
employ back-up electric resistance heating elements due to limitations 
on a 120-volt circuit, but this market is still evolving. As of this 
final rule, there are only a limited number of commercially-available 
120-volt heat pump water heaters, so DOE has determined that it is 
premature to establish specific testing requirements for 120-volt heat 
pump water heaters at this time. Without adequate test data from these 
products, there is uncertainty as to what, if any, specific 
requirements for 120-volt heat pump water heaters would be appropriate.
    Therefore, after considering these comments and the lack of 
available data on this topic, DOE has decided to maintain the current 
language in section 5.1 of appendix E and is not adopting draw patterns 
specific to any type of heat pump water heater. Accordingly, the draw 
patterns for electric water heaters generally will continue to apply to 
these products. DOE will continue to collect information on this topic 
to inform a future test procedure rulemaking.
6. Draw Pattern for Commercial Applications
    In response to the April 2020 RFI and as discussed in the January 
2022 NOPR, EEI suggested DOE consider a test procedure for consumer 
water heaters used in commercial applications that includes a draw 
pattern more demanding than the ``high'' draw pattern, which is 
currently the draw pattern with the largest amount of delivered water 
in the appendix E test procedure. 87 FR 1554, 1575-1576 (Jan. 11, 
2022).
    In the January 2022 NOPR, DOE stated that 42 U.S.C. 6293(b)(3), in 
relevant part, requires that any test procedures prescribed or amended 
shall be reasonably designed to produce test results which measure 
energy efficiency of a covered product during a representative average 
use cycle or period of use. Consumer water heaters are designed for use 
in residential applications, and as such, a draw pattern representative 
of a commercial installation would not be representative of the 
product's average use cycle or period of use. For these reasons, DOE 
declined to propose a draw pattern with a delivered volume greater than 
the high draw pattern in appendix E. 87 FR 1554, 1576 (Jan. 11, 2022).
    BWC agreed that there is no need for a draw pattern above ``high 
draw,'' since the high draw pattern adequately addresses products that 
have high hot water deliverability within the scope of the test 
procedure. (BWC, No. 33 at p. 6)
    As such, DOE is not adding another draw pattern to the appendix E 
test procedure in this final rule for the reasons previously stated.
7. Method for Determining Internal Tank Temperature for Certain Water 
Heaters
    Section 4.5 of appendix E provides the procedure for measuring the 
internal storage tank temperature for water heaters with a rated 
storage volume at or above 2 gallons. Section 4.5 of appendix E 
specifies that the thermocouples be inserted into the storage tank of a 
water heater through either the anodic device opening, the temperature 
and pressure relief valve, or the outlet water line. However, DOE has 
identified consumer water heaters with physical attributes that make 
measuring internal storage tank temperature difficult, such as water 
heaters that have a built-in mixing valve and no anodic device, or that 
have a large heat exchanger that does not accommodate insertion of a 
thermocouple tree. In this rulemaking, DOE sought suggestions from 
stakeholders on how the internal storage tank temperature should be 
measured for these types of designs. After considering the comments 
received, DOE is amending the appendix E test procedure to specify a 
method for determining the internal mean tank temperature for such 
products, as discussed in detail later in this section.
    In response to the April 2020 RFI and as discussed in the January 
2022 NOPR, BWC recommended a ``drain-down'' approach to address water 
heaters that cannot have their internal storage tank

[[Page 40454]]

temperatures measured directly (a position echoed by Rheem). More 
specifically, BWC's suggested approach consisted of the following: (1) 
After the FHR test, purging the water heater with inlet water at 58 
[deg]F  2 [deg]F to establish the mean tank temperature at 
the beginning of the 24-hour simulated-use test; (2) allowing the water 
heater to heat up to the original thermostat setting and recording the 
energy used to do so; (3) running the appropriate draw pattern, then 
fully draining the water heater by gravity, while measuring the mass 
and temperature of the water; and (4) calculating the energy change as: 
energy change = mass x specific heat x the difference between the 
average end temperature and the beginning temperature just after the 58 
[deg]F purge. Rheem also supported a drain-down method, whereby the 
entire volume would be removed and the temperature measured at the end 
of the 24-hour test. 87 FR 1554, 1586 (Jan. 11, 2022).
    However, DOE's primary concern with the suggested drain-down 
approach was that it cannot be conducted at every stage during the 24-
hour simulated-use test when the mean tank temperature measurement is 
required. As discussed in the January 2022 NOPR, the procedures 
recommended by BWC and Rheem could provide an estimate of the mean tank 
temperature at the start and end of the 24-hour simulated-use test but 
would not provide an estimate at the end of the first recovery period, 
the start and end of the standby period, or an average over the standby 
period, all of which are required for determining UEF. Instead of BWC's 
drain-down approach, DOE initially proposed a methodology with a 
modified approach, wherein the mean tank temperature would be estimated 
as the average of the inlet water temperature and the outlet water 
temperature each time a mean tank temperature measurement was required. 
This method assumes that the stored water gradually (i.e., linearly) 
increases in temperature either from the bottom of the tank to the top, 
or the further the water is into the heat exchanger from the water 
inlet, depending on the design of the water heater being tested. As the 
exact internal dimensions of the storage tank or heat exchanger cannot 
be known for every water heater, DOE reasoned that the linear 
assumption is the most representative of the water heater market as a 
whole. 87 FR 1554, 1586-1587 (Jan. 11, 2022).
    In response to DOE's proposal, AHRI, A.O. Smith, and BWC indicated 
that the linear temperature gradient assumption inherent to the 
proposed methodology in the January 2022 NOPR is incorrect, based on 
the companies' own test results. (AHRI, No. 40 at p. 5; A.O. Smith, No. 
37 at pp. 5-6; BWC, No. 33 at p. 10) In contrast, Rheem supported DOE's 
proposed linear temperature gradient assumption. (Rheem, No. 31 at p. 
4) None of the comments received in response to the January 2022 NOPR 
suggested an alternative approach, so in the July 2022 SNOPR, DOE 
revised its proposal to incorporate aspects of BWC's method but 
included additional methods to estimate the intermediate temperatures 
required for efficiency calculations. 87 FR 42270, 42283-42284 (July 
14, 2022).
    In the July 2022 SNOPR, DOE proposed the following methodology for 
water heaters with rated storage volumes greater than or equal to 2 
gallons that are unable to have their internal tank temperatures 
measured using thermocouples:
    (1) After the FHR test (for non-flow-activated products) or Max GPM 
test (for flow-activated products), allow the water heater to fully 
recover.
    (2) When cut-out occurs, deactivate the burner, compressor, and/or 
electrical heating elements.
    (3) Remove the hot water from the tank by performing a continuous 
draw, while measuring the outlet water temperature at 3-second 
intervals, until the outlet water temperature is within 2 [deg]F of the 
inlet water temperature for five consecutive readings. Perform the draw 
at a flow rate of 3.0 gallons per minute (0.25 gallons per 
minute). Compute the mean tank temperature, Tst, as follows and assign 
this value as T0, Tsu,0, and Tmax,1:
[GRAPHIC] [TIFF OMITTED] TR21JN23.005

Where:

    Tst = the estimated average internal storage tank 
temperature.
    Tp = the average of the inlet and the outlet water 
temperatures at the end of the period defined by [tau]p.
    vout,p = the average flow rate during the period.
    Vst = the rated storage volume of the water heater.
    [tau]p = the duration of the period, determined by 
the length of time taken for the outlet water temperature to be 
within 2 [deg]F of the inlet water temperature for 15 consecutive 
seconds. The duration of the period shall include the 15-second 
stabilization period.
    Tin,p = the average of the inlet water temperatures 
during the period.
    Tout,p = the average of the outlet water temperatures 
during the period.

    (4) Re-activate the burner, compressor, and/or electrical elements 
and perform the 24-hour simulated use test as instructed in section 5.4 
of appendix E.
    (5) The standby period will start at five minutes after the end of 
the first recovery period after the last draw of the simulated-use 
test. The standby period shall last eight hours, so testing will extend 
beyond the 24-hour duration of the simulated-use test. At the end of 
the final standby measurement, remove water from the tank once again as 
in step #3, including computing the value of mean tank temperature. 
This calculated mean tank temperature is then assigned as Tsu,f and 
T24.
    (6) Determine Tt,stby,1 as the average of Tsu,0 and Tsu,f.
    The revised proposal relied on a different assumption--supported by 
DOE's test data--that, for typical storage-type water heaters, 
T0, Tsu,0, and Tmax,1 are similar in 
that they represent temperatures near the cut-out control temperature. 
Furthermore, the mean tank temperature at the end of the standby 
period, Tsu,f, can also be measured by removing water and 
measuring its temperature at the end of a sufficiently long standby 
period at the end of the test, and this value could also approximate 
T24. 87 FR 42270, 42284-42285 (July 14, 2022).
    In response to the July 2022 SNOPR, AHRI stated that manufacturers 
would need additional time to complete testing to verify the proposed 
equations and requested that DOE provide additional data and evidence 
that the method is appropriate before adopting it. Further, AHRI asked 
that DOE specify the correct procedure if the initial recovery period 
extends beyond the start of the second draw. (AHRI, No. 55 at p. 8) 
A.O. Smith expressed support for the revised proposal in the SNOPR, but 
the commenter added that manufacturers will need to work with the 
Department as additional testing on the identified products ensues, 
should this proposed change become part of any final rule.

[[Page 40455]]

(A.O. Smith, No. 51 at p. 9) BWC stated that the equation presented in 
the SNOPR is an improvement over the January 2022 NOPR proposal that 
will more effectively measure internal tank temperatures. However, BWC 
also commented that it has insufficient data to support or reject some 
elements of the proposal, and the company provided as an example the 
DOE's assumption made in the SNOPR proposal that Tmax and 
Tsu are similar. BWC explained that it would like to conduct 
additional testing before commenting further. (BWC, No. 48 at p. 5)
    Rheem noted that the procedure as proposed in section 5.4.2.2 of 
the proposed appendix E does not align with steps 1 and 2 of the 
preamble. Specifically, Rheem argued that the preamble states that 
after the FHR or Max GPM test, the unit should be allowed to fully 
recover, and then, one would deactivate the burner, compressor, and/or 
elements, and remove the hot water from the tank, which would result in 
a comparatively ``hot'' water temperature that is representative of a 
Tmax,1 or Tsu,0 value, both of which are measured 
after a draw and that is normally followed by a recovery; however, 
section 5.4.2.2 of the proposed appendix E states that a 1-hour idle 
period is to be performed prior to draining the tank, which would 
result in a comparatively ``low'' water temperature that is 
representative of T0, a measurement taken after an idle 
period where no energy was added to the tank. Rheem requested DOE 
clarify which method should be used. (Rheem, No. 47 at p. 8) Rheem also 
requested DOE clarify when a soak-in period is required when testing a 
water heater that cannot have the internal storage tank temperature 
directly measured, and specifically, the commenter asked whether a 
soak-in period is required between draining the tank after FHR testing 
and starting the 24-hour simulated use portion of the test. (Rheem, No. 
47 at p. 8)
    Rheem stated that the proposed procedure drains water from the unit 
at a flow rate of 3 gpm until the inlet and outlet temperatures match, 
which means all energy in the water and tank/heat exchanger has been 
removed from the unit under test. Rheem requested that DOE clarify that 
this is the intent of the procedure and suggested that as an 
alternative, since the storage volume is known, the test could simply 
remove the stored water and estimate the internal tank temperature 
using the proposed equation. (Rheem, No. 47 at p. 8) Rheem also 
recommended that the flow rate used for draining the tank be the flow 
rate of draw 1 of the 24-hour simulated-use test and that the 
temperatures be measured throughout the draw, not just after the first 
15 seconds, stating that the flow rate of 3 gpm may be too fast for 
some water heaters or would not account for the true energy content of 
the internal water. (Rheem, No. 47 at p. 8) Lastly, Rheem requested 
that DOE provide the derivation of the Tst equation, stating 
that the derivation and assumptions are not immediately apparent. 
(Rheem, No. 47 at, p. 9)
    In response, DOE provides the following clarifications. With 
respect to AHRI's request for clarification of the test procedure in 
terms of whether the initial recovery period extends beyond the start 
of the second draw, DOE notes that the tank would only be drained of 
hot water twice regardless of when the initial recovery period ends--
once after recovery after the FHR or max GPM test, and once at the end 
of the standby period at the end of the test. The mean tank temperature 
determined during the first draining would be used to approximate 
Tmax,1 regardless of when that actually occurs during the 
test, as DOE expects that Tmax,1, which occurs after the 
first recovery period ends, would not vary significantly depending on 
whether it occurs after the second draw. Regarding Rheem's request for 
a clarification of whether a 1-hour idle period is required before the 
first time drawing off all of the hot water in the tank, DOE clarifies 
that the 1-hour idle period is required, as was presented in the 
regulatory text in the SNOPR. As shown in Table III.3 which follows, 
T0 measurements taken after the 1-hour idle period are 
comparable to Tmax,1 and Tsu,f measurements. In 
addition, for tanks for which the internal tank temperature cannot be 
directly measured, the same soak-in provisions apply as those that 
apply generally as described in sections 5.2.4 and 5.4.2 of appendix E.
    Regarding Rheem's suggestion to remove volume of stored water in 
the tank and use the average temperature of that water to represent the 
measured mean tank temperature, DOE notes that when drawing off hot 
water through the hot water outlet, cold water is introduced into the 
tank which could mix with the stored water. Removing only the stored 
volume in the tank could result in an artificially low mean tank 
temperature due to the cold inlet water mixing with the stored water, 
whereas the proposed approach accounts for all of the thermal energy 
contained in the tank to estimate the temperature of the stored water 
prior to removing the hot water from the tank. A valid estimate of the 
tank temperature could be obtained by shutting off the supply (inlet) 
water line and draining the tank by gravity using the drain at the 
bottom. However, such an approach would likely require additional 
equipment for the test set-up, such as an additional temperature 
sensor, a flowmeter to measure the water leaving through the drain, and 
a flow control valve to manage the water exiting the drain, equipment 
not currently included in the typical test set-up. In addition, DOE has 
found that for some water heaters, even after draining by gravity, a 
small volume of water remains in the bottom of the tank, which would be 
difficult to account for under such an approach. After considering 
these comments, DOE has concluded that the methodology proposed in the 
SNOPR would not require changes to the test set-up and, therefore, 
would be less burdensome.
    DOE agrees with Rheem that a flow rate of 3.0 gpm may not be 
appropriate for all water heaters, and in particular it may be too high 
for temperature sampling rates to accurately estimate the mean tank 
temperature of smaller water heaters. Thus, DOE is adopting Rheem's 
suggestion to withdraw water at a flow rate equal to the flow rate of 
the first draw in the applicable draw pattern. DOE also agrees with 
Rheem that starting the measurements immediately, rather than after 15 
seconds, would provide a more accurate representation of tank 
temperature, and, therefore, the Department is adopting that 
recommendation as well.
    In response to these comments, DOE re-evaluated its own test data 
in order to further validate the method for determining internal tank 
temperature outlined above. Underpinning this method is an assumption 
that during a simulated use test, the mean tank temperatures that occur 
after the tank has been in standby for some time, Tsu,f and 
T24, are typically very similar to each other, and that the 
tank temperatures measured soon after a recovery and subsequent ``cut-
out'', Tsu,0, T0, and Tmax,1, are also 
typically very similar to each other. This is because water heaters 
with thermostats have a control band near the setpoint which directs 
the cut-in and cut-out to occur once the setpoint is reached. Table 
III.2 and Table III.3 below show the mean tank temperatures for a 
sample of 29 consumer water heaters.

[[Page 40456]]



                                            Table III.2--Tsu,f and T24 Values for Water Heaters Tested by DOE
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                            Difference
                                                                                                                                          between  Tsu,f
                                                                                                               Tsu,f       T24  ([deg]F)      and T24
                Test No.                            Product type *                   Draw pattern            ([deg]F)                        ([deg]F)
 
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................  ES                                  Low.......................           125.2           127.9            2.72
2.......................................  ES                                  Medium....................           121.2           116.7            4.50
3.......................................  ES                                  Medium....................           124.2           123.8            0.40
4.......................................  ES                                  Medium....................           122.7           122.1            0.56
5.......................................  ES                                  Medium....................           120.2           121.6            1.44
6.......................................  ES                                  Medium....................           123.7           120.7            3.04
7.......................................  ES                                  Medium....................           120.1           119.5            0.60
8.......................................  ES                                  Low.......................           121.7           122.5            0.78
9.......................................  ES                                  Medium....................           124.2           117.8            6.42
10......................................  ES                                  Medium....................           127.1           126.8            0.27
11......................................  ES                                  High......................           124.4           122.9            1.54
12......................................  ES                                  Low.......................           123.4           120.6            2.83
13......................................  ES                                  Medium....................           121.1           116.0            5.13
14......................................  ES                                  Medium....................           121.5           119.5            1.96
15......................................  ES                                  Medium....................           117.4           119.8            2.42
16......................................  ES                                  Medium....................           117.5           123.9            6.43
17......................................  ES                                  Medium....................           125.1           124.2            0.93
18......................................  ES                                  Low.......................           121.3           120.4            0.91
19......................................  ES                                  Medium....................           119.5           119.4            0.10
20......................................  ES                                  Medium....................           122.7           114.5            8.17
21......................................  ES                                  Medium....................           116.3           124.5            8.16
22......................................  ES                                  Medium....................           112.8           118.2            5.38
23......................................  ES                                  Medium....................           126.0           135.8            9.83
24......................................  ES                                  Medium....................           124.9           122.7            2.22
25......................................  ES                                  Low.......................           124.1           122.4            1.72
26......................................  GS                                  Medium....................           125.7           126.3            0.60
27......................................  GS                                  High......................           125.7           126.3            0.60
28......................................  GS                                  Medium....................           125.4           132.8            7.40
29......................................  GS                                  High......................           128.9           130.6            1.70
                                                                                                         -----------------------------------------------
    Minimum.............................  ..................................  ..........................  ..............  ..............            0.10
    Arithmetic Mean.....................  ..................................  ..........................  ..............  ..............            3.06
    Maximum.............................  ..................................  ..........................  ..............  ..............            9.83
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Note: ``ES'' denotes an electric storage water heater, and ``GS'' denotes a gas-fired storage water heater.


                                        Table III.3--T0, Tmax,1, and Tsu,0 Values for Water Heaters Tested by DOE
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Maximum
                                                                                                                                            difference
                                                                                                                                            between T0
                                                                                           T0  ([deg]F)       Tmax,1           Tsu,0        Tmax,1 and
             Test No.                       Product type *              Draw pattern                         ([deg]F)        ([deg]F)          Tsu,0
                                                                                                                                             ([deg]F)
 
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.................................  ES                             Low..................           118.2           116.8           114.0            4.20
2.................................  ES                             Medium...............           117.1           119.8           120.2            3.07
3.................................  ES                             Medium...............           119.0           116.0           119.6            3.60
4.................................  ES                             Medium...............           118.3           119.6           120.2            1.95
5.................................  ES                             Medium...............           124.2           117.8           119.5            6.36
6.................................  ES                             Medium...............           117.7           118.7           119.8            2.13
7.................................  ES                             Medium...............           119.2           116.2           117.5            3.02
8.................................  ES                             Low..................           122.0           117.1           115.6            6.40
9.................................  ES                             Medium...............           124.4           121.3           121.1            3.33
10................................  ES                             Medium...............           122.4           120.5           122.5            2.00
11................................  ES                             High.................           120.8           121.1           122.7            1.91
12................................  ES                             Low..................           123.8           120.7           124.5            3.80
13................................  ES                             Medium...............           116.8           121.9           119.5            5.13
14................................  ES                             Medium...............           120.8           126.0           125.2            5.17
15................................  ES                             Medium...............           121.8           121.2           121.6            0.56
16................................  ES                             Medium...............           120.6           121.8           122.6            1.98
17................................  ES                             Medium...............           121.1           118.6           121.4            2.80
18................................  ES                             Low..................           121.0           121.4           118.6            2.80
19................................  ES                             Medium...............           122.5           115.3           116.5            7.20
20................................  ES                             Medium...............           120.1           124.1           125.8            5.75
21................................  ES                             Medium...............           124.5           116.7           118.8            7.80
22................................  ES                             Medium...............           122.7           113.6           114.9            9.05
23................................  ES                             Medium...............           125.6           120.4           122.2            5.23
24................................  ES                             Medium...............           124.6           124.4           125.4            1.00
25................................  ES                             Low..................           123.4           118.4           119.1            4.97

[[Page 40457]]

 
26................................  GS                             Medium...............           125.0           126.0           128.0            3.00
27................................  GS                             High.................           126.1           125.2           131.8            6.60
28................................  GS                             Medium...............           124.1           128.7           131.4            7.30
29................................  GS                             High.................           124.7           123.8           129.8            6.00
                                                                                         ---------------------------------------------------------------
    Minimum.......................  .............................  .....................  ..............  ..............  ..............          0.5656
    Arithmetic Mean...............  .............................  .....................  ..............  ..............  ..............            4.28
    Maximum.......................  .............................  .....................  ..............  ..............  ..............            9.05
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Note: ``ES'' denotes an electric storage water heater, and ``GS'' denotes a gas-fired storage water heater.

    On average, across multiple product classes, the temperatures 
Tsu,f and T24 vary about 3 [deg]F from each 
other. Similarly, the temperatures T0, Tmax,1, 
and Tsu,0 vary about 4 [deg]F from for each other. In both 
cases, the range of variability between the mean tank temperatures of 
the water heaters in the sample was from less than 1 [deg]F up to 9 
[deg]F. Based on these data, DOE has concluded that both the 
temperatures are similar enough among each other that grouping them 
together for determining internal storage tank temperature, as proposed 
in the July 2022 SNOPR, is reasonably valid when there is no direct 
alternative of measuring these temperatures. As such, in this final 
rule, DOE is adopting the method for determining internal storage tank 
temperature as proposed in the July 2022 SNOPR with the modifications 
discussed in the preceding paragraphs.
    In response to Rheem's request for a derivation of the 
Tst equation, DOE notes that it was derived based on the 
assumption that the withdrawn water has the same amount of energy as 
the water stored in the tank, since there would be no energy input 
(i.e., the burner, compressor, and/or electrical heating elements are 
deactivated) and assuming minimal losses over the course of the draw. 
Specifically, DOE sought to determine the initial mean tank temperature 
of the water, denoted by Tst. The energy in the withdrawn 
water can be calculated based on its mass, specific heat, and the 
temperature difference between the water and the ambient air, which are 
all parameters that can be measured or determined directly as the water 
is being withdrawn from the tank. As noted previously, this value can 
then be assumed to be equal to the energy that would have been stored 
in the tank before withdrawing the water, which can also be determined 
based on its mass, specific heat, and temperature difference. The mass 
of water in the tank can be determined based on the stored volume and 
density; the specific heat can be assumed as 1 Btu/lb[deg]F, and the 
temperature difference can be calculated as Tst. minus the 
ambient temperature. As Tst is the only unknown, the 
equation can be rearranged to solve for Tst to provide an 
estimate of the mean tank temperature prior to withdrawing water.
    In response to requests made by AHRI, A.O. Smith, and BWC for 
additional time to conduct testing, DOE reiterates that test procedures 
must be established for all products within the scope of this 
rulemaking. DOE is finalizing this method for determining internal tank 
temperature based on an evaluation of its own test data, and the 
Department does not believe it is necessary to delay publication of 
this final rule for additional data to be collected on this topic. 
Water heaters with rated storage volumes greater than or equal to 2 
gallons whose internal tank temperatures cannot be measured using 
thermocouples meet the definition of ``consumer water heater'' as 
codified at 10 CFR 430.2; therefore, they are covered products and must 
have applicable test procedures. In this case, based on information 
from its own testing, DOE is establishing these test procedures in this 
final rule.
8. Alternate Order 24-Hour Simulated-Use Test
    As discussed in the January 2022 NOPR, DOE received comments at the 
RFI stage from SMTI recommending that DOE move the standby loss period 
of the test to the beginning of the 24-hour simulated-use test and to 
start the first draw at the 6-hour mark, based on claims that water 
heaters with large storage volumes but low input rates (e.g., storage-
type heat pump water heaters) may receive artificially low recovery 
efficiency results from the current test method with the standby loss 
period occurring in the middle of the test. 87 FR 1554, 1587 (Jan. 11, 
2022).
    In the January 2022 NOPR, DOE noted that as a general matter, the 
result of the standby period has a negligible effect on UEF, so moving 
the standby period to the start of the rest would likewise have a 
negligible effect on UEF in terms of improving the accuracy of the 
standby loss calculations for most water heaters. However, DOE agreed 
that moving the standby period to the start of the test may affect the 
recovery efficiency of the large-volume/low-input-rate water heaters 
described by SMTI, and a large change in recovery efficiency can have a 
significant effect on UEF. DOE tentatively determined that the first 
recovery is rarely delayed past the first draw (based on DOE's own test 
data), but if the order of the 24-hour simulated-use test were to be 
changed (i.e., placing the standby loss period at the beginning), all 
water heaters on the market would need to be retested. Therefore, DOE 
declined to propose such a change, as the associated burden on 
manufacturers to retest would result in a potential increase in 
accuracy for only a small subset of the consumer water heaters 
available on the market. 87 FR 1554, 1587 (Jan. 11, 2022).
    DOE did not receive further comments on this topic. Therefore, DOE 
has decided not to move the standby period to the start of the 24-hour 
simulated-use test because such amendment would be unduly burdensome on 
all manufacturers, as they would be required to retest all of their 
products, even though the representativeness of the efficiency results 
would be improved for only a small subset of water heaters.

F. Computations

1. Mass Calculations
    In sections 6.3.5 and 6.4.2 of appendix E, the mass withdrawn 
during

[[Page 40458]]

each draw (Mi) is used to calculate the daily energy 
consumption of the heated water at the measured average temperature 
rise across the water heater (QHW). However, neither section 
includes a description of how to calculate the mass withdrawn for tests 
in which the mass is indirectly determined using density and volume 
measurements. In the April 2020 RFI, DOE requested feedback on whether 
to update the consumer water heater test procedure to include a 
description of how to calculate the mass withdrawn from each draw in 
cases where mass is indirectly determined using density and volume 
measurements. 85 FR 21104, 21113 (April 16, 2020). Stakeholders 
generally supported including an equation in the computations of 
appendix E, with many suggesting that DOE adopt the calculations in the 
AHRI Operations Manual for Residential Water Heater Certification 
Program. 87 FR 1554, 1582 (Jan. 11, 2022).
    In the January 2022 NOPR, DOE proposed that the volume at the 
outlet would be multiplied by the density, which would be based on the 
average outlet temperature measured during the draw. DOE also proposed 
to add procedures similar to those in the AHRI Operations Manual for 
Residential Water Heater Certification Program; in particular, DOE 
proposed to add a method of converting inlet water volume to outlet 
water volume using the ratio of the water densities at the inlet and 
outlet.\75\ Id.
---------------------------------------------------------------------------

    \75\ The AHRI Operations Manual for Residential Water Heater 
Certification Program specifies that the outlet water volume is 
equal to the inlet water volume times the inlet water density 
divided by the outlet water density.
---------------------------------------------------------------------------

    In response to the January 2022 NOPR, BWC supported DOE's proposed 
clarifications for calculating water mass from indirect measurements. 
(BWC, No. 33 at p. 8)
    After carefully considering the comments, in this final rule, DOE 
is adopting the computations for determining water mass from indirect 
measurements that were proposed in the January 2022 NOPR for the 
reasons previously discussed.
2. Effective Storage Volume
    In this final rule, DOE is establishing provisions to calculate the 
effective storage volume to account for: (1) water heaters which may 
increase storage tank temperature to increase delivery capacity, and 
(2) circulating water heaters. As discussed throughout section III.E.1 
of this document, raising the temperature of the water stored in the 
tank can increase the effective storage capacity of the water heater. 
Additionally, circulating water heaters are instantaneous-type water 
heaters that operate with a separate stored volume of water such that 
the actual amount of hot water that can be provided immediately 
(without additional heat input) is related to the volume of water 
stored in the circulation pipes or in the separate tank--and not the 
rated storage volume of the circulating water heater itself. The 
following subsections describe the approach used for each case.
a. Storage Water Heaters With Elevated Stored Water Temperature
    In the July 2022 SNOPR, DOE addressed multiple comments regarding 
water heaters which boost the tank temperature in order to increase 
effective storage volume. (Operation in high heat mode and high 
temperature testing are discussed in detail in section III.E.1 of this 
final rule.) In particular, DOE noted there are certain consumer 
activities, such as filling a bathtub, for which the FHR metric and the 
rated storage volume metric alone do not sufficiently describe the 
water heater's ability to provide a large amount of hot water 
immediately. 87 FR 42270, 42280-42281 (July 14, 2022).
    For activities such as filling a bathtub, consumers would benefit 
more from knowing the effective storage volume (i.e., the volume of 
immediately available hot water) of a water heater, whereas for 
activities such as taking a shower, consumers could benefit more from 
knowing the FHR (i.e., ability to deliver hot water for an extended 
period of time). In particular, FHR represents one full hour of 
delivery and does not necessarily describe immediate hot water 
availability, as FHR is also impacted by the rate of recovery. In the 
past, rated storage volume has served as an indication of the amount of 
hot water immediately available. However, given the emergence of new 
water heater designs that allow operation in high heat mode, and the 
option that has existed to increase the tank temperature and install an 
external mixing valve, to provide additional capacity, this is no 
longer the case for all water heaters. Hence, in addition to FHR, DOE 
tentatively determined in the July 2022 SNOPR that effective storage 
volume would be a meaningful performance metric for consumers. Id.
    Therefore, in the July 2022 SNOPR, DOE proposed a method to 
determine effective storage volume, Veff (expressed in 
gallons or liters), at section 6.3.1.1 of appendix E. For water heaters 
capable of operating in high heat mode (which DOE proposed be 
determined by Tmax,1 being greater than Tdel,2 
during the 24-hour simulated use test), DOE proposed to calculate the 
effective storage volume based on a volume scaling factor and data 
already collected during the appendix E test. Id. at 87 FR 42281.
    DOE proposed that the volume scaling factor would be determined as 
follows, which is derived by comparing the thermal energy stored by the 
water heater when the water is heated to 125 [deg]F to the thermal 
energy stored at its maximum tank temperature, using temperature data 
collected during the test:
[GRAPHIC] [TIFF OMITTED] TR21JN23.006

Where:

kV is the dimensionless volume scaling factor;
[rho](T) is the density of water evaluated at temperature T;
CP(T) is the heat capacity of water evaluated at 
temperature T;
Tmax,1 is the maximum measured mean tank temperature 
after the first recovery period of the 24-hour simulated-use test, 
and
67.5 [deg]F is the average ambient temperature.

87 FR 42270, 42281 (July 14, 2022).
    DOE proposed to determine the effective storage volume by 
multiplying the measured storage volume by kV. Id.
    In response to DOE's effective storage volume proposal, ASAP, 
ACEEE, and NRDC expressed support for DOE's proposal to use effective 
storage volume as a metric for water heaters with high heat modes. 
(ASAP, ACEEE, and NRDC, No. 54 at pp. 2-3)
    AHRI requested that DOE provide additional data and evidence 
supporting the proposed equations for calculating effective storage 
volume and stated that manufacturers would also need

[[Page 40459]]

additional time to complete testing to verify their accuracy, 
representativeness, and repeatability. AHRI requested that DOE specify 
the correct procedure to evaluate this metric where the initial 
recovery period extends beyond the start of the second draw in this 
test. (AHRI, No. 55 at pp. 7-8)
    BWC requested that DOE conduct further testing for the method to 
determine effective storage volume, stating that manufacturers have not 
had enough time to conduct their own testing for this proposal. (BWC, 
No. 48 at pp. 3-4)
    Rheem suggested that DOE may not have enough information to 
incorporate effective storage volume into its energy conservation 
standards rulemaking without amending certification criteria because 
DOE is not requiring it to be reported. (Rheem, No. 47 at p. 8) 
Additionally, Rheem stated that models without ``high heat modes'' may 
still meet the conditions to be affected by the effective storage 
volume calculation, and the commenter requested that DOE clarify how to 
calculate effective storage volume when the first recovery period 
extends beyond the second draw, raising the concern that the delivery 
temperature can be too low as a result of this condition. (Rheem, No. 
47 at p. 7)
    In order to address these comments, DOE has re-evaluated its own 
test data to further examine the implications of the effective storage 
volume calculation as proposed in the July 2022 SNOPR. In particular, 
DOE sought to address Rheem's concern that the criteria which triggers 
effective storage volume calculation (Tmax,1 > 
Tdel,2) may lead more models to be impacted than just those 
operating with an elevated tank temperature and the request for 
clarification on how to calculate effective storage volume in the 
instance that the first recovery period extends beyond the second draw. 
Table III.3 lists the anonymized test data DOE evaluated to address the 
first of these two concerns. These tests were conducted in accordance 
with the currently applicable appendix E test procedure, with a nominal 
setpoint temperature of 125 [deg]F and no mixing valve installed.

                                           Table III.3--Tmax,1 and Tdel,2 Values for a Sample of Water Heaters
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                          Tmax,1-Tdel,2
             Test No.                       Product type *             Draw pattern          Tmax,1          Tdel,2        ([deg]F) **   kv > 1 [dagger]
                                                                                            ([deg]F)        ([deg]F)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.................................  ES                             Medium..............           116.0           124.6            -8.6  NO.
2.................................  ES                             Medium..............           117.8           125.8            -8.0  NO.
3.................................  ES                             Medium..............           121.3           122.8            -1.5  NO.
4.................................  ES                             Medium..............           120.4           122.6            -2.2  NO.
5.................................  GS                             Medium..............           126.0           128.5            -2.5  NO.
6.................................  GS                             High................           125.2           127.2            -2.0  NO.
7.................................  GS                             Medium..............           128.7           129.5            -0.8  NO.
8.................................  GS                             High................           123.8           127.0            -3.2  NO.
    Minimum.......................  .............................  ....................           116.0  ..............            -8.6
    Mean..........................  .............................  ....................           122.4  ..............            -3.6
    Maximum.......................  .............................  ....................           128.7  ..............            -0.8
    Std. Dev......................  .............................  ....................             4.3  ..............             3.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Note: ``ES'' denotes an electric storage water heater, and ``GS'' denotes a gas-fired storage water heater.
** A value of +5 [deg]F or more in this column would satisfy one of the two criteria for determining kV to be greater than 1.
[dagger] Per the effective storage volume calculation provisions established in this final rule.

    Upon further evaluation of the test data presented in Table III.3 
and based on comments received, in this final rule, DOE is modifying 
the approach in its earlier proposal to ensure that kV 
values greater than 1 are only calculated for water heaters operating 
with a significantly elevated tank temperature--as determined by both 
the difference between the storage tank temperature and the delivery 
temperature, as well as the storage tank temperature itself. 
Specifically, due to the fact that for some of the water heaters in 
Table III.3 Tmax,1 is only slightly less than 
Tdel,2, DOE has amended the criteria for determining 
kV such that a water heater must have both Tmax,1 
> 130 [deg]F and Tmax,1 > Tdel,2 + 5 [deg]F in 
order to have a kV factor greater than 1. If these two 
criteria are not met, then the water heater will be assigned a 
kV factor of 1 and will have an effective storage volume 
equal to its rated storage volume. This update to DOE's proposed 
approach will ensure that effective storage volume is only calculated 
to be greater than the rated storage volume for water heaters operating 
with a mean tank temperature that is both significantly above 125 
[deg]F and significantly above the delivered water temperature. The 
data show that for tests conducted at a nominal 125 [deg]F tank 
temperature setpoint, a kV greater than 1.0 is not expected. 
For additional reference, DOE conducted one test on a water heater set 
to its maximum storage tank temperature, resulting in a 
Tmax,1 of 159.6 [deg]F and a Tdel,2 of 124.3 
[deg]F, which would cause the kV to be equal to 1.59.
    Additionally, in order to address Rheem's concern about models for 
which the first recovery period extends beyond the start of the second 
draw, DOE has examined its own test data for water heaters exhibiting 
this behavior. Table III.4 lists anonymized data from 21 tests for 
which the first recovery period extended beyond the start of the second 
draw. Similar to the previous dataset, these tests were conducted at a 
tank temperature setpoint of 125 [deg]F and no mixing valve installed.
    DOE agrees that it would not be appropriate to base the effective 
storage volume calculation criteria on Tdel,2 if the tank is 
still recovering during the second draw, because Tdel,2 may 
be lower than it would be had the tank fully recovered. Therefore, for 
such cases, DOE has determined that T0 will take the place 
of Tmax,1, and Tdel,1 will take the place of 
Tdel,2 in the criteria specified previously. DOE has 
specified T0 and Tdel,1 as substitutes in this 
instance because they are unaffected by the timing of the first 
recovery period. Tdel,1 is measured during the first draw of 
the test, which will begin prior to the start of a recovery. 
T0 is measured immediately before the first draw (during 
which Tdel,1 is measured) and before the first recovery 
period, and it is, therefore, more representative of internal tank 
temperature as a point of comparison with Tdel,1 to 
determine whether the storage tank temperature is elevated relative to 
the delivery temperature. In reviewing its data for tests whose first 
recovery period

[[Page 40460]]

extended into the second draw, as shown in Table III.4, DOE found that 
the results using T0 and Tdel,1 are very 
comparable to those using Tmax,1 and Tdel,2, as 
shown in Table III.3. However, DOE is not making T0 and 
Tdel,1 the default variables because when T0 is 
paired with Tdel,1, the delta between the two is a slightly 
less reliable indicator of when elevated tank temperatures actually 
occur, compared to the default pair of Tmax,1 and 
Tdel,2. This is evidenced by the fact that the standard 
deviation of the delta, T0-Tdel,1, is slightly 
higher at 3.6, than that of the default variables, Tmax,1-
Tdel,2, which is 3.0. These standard deviations, along with 
other statistics for the test data are shown in Table III.3 and Table 
III.4.

                Table III.4--T0 and Tdel,1 Values for a Sample of Water Heaters Whose First Recovery Period Extends Into the Second Draw
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                            T0-Tdel,1
             Test No.                        Product type              Draw pattern       T0  ([deg]F)       Tdel,1        ([deg]F) **   kv > 1 [dagger]
                                                                                                            ([deg]F)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.................................  ES                             Low.................           118.2           122.8            -4.6  NO.
2.................................  ES                             Medium..............           117.1           128.7           -11.6  NO.
3.................................  ES                             Medium..............           118.3           123.7            -5.5  NO.
4.................................  ES                             Medium..............           117.7           127.7           -10.0  NO.
5.................................  ES                             Medium..............           119.2           125.9            -6.7  NO.
6.................................  ES                             Low.................           122.0           125.2            -3.2  NO.
7.................................  ES                             Medium..............           122.4           128.3            -6.0  NO.
8.................................  ES                             High................           120.8           126.8            -6.0  NO.
9.................................  ES                             Low.................           123.8           125.6            -1.8  NO.
10................................  ES                             Medium..............           116.8           129.5           -12.7  NO.
11................................  ES                             Medium..............           120.8           123.8            -3.0  NO.
12................................  ES                             Medium..............           121.8           123.9            -2.1  NO.
13................................  ES                             Medium..............           120.6           123.1            -2.5  NO.
14................................  ES                             Medium..............           121.1           126.6            -5.5  NO.
15................................  ES                             Low.................           121.0           125.0            -4.0  NO.
16................................  ES                             Medium..............           122.5           125.3            -2.8  NO.
17................................  ES                             Medium..............           120.1           129.0            -9.0  NO.
18................................  ES                             Medium..............           124.5           125.0            -0.5  NO.
19................................  ES                             Medium..............           122.7           124.3            -1.6  NO.
20................................  ES                             Medium..............           124.6           126.3            -1.7  NO.
21................................  ES                             Low.................           123.4           123.0             0.4  NO.
    Minimum.......................  .............................  ....................           116.8  ..............           -12.7  ...............
    Mean..........................  .............................  ....................           120.9  ..............            -4.8  ...............
    Maximum.......................  .............................  ....................           124.6  ..............             0.4  ...............
    Std. Dev......................  .............................  ....................             2.4  ..............             3.6  ...............
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Note: ``ES'' denotes an electric storage water heater.
** A value of +5 [deg]F or more in this column would satisfy one of the two criteria for initiating calculation of kV.
[dagger] Per the effective storage volume calculation provisions established in this final rule.

    AHRI, A.O. Smith, and Rheem expressed concern that because FHR is 
used as a metric for other activities such as building codes, plumbing 
codes, and incentive programs, DOE's proposal may cause misalignment 
with those requirements, as well as increased burden if manufacturers 
were to be required to comply with metrics for both FHR and effective 
storage volume. (AHRI, No. 55 at p. 7; A.O. Smith, No. 51 at pp. 7-8; 
Rheem, No. 47 at pp. 7-8) Rheem suggested that effective storage volume 
is not more appropriate than FHR as a metric of thermal energy storage. 
(Rheem, No. 47 at p. 7) A.O. Smith and Rheem also suggested that FHR is 
a more meaningful metric for consumers and that effective storage 
volume would be confusing. (A.O. Smith, No. 51 at pp. 7-8; Rheem, No. 
47 at p. 7)
    In response to these comments, the Department confirms that FHR is 
not being phased out or fully replaced by effective storage volume in 
the DOE test procedure, and, therefore, this additional metric will not 
cause misalignment with other programs and regulations based on FHR. As 
stated previously, these metrics provide different information: 
effective storage volume indicates the amount of hot water that can be 
delivered immediately without need for heat input and is correlated to 
the standby losses of the tank, whereas the FHR metric is determined by 
a test which allows the heat input to remain on and for the water 
heater to initiate a recovery. Additionally, manufacturer burden would 
be minimal because the effective storage volume can be determined based 
on measurements already taken during the 24-hour simulated use test.
    DOE notes that in contrast to FHR, effective storage volume is 
capable of accounting for the increase in thermal energy associated 
with heating water above the intended delivery temperature in 
comparison with larger units storing water at conventional 
temperatures. It also allows consumers to compare water heaters with 
similar delivery capabilities but different sizes, information which 
DOE considers meaningful, while avoiding the risk of backsliding for 
units with lower-than-normal FHRs, should FHR be used as the metric. 
Contrary to what these commenters suggest, DOE finds that providing a 
measure of effective storage volume is more likely to prevent consumer 
confusion due to the increased transparency it promotes by reflecting 
the immediate hot water capacity of the water heater for certain uses 
such as filling a bathtub. Combined with the high temperature test 
method, consumers would have a way to directly compare the performance 
of water heaters of different sizes that can meet the same user needs.
    In response to DOE's request for comment regarding its proposed 
equations and approach to calculate effective storage volume, Rheem 
agreed that DOE's derivation from an energy balance was appropriate for 
calculating a scaling factor. (Rheem, No. 47 at p. 7) NEEA commented 
that that the

[[Page 40461]]

proposed method appears to contain an error in the calculation of the 
dimensionless volume scaling factor (kv,) by using 67.5 
[deg]F, the standard test condition ambient air temperature, instead of 
58 [deg]F, the standard test condition water inlet temperature. 
Otherwise, NEEA indicated support of DOE's proposed method for 
calculating the effective storage volume metric. (NEEA, No. 56 at p. 3)
    DOE's volume scaling factor is derived by comparing the thermal 
energy stored by the water heater when the water is heated to 125 
[deg]F to the thermal energy stored at its maximum tank temperature. In 
response to NEEA's comment, DOE notes that the method to calculate the 
dimensionless volume scaling factor kv uses ambient air 
temperature because as the water in the storage tank cools, heat is 
lost to the surrounding air. Thus, the water approaches the temperature 
of the surrounding air, not the 58 [deg]F inlet water temperature. 
Therefore, DOE has maintained this calculation method as originally 
proposed.
    Rheem suggested that an effective volume scaled to 125 [deg]F is 
not useful for customers because a typical bath temperature is around 
100 [deg]F. (Rheem, No. 47 at p. 7) In response, DOE notes that the 
effective storage volume calculation is to show how much additional 
thermal energy is stored in the tank compared to a water heater which 
is not raising the internal tank temperature beyond the delivery 
temperature. Because 125 [deg]F is the delivery setpoint temperature 
used in the appendix E test procedure as being representative of 
typical water heater setpoint temperatures, DOE has concluded that it 
is appropriate for the tank temperature has to be compared to 125 
[deg]F.
    The CA IOUs supported DOE's proposed effective storage volume 
metric as being more representative of a storage water heater's hot 
water delivery capacity than rated storage volume. However, the CA IOUs 
asserted that effective storage volume does not account for differences 
in recovery rate between water heaters, a factor which also affects hot 
water delivery capacity and specifically FHR. The CA IOUs pointed out 
that large discrepancies in FHR exist within a given rated storage 
volume for both gas and electric storage water heaters. Therefore, the 
CA IOUs suggested DOE should revise its proposed algorithm for the 
effective storage volume to produce a metric incorporating the volume 
and temperature of the stored water and the water heater recovery rate. 
(CA IOUs, No. 52 at pp. 2-4)
    In response, effective storage volume is intended to measure the 
maximum thermal energy a water heater can store and to indicate the 
amount of hot water that is immediately available. Effective storage 
volume is not intended to measure how fast the unit is able to heat 
water. This is in contrast with FHR, which accounts for the water 
heater's recovery rate as previously described. Accounting for water 
heater recovery rate in the effective storage volume calculation would 
make the effective storage volume metric duplicative of the existing 
FHR metric; DOE reiterates that effective storage volume will not 
replace FHR, which will remain a part of the test procedure. A.O. Smith 
stated that the effective storage volume metric may become obsolete if 
DOE's proposed energy conservation standards effectively limit the 
availability of non-demand response water heaters with user-selectable 
high heat modes. (A.O. Smith, No. 51 at p. 7) In response to A.O. 
Smith's comment, DOE notes that the scope of this comment falls within 
that of the energy conservation standards rulemaking, so it will be 
properly considered in the concurrent standards rulemaking for consumer 
water heaters. Additionally, DOE would again mention that certification 
and representations of effective storage volume will not be required as 
a result of this final rule, but instead may be required at the time of 
any energy conservation standards that specifically address which water 
heaters may be required to carry out high temperature testing.
    Finally, when proposing the calculation of estimated mean tank 
temperature in the July 2022 SNOPR, DOE inadvertently omitted the 
calculation of annual electrical energy consumption from the test 
procedure. DOE has once again included this calculation as originally 
proposed in the January 2022 NOPR at section 6.3.10 of appendix E.
b. Circulating Water Heaters
    As discussed in section III.D.4 of this document, DOE is amending 
the test procedure to require that circulating water heaters must be 
tested with a separate storage tank. Specifically, gas-fired and oil-
fired circulating water heaters and electric resistance circulating 
water heaters must be tested with an UFHWST, and heat pump-type 
circulating water heaters must be tested with an electric storage water 
heater.
    For circulating water heaters, effective storage volume 
calculations will be carried out in a slightly different manner than 
for storage water heaters. The methodology established in this final 
rule takes into consideration the concerns raised by stakeholders and 
discussed in section III.D.4 of this document. In summary, while 
commenters expressed that it would be beneficial to be able to use a 
range of UFHWST volumes for testing non-heat-pump-type circulating 
water heaters, commenters were also concerned that the results of 
testing may not be reproducible without certifying the specific model 
of UFHWST to be used. Regarding the volume, DOE understands that 
circulating water heater designs may be optimized to operate with 
specific storage volumes; thus, in this final rule, DOE is allowing a 
range of volumes to be used. However, manufacturers may represent the 
volume of the UFHWST in terms of the effective storage volume of the 
circulating water heater as follows.
    Because circulating water heaters are to be tested with a separate 
storage tank, they operate, as a system, in a similar manner to 
storage-type water heaters. Although the volume stored by the 
circulating water heater itself may be small, these water heaters 
require a separate volume of water to operate properly. Therefore, DOE 
has determined that it is appropriate for the effective storage volume 
calculation for circulating water heaters to account for the separate 
storage tank, as the volume of the stored water is representative of 
the effective volume that would be available for such a water heater in 
the field, since it is necessary to install a circulating water heater 
with a storage tank or other stored volume of water. The procedure for 
calculating effective storage volume of separate storage tanks paired 
with circulating water heaters is outlined in section 6.3.1.1 of 
appendix E. This procedure will prescribe the value of the measured 
storage volume of the separate storage tank to be the effective storage 
volume of the circulating water heater, and the measured storage volume 
of the separate storage tank shall be determined in accordance with 
section 5.2.1 of the amended appendix E (Determination of Storage Tank 
Volume). This allows the same method of volume measurement to be 
applied to UFHWSTs and separate electric resistance storage tanks. DOE 
has determined that this approach allows for manufacturers to have the 
flexibility to use the appropriate size of UFHWST for the circulating 
water heater while still ensuring that testing can be done in a 
reproducible manner.
    In a separate rulemaking pertaining to certification requirements 
for consumer water heaters and residential-duty commercial water 
heaters, DOE will address any potential amendments

[[Page 40462]]

which would need to be made in order to certify the effective storage 
volume of a product. DOE would consider establishing product-specific 
enforcement provisions for circulating water heaters at such a time 
when energy conservation standards for these products are evaluated.

G. Untested Provisions (Alternative Efficiency Determination Methods)

    At 10 CFR 429.70, DOE specifies alternative methods for determining 
energy efficiency and energy use for certain covered products and 
equipment, including consumer water heaters.\76\ In general, these 
provisions allow a manufacturer to determine the energy efficiency or 
energy use of a basic model using an alternative efficiency 
determination method (AEDM) in lieu of actually testing the basic 
model. Specific to each product or equipment type covered by these AEDM 
provisions, DOE defines the criteria for using an AEDM and, for some 
products and equipment, procedures to be used to validate an AEDM and 
to perform verification testing on units certified using an AEDM.
---------------------------------------------------------------------------

    \76\ Section 429.71 uses the term ``residential,'', which is 
synonymous with the use of the term ``consumer'' in this document.
---------------------------------------------------------------------------

    The provisions at 10 CFR 429.70(g) provide alternative methods for 
determining ratings for ``untested'' basic models of residential water 
heaters and residential-duty commercial water heaters. For models of 
water heaters that differ only in fuel type or power input, these 
provisions allow manufacturers to establish ratings for untested basic 
models based on the ratings of tested basic models if certain 
prescribed requirements are met. (Simulations or other modeling 
predictions or ratings of UEF, volume, first-hour rating, or maximum 
gallons per minute are not permitted (10 CFR 429.70(g)).)
    Specifically, for gas water heaters, the provisions at 10 CFR 
429.70(g)(1) specify that for untested basic models of gas-fired water 
heaters that differ from tested basic models only in whether the basic 
models use natural gas or propane gas, the represented value of UEF, 
FHR, and maximum gallons per minute for an untested basic model can be 
the same as those for a tested basic model, as long as the input 
ratings of the tested and untested basic models are within 10 percent.
    For electric storage water heaters, the provisions at 10 CFR 
429.70(g)(2) specify rating an untested basic model using the FHR and 
the UEF obtained from a tested basic model as a basis for ratings of 
basic models with other input ratings, provided that certain conditions 
are met: (1) each heating element of the untested basic model is rated 
at or above the input rating for the corresponding heating element of 
the tested basic model; and (2) for an untested basic model having any 
heating element with an input rating that is lower than that of the 
corresponding heating element in the tested basic model, the FHR for 
the untested basic model must result in the same draw pattern specified 
in Table I of appendix E for the simulated-use test as was applied to 
the tested basic model.\77\ 10 CFR 429.70(g)(2)(i)-(ii).
---------------------------------------------------------------------------

    \77\ To establish whether this condition is met, the provisions 
at 10 CFR 429.70(g)(2)(ii) specify determining the FHR for the 
tested and the untested basic models in accordance with the 
procedure described in section 5.3.3 of 10 CFR part 430, subpart B, 
appendix E, and then comparing the appropriate draw pattern 
specified in Table I of appendix E for the FHR of the tested basic 
model with that for the untested basic model. If this condition is 
not met, then the untested basic model must be tested and the 
appropriate sampling provisions applied to determine its UEF in 
accordance with appendix E.
---------------------------------------------------------------------------

    In commenting on this topic in response to the January 2022 NOPR, 
Rheem suggested expanding the AEDM provisions for consumer water 
heaters to address circulating water heaters. Specifically, Rheem 
identified three possible AEDM approaches: (1) test the thermal 
efficiency or COP using the commercial water heater test procedure and 
use the result to calculate an estimated UEF for various storage 
capacities; (2) open the commercial HVAC AEDM provisions at 10 CFR 
429.70(c) to circulating consumer water heaters; or (3) add provisions 
similar to the current electric storage water heater AEDM, where a 
change in draw pattern would necessitate a new test. (Rheem, No. 31 at 
pp. 3-4)
    Further, DOE notes that although manufacturers of consumer water 
heaters are not authorized to use an AEDM under 10 CFR 429.70(c) to 
determine ratings for consumer water heaters, as discussed, 
manufacturers may determine UEF for certain models using the methods 
specified under 10 CFR 429.70(g). These models include: (1) gas-fired 
basic models differing only in whether the basic models use natural gas 
or propane and with an input rating within 10 percent and (2) electric 
storage water heater basic models differing only in heating element 
input rating (in addition, for untested basic models with a heating 
element with an input rating that is lower than the input rating of the 
corresponding element in the tested basic model, the FHR for the 
untested basic model must also result in the same draw pattern as was 
applied to the tested basic model). These provisions already provide 
manufacturers with some measure of an alternative method of rating 
consumer water heaters without testing every model, and this 
alternative method reduces manufacturer test burden. Further, DOE 
explained in a 2013 final rule pertaining to AEDMs that the AEDM 
provisions extend to those products or equipment which have ``expensive 
or highly-customized basic models.'' 78 FR 79579, 79580 (Dec. 31, 
2013). The current AEDM provisions for commercial HVAC equipment 
(including commercial water heaters, for example) were in part the 
result of a negotiated rulemaking effort by the Appliance Standards and 
Rulemaking Federal Advisory Committee (ASRAC) in 2013. Id. Consumer 
water heaters were not considered at the time.\78\ Id In this 
rulemaking, DOE did not receive comments indicating that these 
conditions would apply for consumer water heaters or residential-duty 
commercial water heaters, and, hence, DOE has determined that modeling-
based AEDMs are not required at this time. Additionally, the test 
method adopted in this final rule has been determined to be 
representative of energy use over an average use cycle without being 
unduly burdensome.
---------------------------------------------------------------------------

    \78\ Working group meeting transcripts can be found at 
www.regulations.gov under Docket No. EERE-2013-BT-NOC-0023.
---------------------------------------------------------------------------

    Given these factors, DOE is not considering further expansion of 
the AEDM provisions for water heaters within the scope of this test 
procedure, aside from applying the untested model provisions to 
electric instantaneous water heaters, as discussed in section III.G.2 
of this document. The following sections discuss representations of the 
FHR value of certain untested models and the extension of the 
alternative rating method to electric instantaneous-type water heaters.
1. Representations of First-Hour Ratings for Untested Basic Models
    The provisions at 10 CFR 429.70(g) allow for an untested electric 
storage water heater basic model with element wattages less than a 
tested basic model to use the FHR of the tested basic model, provided 
that the untested basic model's FHR is in the same draw pattern as the 
tested basic model. For an untested basic model with an element wattage 
that is lower than the tested basic model's, the tested FHR of the 
untested basic model will generally be less than the FHR of the tested 
basic model. In such cases, using the tested basic model's FHR to 
represent the untested model's FHR may not be as

[[Page 40463]]

representative as using the FHR value directly determined from the 
untested model (the FHR of the untested basic model is determined 
pursuant to the procedures in appendix E specifically for the purpose 
of allowing use of the tested basic model's UEF rating). Instead, using 
the untested basic model's measured FHR for representation purposes, 
rather than the tested model's FHR (as currently required), could 
increase the representativeness of the certified FHR, while potentially 
not increasing burden on the manufacturer.
    The January 2022 NOPR requested comment on the potential to revise 
the existing provisions at 10 CFR 429.70(g)(2)(ii) for electric storage 
water heaters with element wattages less than the tested basic model to 
require that the represented FHR of the untested model be the untested 
basic model's FHR as determined according to the procedures at appendix 
E. Specifically, DOE sought information on whether manufacturers 
collect sufficient data to establish a rated value of FHR based on FHR 
testing for untested basic models, subject to the sampling plan 
requirements at 10 CFR 429.17 (i.e., whether manufacturers currently 
measure the FHR of at least two units of an untested basic model to 
ensure it is in the same draw pattern bin as the tested model). 87 FR 
1554, 1587-1588 (Jan. 11, 2022).
    In commenting on this issue, ASAP, ACEEE, and NCLC supported 
revising the untested provisions for storage water heaters so that the 
first-hour ratings for untested models are used for ratings. Likewise, 
ASAP, ACEEE, and NCLC also supported requiring that the represented 
value of max GPM for untested electric instantaneous water heaters be 
the actual value determined for the untested model. (ASAP, ACEEE, and 
NCLC, No. 34 at p. 3)
    BWC offered a different view, commenting that the current AEDM 
provisions yield accurate results for untested electric storage water 
heaters with element wattages less than the tested basic models. The 
company stated that changing these provisions would result in 
significant burden for manufacturers without producing significantly 
different results. BWC also urged DOE to not apply the more stringent 
AEDM requirements for electric storage water heaters to electric 
instantaneous water heaters. (BWC, No. 33 at pp. 10-11)
    Similarly, AHRI raised concerns about the increased burden 
associated with the proposed additional requirements for alternate 
electric storage water heater input ratings. (AHRI, No. 40 at p. 3) 
AHRI indicated that, because the sampling plan provisions at 10 CFR 
429.17 are not currently required when certifying untested models, 
manufacturers would have to retest and recertify untested models if DOE 
were to adopt such requirements. (AHRI, No. 40 at pp. 5-6) A.O. Smith 
requested additional clarity on exactly which untested models would 
need to be tested to confirm FHR ratings under the proposed untested 
provisions. (A.O. Smith, Jan. 27, 2022 Public Meeting Transcript, No. 
27 at pp. 48-49) A.O. Smith claimed that the established practice has 
been to evaluate untested electric storage water heater tank inputs to 
confirm that these models would perform in the same draw pattern as the 
tested model. A.O. Smith also stated that certifying data for untested 
models would be an extra testing burden for manufacturers which have 
relied on the procedures pursuant to alternative methods for 
determining energy efficiency and energy use to establish the ratings, 
and, therefore, the commenter recommended against the Department 
changing the relevant data collection methodology. (A.O. Smith, No. 37 
at pp. 4-5)
    After consideration of the comments and the additional burden that 
an amendment relating to the FHR representations for certain untested 
water heaters would impose, DOE has decided not to amend these 
provisions at this time. However, DOE reiterates that, per the current 
AEDM requirements, manufacturers are required to test the FHR of an 
untested model prior to making a determination as to whether or not the 
untested model will fall under the same draw pattern as the tested 
model. This determination should not be made on the basis of input 
rates alone. Manufacturers should consult 10 CFR 429.70(g), which 
states, ``simulations or other modeling predictions for ratings of the 
uniform energy factor, volume, first-hour rating, or maximum gallons 
per minute (GPM) are not permitted.'' Furthermore, as a clarification 
of the existing reporting requirements, manufacturers using the 
untested provisions to certify certain water heater models to DOE must 
identify these models as being tested to an AEDM (see 10 CFR 
429.17(b)(1), which references 10 CFR 429.12).
2. Alternative Rating Method for Electric Instantaneous Water Heaters
    In the January 2022 NOPR, in response to earlier stakeholder 
comments, DOE proposed to expand the untested provisions (described in 
detail in section III.G.1 of this document) so as to apply similar 
provisions to electric instantaneous water heaters. The proposed 
expansion would allow electric instantaneous water heaters and electric 
storage water heaters to have similar AEDM requirements. 87 FR 1554, 
1588 (Jan. 11, 2022).
    As discussed in further detail in the January 2022 NOPR, because 
electric instantaneous water heaters exhibit the same trends in 
performance that justify the use of an alternative rating determination 
method for electric storage water heaters, DOE tentatively determined 
that extending the use of the untested provisions to electric 
instantaneous water heaters in 10 CFR 429.70(g) would maintain a 
representative rating of these products' energy efficiency, while 
reducing manufacturer burden. Therefore, DOE proposed to permit use of 
the untested provisions for electric instantaneous water heaters 
through newly proposed provisions at 10 CFR 429.70(g)(3). Specifically, 
the January 2022 NOPR proposed that the criteria that currently apply 
to electric storage water heaters at 10 CFR 429.70(g)(2) would apply to 
electric instantaneous type water heaters at 10 CFR 429.70(g)(3), with 
the exceptions that: (1) The criteria for electric instantaneous water 
heaters would reference the maximum GPM rather than the FHR, as FHR 
applies only to storage water heaters; and (2) the criteria for 
electric instantaneous water heaters would reference the ``input rate'' 
rather than the ``heating element'' or ``input rating for the 
corresponding heating element.''. 87 FR 1554, 1588 (Jan. 11, 2022).
    On this topic, AHRI and A.O. Smith expressed support for the 
inclusion of electric instantaneous water heaters in the untested 
provisions. (AHRI, No. 40 at pp. 5-6; A.O. Smith, No. 37 at p. 2) Based 
upon its previous reasoning and after considering the relevant 
comments, DOE is adopting the untested provisions for electric 
instantaneous water heaters as proposed in the January 2022 NOPR, with 
only a minor modification.
    Section III.H.1 of this document discusses terminology used with 
respect to storage vs. instantaneous and flow-activated vs. non-flow-
activated water heaters. Specifically, DOE has determined that not all 
instantaneous water heaters are flow-activated, and also that storage 
water heaters do not necessarily have to be non-flow-activated, either. 
As such, in this final rule, DOE is amending the language in all of the 
untested provisions (those which currently exist and those which are 
being newly established) such that the delivery capacity metric may be 
either FHR or Max GPM. This correction

[[Page 40464]]

will harmonize the requirements at 10 CFR 429.70(g) with the test 
procedure, which specifies that the Max GPM metric is for flow-
activated water heaters, and the FHR metric is for all others, 
regardless of the water heater's classification as storage-type or 
instantaneous-type (see section 5.3 of appendix E).

H. Corrections and Clarifications

    DOE is adopting certain corrections and clarifications to the 
appendix E test procedure that are intended to improve the 
repeatability and reproducibility of the test procedure. These changes 
are described in more detail in the subsections that follow.
1. Flow-Activated Terminology
    In sections 5.3.3.1 and 5.3.3.2 of appendix E, which describe 
general requirements and draw initiation criteria, respectively, for 
the FHR test, the term ``storage-type water heaters'' is used. However, 
the FHR test applies to all water heaters that are not flow-activated, 
which includes non-flow-activated instantaneous water heaters. In this 
rulemaking, DOE sought feedback on updating the phrase ``storage-type 
water heaters'' in section 5.3.3 to ``non-flow-activated water 
heaters.'' 85 FR 21104, 21112 (April 16, 2020). Multiple stakeholders 
provided comments on the use of ``flow-activated'' and ``non-flow-
activated'' in response to the April 2020 RFI and the January 2022 
NOPR.
    Initially, commenters such as AHRI and some manufacturers stated 
that there is no need to change the phrase ``storage-type water 
heaters'' in section 5.3.3 of appendix E. However, when DOE submitted a 
comment to the ASHRAE 118.2 drafting committee suggesting the change 
from ``storage-type'' to ``non-flow activated'' in the corresponding 
sections of ASHRAE 118.2, this change was accepted by the committee and 
used in ASHRAE 118.2-2022. Thus, DOE proposed to update the terminology 
in the January 2022 NOPR in an effort to align terminology with that 
recognized by industry. 87 FR 1554, 1576 (Jan. 11, 2022).
    Specifically, section 7.3.3.1 of ASHRAE 118.2-2022 uses the term 
``non-flow-activated'' water heaters, whereas section 5.3.3.1 of the 
current appendix E test procedure uses the term ``storage-type'' water 
heaters. Yet section 7.3.3.2 of ASHRAE 118.2-2022 still uses the 
``storage-type'' term that is present in section 5.3.3.2 of appendix E. 
By contrast, DOE's proposal, as delineated in the January 2022 NOPR, 
would effectively ensure that language related to the FHR test did not 
inadvertently narrow the scope of that test to only storage-type water 
heaters whenever the term ``storage-type'' was used in this context.
    On this topic, Rheem supported the proposed amendments to the 
language throughout appendix E to use ``non-flow activated'' and 
``flow-activated,'' and to refer to water heaters with or without 
storage volumes greater than 2 gallons as such. Rheem stated that these 
changes eliminate the storage or instantaneous type language except 
where helpful to navigate the appendix. (Rheem, No. 31 at p. 2)
    Many commenters expressed confusion regarding DOE's proposed 
changes in terminology in appendix E, however. At the public meeting 
webinar for the January 2022 NOPR, AHRI requested further explanation 
of the intent behind the proposed terminology update changing 
``storage-type'' and ``instantaneous-type'' to ``non-flow-activated'' 
and ``flow-activated,'' especially since the proposed terms are not 
used in EPCA. AHRI requested that DOE clarify whether or not the 
terminology change would have any impact on testing. (AHRI, Jan. 27, 
2022 Public Meeting Transcript, No. 27 at pp. 41-42) In its written 
comments, AHRI stated that replacing the ``instantaneous-type'' and 
``storage-type'' terminology with ``flow-activated'' and ``non-flow 
activated'' may cause confusion for the test methods relevant to water 
heaters larger than 20 gallons in rated storage volume. AHRI suggested 
that DOE should consider adding steps to the test procedure to 
determine: (1) if a unit is ``storage-type'' or ``instantaneous-type'' 
and (2) if a unit is ``flow-activated'' or ``non-flow activated.'' 
(AHRI, No. 40 at p. 4) BWC did not support a change from the terms 
``storage-type'' and ``instantaneous-type'' to ``non-flow-activated'' 
and ``flow-activated'' for water heaters above 20 gallons, stating that 
it would create confusion for manufacturers and testing laboratories. 
(BWC, No. 33 at p. 6)
    AET commented that a flow-activated electric instantaneous water 
heater will need to be able to heat its stored volume of water to the 
67 [deg]F temperature rise in appendix E in no more than about 30 
seconds based on a calculation of recovery efficiency and flow rate. 
(AET, No. 29 at pp. 3-5) However, DOE notes that this calculation is 
only possible because the recovery efficiency of an electric resistance 
water heater is defined as 98 percent in the appendix E test procedure; 
the time criterion would vary for other types of water heaters.
    Furthermore, AET commented that DOE should be careful in its use of 
the term ``instantaneous'' water heater to ensure the test procedure 
for these products applies to all products which have more than 4,000 
Btu/h of input per gallon of storage, adding that there are 
instantaneous water heaters have several gallons of storage capacity or 
are thermostatically-activated (which should be tested under a non-
flow-activated test method). The commenter stressed that water heaters 
should be tested per the flow-activated or non-flow-activated test 
method based on whether or not they are indeed flow-activated, and not 
whether they are instantaneous-type or storage-type. AET commented that 
a thermostatically-activated unit does not necessarily mean that stored 
water is kept fully heated, but rather that the rate of change of 
temperature of stored water can be used to indicate whether a flow is 
occurring, and, therefore, the distinction between flow-activation and 
non-flow-activation (i.e., thermostatic activation) may be difficult to 
make for water heaters with very small volumes. AET claimed that hybrid 
instantaneous water heaters activated by both flow and water 
temperature are under development, and such appliances should be 
addressed in the test procedure. AET also noted that the largest 
possible instantaneous-type gas-fired unit may have up to 50 gallons of 
storage volume per the codified definitions, and the largest possible 
instantaneous-type oil-fired unit may have up to 52.5 gallons of 
storage volume. Additionally, AET provided detailed comments indicating 
that not all instantaneous water heaters are flow-activated within the 
scope of the standards of consumer water heaters, so DOE should not use 
the terms interchangeably. (AET, No. 29 at pp. 2-6)
    To clarify the intent of the January 2022 NOPR's proposal: DOE 
agrees with AET that the distinction between storage-type water heaters 
and instantaneous-type water heaters is different from the distinction 
between flow-activated water heaters and water heaters with other 
activation schemes. Comments from manufacturers seem to indicate that 
there could be a misconception that ``instantaneous-type water heater'' 
and ``flow-activated water heater'' are interchangeable, because these 
comments opposed DOE's correction to remove the ``storage-type'' term 
from the description of the FHR test and replace it with the ``non-
flow-activated'' term; however, these terms are not interchangeable. 
When a water heater is referred to as ``storage-type'' or 
``instantaneous-type,'' those terms specifically refer to the ratio 
between

[[Page 40465]]

the storage volume and the input rate. These terms are defined in EPCA 
(see 42 U.S.C. 6291(27)(A) and (B)) and at 10 CFR 430.2. For example, 
DOE's energy conservation standards at 10 CFR 430.32(d) distinguish 
between storage-type and instantaneous-type water heaters. Section 1.6 
of appendix E defines ``flow-activated'' as an operational scheme in 
which a water heater initiates and terminates heating based on sensing 
flow in order to determine which method of testing is most appropriate 
for the water heater's operational scheme. Therefore, whether a water 
heater is storage-type or instantaneous-type has no bearing on whether 
it is determined to be ``flow-activated.'' There. can be flow-activated 
storage water heaters or even non-flow-activated instantaneous water 
heaters. In fact, circulating water heaters are defined as non-flow-
activated instantaneous water heaters (see section III.A.4.a of this 
final rule).
    Section 5.3.1 of appendix E states, ``For flow-activated water 
heaters, conduct the maximum GPM test, as described in section 5.3.2, 
Maximum GPM Rating Test for Flow-Activated Water Heaters, of this 
appendix. For all other water heaters, conduct the first-hour rating 
test as described in section 5.3.3 of this appendix.'' In this final 
rule, the Department is maintaining this requirement in the revised 
appendix E test procedure.
    With respect to comments related to how to determine whether a 
water heater is flow activated, DOE has concluded that the definition 
of ``flow-activated'' in proposed section 1.6 of appendix E is 
sufficient for manufacturers and testing laboratories to determine 
whether a product meets that definition. Specifically, if a water 
heater initiates or terminates heating as a result of sensing flow--
regardless of what type of sensor is used to determine whether a flow 
is occurring--then the water heater is flow-activated. If a water 
heater has two activation schemes, one of which is based on sensing 
flow (e.g., heating can also be initiated due to the tank temperature 
crossing below a certain thermostat limit), then it still meets the 
description of a flow-activated water heater, and, therefore, must be 
tested as such. This is a clarification of the current test procedure 
and not an amendment, and, thus, DOE is maintaining the language in the 
definition of ``flow-activated'' in appendix E (which will now appear 
at section 1.7).
    DOE understands that the term ``non-flow-activated,'' which was 
used in the January 2022 NOPR's proposal, could be a source of 
confusion, because, as AET states, there are products which are dually 
activated. Hence, in this final rule, DOE is not introducing this term 
into the appendix E test procedure. Instead, DOE is striking out the 
references to storage-type water heaters in provisions related to water 
heaters which require the FHR test and striking out the reference to 
instantaneous-type water heaters in provisions related to water heaters 
which require the Max GPM test. Because section 5.3.1 already instructs 
which test is required, these instances of the terms ``storage-type'' 
and ``instantaneous-type'' are inaccurate and extraneous. DOE has 
determined that these corrections and clarifications do not change the 
way in which the appendix E test procedure is conducted.
2. Second Identical 24-Hour Simulated-Use Test
    For water heaters that are not flow-activated, the water heaters 
test procedure in section 5.2.2.2 of the currently applicable appendix 
E includes directions for setting the temperature controllers such that 
the test method is repeatable and reproducible.
    A.O. Smith requested DOE to clarify that, when testing water 
heaters larger than or equal to 20 gallons, the second identical 
simulated-use test is not a requirement of the procedure but only a 
means by which to validate the stability of the setting, if it is 
deemed necessary to perform. (A.O. Smith, No. 37 at p. 7)
    In response, the Department notes that there is no requirement for 
a second identical 24-hour simulated-use test in appendix E. Sections 
5.2.2.2.1.1 and 5.2.2.2.1.2 of the currently applicable test procedure 
states that once the proper temperature control setting is achieved, 
the setting must remain fixed for the duration of the first-hour rating 
test and the simulated-use test such that a second identical simulated-
use test run immediately following the one specified in section 5.4 
would result in average delivered water temperatures that are within 
the bounds specified in section 2.4 of this appendix. This language was 
included to explain the intent of the temperature control. However, for 
units which have an integrated mixing valve or that are intended for 
use with a mixing valve, the language describing the second identical 
24-hour simulated-use test may be misleading, as there may be 
individual draws where the outlet temperature is outside the bounds 
specified in section 2.4 of appendix E. As a result, the Department is 
amending the language to remove reference to a second 24-hour 
simulated-use test. The procedure to ensure the stability of the 
temperature control as described in sections 5.2.2.2.1.1 and 
5.2.2.2.1.2 remains unchanged.
3. Connected Products
    Section 5.1 of appendix E currently specifies the operational mode 
selection for water heaters but does not explicitly address ``smart'' 
or ``connected'' modes of operation. For water heaters that allow for 
multiple user-selected operational modes, all procedures specified in 
appendix E must be carried out with the water heater in the same 
operational mode (i.e., only one mode). This operational mode must be 
the default mode (or similarly named, suggested mode for normal 
operation) as defined by the manufacturer in its product literature for 
giving selection guidance to the consumer.
    On September 17, 2018, DOE published an RFI seeking information on 
the emerging smart technology appliance and equipment market. 83 FR 
46886 (September 2018 RFI). In the September 2018 RFI, DOE sought 
information to better understand market trends and issues in the 
emerging market for appliances and commercial equipment that 
incorporate smart technology. Id. at 83 FR 46887. DOE's intent in 
issuing the September 2018 RFI was to ensure that DOE did not 
inadvertently impede such innovation when fulfilling its statutory 
obligations to set efficiency standards for covered products and 
equipment. Id. In the April 2020 RFI, DOE sought comment on the same 
issues presented in the September 2018 RFI as they may be specifically 
applicable to consumer water heaters. 85 FR 21104, 21114 (April 16, 
2020).
    Responding to the April 2020 RFI, commenters urged DOE to update 
the test procedure to better capture the performance differences 
between traditional and connected products, provided some recommended 
definitions delineating the types of connected products, and suggested 
that DOE adopt additional and/or optional performance metrics related 
to grid connectivity. These comments are discussed in detail in the 
January 2022 NOPR. 87 FR 1554, 1585 (Jan. 11, 2022). In the January 
2022 NOPR, DOE proposed to explicitly state that any connection to an 
external network or control would be disconnected during testing. DOE 
proposed this given that there were insufficient data on consumer usage 
of connected features for the Department to develop a representative 
test configuration for assessing the energy consumption of connected 
functionality for water

[[Page 40466]]

heaters. 87 FR 1554, 1585-1586 (Jan. 11, 2022).
    On this topic, BWC agreed with DOE's tentative determinations and 
clarifications regarding the testing of connected water heaters. (BWC, 
No. 33 at p. 9) NYSERDA recommended that DOE ensure the test procedure 
supports grid-enabled water heaters specifically, as well as connected 
water heaters generally. To this point, NYSERDA recommended that DOE 
should specify how manufacturers can demonstrate their products are 
``connected'' and include this as an item for reporting to the agency. 
NYSERDA encouraged DOE to consider the power usage for connectedness, 
as this would be informative for utilities planning for 
decarbonization. Additionally, NYSERDA stated that including the power 
usage for connected functions would encourage the load to be minimal 
and better inform consumers regarding anticipated operating costs. 
(NYSERDA, No. 32 at pp. 2-3)
    In response, while DOE acknowledges the potential benefits that 
could be provided by connected capability, such as providing energy 
saving benefits to consumers and enabling peak load shifting on the 
grid, the Department has concluded that requiring measurement and 
reporting of the energy consumed by connected features at this time may 
prematurely hinder the development and incorporation of such features 
in water heaters. As such, DOE is clarifying that connected features on 
water heaters should remain on but disconnected from any external 
network or control for the duration of the appendix E test. This 
approach will allow some baseline energy consumption to be accounted 
for without imposing any specific network connection test requirements.
4. Heating Value of Gas
    In this rulemaking, DOE considered the need for a clarification 
regarding the correction of the heating value to a standard temperature 
and pressure. Section 3.7 of appendix E states that the heating values 
of natural gas and propane must be corrected from those reported at 
standard temperature and pressure conditions to provide the heating 
value at the temperature and pressure measured at the fuel meter, but 
does not specify standard temperature and pressure conditions. Without 
a specified standard temperature and pressure, the heating values used 
in calculations may not be consistent from laboratory to laboratory.
    As discussed in the January 2022 NOPR, there are several sources 
which do specify the standard temperature and pressure conditions for 
natural gas calculations. 87 FR 1554, 1578 (Jan. 11, 2022). For 
example, AHRI maintains an Operations Manual for Residential Water 
Heater Certification Program (AHRI Operations Manual), which includes 
an equation that corrects the measured heating value, when using a dry 
gas and a wet test meter, to the heating value at the standard 
temperature and pressure of 60 [deg]F (15.6 [deg]C) and 30 inches of 
mercury column (101.6 kPa), respectively. Annex B of the March 2019 
ASHRAE Draft 118.2 also provides a method for correcting the heating 
value from measured to standard conditions, which allows for the use of 
either dry or saturated gas and either a dry or wet test meter--and 
this calculation was finalized in ASHRAE 118.2-2022 with an example 
provided for 60 [deg]F (15.6 [deg]C) and 30 inches of mercury column 
(101.6 kPa). Lastly, sections 2.4.1 and 3.1.1 of appendix O to subpart 
B of 10 CFR part 430 (Uniform Test Method for Measuring the Energy 
Consumption of Vented Home Heating Equipment) correct the input rate to 
the standard conditions of 60 [deg]F (15.6 [deg]C) and 30 inches of 
mercury column (101.6 kPa). Therefore, to align with the AHRI 
Operations Manual and the current practice in other appendices within 
part 430 of the CFR, DOE proposed in the January 2022 NOPR to establish 
the standard temperature and pressure conditions for gas measurements 
as 60 [deg]F (15.6 [deg]C) and 30 inches of mercury column (101.6 kPa), 
respectively. Further, DOE proposed to adopt the method used in Annex B 
of a finalized ASHRAE 118.2-2022 to correct the heating value of gas to 
standard conditions. 87 FR 1554, 1578 (Jan. 11, 2022).
    DOE did not receive comments from stakeholders regarding this 
proposal. Accordingly, DOE is adopting these proposals in this final 
rule for the reasons previously discussed.

I. Effective and Compliance Dates

    The effective date for the adopted test procedure amendments will 
be 30 days after publication of this final rule in the Federal 
Register.
    As to the compliance date, EPCA prescribes that all representations 
of energy efficiency and energy use for consumer products (including 
consumer water heaters),), including those made on marketing materials 
and product labels, must be made in accordance with an amended test 
procedure, beginning 180 days after publication of the final rule in 
the Federal Register. (42 U.S.C. 6293(c)(2)) For residential-duty 
commercial water heaters, this requirement is beginning 360 days after 
publication of the final rule in the Federal Register. (42 U.S.C. 
6314(d)(1)) For consumer products, EPCA provides an allowance for 
individual manufacturers to petition DOE for an extension of the 180-
day period if the manufacturer may experience undue hardship in meeting 
the deadline. (42 U.S.C. 6293(c)(3)) To receive such an extension, 
petitions must be filed with DOE no later than 60 days before the end 
of the 180-day period and must detail how the manufacturer will 
experience undue hardship. (Id.)
    With the exception of two test method provisions (i.e., high 
temperature testing and separate storage tank testing), compliance with 
the modified test procedure adopted in this final rule is required for 
consumer water heaters beginning 180 days after the date of publication 
of this final rule in the Federal Register. Similarly, with the 
exception of the separate storage tank testing requirement, compliance 
with the modified test procedure is required for residential-duty 
commercial water heaters beginning 360 days after the date of 
publication of this final rule in the Federal Register.
    Beginning on the effective date of this final rule, the use of the 
high temperature test method (section 5.1.2 of the amended appendix E 
test procedure) will be allowed for voluntary additional 
representations until the compliance date of amended energy 
conservation standards for consumer water heaters that address high 
temperature operation, should such standards be adopted. Until such a 
time, the normal temperature test method (section 5.1.1 of the amended 
appendix E test procedure) is required as the basis for ratings used to 
determine compliance with energy conservation standards. During this 
voluntary usage period, manufacturers who choose to publish two sets of 
ratings must clearly indicate which values correspond to the high 
temperature test method. In the standards rulemaking, DOE plans to 
clarify which type(s) of water heaters would be required to utilize the 
high temperature test method when determining compliance with potential 
amended standards.
    The use of the separate storage tank test method for circulating 
water heaters (section 4.10 of the amended appendix E test procedure) 
will be allowed for voluntary representations and compliance with 
standards beginning on the effective date of this final rule. This test 
method will become mandatory when compliance with amended energy 
conservation standards for consumer water heaters and

[[Page 40467]]

residential-duty commercial water heaters is required, should such 
standards addressing circulating water heaters be adopted.
    Upon the compliance date of test procedure provisions in this final 
rule, any waivers that had been previously issued and are in effect 
that pertain to issues addressed by such provisions are terminated. 10 
CFR 430.27(h)(3) and 431.401(h)(3). Recipients of any such waivers are 
required to test the products subject to the waiver according to the 
amended test procedure as of the compliance date of the amended test 
procedure. The amendments adopted in this document pertain to issues 
addressed by a waiver granted to Bradford White Corporation (Case No. 
2019-006). See 85 FR 5648 (Jan. 31, 2020). On January 31, 2020, DOE 
published a Notice of Decision and Order in the Federal Register 
granting Bradford White Corporation a waiver for a specified basic 
model that experiences the first cut-out of the 24-hour simulated-use 
test during a draw. 85 FR 5648. The Decision and Order requires 
Bradford White Corporation to use an alternate test procedure that DOE 
determined more accurately calculates the recovery efficiency when the 
first cut-out occurs during a draw. Id. at 85 FR 5651. As described in 
section III.B.2.b of this document, DOE is adopting the alternate test 
procedure prescribed in the Decision and Order granted to Bradford 
White Corporation into the test procedure at appendix E.

J. Test Procedure Costs

    EPCA requires that test procedures proposed by DOE not be unduly 
burdensome to conduct. (42 U.S.C. 6293(b)(3)) The following sections 
discuss DOE's evaluation of estimated costs associated with the 
proposed amendments for consumer water heaters and residential-duty 
commercial water heaters.
1. Separate Storage Tanks
    In the January 2022 NOPR, DOE tentatively concluded that the cost 
of running the test procedure using an 80-gallon unfired hot water 
storage tank should be the same as testing a water heater with an 
integrated tank with a comparable storage volume. The Department 
estimated that testing a fossil fuel-fired or electric storage water 
heater would cost approximately $3,000 and that testing an electric 
storage water heater which uses heat pump technology would cost 
approximately $4,500. In addition to the testing cost, the manufacturer 
or third-party testing facility would incur a one-time cost to purchase 
an unfired hot water storage tank which are commercially available for 
approximately $900. 87 FR 1554, 1589 (Jan. 11, 2022).
    In the July 2022 SNOPR, DOE revised its proposal. DOE estimated 
that, for gas-fired circulating water heaters, these proposed changes 
could require a one-time purchase of an 80- to 120-gallon unfired hot 
water storage tank, which are readily commercially available for 
approximately $2,000. For heat pump-only water heaters, the proposed 
changes could result in a one-time purchase of a 40-gallon (4 gallons) electric storage water heater readily available for 
approximately $500. 87 FR 42270, 42283 (July 14, 2022).
    DOE evaluated stakeholder feedback regarding this testing 
requirement and further revised its amended provision. This final rule 
adopts the following changes concerning the testing of circulating 
water heaters:
    (1) Gas-fired circulating water heaters be tested using an unfired 
hot water storage tank with a storage volume between 80 and 120 gallons 
and an R-value exactly at the minimum R-value required at 10 CFR 
431.110(a).
    (2) Heat pump circulating water heaters be tested using a 40-gallon 
(5 gallons) electric storage water heater at the minimum 
UEF standard required at 10 CFR 430.32(d).
    AHRI generally agreed with the estimated costs presented in the 
January 2022 NOPR, with the exception that $900 may be an underestimate 
of the cost of purchasing an unfired hot water storage tank. (AHRI, No. 
40 at p. 3) No further comments on test costs were received in response 
to the July 2022 SNOPR. Based upon its subsequent review in light of 
AHRI's comment, DOE notes that its estimate for the retail price of an 
unfired hot water storage tank has been raised from $900 to $2,000.
    In response, DOE recognizes that these amendments will require 
manufacturers to make one-time purchases of the necessary storage tanks 
for each testing facility. DOE's research indicates that the tanks 
required for testing gas-fired circulating water heaters and heat pump 
circulating water heaters are commercially available at retail prices 
of $2,000 and $500, respectively, thereby reflecting third-party 
laboratory testing costs.
    These amendments to appendix E regarding storage tank requirements 
will allow affected models to be certified for the first time. 
Manufacturers will not be able to rely on data generated under test 
procedures in effect prior to this final rule.
2. Method for Determining Internal Tank Temperature for Certain Water 
Heaters
    This final rule amends section 5.4 of appendix E by the addition of 
section 5.4.2.2, which allows internal tank temperature to be estimated 
by removing water from the water heater for models with rated storage 
volumes greater than or equal to 2 gallons whose internal tank 
temperatures are unable to be measured using thermocouples.
    DOE estimates that this testing method may extend test duration by 
up to 8 hours as part of the final standby period of the 24-hour 
simulated use test. This additional duration is estimated to increase 
testing costs by up to $1,000 for affected fossil-fuel-fired and 
electric water heaters and $1,500 for affected heat pump water heaters.
    The addition of section 5.4.2.2 to appendix E will allow affected 
models to be certified for the first time. Because these water heaters 
could not previously be accurately tested, manufacturers will not be 
able to rely on data generated under test procedures in effect prior to 
this final rule.
3. High Temperature Testing
    DOE recognizes that the amendment specifying the high temperature 
testing method would likely cause UEF ratings for any products that 
would become subject to this test method (i.e., a subset of electric 
resistance storage water heaters) to decrease if they are currently 
certified using a default temperature setting. In order to limit 
potential retesting and recertification burden for manufacturers, any 
requirement to test certain products using the high temperature testing 
method will be established only once DOE completes its ongoing reviews 
of potential amended energy conservation standards for consumer water 
heaters, should such standards be adopted. The cost to test per this 
amended method would not be different from the cost to test per the 
method in the currently applicable appendix E test procedure (i.e., 
testing an electric storage water heater would cost approximately 
$3,000).
4. Additional Amendments
    The remainder of the test procedure amendments adopted in this 
final rule will not impact test costs.
    DOE is amending section 2.5 of appendix E, ``Set Point 
Temperature,'' to allow low-temperature water heaters to deliver water 
at the maximum outlet temperature that they are capable of producing. 
This aligns with how these products are tested currently. Manufacturers 
already should have

[[Page 40468]]

requested a waiver for these products, as the current test procedure 
cannot be used as written to test low-temperature water heaters. As 
these products are currently tested and rated to the procedures which 
DOE is adopting, there should be no additional cost associated with 
this change.
    DOE is also amending the existing test procedure for consumer and 
residential-duty commercial water heaters by modifying the flow rate 
requirements during the FHR test for water heaters with a rated storage 
volume less than 20 gallons. This change does not significantly affect 
the test results of the FHR test, and, thus, DOE expects that 
manufacturers may rely on existing test data where available. Further, 
storage-type water heaters (which comprise the majority of water 
heaters that need to be tested for an FHR rating) with less than 20 
gallons of rated storage volume currently do not have energy 
conservation standards codified at 10 CFR 430.32(d) and are, therefore, 
not rated and certified to DOE. Instantaneous-type water heaters that 
will require an FHR rating are expected to be circulating water 
heaters, and this final rule amends the appendix E test procedure in 
such a way that allows these products to be tested and rated for the 
first time (test costs for water heaters requiring separate storage 
tanks are discussed in section III.J.1 of this document). Therefore, 
the update to the FHR test method does not change the expected testing 
costs for products which have been tested per appendix E previously.
    DOE is also amending the timing of the first measurement in each 
draw of the 24-hour simulated-use test and the test condition 
specifications and tolerances, including electric supply voltage 
tolerance, ambient temperature, ambient dry-bulb temperature, ambient 
relative humidity, standard temperature and pressure definition, gas 
supply pressure, and manifold pressure. These changes are intended to 
reduce retesting associated with having a single measurement out of 
tolerance, while maintaining the current representativeness of the test 
conditions and the stringency of the tolerances for the test 
conditions. DOE also has determined that the amendment to the flow rate 
tolerances for water heaters less than 2 gallons in rated storage 
volume would not alter the measured efficiency of consumer water 
heaters and residential-duty commercial water heaters, nor require 
retesting or recertification. In the absence of an explicit instruction 
for the flow rate tolerance applicable to water heaters with rated 
storage volume under 2 gallons, DOE expects that general industry best 
practice is to apply the flow rate tolerances being adopted for section 
5.4.3 of appendix E for water heaters with rated storage volume less 
than 2 gallons (based on DOE's review of third-party laboratory test 
data), such that this proposal is expected to be consistent with 
current methodology.
    Manufacturers will be able to rely on data generated under the 
current water heaters test procedure for the remainder of the 
amendments set forth in this final rule, so accordingly, such changes 
should result in no associated increase in costs.

IV. Procedural Issues and Regulatory Review

A. Review Under Executive Orders 12866, 13563, and 14094

    Executive Order (E.O.) 12866, ``Regulatory Planning and Review,'' 
58 FR 51735 (Oct. 4, 1993), as supplemented and reaffirmed by E.O. 
13563, ``Improving Regulation and Regulatory Review,'' 76 FR 3821 (Jan. 
21, 2011) and E.O. 14094, ``Modernizing Regulatory Review,'' 88 FR 
21879 (April 11, 2023), requires agencies, to the extent permitted by 
law, to: (1) propose or adopt a regulation only upon a reasoned 
determination that its benefits justify its costs (recognizing that 
some benefits and costs are difficult to quantify); (2) tailor 
regulations to impose the least burden on society, consistent with 
obtaining regulatory objectives, taking into account, among other 
things, and to the extent practicable, the costs of cumulative 
regulations; (3) select, in choosing among alternative regulatory 
approaches, those approaches that maximize net benefits (including 
potential economic, environmental, public health and safety, and other 
advantages; distributive impacts; and equity); (4) to the extent 
feasible, specify performance objectives, rather than specifying the 
behavior or manner of compliance that regulated entities must adopt; 
and (5) identify and assess available alternatives to direct 
regulation, including providing economic incentives to encourage the 
desired behavior, such as user fees or marketable permits, or providing 
information upon which choices can be made by the public. DOE 
emphasizes as well that E.O. 13563 requires agencies to use the best 
available techniques to quantify anticipated present and future 
benefits and costs as accurately as possible. In its guidance, the 
Office of Information and Regulatory Affairs (OIRA) in the Office of 
Management and Budget (OMB) has emphasized that such techniques may 
include identifying changing future compliance costs that might result 
from technological innovation or anticipated behavioral changes. For 
the reasons stated in the preamble, this final regulatory action is 
consistent with these principles.
    Section 6(a) of E.O. 12866 also requires agencies to submit 
``significant regulatory actions'' to OIRA for review. OIRA has 
determined that this final regulatory action does not constitute a 
``significant regulatory action'' under section 3(f) of E.O. 12866. 
Accordingly, this action was not submitted to OIRA for review under 
E.O. 12866.

B. Review Under the Regulatory Flexibility Act

    The Regulatory Flexibility Act (5 U.S.C. 601 et seq.) requires 
preparation of a final regulatory flexibility analysis (FRFA) for any 
final rule where the agency was first required by law to publish a 
proposed rule for public comment, unless the agency certifies that the 
rule, if promulgated, will not have a significant economic impact on a 
substantial number of small entities. As required by Executive Order 
13272, ``Proper Consideration of Small Entities in Agency Rulemaking,'' 
67 FR 53461 (August 16, 2002), DOE published procedures and policies on 
February 19, 2003 to ensure that the potential impacts of its rules on 
small entities are properly considered during the DOE rulemaking 
process. 68 FR 7990. DOE has made its procedures and policies available 
on the Office of the General Counsel's website: www.energy.gov/gc/office-general-counsel. DOE reviewed this final rule under the 
provisions of the Regulatory Flexibility Act and the procedures and 
policies published on February 19, 2003.
    DOE is amending test procedures for consumer water heaters and 
residential-duty commercial water heaters. DOE is publishing this final 
rule in satisfaction of the 7-year-lookback review requirement 
specified in EPCA. (42 U.S.C. 6293(b)(1)(A); 6314(a)(1)) Further, 
amending test procedures for consumer and residential-duty commercial 
water heaters assists DOE in fulfilling its statutory deadline for 
amending energy conservation standards for products and equipment that 
achieve the maximum improvement in energy efficiency that is 
technologically feasible and economically justified. (42 U.S.C. 
6295(o)(2)(A); 42 U.S.C. 6313(a)(6)) Additionally, amending test 
procedures for consumer and residential-duty commercial water heaters 
allows manufacturers to produce measurements of energy efficiency that

[[Page 40469]]

are representative of an average use cycle and uniform for all 
manufacturers.
    On January 11, 2022, DOE published a test procedure NOPR (January 
2022 NOPR) in the Federal Register proposing to amend the test 
procedure for consumer water heaters and residential-duty commercial 
gas water heaters. See 87 FR 1554. DOE published a supplemental test 
procedure NOPR on July 14, 2022 (July 2022 SNOPR) in the Federal 
Register, proposing certain modifications to the January 2022 NOPR. See 
87 FR 42270.
    DOE conducted an initial regulatory flexibility analysis (IRFA) as 
part of the January 2022 NOPR and July 2022 SNOPR. See 87 FR 1554, 
1590-1592 (Jan. 11, 2022); 87 FR 42270, 42285-42287 (July 14, 2022). 
The following sections outline DOE's determination that this final rule 
does not have a ``significant economic impact on a substantial number 
of small entities,'' and that the preparation of a FRFA is not 
warranted. DOE did not receive comment specific to the impacts on small 
business manufacturers as part of the above-referenced IRFAs.
    For manufacturers of consumer water heaters and residential-duty 
commercial water heaters, the Small Business Administration (SBA) has 
set a size threshold, which defines those entities classified as 
``small businesses'' for the purposes of the statute. DOE used the 
SBA's small business size standards to determine whether any small 
entities would be subject to the requirements of the rule. (See 13 CFR 
part 121.) The size standards are listed by North American Industry 
Classification System (NAICS) code and industry description and are 
available at: www.sba.gov/document/support--table-size-standards. 
Manufacturing of consumer water heaters and residential-duty commercial 
water heaters is classified under NAICS 335220, ``Major Household 
Appliance Manufacturing.'' The SBA sets a threshold of 1,500 employees 
or fewer for an entity to be considered as a small business for this 
category. DOE used available public information to identify potential 
small manufacturers. DOE accessed CCMS,\79\ the certified product 
directory of the AHRI,\80\ company websites, and manufacturer 
literature to identify companies that import, private label, or produce 
the consumer water heaters and residential-duty commercial water 
heaters covered by this rulemaking. Using these sources, DOE has 
identified a total of 27 manufacturers of consumer water heaters and 
residential-duty commercial water heaters.\81\ Of these 27 
manufacturers, DOE identified one domestic small business that 
manufactures products covered by the test procedure amendments.
---------------------------------------------------------------------------

    \79\ U.S. Department of Energy Compliance Certification 
Management System, available at: www.regulations.doe.gov/ccms. (Last 
accessed July 19, 2022).
    \80\ AHRI Directory of Certified Product Performance is 
available at: www.ahridirectory.org/Search/SearchHome (Last accessed 
July 19, 2022).
    \81\ The January 2022 NOPR identified 31 manufacturers. 87 FR 
1554, 1591 (Jan. 11, 2022). The July 2022 SNOPR identified 27 
manufacturers. The changes reflect revisions based on manufacturer 
feedback and additional public information.
---------------------------------------------------------------------------

    More specifically, in the January 2022 NOPR IRFA, DOE evaluated a 
range of potential test procedure amendments, with one amendment that 
could lead to additional testing costs for small business. The existing 
DOE test procedure does not accommodate testing of circulating water 
heaters that require a separately sold hot water storage tank to 
properly operate. In the January 2022 NOPR, DOE proposed to add 
procedures to test such circulating water heaters to improve the 
representativeness of the test procedure. The January 2022 NOPR 
proposed testing be based on a commonly available 80-gallon unfired hot 
water storage tank which minimally meets the energy conservation 
standard requirements at 10 CFR 431.110(a). DOE estimated that the cost 
of running the amended test procedure should be the same as testing a 
comparable water heater with storage volume (i.e., third-party testing 
of a fossil fuel-fired or electric storage water heater would cost 
approximately $3,000; third-party testing of an electric storage water 
heater which uses heat pump technology would cost approximately 
$4,500). If a manufacturer chose to perform in-house testing rather 
than use a third-party, the unfired hot water storage tank was stated 
to be commercially available for approximately $900. The January 2022 
IRFA identified one small manufacturer and estimated compliance costs 
to be $4,500. 87 FR 1554, 1591 (Jan. 11, 2022).
    The July 2022 SNOPR further updated DOE's proposal for testing 
circulating water heaters that require a separately-sold hot water 
storage tank to properly operate. Specifically, the July 2022 SNOPR 
differentiated the test requirements for gas-fired circulating water 
heaters and heat pump circulating water heaters. The July 2022 SNOPR 
proposed that heat pump circulating water heaters be tested using an 
electric storage water heaters that have a rated storage volume of 40 
gallons  4 gallons, have an FHR that results in 
classification at the medium draw pattern, and be rated at exactly the 
minimum required UEF. Compared to the January 2022 NOPR, DOE revised 
the requirements for circulating heat pump water heaters to better 
reflect how heat pump water heaters may be installed in the field. To 
determine cost of testing, DOE utilized a third-party test estimate of 
$4,500. The July 2022 IRFA identified one small manufacturer and 
estimated compliance costs to be $4,500. The proposal for heat pump 
circulating water heaters was the only amendment in the July 2022 SNOPR 
that could cause the small manufacturer to incur additional costs. 87 
FR 42270, 42286-42287 (July 14, 2022).
    In this final rule, DOE is establishing testing requirements 
consistent with the proposal for heat pump circulating water heaters in 
the July 2022 SNOPR, except that the acceptable volume range for the 
separate tank has been expanded to 40 gallons  5 gallons. 
For this final rule, DOE is aware of one domestic small manufacturer. 
The small manufacturers has a single model (a circulating heat pump 
water heater that requires a separately-sold hot water tank) that would 
be affected by the amendments being adopted and that would need to be 
re-tested. DOE estimates that testing would cost $4,500. If the 
manufacturer conducts two rounds of physical testing, DOE expects the 
cost impact on the small manufacturer to be $9,000, which is less than 
0.01% of company revenue.
    DOE has determined the cost impact to small businesses as result of 
the amendments in this final rule to be minimal. DOE did not receive 
any comments specifically pertaining to small business impacts. 
Therefore, on the basis of the de minimis compliance burden, DOE 
certifies that this test procedure final rule does not have a 
``significant economic impact on a substantial number of small 
entities,'' and that the preparation of a FRFA is not warranted. DOE 
has submitted a certification and supporting statement of factual basis 
to the Chief Counsel for Advocacy of the Small Business Administration 
for review under 5 U.S.C. 605(b).

C. Review Under the Paperwork Reduction Act of 1995

    Manufacturers of consumer water heaters and manufacturers of 
residential-duty commercial water heaters must certify to DOE that 
their products comply with any applicable energy conservation 
standards. To certify compliance, manufacturers must first obtain test 
data for their products according to the DOE test procedures, including 
any amendments adopted for

[[Page 40470]]

those test procedures. DOE has established regulations for the 
certification and recordkeeping requirements for all covered consumer 
products and commercial equipment, including consumer water heaters and 
residential-duty commercial water heaters. (See generally 10 CFR part 
429.) The collection-of-information requirement for the certification 
and recordkeeping is subject to review and approval by OMB under the 
Paperwork Reduction Act (PRA). This requirement has been approved by 
OMB under OMB control number 1910-1400. Public reporting burden for the 
certification is estimated to average 35 hours per response, including 
the time for reviewing instructions, searching existing data sources, 
gathering and maintaining the data needed, and completing and reviewing 
the collection of information.
    DOE is not amending the certification or reporting requirements for 
consumer water heaters and residential-duty commercial water heaters in 
this final rule. Instead, DOE may consider proposals to amend the 
certification requirements and reporting for these products and 
equipment under a separate rulemaking regarding appliance and equipment 
certification. DOE will address changes to OMB Control Number 1910-1400 
at that time, as necessary.
    Notwithstanding any other provision of the law, no person is 
required to respond to, nor shall any person be subject to a penalty 
for failure to comply with, a collection of information subject to the 
requirements of the PRA, unless that collection of information displays 
a currently valid OMB Control Number.

D. Review Under the National Environmental Policy Act of 1969

    In this final rule, DOE amends the test procedure for consumer 
water heaters and residential-duty commercial water heaters, amendments 
which it expects will be used to develop and implement future energy 
conservation standards for such products and equipment. DOE has 
determined that this rule falls into a class of actions that are 
categorically excluded from review under the National Environmental 
Policy Act of 1969 (42 U.S.C. 4321 et seq.) and DOE's implementing 
regulations at 10 CFR part 1021. Specifically, DOE has determined that 
adopting test procedures for measuring energy efficiency of consumer 
products and industrial equipment is consistent with activities 
identified in 10 CFR part 1021, subpart D, appendix A, sections A5 and 
A6. Accordingly, neither an environmental assessment nor an 
environmental impact statement is required.

E. Review Under Executive Order 13132

    Executive Order 13132, ``Federalism,'' 64 FR 43255 (August 1010, 
1999), imposes certain requirements on agencies formulating and 
implementing policies or regulations that preempt State law or that 
have federalism implications. The Executive order requires agencies to 
examine the constitutional and statutory authority supporting any 
action that would limit the policymaking discretion of the States and 
to carefully assess the necessity for such actions. The Executive order 
also requires agencies to have an accountable process to ensure 
meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications. 
On March 14, 2000, DOE published a statement of policy describing the 
intergovernmental consultation process it will follow in the 
development of such regulations. 65 FR 13735. DOE examined this final 
rule and determined that it will not have a substantial direct effect 
on the States, on the relationship between the national government and 
the States, or on the distribution of power and responsibilities among 
the various levels of government. EPCA governs and prescribes Federal 
preemption of State regulations as to energy conservation for the 
products and equipment that are the subject of this final rule. States 
can petition DOE for exemption from such preemption to the extent, and 
based on criteria, set forth in EPCA. (42 U.S.C. 6297(d)) No further 
action is required by Executive Order 13132.

F. Review Under Executive Order 12988

    Regarding the review of existing regulations and the promulgation 
of new regulations, section 3(a) of Executive Order 12988, ``Civil 
Justice Reform,'' 61 FR 4729 (Feb. 7, 1996), imposes on Federal 
agencies the general duty to adhere to the following requirements: (1) 
eliminate drafting errors and ambiguity; (2) write regulations to 
minimize litigation; (3) provide a clear legal standard for affected 
conduct rather than a general standard; and (4) promote simplification 
and burden reduction. Section 3(b) of Executive Order 12988 
specifically requires that Executive agencies make every reasonable 
effort to ensure that the regulation: (1) clearly specifies the 
preemptive effect, if any; (2) clearly specifies any effect on existing 
Federal law or regulation; (3) provides a clear legal standard for 
affected conduct while promoting simplification and burden reduction; 
(4) specifies the retroactive effect, if any; (5) adequately defines 
key terms; and (6) addresses other important issues affecting clarity 
and general draftsmanship under any guidelines issued by the Attorney 
General. Section 3(c) of Executive Order 12988 requires executive 
agencies to review regulations in light of applicable standards in 
sections 3(a) and 3(b) to determine whether they are met or it is 
unreasonable to meet one or more of them. DOE has completed the 
required review and determined that, to the extent permitted by law, 
this final rule meets the relevant standards of Executive Order 12988.

G. Review Under the Unfunded Mandates Reform Act of 1995

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA) 
requires each Federal agency to assess the effects of Federal 
regulatory actions on State, local, and Tribal governments and the 
private sector. Public Law 104-4, sec. 201 (codified at 2 U.S.C. 1531). 
For a regulatory action resulting in a rule that may cause the 
expenditure by State, local, and Tribal governments, in the aggregate, 
or by the private sector of $100 million or more in any one year 
(adjusted annually for inflation), section 202 of UMRA requires a 
Federal agency to publish a written statement that estimates the 
resulting costs, benefits, and other effects on the national economy. 
(2 U.S.C. 1532(a), (b)) The UMRA also requires a Federal agency to 
develop an effective process to permit timely input by elected officers 
of State, local, and Tribal governments on a proposed ``significant 
intergovernmental mandate,'' and requires an agency plan for giving 
notice and opportunity for timely input to potentially affected small 
governments before establishing any requirements that might 
significantly or uniquely affect small governments. On March 18, 1997, 
DOE published a statement of policy on its process for 
intergovernmental consultation under UMRA. 62 FR 12820; also available 
at www.energy.gov/gc/office-general-counsel. DOE examined this final 
rule according to UMRA and its statement of policy and determined that 
the rule contains neither an intergovernmental mandate, nor a mandate 
that may result in the expenditure of $100 million or more in any year, 
so these requirements do not apply.

H. Review Under the Treasury and General Government Appropriations Act, 
1999

    Section 654 of the Treasury and General Government Appropriations

[[Page 40471]]

Act, 1999 (Pub. L. 105-277) requires Federal agencies to issue a Family 
Policymaking Assessment for any rule that may affect family well-being. 
This final rule will not have any impact on the autonomy or integrity 
of the family as an institution. Accordingly, DOE has concluded that it 
is not necessary to prepare a Family Policymaking Assessment.

I. Review Under Executive Order 12630

    DOE has determined, under Executive Order 12630, ``Governmental 
Actions and Interference with Constitutionally Protected Property 
Rights,'' 53 FR 8859 (March 18, 1988), that this regulation will not 
result in any takings that might require compensation under the Fifth 
Amendment to the U.S. Constitution.

J. Review Under Treasury and General Government Appropriations Act, 
2001

    Section 515 of the Treasury and General Government Appropriations 
Act, 2001 (44 U.S.C. 3516 note) provides for agencies to review most 
disseminations of information to the public under guidelines 
established by each agency pursuant to general guidelines issued by 
OMB. OMB's guidelines were published at 67 FR 8452 (Feb. 22, 2002), and 
DOE's guidelines were published at 67 FR 62446 (Oct. 7, 2002). Pursuant 
to OMB Memorandum M-19-15, Improving Implementation of the Information 
Quality Act (April 24, 2019), DOE published updated guidelines which 
are available at: www.energy.gov/sites/prod/files/2019/12/f70/DOE%20Final%20Updated%20IQA%20Guidelines%20Dec%202019.pdf. DOE has 
reviewed this final rule under the OMB and DOE guidelines and has 
concluded that it is consistent with applicable policies in those 
guidelines.

K. Review Under Executive Order 13211

    Executive Order 13211, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use,'' 66 FR 28355 
(May 22, 2001), requires Federal agencies to prepare and submit to OMB, 
a Statement of Energy Effects for any significant energy action. A 
``significant energy action'' is defined as any action by an agency 
that promulgated or is expected to lead to promulgation of a final 
rule, and that: (1) is a significant regulatory action under Executive 
Order 12866, or any successor order; and (2) is likely to have a 
significant adverse effect on the supply, distribution, or use of 
energy; or (3) is designated by the Administrator of OIRA as a 
significant energy action. For any significant energy action, the 
agency must give a detailed statement of any adverse effects on energy 
supply, distribution, or use if the regulation is implemented, and of 
reasonable alternatives to the action and their expected benefits on 
energy supply, distribution, and use.
    This regulatory action is not a significant regulatory action under 
Executive Order 12866. Moreover, it would not have a significant 
adverse effect on the supply, distribution, or use of energy, nor has 
it been designated as a significant energy action by the Administrator 
of OIRA. Therefore, it is not a significant energy action, and, 
accordingly, DOE has not prepared a Statement of Energy Effects.

L. Review Under Section 32 of the Federal Energy Administration Act of 
1974

    Under section 301 of the Department of Energy Organization Act 
(Pub. L. 95-91; 42 U.S.C. 7101), DOE must comply with section 32 of the 
Federal Energy Administration Act of 1974, as amended by the Federal 
Energy Administration Authorization Act of 1977. (15 U.S.C. 788; 
``FEAA'') Section 32 essentially provides in relevant part that, where 
a proposed rule authorizes or requires use of commercial standards, the 
notice of proposed rulemaking must inform the public of the use and 
background of such standards. In addition, section 32(c) requires DOE 
to consult with the Attorney General and the Chairman of the Federal 
Trade Commission (FTC) concerning the impact of the commercial or 
industry standards on competition.
    The modifications to the Federal test procedure for consumer water 
heaters and residential-duty commercial water heaters adopted in this 
final rule incorporate testing methods contained in certain sections of 
the following applicable commercial test standards: ASHRAE 41.1-2020, 
ASTM D2156-09 (RA 2018), and ASHRAE 118.2-2022. DOE has evaluated these 
standards and is unable to conclude whether they fully comply with the 
requirements of section 32(b) of the FEAA (i.e., whether it was 
developed in a manner that fully provides for public participation, 
comment, and review.) DOE has consulted with both the Attorney General 
and the Chairman of the FTC about the impact on competition of using 
the methods contained in these standards and has received no comments 
objecting to their use.

M. Congressional Notification

    As required by 5 U.S.C. 801, DOE will report to Congress on the 
promulgation of this rule before its effective date. The report will 
state that it has been determined that the final rule is not a ``major 
rule'' as defined by 5 U.S.C. 804(2).

N. Description of Materials Incorporated by Reference

    In this final rule, DOE incorporates by reference the following 
test standards:
    ASHRAE 41.1-2020 prescribes methods for measuring temperature under 
laboratory and field conditions which are required for system 
performance tests and for testing heating, ventilating, air-
conditioning, and refrigerating components.
    ASHRAE 41.6-2014 prescribes methods for measuring the humidity of 
moist air with instruments.
    ASHRAE 118.2-2022 provides test procedures for rating the 
efficiency and hot water delivery capabilities of directly heated 
residential water heaters and residential-duty commercial water 
heaters.
    ASTM D2156-09 (RA 2018) provides a test method to evaluate the 
density of smoke in the flue gases from burning distillate fuels, which 
is intended primarily for use with home heating equipment burning 
kerosene or heating oils, and can be used in the laboratory or in the 
field to compare fuels for clean burning or to compare heating 
equipment.
    ASTM E97-1987 (W1991) provides a method to determine the 45-deg, 0-
deg directional reflectance factor of nonfluorescent opaque specimens 
by means of filter photometers.
    Copies of ASHRAE 41.1-2020, ASHRAE 41.6-2014, and ASHRAE 118.2-2022 
are reasonably available from the American Society of Heating, 
Refrigerating, and Air-Conditioning Engineers, Inc., 180 Technology 
Parkway NW, Peachtree Corners, GA 30092, (800) 527-4723 or (404) 636-
8400, or online at: www.ashrae.org.
    Copies of ASTM D2156-09 (RA 2018) are reasonably available from 
ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959 or online at: www.astm.org.
    Copies of ASTM E97-1987 (W1991) are reasonably available from 
standards resellers including GlobalSpec's Engineering 360 (https://standards.globalspec.com/std/3801495/astm-e97-82-1987) and IHS Markit 
(https://global.ihs.com/doc_detail.cfm?document_name=ASTM%20E97&item_s_key=00020483).

V. Approval of the Office of the Secretary

    The Secretary of Energy has approved publication of this final 
rule.

[[Page 40472]]

List of Subjects

10 CFR Part 429

    Administrative practice and procedure, Confidential business 
information, Energy conservation, Household appliances, Imports, 
Intergovernmental relations, Reporting and recordkeeping requirements, 
Small businesses.

10 CFR Part 430

    Administrative practice and procedure, Confidential business 
information, Energy conservation, Household appliances, Imports, 
Incorporation by reference, Intergovernmental relations, Reporting and 
recordkeeping requirements, Small businesses.

10 CFR Part 431

    Administrative practice and procedure, Confidential business 
information, Energy conservation, Household appliances, Imports, 
Intergovernmental relations, Laboratories, Reporting and recordkeeping 
requirements, Small businesses.

Signing Authority

    This document of the Department of Energy was signed on May 22, 
2023, by Francisco Alejandro Moreno, Acting Assistant Secretary for 
Energy Efficiency and Renewable Energy, pursuant to delegated authority 
from the Secretary of Energy. That document with the original signature 
and date is maintained by DOE. For administrative purposes only, and in 
compliance with requirements of the Office of the Federal Register, the 
undersigned DOE Federal Register Liaison Officer has been authorized to 
sign and submit the document in electronic format for publication, as 
an official document of the Department of Energy. This administrative 
process in no way alters the legal effect of this document upon 
publication in the Federal Register.

    Signed in Washington, DC, on May 24, 2023.
Treena V. Garrett,
Federal Register Liaison Officer, U.S. Department of Energy.

    For the reasons stated in the preamble, DOE amends parts 429, 430, 
and 431 of Chapter II of Title 10, Code of Federal Regulations, as set 
forth below:

PART 429--CERTIFICATION, COMPLIANCE, AND ENFORCEMENT FOR CONSUMER 
PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT

0
1. The authority citation for part 429 continues to read as follows:

    Authority: 42 U.S.C. 6291-6317; 28 U.S.C. 2461 note.


0
2. Amend Sec.  429.70 by revising paragraph (g)(2) and adding paragraph 
(g)(3) to read as follows:


Sec.  429.70  Alternative methods for determining energy efficiency and 
energy use.

* * * * *
    (g) * * *
    (2) Electric Storage Water Heaters. Rate an untested basic model of 
an electric storage-type water heater using the first-hour rating or 
maximum GPM (whichever is applicable under section 5.3.1 of appendix E 
to subpart B of this part) and uniform energy factor obtained from a 
tested basic model as the basis for ratings of basic models with other 
input ratings, provided that certain conditions are met:
    (i) For an untested basic model, the represented value of the 
first-hour rating or maximum GPM and the uniform energy factor is the 
same as that of a tested basic model, provided that each heating 
element of the untested basic model is rated at or above the input 
rating for the corresponding heating element of the tested basic model.
    (ii) For an untested basic model having any heating element with an 
input rating that is lower than that of the corresponding heating 
element in the tested basic model, the represented value of the first-
hour rating or maximum GPM and the uniform energy factor is the same as 
that of a tested basic model, provided that the first-hour rating for 
the untested basic model results in the same draw pattern specified in 
Table I of appendix E for the simulated-use test as was applied to the 
tested basic model. To establish whether this condition is met, 
determine the first-hour ratings or maximum GPMs for the tested and the 
untested basic models in accordance with the procedure described in 
section 5.3 of 10 CFR part 430, subpart B, appendix E, then compare the 
appropriate draw pattern specified in Table I of appendix E for the 
first-hour rating of the tested basic model with that for the untested 
basic model. If this condition is not met, then the untested basic 
model must be tested, and the appropriate sampling provisions must be 
applied to determine its uniform energy factor in accordance with 
appendix E and this part.
    (3) Electric Instantaneous Water Heaters. Rate an untested basic 
model of an electric instantaneous-type water heater using the first-
hour rating or maximum GPM and the uniform energy factor obtained from 
a tested basic model as a basis for ratings of basic models with other 
input ratings, provided that certain conditions are met:
    (i) For an untested basic model, the represented value of the 
first-hour rating or maximum GPM and the uniform energy factor is the 
same as that of a tested basic model, provided that the untested basic 
model's input is rated at or above the input rating for the 
corresponding tested basic model.
    (ii) For an untested basic model having an input rating that is 
lower than that of the corresponding tested basic model, the 
represented value of the first-hour rating or maximum GPM and the 
uniform energy factor is the same as that of a tested basic model, 
provided that the first-hour rating or maximum GPM for the untested 
basic model results in the same draw pattern specified in Table II of 
appendix E for the 24-hour simulated-use test as was applied to the 
tested basic model. To establish whether this condition is met, 
determine the first-hour rating or maximum GPM for the tested and the 
untested basic models in accordance with the procedure described in 
section 5.3 of 10 CFR part 430, subpart B, appendix E, then compare the 
appropriate draw pattern specified in Table II of appendix E for the 
first-hour rating or maximum GPM of the tested basic model with that 
for the untested basic model. If this condition is not met, then the 
untested basic model must be tested, and the appropriate sampling 
provisions must be applied to determine its uniform energy factor in 
accordance with appendix E and this part.
* * * * *

0
3. Amend Sec.  429.134 by adding paragraph (d)(3) to read as follows:


Sec.  429.134  Product-specific enforcement provisions.

* * * * *
    (d) * * *
    (3) Verification of fuel input rate. The fuel input rate of each 
tested unit of the basic model will be measured pursuant to the test 
requirements of section 5.2.3 of 10 CFR part 430, subpart B, appendix 
E. The measured fuel input rate (either the measured fuel input rate 
for a single unit sample or the average of the measured fuel input 
rates for a multiple unit sample) will be compared to the rated input 
certified by the

[[Page 40473]]

manufacturer. The certified rated input will be considered valid only 
if the measured fuel input rate is within 2 percent of the 
certified rated input.
    (i) If the certified rated input is found to be valid, then the 
certified rated input will be used to determine compliance with the 
associated energy conservation standard.
    (ii) If the measured fuel input rate for gas-fired or oil-fired 
water heating products is not within 2 percent of the 
certified rated input, the measured fuel input rate will be used to 
determine compliance with the associated energy conservation standard.
* * * * *

PART 430--ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS

0
4. The authority citation for part 430 continues to read as follows:

    Authority: 42 U.S.C. 6291-6309; 28 U.S.C. 2461 note.


0
5. Amend Sec.  430.2 by adding in alphabetical order definitions for 
``Circulating water heater'', ``Low-temperature water heater'', and 
``Tabletop water heater'' to read as follows:


Sec.  430.2  Definitions.

* * * * *
    Circulating water heater means an instantaneous or heat pump-type 
water heater that does not have an operational scheme in which the 
burner, heating element, or compressor initiates and/or terminates 
heating based on sensing flow; has a water temperature sensor located 
at the inlet or the outlet of the water heater or in a separate storage 
tank that is the primary means of initiating and terminating heating; 
and must be used in combination with a recirculating pump and either a 
separate storage tank or water circulation loop in order to achieve the 
water flow and temperature conditions recommended in the manufacturer's 
installation and operation instructions.
* * * * *
    Low-temperature water heater means an electric instantaneous water 
heater that is not a circulating water heater and cannot deliver water 
at a temperature greater than or equal to the set point temperature 
specified in section 2.5 of appendix E to subpart B of this part when 
supplied with water at the supply water temperature specified in 
section 2.3 of appendix E to subpart B of this part and the flow rate 
specified in section 5.2.2.1 of appendix E to subpart B of this part.
* * * * *
    Tabletop water heater means a heater in a rectangular box enclosure 
designed to slide into a kitchen countertop space with typical 
dimensions of 36 inches high, 25 inches deep, and 24 inches wide.
* * * * *

0
6. Section 430.3 is amended by:
0
a. In paragraph (g)(5), removing the text ``appendices E, AA'' and 
adding, in its place, the text ``appendices AA'';
0
b. Redesignating paragraph (g)(20) as paragraph (g)(22);
0
c. Redesignating paragraph (g)(8) through (19) as paragraphs (g)(9) 
through (20);
0
d. Adding new paragraph (g)(8);
0
e. In newly redesignated paragraph (g)(13), removing the text ``F and 
EE'' and adding, in its place, the text ``E, F, and EE'';
0
f. Adding new paragraph (g)(21);
0
g. Revising paragraph (j).
    The revisions and additions read as follows:


Sec.  430.3  Materials incorporated by reference.

* * * * *
    (g) * * *
    (8) ANSI/ASHRAE Standard 41.1-2020 (``ASHRAE 41.1-2020''), Standard 
Methods for Temperature Measurement, ANSI-approved June 30, 2020; IBR 
approved for appendix E to subpart B.
* * * * *
    (21) ANSI/ASHRAE Standard 118.2-2022 (``ASHRAE 118.2-2022''), 
Method of Testing for Rating Residential Water Heaters and Residential-
Duty Commercial Water Heaters, ANSI-approved March 1, 2022; IBR 
approved for appendix E to subpart B.
* * * * *
    (j) ASTM. ASTM International, 100 Barr Harbor Drive, P.O. Box C700, 
West Conshohocken, PA 19428-2959; 877-909-2786; [email protected]; 
www.astm.org.
    (1) ASTM D2156-09 (Reapproved 2013) (``ASTM D2156R13''), Standard 
Test Method for Smoke Density in Flue Gases from Burning Distillate 
Fuels, approved October 1, 2013; IBR approved for appendix N to subpart 
B.
    (2) ASTM D2156-09 (Reapproved 2018) (``ASTM D2156 (R2018)''), 
Standard Test Method for Smoke Density in Flue Gases from Burning 
Distillate Fuels, approved October 1, 2018; IBR approved for appendices 
E, O, and EE to subpart B.
    (3) ASTM E97-82 (Reapproved 1987) (``ASTM E97-1987''), Standard 
Test Method for Directional Reflectance Factor, 45-deg 0-deg, of Opaque 
Specimens by Broad-Band Filter Reflectometry, ASTM-approved October 29, 
1982; IBR approved for appendix E to subpart B.

    Note 2 to paragraph (j)(3): ASTM E97-1987 was withdrawn in 1991. 
It is reasonably available from standards resellers including 
GlobalSpec's Engineering 360 (https://standards.globalspec.com/std/3801495/astm-e97-82-1987) and IHS Markit (https://global.ihs.com/doc_detail.cfm?document_name=ASTM%20E97&item_s_key=00020483).

    (4) ASTM E741-11 (Reapproved 2017) (``ASTM E741-11(2017)''), 
Standard Test Method for Determining Air Change in a Single Zone Means 
of a Tracer Gas Dilution Approved Sept. 1, 2017; IBR approved for 
appendix FF to subpart B.
* * * * *

0
7. Appendix E to subpart B of part 430 is revised to read as follows:

Appendix E to Subpart B of Part 430--Uniform Test Method for Measuring 
the Energy Consumption of Water Heaters

    Note:  Prior to December 18, 2023, representations with respect 
to the energy use or efficiency of consumer water heaters covered by 
this test method, including compliance certifications, must be based 
on testing conducted in accordance with either this appendix as it 
now appears or appendix E as it appeared at 10 CFR part 430, subpart 
B revised as of January 1, 2021.
    On and after December 18, 2023, representations with respect to 
energy use or efficiency of consumer water heaters covered by this 
test method, including compliance certifications, must be based on 
testing conducted in accordance with this appendix, except as 
outlined in the following paragraphs.
    Prior to June 17, 2024, representations with respect to the 
energy use or efficiency of residential-duty commercial water 
heaters covered by this test method, including compliance 
certifications, must be based on testing conducted in accordance 
with either this appendix as it now appears or appendix E as it 
appeared at 10 CFR part 430, subpart B revised as of January 1, 
2021.
    On and after June 17, 2024, representations with respect to 
energy use or efficiency of residential-duty commercial water 
heaters covered by this test method, including compliance 
certifications, must be based on testing conducted in accordance 
with this appendix.
    Water heaters subject to section 4.10 of this appendix may 
optionally apply the requirements in section 4.10 of this appendix 
prior to the compliance date of a final rule reviewing potential 
amended energy conservation standards for these products and 
equipment published after June 21, 2023. After the compliance date 
of such standards final rule, the requirements of section 4.10 are 
mandatory.
    In addition, certain electric resistance storage water heaters 
may optionally apply the requirements in section 5.1.2 of this 
appendix in lieu of the requirements in section 5.1.1 of this 
appendix for additional

[[Page 40474]]

voluntary representations only. Water heaters must certify according 
to the requirements in section 5.1.1 until the publication of a 
final rule reviewing potential amended energy conservation standards 
and specifying the required use of section 5.1.2 for these products 
published after June 21, 2023.

    0. Incorporation by Reference.
    DOE incorporated by reference in Sec.  430.3 the entire standard 
for: ASHRAE 41.1-2020; ASHRAE 41.6-2014; ASHRAE 118.2-2022; ASTM 
D2156-09 (R2018); and ASTM E97-1987. However, only enumerated 
provisions of ASHRAE 118.2-2022 are applicable to this appendix, as 
follows:
    0.1 ASHRAE 118.2-2022
    (a) Annex B--Gas Heating Value Correction Factor;
    (b) [Reserved]
    0.2 [Reserved]
    1. Definitions.
    1.1. Cut-in means the time when or water temperature at which a 
water heater control or thermostat acts to increase the energy or 
fuel input to the heating elements, compressor, or burner.
    1.2. Cut-out means the time when or water temperature at which a 
water heater control or thermostat acts to reduce to a minimum the 
energy or fuel input to the heating elements, compressor, or burner.
    1.3. Design Power Rating means the power rating or input rate 
that a water heater manufacturer assigns to a particular design of 
water heater and that is included on the nameplate of the water 
heater, expressed in kilowatts or Btu (kJ) per hour as appropriate. 
For modulating water heaters, the design power rating is the maximum 
power rating or input rate that is specified by the manufacturer on 
the nameplate of the water heater.
    1.4. Draw Cluster means a collection of water draws initiated 
during the 24-hour simulated-use test during which no successive 
draws are separated by more than 2 hours.
    1.5. First-Hour Rating means an estimate of the maximum volume 
of ``hot'' water that a non-flow activated water heater can supply 
within an hour that begins with the water heater fully heated (i.e., 
with all thermostats satisfied).
    1.6. Flow-Activated describes an operational scheme in which a 
water heater initiates and terminates heating based on sensing flow.
    1.7. Heat Trap means a device that can be integrally connected 
or independently attached to the hot and/or cold water pipe 
connections of a water heater such that the device will develop a 
thermal or mechanical seal to minimize the recirculation of water 
due to thermal convection between the water heater tank and its 
connecting pipes.
    1.8. Maximum GPM (L/min) Rating means the maximum gallons per 
minute (liters per minute) of hot water that can be supplied by a 
flow-activated water heater when tested in accordance with section 
5.3.2 of this appendix.
    1.9. Modulating Water Heater means a water heater that can 
automatically vary its power or input rate from the minimum to the 
maximum power or input rate specified on the nameplate of the water 
heater by the manufacturer.
    1.10. Rated Storage Volume means the water storage capacity of a 
water heater, in gallons (liters), as certified by the manufacturer 
pursuant to 10 CFR part 429.
    1.11. Recovery Efficiency means the ratio of energy delivered to 
the water to the energy content of the fuel consumed by the water 
heater.
    1.12. Recovery Period means the time when the main burner of a 
water heater with a rated storage volume greater than or equal to 2 
gallons is raising the temperature of the stored water.
    1.13. Split-system heat pump water heater means a heat pump-type 
water heater in which at least the compressor, which may be 
installed outdoors, is separate from the storage tank.
    1.14. Standby means the time, in hours, during which water is 
not being withdrawn from the water heater.
    1.15. Symbol Usage. The following identity relationships are 
provided to help clarify the symbology used throughout this 
procedure:

Cp--specific heat of water
Eannual--annual energy consumption of a water heater
Eannual,e--annual electrical energy consumption of a 
water heater
Eannual,f--annual fossil-fuel energy consumption of a 
water heater
EX--energy efficiency of a heat pump-type water heater 
when the 24-hour simulated use test is optionally conducted at any 
of the additional air temperature conditions as specified in section 
2.8 of this appendix, where the subscript ``X'' corresponds to the 
dry-bulb temperature at which the test is conducted.
Fhr--first-hour rating of a non-flow activated water 
heater
Fmax--maximum GPM (L/min) rating of a flow-activated 
water heater
i--a subscript to indicate the draw number during a test
kV--storage tank volume scaling ratio for water heaters 
with a rated storage volume greater than or equal to 2 gallons
Mdel,i--mass of water removed during the ith draw of the 
24-hour simulated-use test
Min,i--mass of water entering the water heater during the 
ith draw of the 24-hour simulated-use test
M*del,i--for non-flow activated water heaters, mass of 
water removed during the ith draw during the first-hour rating test
M*in,i--for non-flow activated water heaters, mass of 
water entering the water heater during the ith draw during the 
first-hour rating test
Mdel,10m--for flow-activated water heaters, mass of water 
removed continuously during the maximum GPM (L/min) rating test
Min,10m--for flow-activated water heaters, mass of water 
entering the water heater continuously during the maximum GPM (L/
min) rating test
n--for non-flow activated water heaters, total number of draws 
during the first-hour rating test
N--total number of draws during the 24-hour simulated-use test
Nr--number of draws from the start of the 24-hour 
simulated-use test to the end to the first recovery period as 
described in section 5.4.2 of this appendix
Q--total fossil fuel and/or electric energy consumed during the 
entire 24-hour simulated-use test
Qd--daily water heating energy consumption adjusted for 
net change in internal energy
Qda--Qd with adjustment for variation of tank 
to ambient air temperature difference from nominal value
Qdm--overall adjusted daily water heating energy 
consumption including Qda and QHWD
Qe--total electrical energy used during the 24-hour 
simulated-use test
Qf--total fossil fuel energy used by the water heater 
during the 24-hour simulated-use test
Qhr--hourly standby losses of a water heater with a rated 
storage volume greater than or equal to 2 gallons
QHW--daily energy consumption to heat water at the 
measured average temperature rise across the water heater
QHW,67 [deg]F--daily energy consumption to heat quantity 
of water removed during test over a temperature rise of 67 [deg]F 
(37.3 [deg]C)
QHWD--adjustment to daily energy consumption, 
QHW, due to variation of the temperature rise across the 
water heater not equal to the nominal value of 67 [deg]F (37.3 
[deg]C)
Qr--energy consumption of water heater from the beginning 
of the test to the end of the first recovery period
Qstby--total energy consumed during the standby time 
interval [tau]stby,1, as determined in section 5.4.2 of 
this appendix
Qsu,0--cumulative energy consumption, including all 
fossil fuel and electrical energy use, of the water heater from the 
start of the 24-hour simulated-use test to the start of the standby 
period as determined in section 5.4.2 of this appendix
Qsu,f--cumulative energy consumption, including all 
fossil fuel and electrical energy use, of the water heater from the 
start of the 24-hour simulated-use test to the end of the standby 
period as determined in section 5.4.2 of this appendix
T0--mean tank temperature at the beginning of the 24-hour 
simulated-use test as determined in section 5.4.2 of this appendix
T24--mean tank temperature at the end of the 24-hour 
simulated-use test as determined in section 5.4.2 of this appendix
Ta,stby--average ambient air temperature during all 
standby periods of the 24-hour simulated-use test as determined in 
section 5.4.2 of this appendix
Ta,stby,1--overall average ambient temperature between 
the start and end of the standby period as determined in section 
5.4.2 of this appendix
Tt,stby,1-- overall average mean tank temperature between 
the start and end of the standby period as determined in section 
5.4.2 of this appendix
Tdel--for flow-activated water heaters, average outlet 
water temperature during the maximum GPM (L/min) rating test
Tdel,i--average outlet water temperature during the ith 
draw of the 24-hour simulated-use test

[[Page 40475]]

Tin--for flow-activated water heaters, average inlet 
water temperature during the maximum GPM (L/min) rating test
Tst--for water heaters which cannot have internal tank 
temperature directly measured, estimated average internal storage 
tank temperature
Tp--for water heaters which cannot have internal tank 
temperature directly measured, average of the inlet and the outlet 
water temperatures at the end of the period defined by 
[tau]p
Tin,p--for water heaters which cannot have internal tank 
temperature directly measured, average of the inlet water 
temperatures
Tout,p--for water heaters which cannot have internal tank 
temperature directly measured, average of the outlet water 
temperatures
Tin,i--average inlet water temperature during the ith 
draw of the 24-hour simulated-use test
Tmax,1--maximum measured mean tank temperature after the 
first recovery period of the 24-hour simulated-use test as 
determined in section 5.4.2 of this appendix
Tsu,0--maximum measured mean tank temperature at the 
beginning of the standby period as determined in section 5.4.2 of 
this appendix
Tsu,f--measured mean tank temperature at the end of the 
standby period as determined in section 5.4.2 of this appendix
T*del,i--for non-flow activated water heaters, average 
outlet water temperature during the ith draw (i = 1 to n) of the 
first-hour rating test
T*max,i--for non-flow activated water heaters, maximum 
outlet water temperature observed during the ith draw (i = 1 to n) 
of the first-hour rating test
T*min,i--for non-flow activated water heaters, minimum 
outlet water temperature to terminate the ith draw (i = 1 to n) of 
the first-hour rating test
UA--standby loss coefficient of a water heater with a rated storage 
volume greater than or equal to 2 gallons
UEF--uniform energy factor of a water heater
V--the volume of hot water drawn during the applicable draw pattern
Vdel,i--volume of water removed during the ith draw (i = 
1 to N) of the 24-hour simulated-use test
Vin,i--volume of water entering the water heater during 
the ith draw (i = 1 to N) of the 24-hour simulated-use test
V*del,i--for non-flow activated water heaters, volume of 
water removed during the ith draw (i = 1 to n) of the first-hour 
rating test
V*in,i--for non-flow activated water heaters, volume of 
water entering the water heater during the ith draw (i = 1 to n) of 
the first-hour rating test
Vdel,10m--for flow-activated water heaters, volume of 
water removed during the maximum GPM (L/min) rating test
Vin,10m--for flow-activated water heaters, volume of water entering 
the water heater during the maximum GPM (L/min) rating test
Vst--measured storage volume of the storage tank for water heaters 
with a rated storage volume greater than or equal to 2 gallons
Veff--effective storage volume
vout,p--for water heaters which cannot have internal tank 
temperature directly measured, average flow rate
Wf--weight of storage tank when completely filled with water for 
water heaters with a rated storage volume greater than or equal to 2 
gallons
Wt--tare weight of storage tank when completely empty of water for 
water heaters with a rated storage volume greater than or equal to 2 
gallons
[eta]r--recovery efficiency
[rho]--density of water
[tau]p--for water heaters which cannot have internal tank 
temperature directly measured, duration of the temperature 
measurement period, determined by the length of time taken for the 
outlet water temperature to be within 2 [deg]F of the inlet water 
temperature for 15 consecutive seconds (including the 15-second 
stabilization period)
[tau]stby,1--elapsed time between the start and end of the standby 
period as determined in section 5.4.2 of this appendix
[tau]stby,2--overall time of standby periods when no water is 
withdrawn during the 24-hour simulated-use test as determined in 
section 5.4.2 of this appendix

    1.16. Temperature Controller means a device that is available to 
the user to adjust the temperature of the water inside a water 
heater that stores heated water or the outlet water temperature.
    1.17. Thermal break means a thermally non-conductive material 
that can withstand a pressure of 150 psi (1.034 MPa) at a 
temperature greater than the maximum temperature the water heater is 
designed to produce and is utilized to insulate a bypass loop, if 
one is used in the test set-up, from the inlet piping.
    1.18. Uniform Energy Factor means the measure of water heater 
overall efficiency.
    1.19. Water Heater Requiring a Storage Tank means a water heater 
without a storage tank specified or supplied by the manufacturer 
that cannot meet the requirements of sections 2 and 5 of this 
appendix without the use of a storage water heater or unfired hot 
water storage tank.
    2. Test Conditions.
    2.1 Installation Requirements. Tests shall be performed with the 
water heater and instrumentation installed in accordance with 
section 4 of this appendix.
    2.2 Ambient Air Temperature and Relative Humidity.
    2.2.1 Non-Heat Pump Water Heaters. The ambient air temperature 
shall be maintained between 65.0 [deg]F and 70.0 [deg]F (18.3 [deg]C 
and 21.1 [deg]C) on a continuous basis.
    2.2.2 Heat Pump Water Heaters. The dry-bulb temperature shall be 
maintained at an average of 67.5 [deg]F  1 [deg]F (19.7 
[deg]C  0.6 [deg]C) after a cut-in and before the next 
cut-out, an average of 67.5 [deg]F  2.5 [deg]F (19.7 
[deg]C  1.4 [deg]C) after a cut-out and before the next 
cut-in, and at 67.5 [deg]F  5 [deg]F (19.7 [deg]C  2.8 [deg]C) on a continuous basis throughout the test. The 
relative humidity shall be maintained within a range of 50%  5% throughout the test, and at an average of 50%  
2% after a cut-in and before the next cut-out.
    When testing a split-system heat pump water heater or heat pump 
water heater requiring a separate storage tank, the heat pump 
portion of the system shall be tested at the conditions within this 
section and the separate water heater or unfired hot water storage 
tank shall be tested at either the conditions within this section or 
the conditions specified in section 2.2.1 of this appendix.
    2.3 Supply Water Temperature. The temperature of the water being 
supplied to the water heater shall be maintained at 58 [deg]F  2 [deg]F (14.4 [deg]C  1.1 [deg]C) throughout the 
test.
    2.4 Outlet Water Temperature. The temperature controllers of a 
non-flow activated water heater shall be set so that water is 
delivered at a temperature of 125 [deg]F  5 [deg]F (51.7 
[deg]C  2.8 [deg]C).
    2.5 Set Point Temperature. The temperature controller of a flow-
activated water heater shall be set to deliver water at a 
temperature of 125 [deg]F  5 [deg]F (51.7 [deg]C  2.8 [deg]C). If the flow-activated water heater is not 
capable of delivering water at a temperature of 125 [deg]F  5 [deg]F (51.7 [deg]C  2.8 [deg]C) when supplied 
with water at the supply water temperature specified in section 2.3 
of this appendix, then the flow-activated water heater shall be set 
to deliver water at its maximum water temperature.
    2.6 Supply Water Pressure. During the test when water is not 
being withdrawn, the supply pressure shall be maintained between 40 
psig (275 kPa) and the maximum allowable pressure specified by the 
water heater manufacturer.
    2.7 Electrical and/or Fossil Fuel Supply.
    2.7.1 Electrical. Maintain the electrical supply voltage to 
within 2% of the center of the voltage range specified 
on the nameplate of the water heater by the water heater and/or heat 
pump manufacturer, from 5 seconds after a cut-in to 5 seconds before 
next cut-out.
    2.7.2 Natural Gas. Maintain the supply pressure in accordance 
with the supply pressure specified on the nameplate of the water 
heater by the manufacturer. If the supply pressure is not specified, 
maintain a supply pressure of 7-10 inches of water column (1.7-2.5 
kPa). If the water heater is equipped with a gas appliance pressure 
regulator and the gas appliance pressure regulator can be adjusted, 
the regulator outlet pressure shall be within the greater of 10% of the manufacturer's specified manifold pressure, found 
on the nameplate of the water heater, or 0.2 inches 
water column (0.05 kPa). Maintain the gas supply pressure and 
manifold pressure only when operating at the design power rating. 
For all tests, use natural gas having a heating value of 
approximately 1,025 Btu per standard cubic foot (38,190 kJ per 
standard cubic meter).
    2.7.3 Propane Gas. Maintain the supply pressure in accordance 
with the supply pressure specified on the nameplate of the water 
heater by the manufacturer. If the supply pressure is not specified, 
maintain a supply pressure of 11-13 inches of water column (2.7-3.2 
kPa). If the water heater is equipped with a gas appliance pressure 
regulator and the gas appliance pressure regulator can be adjusted, 
the regulator outlet pressure shall be within the greater of 10% of the manufacturer's specified manifold pressure, found 
on the nameplate of the

[[Page 40476]]

water heater, or 0.2 inches water column (0.05 kPa). 
Maintain the gas supply pressure and manifold pressure only when 
operating at the design power rating. For all tests, use propane gas 
with a heating value of approximately 2,500 Btu per standard cubic 
foot (93,147 kJ per standard cubic meter).
    2.7.4 Fuel Oil Supply. Maintain an uninterrupted supply of fuel 
oil. The fuel pump pressure shall be within 10% of the 
pump pressure specified on the nameplate of the water heater or the 
installation and operations (I&O) manual by the manufacturer. Use 
fuel oil having a heating value of approximately 138,700 Btu per 
gallon (38,660 kJ per liter).
    2.8 Optional Test Conditions (Heat Pump-Type Water Heaters). The 
following test conditions may be used for optional representations 
of EX for heat pump-type water heaters. When conducting a 
24-hour simulated use test to determine EX, the test 
conditions in section 2.1 and sections 2.4 through 2.7 apply. The 
ambient air temperature and humidity conditions in section 2.2 and 
the supply water temperature in section 2.3 are replaced with the 
air temperature, humidity, and supply water temperature conditions 
as shown in the following table. Testing may optionally be performed 
at any or all of the conditions in the table, and the sampling plan 
found at 10 CFR 429.17(a) may be applied for voluntary 
representations.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Outdoor air conditions           Indoor air conditions
                                                                         ----------------------------------------------------------------  Supply water
               Heat pump type                           Metric               Dry-bulb                        Dry-bulb                       temperature
                                                                            temperature      Relative       temperature      Relative        ([deg]F)
                                                                             ([deg]F)      humidity (%)      ([deg]F)      humidity (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Split-System or Circulating.................  E5                                     5.0              30            67.5              50            42.0
                                              E34                                   34.0              72  ..............  ..............            47.0
                                              E95                                   95.0              25  ..............  ..............            67.0
Integrated, Split-System, or Circulating....  E50                                    N/A             N/A            50.0              58            50.0
                                              E95                                    N/A             N/A            95.0              40            67.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    3. Instrumentation.
    3.1 Pressure Measurements. Pressure-measuring instruments shall 
have an error no greater than the following values:

------------------------------------------------------------------------
                                      Instrument          Instrument
          Item measured                accuracy            precision
------------------------------------------------------------------------
Gas pressure....................  0.1     0.05
                                   inch of water       inch of water
                                   column (0.025 kPa).   minus>0.012 kPa).
Atmospheric pressure............  0.1     0.05
                                   inch of mercury     inch of mercury
                                   column (0.34 kPa).    minus>0.17 kPa).
Water pressure..................  1.0     0.50
                                   pounds per square   pounds per square
                                   inch (6.9 kPa).     minus>3.45 kPa).
------------------------------------------------------------------------

    3.2 Temperature Measurement
    3.2.1 Measurement. Temperature measurements shall be made in 
accordance with the Standard Method for Temperature Measurement, 
ASHRAE 41.1-2020, including the conditions as specified in ASHRAE 
41.6-2014 as referenced in ASHRAE 41.1-2020, and excluding the 
steady-state temperature criteria in section 5.5 of ASHRAE 41.1-
2020.
    3.2.2 Accuracy and Precision. The accuracy and precision of the 
instruments, including their associated readout devices, shall be 
within the following limits:

------------------------------------------------------------------------
                                      Instrument          Instrument
          Item measured                accuracy            precision
------------------------------------------------------------------------
Air dry-bulb temperature........  0.2     0.1
                                   [deg]F (0.1 [deg]C).  minus>0.06
                                                       [deg]C).
Air wet-bulb temperature........  0.2     0.1
                                   [deg]F (0.1 [deg]C).  minus>0.06
                                                       [deg]C).
Inlet and outlet water            0.2     0.1
 temperatures.                     [deg]F (0.1 [deg]C).  minus>0.06
                                                       [deg]C).
Storage tank temperatures.......  0.5     0.25
                                   [deg]F (0.3 [deg]C).  minus>0.14
                                                       [deg]C).
------------------------------------------------------------------------

    3.2.3 Scale Division. In no case shall the smallest scale 
division of the instrument or instrument system exceed 2 times the 
specified precision.
    3.2.4 Temperature Difference. Temperature difference between the 
entering and leaving water may be measured with any of the 
following:

(a) A thermopile
(b) Calibrated resistance thermometers
(c) Precision thermometers
(d) Calibrated thermistors
(e) Calibrated thermocouples
(f) Quartz thermometers

    3.2.5 Thermopile Construction. If a thermopile is used, it shall 
be made from calibrated thermocouple wire taken from a single spool. 
Extension wires to the recording device shall also be made from that 
same spool.
    3.2.6 Time Constant. The time constant of the instruments used 
to measure the inlet and outlet water temperatures shall be no 
greater than 2 seconds.
    3.3 Liquid Flow Rate Measurement. The accuracy of the liquid 
flow rate measurement, using the calibration if furnished, shall be 
equal to or less than 1% of the measured value in mass 
units per unit time.
    3.4 Electrical Energy. The electrical energy used shall be 
measured with an instrument and associated readout device that is 
accurate within 0.5% of the reading.
    3.5 Fossil Fuels. The quantity of fuel used by the water heater 
shall be measured with an instrument and associated readout device 
that is accurate within 1% of the reading.
    3.6 Mass Measurements. For mass measurements greater than or 
equal to 10 pounds (4.5 kg), a scale that is accurate within 0.5% of the reading shall be used to make the measurement. For 
mass measurements less than 10 pounds (4.5 kg), the scale shall 
provide a measurement that is accurate within 0.1 pound 
(0.045 kg).
    3.7 Heating Value. The higher heating value of the natural gas, 
propane, or fuel oil shall be measured with an instrument and 
associated readout device that is accurate within 1% of 
the reading. The heating values of natural gas and propane must be 
corrected from those measured to the standard temperature of 60.0 
[deg]F (15.6 [deg]C) and standard pressure of 30 inches of mercury 
column (101.6 kPa) using the method described in Annex B of ASHRAE 
118.2-2022.
    3.8 Time. The elapsed time measurements shall be measured with 
an instrument that is accurate within 0.5 seconds per 
hour.
    3.9 Volume. Volume measurements shall be measured with an 
accuracy of 2% of the total volume.
    3.10 Relative Humidity. If a relative humidity (RH) transducer 
is used to measure the relative humidity of the surrounding air 
while testing heat pump water heaters, the

[[Page 40477]]

relative humidity shall be measured with an accuracy of 1.5% RH.
    4. Installation.
    4.1 Water Heater Mounting. A water heater designed to be 
freestanding shall be placed on a \3/4\ inch (2 cm) thick plywood 
platform supported by three 2x4 inch (5 cm x 10 cm) runners. If the 
water heater is not approved for installation on combustible 
flooring, suitable non-combustible material shall be placed between 
the water heater and the platform. Water heaters designed to be 
installed into a kitchen countertop space shall be placed against a 
simulated wall section. Wall-mounted water heaters shall be 
supported on a simulated wall in accordance with the manufacturer-
published installation instructions. When a simulated wall is used, 
the construction shall be 2x4 inch (5 cm x 10 cm) studs, faced with 
\3/4\ inch (2 cm) plywood. For heat pump water heaters not delivered 
as a single package, the units shall be connected in accordance with 
the manufacturer-published installation instructions, and the 
overall system shall be placed on the above-described plywood 
platform. If installation instructions are not provided by the heat 
pump manufacturer, uninsulated 8 foot (2.4 m) long connecting hoses 
having an inside diameter of \5/8\ inch (1.6 cm) shall be used to 
connect the storage tank and the heat pump water heater. With the 
exception of using the storage tank described in section 4.10 of 
this appendix, the same requirements shall apply for water heaters 
requiring a storage tank. The testing of the water heater shall 
occur in an area that is protected from drafts of more than 50 ft/
min (0.25 m/s) from room ventilation registers, windows, or other 
external sources of air movement.
    4.2 Water Supply. Connect the water heater to a water supply 
capable of delivering water at conditions as specified in sections 
2.3 and 2.6 of this appendix.
    4.3 Water Inlet and Outlet Configuration. For freestanding water 
heaters that are taller than 36 inches (91.4 cm), inlet and outlet 
piping connections shall be configured in a manner consistent with 
Figures 1 and 2 of section 7 of this appendix. Inlet and outlet 
piping connections for wall-mounted water heaters shall be 
consistent with Figure 3 of section 7 of this appendix. For 
freestanding water heaters that are 36 inches or less in height and 
not supplied as part of a counter-top enclosure (commonly referred 
to as an under-the-counter model), inlet and outlet piping shall be 
installed in a manner consistent with Figures 4, 5, or 6 of section 
7 of this appendix. For water heaters that are supplied with a 
counter-top enclosure, inlet and outlet piping shall be made in a 
manner consistent with Figures 7a and 7b of section 7 of this 
appendix, respectively. The vertical piping noted in Figures 7a and 
7b shall be located (whether inside the enclosure or along the 
outside in a recessed channel) in accordance with the manufacturer-
published installation instructions.
    All dimensions noted in Figures 1 through 7 of section 7 of this 
appendix must be achieved. All piping between the water heater and 
inlet and outlet temperature sensors, noted as TIN and 
TOUT in the figures, shall be Type ``L'' hard copper 
having the same diameter as the connections on the water heater. 
Unions may be used to facilitate installation and removal of the 
piping arrangements. Install a pressure gauge and diaphragm 
expansion tank in the supply water piping at a location upstream of 
the inlet temperature sensor. Install an appropriately rated 
pressure and temperature relief valve on all water heaters at the 
port specified by the manufacturer. Discharge piping for the relief 
valve must be non-metallic. If heat traps, piping insulation, or 
pressure relief valve insulation are supplied with the water heater, 
they must be installed for testing. Except when using a simulated 
wall, provide sufficient clearance such that none of the piping 
contacts other surfaces in the test room.
    At the discretion of the test laboratory, the mass or water 
delivered may be measured on either the inlet or outlet of the water 
heater.
    For water heaters designed to be used with a mixing valve and 
that do not have a self-contained mixing valve, a mixing valve shall 
be installed according to the water heater and/or mixing valve 
manufacturer's installation instructions. If permitted by the water 
heater and mixing valve manufacturer's instructions, the mixing 
valve and cold water junction may be installed where the elbows are 
located in the outlet and inlet line, respectively. If there are no 
installation instructions for the mixing valve in the water heater 
or mixing valve manufacturer's instructions, then the mixing valve 
shall be installed on the outlet line and the cold water shall be 
supplied from the inlet line from a junction installed downstream 
from the location where the inlet water temperature is measured. The 
outlet water temperature, water flow rate, and/or mass measuring 
instrumentation, if installed on the outlet side of the water 
heater, shall be installed downstream from the mixing valve.
    4.4 Fuel and/or Electrical Power and Energy Consumption. Install 
one or more instruments that measure, as appropriate, the quantity 
and rate of electrical energy and/or fossil fuel consumption in 
accordance with section 3 of this appendix.
    4.5 Internal Storage Tank Temperature Measurements. For water 
heaters with rated storage volumes greater than or equal to 20 
gallons, install six temperature measurement sensors inside the 
water heater tank with a vertical distance of at least 4 inches (100 
mm) between successive sensors. For water heaters with rated storage 
volumes between 2 and 20 gallons, install three temperature 
measurement sensors inside the water heater tank. Position a 
temperature sensor at the vertical midpoint of each of the six equal 
volume nodes within a tank larger than 20 gallons or the three equal 
volume nodes within a tank between 2 and 20 gallons. Nodes designate 
the equal volumes used to evenly partition the total volume of the 
tank. As much as is possible, the temperature sensor should be 
positioned away from any heating elements, anodic protective 
devices, tank walls, and flue pipe walls. If the tank cannot 
accommodate six temperature sensors and meet the installation 
requirements specified in this section, install the maximum number 
of sensors that comply with the installation requirements. Install 
the temperature sensors through:
    (a) The anodic device opening;
    (b) The relief valve opening; or
    (c) The hot water outlet.
    If installed through the relief valve opening or the hot water 
outlet, a tee fitting or outlet piping, as applicable, must be 
installed as close as possible to its original location. If the 
relief valve temperature sensor is relocated, and it no longer 
extends into the top of the tank, install a substitute relief valve 
that has a sensing element that can reach into the tank. If the hot 
water outlet includes a heat trap, install the heat trap on top of 
the tee fitting. Cover any added fittings with thermal insulation 
having an R value between 4 and 8 h[middot]ft\2\[middot] [deg]F/Btu 
(0.7 and 1.4 m\2\[middot] [deg]C/W). If temperature measurement 
sensors cannot be installed within the water heater, follow the 
alternate procedures in section 5.4.2.2 of this appendix.
    4.6 Ambient Air Temperature Measurement. Install an ambient air 
temperature sensor at the vertical midpoint of the water heater and 
approximately 2 feet (610 mm) from the surface of the water heater. 
Shield the sensor against radiation.
    4.7 Inlet and Outlet Water Temperature Measurements. Install 
temperature sensors in the cold-water inlet pipe and hot-water 
outlet pipe as shown in Figures 1, 2, 3, 4, 5, 6, 7a, and 7b of 
section 7 of this appendix, as applicable.
    4.8 Flow Control. Install a valve or valves to provide flow as 
specified in sections 5.3 and 5.4 of this appendix.
    4.9 Flue Requirements.
    4.9.1 Gas-Fired Water Heaters. Establish a natural draft in the 
following manner. For gas-fired water heaters with a vertically 
discharging draft hood outlet, connect to the draft hood outlet a 5-
foot (1.5-meter) vertical vent pipe extension with a diameter equal 
to the largest flue collar size of the draft hood. For gas-fired 
water heaters with a horizontally discharging draft hood outlet, 
connect to the draft hood outlet a 90-degree elbow with a diameter 
equal to the largest flue collar size of the draft hood, connect a 
5-foot (1.5-meter) length of vent pipe to that elbow, and orient the 
vent pipe to discharge vertically upward. Install direct-vent gas-
fired water heaters with venting equipment specified by the 
manufacturer in the I&O manual using the minimum vertical and 
horizontal lengths of vent pipe recommended by the manufacturer.
    4.9.2 Oil-Fired Water Heaters. Establish a draft at the flue 
collar at the value specified by the manufacturer in the I&O manual. 
Establish the draft by using a sufficient length of vent pipe 
connected to the water heater flue outlet, and directed vertically 
upward. For an oil-fired water heater with a horizontally 
discharging draft hood outlet, connect to the draft hood outlet a 
90-degree elbow with a diameter equal to the largest flue collar 
size of the draft hood, connect to the elbow fitting a length of 
vent pipe sufficient to establish the draft, and orient the vent 
pipe to discharge vertically upward. Direct-vent oil-fired water 
heaters should be installed with venting equipment as specified by 
the manufacturer in the I&O manual, using the minimum vertical and 
horizontal

[[Page 40478]]

lengths of vent pipe recommended by the manufacturer.
    4.10 Storage Tank Requirement for Circulating Water Heaters. On 
or after the compliance date of a final rule reviewing potential 
amended energy conservation standards for these products published 
after June 21, 2023,when testing a gas-fired, oil-fired, or electric 
resistance circulating water heater (i.e., any circulating water 
heater that does not use a heat pump), the tank to be used for 
testing shall be an unfired hot water storage tank having volume 
between 80 and 120 gallons (364-546 liters) determined using the 
method specified in section 5.2.1 that meets but does not exceed the 
minimum energy conservation standards required according to 10 CFR 
431.110. When testing a heat pump circulating water heater, the tank 
to be used for testing shall be an electric storage water heater 
that has a measured volume of 40 gallons (5 gallons), 
has a First-Hour Rating greater than or equal to 51 gallons and less 
than 75 gallons resulting in classification under the medium draw 
pattern, and has a rated UEF equal to the minimum UEF standard 
specified at Sec.  430.32(d), rounded to the nearest 0.01. The 
operational mode of the heat pump circulating water heater and 
storage water heater paired system shall be set in accordance with 
section 5.1.1 of this appendix. If the circulating water heater is 
supplied with a separate non-integrated circulating pump, install 
this pump as per the manufacturer's installation instructions and 
include its power consumption in energy use measurements.
    4.11 External Communication. If the water heater can connect to 
an external network or controller, any external communication or 
connection shall be disabled for the duration of testing; however, 
the communication module shall remain in an ``on'' state.
    5. Test Procedures.
    5.1 Operational Mode Selection. For water heaters that allow for 
multiple user-selected operational modes, all procedures specified 
in this appendix shall be carried out with the water heater in the 
same operational mode (i.e., only one mode).
    5.1.1 Testing at Normal Setpoint. The operational mode shall be 
the default mode (or similarly named, suggested mode for normal 
operation) as defined by the manufacturer in the I&O manual for 
giving selection guidance to the consumer. For heat pump water 
heaters, if a default mode is not defined in the product literature, 
each test shall be conducted under an operational mode in which both 
the heat pump and any electric resistance back-up heating element(s) 
are activated by the unit's control scheme, and which can achieve 
the internal storage tank temperature specified in this test 
procedure; if multiple operational modes meet these criteria, the 
water heater shall be tested under the most energy-intensive mode. 
If no default mode is specified and the unit does not offer an 
operational mode that utilizes both the heat pump and the electric 
resistance back-up heating element(s), the first-hour rating test 
and the 24-hour simulated-use test shall be tested in heat-pump-only 
mode. For other types of water heaters where a default mode is not 
specified, test the unit in all modes and rate the unit using the 
results of the most energy-intensive mode.
    5.1.2 High Temperature Testing. This paragraph applies to 
electric storage water heaters that are capable of heating their 
stored water above the target delivery temperature without 
initiation from a utility or third-party demand-response program, 
except for those that meet the definition of ``heat pump-type'' 
water heater at 10 CFR 430.2.
    For those equipped with factory-installed or built-in mixing 
valves, set the unit to maintain the highest mean tank temperature 
possible while delivering water at 125 [deg]F  5 [deg]F. 
For those not so equipped, install an ASSE 1017-certified mixing 
valve in accordance with the provisions in section 4.3 and adjust 
the valve to deliver water at 125 [deg]F  5 [deg]F when 
the water heater is operating at its highest storage tank 
temperature setpoint. Maintain this setting throughout the entirety 
of the test.
    5.2 Water Heater Preparation.
    5.2.1 Determination of Storage Tank Volume. For water heaters 
with a rated storage volume greater than or equal to 2 gallons and 
for separate storage tanks used for testing circulating water 
heaters, determine the storage capacity, Vst, of the 
water heater or separate storage tank under test, in gallons 
(liters), by subtracting the tare weight, Wt, (measured 
while the tank is empty) from the gross weight of the storage tank 
when completely filled with water at the supply water temperature 
specified in section 2.3 of this appendix, Wf, (with all 
air eliminated and line pressure applied as described in section 2.6 
of this appendix) and dividing the resulting net weight by the 
density of water at the measured temperature.
    5.2.2 Setting the Outlet Discharge Temperature.
    5.2.2.1 Flow-Activated Water Heaters, including certain 
instantaneous water heaters and certain storage-type water heaters. 
Initiate normal operation of the water heater at the design power 
rating. Monitor the discharge water temperature and set to the value 
specified in section 2.5 of this appendix in accordance with the 
manufacturer's I&O manual. If the water heater is not capable of 
providing this discharge temperature when the flow rate is 1.7 
gallons  0.25 gallons per minute (6.4 liters  0.95 liters per minute), then adjust the flow rate as 
necessary to achieve the specified discharge water temperature. Once 
the proper temperature control setting is achieved, the setting must 
remain fixed for the duration of the maximum GPM test and the 24-
hour simulated-use test.
    5.2.2.2 All Other Water Heaters.
    5.2.2.2.1 Water Heaters with a Single Temperature Controller.
    5.2.2.2.1.1 Water Heaters with Rated Volumes Less than 20 
Gallons. Starting with a tank at the supply water temperature as 
specified in section 2.3 of this appendix, initiate normal operation 
of the water heater. After cut-out, initiate a draw from the water 
heater at a flow rate of 1.0 gallon  0.25 gallons per 
minute (3.8 liters  0.95 liters per minute) for 2 
minutes. Starting 15 seconds after commencement of the draw, record 
the outlet temperature at 15-second intervals until the end of the 
2-minute period. Determine whether the maximum outlet temperature is 
within the range specified in section 2.4 of this appendix. If not, 
turn off the water heater, adjust the temperature controller, and 
then drain and refill the tank with supply water at the temperature 
specified in section 2.3 of this appendix. Then, once again, 
initiate normal operation of the water heater, and repeat the 2-
minute outlet temperature test following cut-out. Repeat this 
sequence until the maximum outlet temperature during the 2-minute 
test is within the range specified in section 2.4 of this appendix. 
Once the proper temperature control setting is achieved, the setting 
must remain fixed for the duration of the first-hour rating test and 
the 24-hour simulated-use test.
    5.2.2.2.1.2 Water Heaters with Rated Volumes Greater than or 
Equal to 20 Gallons. Starting with a tank at the supply water 
temperature specified in section 2.3 of this appendix, initiate 
normal operation of the water heater. After cut-out, initiate a draw 
from the water heater at a flow rate of 1.7 gallons  
0.25 gallons per minute (6.4 liters  0.95 liters per 
minute) for 5 minutes. Starting 15 seconds after commencement of the 
draw, record the outlet temperature at 15-second intervals until the 
end of the 5-minute period. Determine whether the maximum outlet 
temperature is within the range specified in section 2.4 of this 
appendix. If not, turn off the water heater, adjust the temperature 
controller, and then drain and refill the tank with supply water at 
the temperature specified in section 2.3 of this appendix. Then, 
once again, initiate normal operation of the water heater, and 
repeat the 5-minute outlet temperature test following cut-out. 
Repeat this sequence until the maximum outlet temperature during the 
5-minute test is within the range specified in section 2.4 of this 
appendix. Once the proper temperature control setting is achieved, 
the setting must remain fixed for the duration of the first-hour 
rating test and the 24-hour simulated-use test.
    5.2.2.2.2 Water Heaters with Two or More Temperature 
Controllers. Verify the temperature controller set-point while 
removing water in accordance with the procedure set forth for the 
first-hour rating test in section 5.3.3 of this appendix. The 
following criteria must be met to ensure that all temperature 
controllers are set to deliver water in the range specified in 
section 2.4 of this appendix:
    (a) At least 50 percent of the water drawn during the first draw 
of the first-hour rating test procedure shall be delivered at a 
temperature within the range specified in section 2.4 of this 
appendix.
    (b) No water is delivered above the range specified in section 
2.4 of this appendix during first-hour rating test.
    (c) The delivery temperature measured 15 seconds after 
commencement of each draw begun prior to an elapsed time of 60 
minutes from the start of the test shall be within the range 
specified in section 2.4 of this appendix.

[[Page 40479]]

    If these conditions are not met, turn off the water heater, 
adjust the temperature controllers, and then drain and refill the 
tank with supply water at the temperature specified in section 2.3 
of this appendix. Repeat the procedure described at the start of 
section 5.2.2.2.2 of this appendix until the criteria for setting 
the temperature controllers is met.
    If the conditions stated above are met, the data obtained during 
the process of verifying the temperature control set-points may be 
used in determining the first-hour rating provided that all other 
conditions and methods required in sections 2 and 5.2.4 of this 
appendix in preparing the water heater were followed.
    5.2.3 Power Input Determination. For all water heaters except 
electric types, initiate normal operation (as described in section 
5.1 of this appendix) and determine the power input, P, to the main 
burners (including pilot light power, if any) after 15 minutes of 
operation. Adjust all burners to achieve an hourly Btu (kJ) rating 
that is within 2% of the maximum input rate value 
specified by the manufacturer. For an oil-fired water heater, adjust 
the burner to give a CO2 reading recommended by the 
manufacturer and an hourly Btu (kJ) rating that is within 2% of the maximum input rate specified by the manufacturer. 
Smoke in the flue may not exceed No. 1 smoke as measured by the 
procedure in ASTM D2156 (R2018), including the conditions as 
specified in ASTM E97-1987 as referenced in ASTM D2156 (R2018). If 
the input rating is not within 2%, first increase or 
decrease the fuel pressure within the tolerances specified in 
section 2.7.2, 2.7.3 or 2.7.4 (as applicable) of this appendix until 
it is 2% of the maximum input rate value specified by 
the manufacturer. If, after adjusting the fuel pressure, the fuel 
input rate cannot be achieved within 2 percent of the 
maximum input rate value specified by the manufacturer, for gas-
fired models increase or decrease the gas supply pressure within the 
range specified by the manufacturer. Finally, if the measured fuel 
input rate is still not within 2 percent of the maximum 
input rate value specified by the manufacturer, modify the gas inlet 
orifice, if so equipped, as necessary to achieve a fuel input rate 
that is within 2 percent of the maximum input rate value 
specified by the manufacturer.
    5.2.4 Soak-In Period for Water Heaters with Rated Storage 
Volumes Greater than or Equal to 2 Gallons. For water heaters with a 
rated storage volume greater than or equal to 2 gallons (7.6 
liters), the water heater must sit filled with water, connected to a 
power source, and without any draws taking place for at least 12 
hours after initially being energized so as to achieve the nominal 
temperature set-point within the tank and with the unit connected to 
a power source.
    5.3 Delivery Capacity Tests.
    5.3.1 General. For flow-activated water heaters, conduct the 
maximum GPM test, as described in section 5.3.2, Maximum GPM Rating 
Test for Flow-Activated Water Heaters, of this appendix. For all 
other water heaters, conduct the first-hour rating test as described 
in section 5.3.3 of this appendix.
    5.3.2 Maximum GPM Rating Test for Flow-Activated Water Heaters. 
Establish normal water heater operation at the design power rating 
with the discharge water temperature set in accordance with section 
5.2.2.1 of this appendix.
    For this 10-minute test, either collect the withdrawn water for 
later measurement of the total mass removed or use a water meter to 
directly measure the water mass of volume removed. Initiate water 
flow through the water heater and record the inlet and outlet water 
temperatures beginning 15 seconds after the start of the test and at 
subsequent 5-second intervals throughout the duration of the test. 
At the end of 10 minutes, turn off the water. Determine and record 
the mass of water collected, M10m, in pounds (kilograms), 
or the volume of water, V10m, in gallons (liters).
    5.3.3 First-Hour Rating Test.
    5.3.3.1 General. During hot water draws for water heaters with 
rated storage volumes greater than or equal to 20 gallons, remove 
water at a rate of 3.0  0.25 gallons per minute (11.4 
 0.95 liters per minute). During hot water draws for 
water heaters with rated storage volumes below 20 gallons, remove 
water at a rate of 1.5  0.25 gallon per minute (5.7 
 0.95 liters per minute). Collect the water in a 
container that is large enough to hold the volume removed during an 
individual draw and is suitable for weighing at the termination of 
each draw to determine the total volume of water withdrawn. As an 
alternative to collecting the water, a water meter may be used to 
directly measure the water mass or volume withdrawn during each 
draw.
    5.3.3.2 Draw Initiation Criteria. Begin the first-hour rating 
test by starting a draw on the water heater. After completion of 
this first draw, initiate successive draws based on the following 
criteria. For gas-fired and oil-fired water heaters, initiate 
successive draws when the temperature controller acts to reduce the 
supply of fuel to the main burner. For electric water heaters having 
a single element or multiple elements that all operate 
simultaneously, initiate successive draws when the temperature 
controller acts to reduce the electrical input supplied to the 
element(s). For electric water heaters having two or more elements 
that do not operate simultaneously, initiate successive draws when 
the applicable temperature controller acts to reduce the electrical 
input to the energized element located vertically highest in the 
storage tank. For heat pump water heaters that do not use 
supplemental, resistive heating, initiate successive draws 
immediately after the electrical input to the compressor is reduced 
by the action of the water heater's temperature controller. For heat 
pump water heaters that use supplemental resistive heating, initiate 
successive draws immediately after the electrical input to the first 
of either the compressor or the vertically highest resistive element 
is reduced by the action of the applicable water heater temperature 
controller. This draw initiation criterion for heat pump water 
heaters that use supplemental resistive heating, however, shall only 
apply when the water located above the thermostat at cut-out is 
heated to within the range specified in section 2.4 of this 
appendix. If this criterion is not met, then the next draw should be 
initiated once the heat pump compressor cuts out.
    5.3.3.3 Test Sequence. Establish normal water heater operation. 
If the water heater is not presently operating, initiate a draw. The 
draw may be terminated any time after cut-in occurs. After cut-out 
occurs (i.e., all temperature controllers are satisfied), if the 
water heater can have its internal tank temperatures measured, 
record the internal storage tank temperature at each sensor 
described in section 4.5 of this appendix every one minute, and 
determine the mean tank temperature by averaging the values from 
these sensors.
    Initiate a draw after a maximum mean tank temperature (the 
maximum of the mean temperatures of the individual sensors) has been 
observed following a cut-out. If the water heater cannot have its 
internal tank temperatures measured, wait 5 minutes after cut-out. 
Record the time when the draw is initiated and designate it as an 
elapsed time of zero ([tau]* = 0). (The superscript * is used to 
denote variables pertaining to the first-hour rating test). Record 
the outlet water temperature beginning 15 seconds after the draw is 
initiated and at 5-second intervals thereafter until the draw is 
terminated. Determine the maximum outlet temperature that occurs 
during this first draw and record it as T*max,1. For the 
duration of this first draw and all successive draws, in addition, 
monitor the inlet temperature to the water heater to ensure that the 
required supply water temperature test condition specified in 
section 2.3 of this appendix is met. Terminate the hot water draw 
when the outlet temperature decreases to T*max,1-15 
[deg]F (T*max,1-8.3 [deg]C). (Note, if the outlet 
temperature does not decrease to T*max,1-15 [deg]F 
(T*max,1-8.3 [deg]C) during the draw, then hot water 
would be drawn continuously for the duration of the test. In this 
instance, the test would end when the temperature decreases to 
T*max,1-15 [deg]F (T*max,1-8.3 [deg]C) after 
the electrical power and/or fuel supplied to the water heater is 
shut off, as described in the following paragraphs.) Record this 
temperature as T*min,1. Following draw termination, 
determine the average outlet water temperature and the mass or 
volume removed during this first draw and record them as 
T*del,i and M*1 or V*1, 
respectively.
    Initiate a second and, if applicable, successive draw(s) each 
time the applicable draw initiation criteria described in section 
5.3.3.2 of this appendix are satisfied. As required for the first 
draw, record the outlet water temperature 15 seconds after 
initiating each draw and at 5-second intervals thereafter until the 
draw is terminated. Determine the maximum outlet temperature that 
occurs during each draw and record it as T*max,i, where 
the subscript i refers to the draw number. Terminate each hot water 
draw when the outlet temperature decreases to T*max,i-15 
[deg]F (T*max,i-8.3 [deg]C). Record this temperature as 
T*min,i. Calculate and record the average outlet 
temperature and the mass or volume removed during each draw 
(T*del,i and M*i or V*i, 
respectively). Continue this sequence of draw and recovery until one 
hour after the start of the test, then shut off the electrical power 
and/or fuel supplied to the water heater.

[[Page 40480]]

    If a draw is occurring at one hour from the start of the test, 
continue this draw until the outlet temperature decreases to 
T*max,n-15 [deg]F (T*max,n-8.3 [deg]C), at 
which time the draw shall be immediately terminated. (The subscript 
n shall be used to denote measurements associated with the final 
draw.) If a draw is not occurring one hour after the start of the 
test, initiate a final draw at one hour, regardless of whether the 
criteria described in section 5.3.3.2 of this appendix are 
satisfied. This draw shall proceed for a minimum of 30 seconds and 
shall terminate when the outlet temperature first indicates a value 
less than or equal to the cut-off temperature used for the previous 
draw (T*min,n-1). If an outlet temperature greater than 
T*min,n-1 is not measured within 30 seconds of initiation 
of the draw, zero additional credit shall be given towards first-
hour rating (i.e., M*n = 0 or V*n = 0) based 
on the final draw. After the final draw is terminated, calculate and 
record the average outlet temperature and the mass or volume removed 
during the final draw (T*del,n and M*n or 
V*n, respectively).
    5.4 24-Hour Simulated-Use Test.
    5.4.1 Selection of Draw Pattern. The water heater will be tested 
under a draw profile that depends upon the first-hour rating 
obtained following the test prescribed in section 5.3.3 of this 
appendix, or the maximum GPM rating obtained following the test 
prescribed in section 5.3.2 of this appendix, whichever is 
applicable. For water heaters that have been tested according to the 
first-hour rating procedure, one of four different patterns shall be 
applied based on the measured first-hour rating, as shown in Table I 
of this section. For water heater that have been tested according to 
the maximum GPM rating procedure, one of four different patterns 
shall be applied based on the maximum GPM, as shown in Table II of 
this section.

       Table I--Draw Pattern To Be Used Based on First-Hour Rating
------------------------------------------------------------------------
                                                      Draw pattern to be
 First-hour rating greater than    . . . and first-     used in the 24-
          or equal to:             hour rating less   hour simulated-use
                                         than:               test
------------------------------------------------------------------------
0 gallons.......................  18 gallons........  Very-Small-Usage
                                                       (Table III.1).
18 gallons......................  51 gallons........  Low-Usage (Table
                                                       III.2).
51 gallons......................  75 gallons........  Medium-Usage
                                                       (Table III.3).
75 gallons......................  No upper limit....  High-Usage (Table
                                                       III.4).
------------------------------------------------------------------------


      Table II--Draw Pattern To Be Used Based on Maximum GPM Rating
------------------------------------------------------------------------
                                                      Draw pattern to be
 Maximum GPM rating greater than    and maximum GPM     used in the 24-
          or equal to:             rating less than:  hour simulated-use
                                                             test
------------------------------------------------------------------------
0 gallons/minute................  1.7 gallons/minute  Very-Small-Usage
                                                       (Table III.1).
1.7 gallons/minute..............  2.8 gallons/minute  Low-Usage (Table
                                                       III.2).
2.8 gallons/minute..............  4 gallons/minute..  Medium-Usage
                                                       (Table III.3).
4 gallons/minute................  No upper limit....  High-Usage (Table
                                                       III.4).
------------------------------------------------------------------------

    The draw patterns are provided in Tables III.1 through III.4 in 
section 5.5 of this appendix. Use the appropriate draw pattern when 
conducting the test sequence provided in section 5.4.2 of this 
appendix for water heaters with rated storage volumes greater than 
or equal to 2 gallons or section 5.4.3 of this appendix for water 
heaters with rated storage volumes less than 2 gallons.
    5.4.2 Test Sequence for Water Heater With Rated Storage Volume 
Greater Than or Equal to 2 Gallons.
    If the water heater is turned off, fill the water heater with 
supply water at the temperature specified in section 2.3 of this 
appendix and maintain supply water pressure as described in section 
2.6 of this appendix. Turn on the water heater and associated heat 
pump unit, if present. If turned on in this fashion, the soak-in 
period described in section 5.2.4 of this appendix shall be 
implemented. If the water heater has undergone a first-hour rating 
test prior to conduct of the 24-hour simulated-use test, allow the 
water heater to fully recover after completion of that test such 
that the main burner, heating elements, or heat pump compressor of 
the water heater are no longer raising the temperature of the stored 
water. In all cases, the water heater shall sit idle for 1 hour 
prior to the start of the 24-hour test; during which time no water 
is drawn from the unit, and there is no energy input to the main 
heating elements, heat pump compressor, and/or burners.
    For water heaters that can have their internal storage tank 
temperature measured directly, perform testing in accordance with 
the instructions in section 5.4.2.1 of this appendix. For water 
heaters that cannot have their internal tank temperatures measured, 
perform testing in accordance with the instructions in section 
5.4.2.2. of this appendix.
    5.4.2.1 Water Heaters Which Can Have Internal Storage Tank 
Temperature Measured Directly.
    After the 1-hour period specified in section 5.4.2 of this 
appendix, the 24-hour simulated-use test will begin. One minute 
prior to the start of the 24-hour simulated-use test, record the 
mean tank temperature (T0).
    At the start of the 24-hour simulated-use test, record the 
electrical and/or fuel measurement readings, as appropriate. Begin 
the 24-hour simulated-use test by withdrawing the volume specified 
in the appropriate table in section 5.5 of this appendix (i.e., 
Table III.1, Table III.2, Table III.3, or Table III.4, depending on 
the first-hour rating or maximum GPM rating) for the first draw at 
the flow rate specified in the applicable table. Record the time 
when this first draw is initiated and assign it as the test elapsed 
time ([tau]) of zero (0). Record the average storage tank and 
ambient temperature every minute throughout the 24-hour simulated-
use test. At the elapsed times specified in the applicable draw 
pattern table in section 5.5 of this appendix for a particular draw 
pattern, initiate additional draws pursuant to the draw pattern, 
removing the volume of hot water at the prescribed flow rate 
specified by the table. The maximum allowable deviation from the 
specified volume of water removed for any single draw taken at a 
nominal flow rate of 1.0 GPM or 1.7 GPM is 0.1 gallons 
(0.4 liters). The maximum allowable deviation from the 
specified volume of water removed for any single draw taken at a 
nominal flow rate of 3.0 GPM is 0.25 gallons (0.9 
liters). The quantity of water withdrawn during the last draw shall 
be increased or decreased as necessary such that the total volume of 
water withdrawn equals the prescribed daily amount for that draw 
pattern 1.0 gallon (3.8 liters). If this 
adjustment to the volume drawn during the last draw results in no 
draw taking place, the test is considered invalid.
    All draws during the 24-hour simulated-use test shall be made at 
the flow rates specified in the applicable draw pattern table in 
section 5.5 of this appendix, within a tolerance of 0.25 
gallons per minute (0.9 liters per minute). Measurements 
of the inlet and outlet temperatures shall be made 15 seconds after 
the draw is initiated and at every subsequent 3-second interval 
throughout the duration of each draw. Calculate and record the mean 
of the hot water discharge temperature and the cold water inlet 
temperature for each draw Tdel,i and Tin,i). 
Determine and record the net mass or volume removed (Mi 
or Vi), as appropriate, after each draw.
    The first recovery period is the time from the start of the 24-
hour simulated-use test and continues during the temperature rise of 
the stored water until the first cut-out; if the cut-out occurs 
during a subsequent draw, the first recovery period includes the 
time until the draw of water from the tank stops. If, after the 
first cut-out occurs but during a subsequent draw, a subsequent cut-
in occurs prior to the draw completion, the first

[[Page 40481]]

recovery period includes the time until the subsequent cut-out 
occurs, prior to another draw. The first recovery period may 
continue until a cut-out occurs when water is not being removed from 
the water heater or a cut-out occurs during a draw and the water 
heater does not cut-in prior to the end of the draw.
    At the end of the first recovery period, record the maximum mean 
tank temperature observed after cut-out (Tmax,1). At the 
end of the first recovery period, record the total energy consumed 
by the water heater from the beginning of the test (Qr), 
including all fossil fuel and/or electrical energy use, from the 
main heat source and auxiliary equipment including, but not limited 
to, burner(s), resistive elements(s), compressor, fan, controls, 
pump, etc., as applicable.
    The start of the portion of the test during which the standby 
loss coefficient is determined depends upon whether the unit has 
fully recovered from the first draw cluster. If a recovery is 
occurring at or within five minutes after the end of the final draw 
in the first draw cluster, as identified in the applicable draw 
pattern table in section 5.5 of this appendix, then the standby 
period starts when a maximum mean tank temperature is observed 
starting five minutes after the end of the recovery period that 
follows that draw. If a recovery does not occur at or within five 
minutes after the end of the final draw in the first draw cluster, 
as identified in the applicable draw pattern table in section 5.5 of 
this appendix, then the standby period starts five minutes after the 
end of that draw. Determine and record the total electrical energy 
and/or fossil fuel consumed from the beginning of the test to the 
start of the standby period (Qsu,0).
    In preparation for determining the energy consumed during 
standby, record the reading given on the electrical energy (watt-
hour) meter, the gas meter, and/or the scale used to determine oil 
consumption, as appropriate. Record the mean tank temperature at the 
start of the standby period (Tsu,0). At 1-minute 
intervals, record ambient temperature, the electric and/or fuel 
instrument readings, and the mean tank temperature until the next 
draw is initiated. The end of the standby period is when the final 
mean tank temperature is recorded, as described. Just prior to 
initiation of the next draw, record the mean tank temperature 
(Tsu,f). If the water heater is undergoing recovery when 
the next draw is initiated, record the mean tank temperature 
(Tsu,f) at the minute prior to the start of the recovery. 
Determine the total electrical energy and/or fossil fuel energy 
consumption from the beginning of the test to the end of the standby 
period (Qsu,f). Record the time interval between the 
start of the standby period and the end of the standby period 
([tau]stby,1).
    Following the final draw of the prescribed draw pattern and 
subsequent recovery, allow the water heater to remain in the standby 
mode until exactly 24 hours have elapsed since the start of the 24-
hour simulated-use test (i.e., since [tau] = 0). During the last 
hour of the 24-hour simulated-use test (i.e., hour 23 of the 24-hour 
simulated-use test), power to the main burner, heating element, or 
compressor shall be disabled. At 24 hours, record the reading given 
by the gas meter, oil meter, and/or the electrical energy meter as 
appropriate. Determine the fossil fuel and/or electrical energy 
consumed during the entire 24-hour simulated-use test and designate 
the quantity as Q.
    In the event that the recovery period continues from the end of 
the last draw of the first draw cluster until the subsequent draw, 
the standby period will start after the end of the first recovery 
period after the last draw of the 24-hour simulated-use test, when 
the temperature reaches the maximum mean tank temperature, though no 
sooner than five minutes after the end of this recovery period. The 
standby period shall last eight hours, so testing may extend beyond 
the 24-hour duration of the 24-hour simulated-use test. Determine 
and record the total electrical energy and/or fossil fuel consumed 
from the beginning of the 24-hour simulated-use test to the start of 
the 8-hour standby period (Qsu,0). In preparation for 
determining the energy consumed during standby, record the 
reading(s) given on the electrical energy (watt-hour) meter, the gas 
meter, and/or the scale used to determine oil consumption, as 
appropriate. Record the mean tank temperature at the start of the 
standby period (Tsu,0). Record the mean tank temperature, 
the ambient temperature, and the electric and/or fuel instrument 
readings at 1-minute intervals until the end of the 8-hour period. 
Record the mean tank temperature at the end of the 8-hour standby 
period (Tsu,f). If the water heater is undergoing 
recovery at the end of the standby period, record the mean tank 
temperature (Tsu,f) at the minute prior to the start of 
the recovery, which will mark the end of the standby period. 
Determine the total electrical energy and/or fossil fuel energy 
consumption from the beginning of the test to the end of the standby 
period (Qsu,f). Record the time interval between the 
start of the standby period and the end of the standby period as 
[tau]stby,1. Record the average ambient temperature from 
the start of the standby period to the end of the standby period 
(Ta,stby,1). Record the average mean tank temperature 
from the start of the standby period to the end of the standby 
period (Tt,stby,1).
    If the standby period occurred at the end of the first recovery 
period after the last draw of the 24-hour simulated-use test, allow 
the water heater to remain in the standby mode until exactly 24 
hours have elapsed since the start of the 24-hour simulated-use test 
(i.e., since [tau] = 0) or the end of the standby period, whichever 
is longer. At 24 hours, record the mean tank temperature 
(T24) and the reading given by the gas meter, oil meter, 
and/or the electrical energy meter as appropriate. If the water 
heater is undergoing a recovery at 24 hours, record the reading 
given by the gas meter, oil meter, and/or electrical energy meter, 
as appropriate, and the mean tank temperature (T24) at 
the minute prior to the start of the recovery. Determine the fossil 
fuel and/or electrical energy consumed during the 24 hours and 
designate the quantity as Q.
    Record the time during which water is not being withdrawn from 
the water heater during the entire 24-hour period 
([tau]stby,2). When the standby period occurs after the 
last draw of the 24-hour simulated-use test, the test may extend 
past hour 24. When this occurs, the measurements taken after hour 24 
apply only to the calculations of the standby loss coefficient. All 
other measurements during the time between hour 23 and hour 24 
remain the same.
    5.4.2.2 Water Heaters Which Cannot Have Internal Storage Tank 
Temperature Measured Directly.
    After the water heater has undergone a 1-hour idle period (as 
described in section 5.4.2 of this appendix), deactivate the burner, 
compressor, or heating element(s).
    Remove water from the storage tank by performing a continuous 
draw at the flow rate specified for the first draw of applicable 
draw pattern for the 24-hour simulated use test in section 5.5 of 
this appendix within a tolerance of 0.25 gallons per 
minute (0.9 liters per minute). While removing the hot 
water, measure the inlet and outlet temperature after initiating the 
draw at 3-second intervals. Remove water until the outlet water 
temperature is within 2 [deg]F (1.1 [deg]C) 
of the inlet water temperature for 15 consecutive seconds. Determine 
the mean tank temperature using section 6.3.77 of this appendix and 
assign this value of Tst for T0, 
Tmax,1, and Tsu,0.
    After completing the draw, reactivate the burner, compressor, or 
heating elements(s) and allow the unit to fully recover such that 
the main burner, heating elements, or heat pump compressor is no 
longer raising the temperature of the stored water. Let the water 
heater sit idle again for 1 hour prior to beginning the 24-hour 
test, during which time no water shall be drawn from the unit, and 
there shall be no energy input to the main heating elements. After 
the 1-hour period, the 24-hour simulated-use test will begin.
    At the start of the 24-hour simulated-use test, record the 
electrical and/or fuel measurement readings, as appropriate. Begin 
the 24-hour simulated-use test by withdrawing the volume specified 
in the appropriate table in section 5.5 of this appendix (i.e., 
Table III.1, Table III.2, Table III.3, or Table III.4, depending on 
the first-hour rating or maximum GPM rating) for the first draw at 
the flow rate specified in the applicable table. Record the time 
when this first draw is initiated and assign it as the test elapsed 
time ([tau]) of zero (0). Record the average ambient temperature 
every minute throughout the 24-hour simulated-use test. At the 
elapsed times specified in the applicable draw pattern table in 
section 5.5 of this appendix for a particular draw pattern, initiate 
additional draws pursuant to the draw pattern, removing the volume 
of hot water at the prescribed flow rate specified by the table. The 
maximum allowable deviation from the specified volume of water 
removed for any single draw taken at a nominal flow rate of 1.0 GPM 
or 1.7 GPM is  0.1 gallons ( 0.4 liters). 
The maximum allowable deviation from the specified volume of water 
removed for any single draw taken at a nominal flow rate of 3.0 GPM 
is  0.25 gallons (0.9 liters). The quantity of water 
withdrawn during the last draw shall be increased or decreased as 
necessary such that the total volume of water withdrawn equals the 
prescribed daily amount for that draw

[[Page 40482]]

pattern  1.0 gallon ( 3.8 liters). If this 
adjustment to the volume drawn during the last draw results in no 
draw taking place, the test is considered invalid.
    All draws during the 24-hour simulated-use test shall be made at 
the flow rates specified in the applicable draw pattern table in 
section 5.5 of this appendix, within a tolerance of 0.25 
gallons per minute (0.9 liters per minute). Measurements 
of the inlet and outlet temperatures shall be made 15 seconds after 
the draw is initiated and at every subsequent 3-second interval 
throughout the duration of each draw. Calculate and record the mean 
of the hot water discharge temperature and the cold water inlet 
temperature for each draw Tdel,i and Tin,i). 
Determine and record the net mass or volume removed (Mi 
or Vi), as appropriate, after each draw.
    The first recovery period is the time from the start of the 24-
hour simulated-use test and continues until the first cut-out; if 
the cut-out occurs during a subsequent draw, the first recovery 
period includes the time until the draw of water from the tank 
stops. If, after the first cut-out occurs but during a subsequent 
draw, a subsequent cut-in occurs prior to the draw completion, the 
first recovery period includes the time until the subsequent cut-out 
occurs, prior to another draw. The first recovery period may 
continue until a cut-out occurs when water is not being removed from 
the water heater or a cut-out occurs during a draw and the water 
heater does not cut-in prior to the end of the draw.
    At the end of the first recovery period, record the total energy 
consumed by the water heater from the beginning of the test 
(Qr), including all fossil fuel and/or electrical energy 
use, from the main heat source and auxiliary equipment including, 
but not limited to, burner(s), resistive elements(s), compressor, 
fan, controls, pump, etc., as applicable.
    The standby period begins at five minutes after the first time a 
recovery ends following last draw of the simulated-use test and 
shall continue for 8 hours. At the end of the 8-hour standby period, 
record the total amount of time elapsed since the start of the 24-
hour simulated-use test (i.e., since [tau] = 0).
    Determine and record the total electrical energy and/or fossil 
fuel consumed from the beginning of the 24-hour simulated-use test 
to the start of the 8-hour standby period (Qsu,0). In 
preparation for determining the energy consumed during standby, 
record the reading(s) given on the electrical energy (watt-hour) 
meter, the gas meter, and/or the scale used to determine oil 
consumption, as appropriate. Record the ambient temperature and the 
electric and/or fuel instrument readings at 1-minute intervals until 
the end of the 8-hour period. At the 8-hour mark, deactivate the 
water heater before drawing water from the tank. Remove water from 
the storage tank by performing a continuous draw atthe flow rate 
specified for the first draw of applicable draw pattern for the 24-
hour simulated use test in section 5.5 of this appendix within a 
tolerance of 0.25 gallons per minute (0.9 
liters per minute). While removing the hot water, measure the inlet 
and outlet temperature after initiating the draw at 3-second 
intervals. Remove water until the outlet water temperature is within 
2 [deg]F (1.1 [deg]C) of the inlet water 
temperature for 15 consecutive seconds. Determine the mean tank 
temperature using section 6.3.77 of this appendix and assign this 
value of Tst for Tsu,f and T24.
    Determine the total electrical energy and/or fossil fuel energy 
consumption from the beginning of the test to the end of the standby 
period (Qsu,f). Record the time interval between the 
start of the standby period and the end of the standby period as 
[tau]stby,1. Record the average ambient temperature from 
the start of the standby period to the end of the standby period 
(Ta,stby,1). The average mean tank temperature from the 
start of the standby period to the end of the standby period 
(Tt,stby,1) shall be the average of Tsu,0 and 
Tsu,f.
    5.4.3 Test Sequence for Water Heaters With Rated Storage Volume 
Less Than 2 Gallons.
    Establish normal operation with the discharge water temperature 
at 125 [deg]F  5 [deg]F (51.7 [deg]C  2.8 
[deg]C) and set the flow rate as determined in section 5.2 of this 
appendix. Prior to commencement of the 24-hour simulated-use test, 
the unit shall remain in an idle state in which controls are active 
but no water is drawn through the unit for a period of one hour. 
With no draw occurring, record the reading given by the gas meter 
and/or the electrical energy meter as appropriate. Begin the 24-hour 
simulated-use test by withdrawing the volume specified in Tables 
III.1 through III.4 of section 5.5 of this appendix for the first 
draw at the flow rate specified. Record the time when this first 
draw is initiated and designate it as an elapsed time, [tau], of 0. 
At the elapsed times specified in Tables III.1 through III.4 for a 
particular draw pattern, initiate additional draws, removing the 
volume of hot water at the prescribed flow rate specified in Tables 
III.1 through III.4. The maximum allowable deviation from the 
specified volume of water removed for any single draw taken at a 
nominal flow rate less than or equal to 1.7 GPM (6.4 L/min) is 
0.1 gallons (0.4 liters). The maximum 
allowable deviation from the specified volume of water removed for 
any single draw taken at a nominal flow rate of 3.0 GPM (11.4 L/min) 
is 0.25 gallons (0.9 liters). The quantity of water 
drawn during the final draw shall be increased or decreased as 
necessary such that the total volume of water withdrawn equals the 
prescribed daily amount for that draw pattern 1.0 gallon 
(3.8 liters). If this adjustment to the volume drawn in 
the last draw results in no draw taking place, the test is 
considered invalid.
    All draws during the 24-hour simulated-use test shall be made at 
the flow rates specified in the applicable draw pattern table in 
section 5.5 of this appendix within a tolerance of 0.25 
gallons per minute (0.9 liters per minute) unless the 
unit being tested is flow-activated and has a rated Max GPM of less 
than 1 gallon per minute, in which case the tolerance shall be 
25% of the rated Max GPM. Measurements of the inlet and 
outlet water temperatures shall be made 15 seconds after the draw is 
initiated and at every 3-second interval thereafter throughout the 
duration of the draw. Calculate the mean of the hot water discharge 
temperature and the cold-water inlet temperature for each draw. 
Record the mass of the withdrawn water or the water meter reading, 
as appropriate, after each draw. At the end of the first recovery 
period following the first draw, determine and record the fossil 
fuel and/or electrical energy consumed, Qr. Following the 
final draw and subsequent recovery, allow the water heater to remain 
in the standby mode until exactly 24 hours have elapsed since the 
start of the test (i.e., since [tau] = 0). At 24 hours, record the 
reading given by the gas meter, oil meter, and/or the electrical 
energy meter, as appropriate. Determine the fossil fuel and/or 
electrical energy consumed during the entire 24-hour simulated-use 
test and designate the quantity as Q.
    5.5 Draw Patterns.
    The draw patterns to be imposed during 24-hour simulated-use 
tests are provided in Tables III.1 through III.4. Subject each water 
heater under test to one of these draw patterns based on its first-
hour rating or maximum GPM rating, as discussed in section 5.4.1 of 
this appendix. Each draw pattern specifies the elapsed time in hours 
and minutes during the 24-hour test when a draw is to commence, the 
total volume of water in gallons (liters) that is to be removed 
during each draw, and the flow rate at which each draw is to be 
taken, in gallons (liters) per minute.

                                   Table III.1--Very-Small-Usage Draw Pattern
----------------------------------------------------------------------------------------------------------------
                                                                    Time during
                            Draw No.                                  test **         Volume       Flow rate ***
                                                                      [hh:mm]      [gallons (L)]   [GPM (L/min)]
----------------------------------------------------------------------------------------------------------------
1 *.............................................................            0:00       2.0 (7.6)         1 (3.8)
2 *.............................................................            1:00       1.0 (3.8)         1 (3.8)
3 *.............................................................            1:05       0.5 (1.9)         1 (3.8)
4 *.............................................................            1:10       0.5 (1.9)         1 (3.8)
5 *.............................................................            1:15       0.5 (1.9)         1 (3.8)
6...............................................................            8:00       1.0 (3.8)         1 (3.8)
7...............................................................            8:15       2.0 (7.6)         1 (3.8)

[[Page 40483]]

 
8...............................................................            9:00       1.5 (5.7)         1 (3.8)
9...............................................................            9:15       1.0 (3.8)         1 (3.8)
----------------------------------------------------------------------------------------------------------------
                                  Total Volume Drawn Per Day: 10 gallons (38 L)
----------------------------------------------------------------------------------------------------------------
* Denotes draws in first draw cluster.
** If a draw extends to the start of the subsequent draw, then the subsequent draw shall start when the required
  volume of the previous draw has been delivered.
*** Should the water heater have a maximum GPM rating less than 1 GPM (3.8 L/min), then all draws shall be
  implemented at a flow rate equal to the rated maximum GPM.


                                       Table III.2--Low-Usage Draw Pattern
----------------------------------------------------------------------------------------------------------------
                                                                    Time during       Volume      Flow rate [GPM
                            Draw No.                               test [hh:mm]    [gallons (L)]     (L/min)]
----------------------------------------------------------------------------------------------------------------
1 *.............................................................            0:00     15.0 (56.8)       1.7 (6.4)
2 *.............................................................            0:30       2.0 (7.6)         1 (3.8)
3 *.............................................................            1:00       1.0 (3.8)         1 (3.8)
4...............................................................           10:30      6.0 (22.7)       1.7 (6.4)
5...............................................................           11:30      4.0 (15.1)       1.7 (6.4)
6...............................................................           12:00       1.0 (3.8)         1 (3.8)
7...............................................................           12:45       1.0 (3.8)         1 (3.8)
8...............................................................           12:50       1.0 (3.8)         1 (3.8)
9...............................................................           16:15       2.0 (7.6)         1 (3.8)
10..............................................................           16:45       2.0 (7.6)       1.7 (6.4)
11..............................................................           17:00      3.0 (11.4)       1.7 (6.4)
----------------------------------------------------------------------------------------------------------------
                                 Total Volume Drawn Per Day: 38 gallons (144 L)
----------------------------------------------------------------------------------------------------------------
 *Denotes draws in first draw cluster.


                                     Table III.3--Medium-Usage Draw Pattern
----------------------------------------------------------------------------------------------------------------
                                                                    Time during       Volume      Flow Rate [GPM
                            Draw No.                               test [hh:mm]    [gallons (L)]     (L/min)]
----------------------------------------------------------------------------------------------------------------
1 *.............................................................            0:00     15.0 (56.8)       1.7 (6.4)
2 *.............................................................            0:30       2.0 (7.6)         1 (3.8)
3 *.............................................................            1:40      9.0 (34.1)       1.7 (6.4)
4...............................................................           10:30      9.0 (34.1)       1.7 (6.4)
5...............................................................           11:30      5.0 (18.9)       1.7 (6.4)
6...............................................................           12:00       1.0 (3.8)         1 (3.8)
7...............................................................           12:45       1.0 (3.8)         1 (3.8)
8...............................................................           12:50       1.0 (3.8)         1 (3.8)
9...............................................................           16:00       1.0 (3.8)         1 (3.8)
10..............................................................           16:15       2.0 (7.6)         1 (3.8)
11..............................................................           16:45       2.0 (7.6)       1.7 (6.4)
12..............................................................           17:00      7.0 (26.5)       1.7 (6.4)
----------------------------------------------------------------------------------------------------------------
                                 Total Volume Drawn Per Day: 55 gallons (208 L)
----------------------------------------------------------------------------------------------------------------
* Denotes draws in first draw cluster.


                                      Table III.4--High-Usage Draw Pattern
----------------------------------------------------------------------------------------------------------------
                                                                    Time during       Volume         Flow rate
                            Draw No.                               test  [hh:mm]   [gallons (L)]   [GPM (L/min)]
----------------------------------------------------------------------------------------------------------------
1 *.............................................................            0:00      27.0 (102)        3 (11.4)
2 *.............................................................            0:30       2.0 (7.6)         1 (3.8)
3 *.............................................................            0:40       1.0 (3.8)         1 (3.8)
4 *.............................................................            1:40      9.0 (34.1)       1.7 (6.4)
5...............................................................           10:30     15.0 (56.8)        3 (11.4)
6...............................................................           11:30      5.0 (18.9)       1.7 (6.4)
7...............................................................           12:00       1.0 (3.8)         1 (3.8)
8...............................................................           12:45       1.0 (3.8)         1 (3.8)
9...............................................................           12:50       1.0 (3.8)         1 (3.8)
10..............................................................           16:00       2.0 (7.6)         1 (3.8)

[[Page 40484]]

 
11..............................................................           16:15       2.0 (7.6)         1 (3.8)
12..............................................................           16:30       2.0 (7.6)       1.7 (6.4)
13..............................................................           16:45       2.0 (7.6)       1.7 (6.4)
14..............................................................           17:00     14.0 (53.0)        3 (11.4)
----------------------------------------------------------------------------------------------------------------
                                 Total Volume Drawn Per Day: 84 gallons (318 L)
----------------------------------------------------------------------------------------------------------------
* Denotes draws in first draw cluster.

    5.6 Optional Tests (Heat Pump-Type Water Heaters). Optional 
testing may be conducted on heat pump-type water heaters to 
determine EX. If optional testing is performed, conduct 
the additional 24-hour simulated use test(s) at one or multiple of 
the test conditions specified in section 2.8 of this appendix. Prior 
to conducting a 24-hour simulated use test at an optional condition, 
confirm the air and water conditions specified in section 2.8 are 
met and re-set the outlet discharge temperature in accordance with 
section 5.2.2 of this appendix. Perform the optional 24-hour 
simulated use test(s) in accordance with section 5.4 of this 
appendix using the same draw pattern used for the determination of 
UEF.
    6. Computations.
    6.1 First-Hour Rating Computation. For the case in which the 
final draw is initiated at or prior to one hour from the start of 
the test, the first-hour rating, Fhr, shall be computed 
using,
[GRAPHIC] [TIFF OMITTED] TR21JN23.007

Where:

n = the number of draws that are completed during the first-hour 
rating test.
V*del,i = the volume of water removed during the ith draw 
of the first-hour rating test, gal (L) or, if the mass of water 
removed is being measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.008

Where:

M*del,i = the mass of water removed during the ith draw 
of the first-hour rating test, lb (kg).
[rho]del,i = the density of water removed, evaluated at 
the average outlet water temperature measured during the ith draw of 
the first-hour rating test, (T*del,i), lb/gal (kg/L).
or, if the volume of the water entering the water heater is being 
measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.009

Where:

V*in,i = the volume of water entering the water heater 
during the ith draw of the first-hour rating test, gal (L).
[rho]in,i = the density of water entering the water 
heater, evaluated at the average inlet water temperature measured 
during the ith draw of the first-hour rating test, 
(T*in,i), lb/gal (kg/L).
or, if the mass of water entering the water heater is being 
measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.010

Where:

M*in,i = the mass of water entering the water heater 
during the ith draw of the first-hour rating test, lb (kg).

    For the case in which a draw is not in progress at one hour from 
the start of the test and a final draw is imposed at the elapsed 
time of one hour, the first-hour rating shall be calculated using,
[GRAPHIC] [TIFF OMITTED] TR21JN23.011

where n and V*del,i are the same quantities as defined 
above, and
V*del,n = the volume of water removed during the nth 
(final) draw of the first-hour rating test, gal (L).
T*del,n-1 = the average water outlet temperature measured 
during the (n-1)th draw of the first-hour rating test, [deg]F 
([deg]C).
T*del,n = the average water outlet temperature measured 
during the nth (final) draw of the first-hour rating test, [deg]F 
([deg]C).
T*min,n-1 = the minimum water outlet temperature measured 
during the (n-1)th draw of the first-hour rating test, [deg]F 
([deg]C).

    6.2 Maximum GPM (L/min) Rating Computation. Compute the maximum 
GPM (L/min) rating, Fmax, as:

[GRAPHIC] [TIFF OMITTED] TR21JN23.012

Where:

Vdel,10m = the volume of water removed during the maximum 
GPM (L/min) rating test, gal (L).
Tdel = the average delivery temperature, [deg]F ([deg]C).
Tin = the average inlet temperature, [deg]F ([deg]C).
10 = the number of minutes in the maximum GPM (L/min) rating test, 
min.
or, if the mass of water removed is measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.013

Where:

Mdel,10m = the mass of water removed during the maximum 
GPM (L/min) rating test, lb (kg).
[rho]del = the density of water removed, evaluated at the 
average delivery water temperature of the maximum GPM (L/min) rating 
test (Tdel), lb/gal (kg/L).
or, if the volume of water entering the water heater is measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.014

Where:

Vin,10m = the volume of water entering the water heater 
during the maximum GPM (L/min) rating test, gal (L).
[rho]in = the density of water entering the water heater, 
evaluated at the average inlet

[[Page 40485]]

water temperature of the maximum GPM (L/min) rating test 
(Tdel), lb/gal (kg/L).
or, if the mass of water entering the water heater is measured,
[GRAPHIC] [TIFF OMITTED] TR21JN23.015

Where:

Min,10m = the mass of water entering the water heater 
during the maximum GPM (L/min) rating test, lb (kg).

    6.3 Computations for Water Heaters with a Rated Storage Volume 
Greater Than or Equal to 2 Gallons and Circulating Water Heaters.
    6.3.1 Storage Tank Capacity. The storage tank capacity, 
Vst, is computed as follows:
[GRAPHIC] [TIFF OMITTED] TR21JN23.016

Where:

Vst = the storage capacity of the water heater, or, for 
circulating water heaters, the storage capacity of the separate 
storage tank used in accordance with section 4.10, gal (L).
Wf = the weight of the storage tank when completely 
filled with water, lb (kg).
Wt = the (tare) weight of the storage tank when 
completely empty, lb (kg).
[rho] = the density of water used to fill the tank measured at the 
temperature of the water, lb/gal (kg/L).

    6.3.1.1 Effective Storage Volume. The effective storage tank 
capacity, Veff, is computed as follows:
    For water heaters requiring a separate storage tank, 
Veff is the storage tank capacity of the separate storage 
tank as determined per section 6.3.1.

    For all other water heaters:

    Veff = kVVst
Where:

Vst = as defined in section 6.3.1 and
kV = a dimensionless volume scaling factor determined as 
follows:

    If the first recovery period extends into the second draw of the 
24-hour simulated use test, and

    If T0 > (Tdel,1 + 5 [deg]F) and 
T0 >= 130 [deg]F,

    (if T0 > (Tdel,1 + 2.8 [deg]C) and 
T0 >= 54.4 [deg]C),
[GRAPHIC] [TIFF OMITTED] TR21JN23.017

[GRAPHIC] [TIFF OMITTED] TR21JN23.018

    If the first recovery period does not extend into the second 
draw of the 24-hour simulated use test, and

    If Tmax,1 > (Tdel,2 + 5 [deg]F) and 
Tmax,1 >= 130 [deg]F,

    (if Tmax,1 > (Tdel,2 + 2.8 [deg]C) and 
Tmax,1 >= 54.4 [deg]C),
[GRAPHIC] [TIFF OMITTED] TR21JN23.019

[GRAPHIC] [TIFF OMITTED] TR21JN23.020

    Otherwise, kV = 1.

Where:

T0= the mean tank temperature at the beginning of the 24-
hour simulated-use test, [deg]F([deg]C).
Tdel,1= the average outlet water temperature during the 
first draw of the 24-hour simulated-use test, [deg]F([deg]C).
[rho](T0) = the density of the stored hot water evaluated 
at the mean tank temperature at the beginning of the 24-hour 
simulated-use test (T0), lb/gal (kg/L).
Cp(T0) = the specific heat of the stored hot 
water, evaluated at T0, Btu/(lb[middot][deg]F) (kJ/
(kg[middot][deg]C)).
Tmax,1 = the maximum measured mean tank temperature after 
cut-out following the first draw of the 24-hour simulated-use test, 
[deg]F([deg]C).
Tdel,2= the average outlet water temperature during the 
second draw of the 24-hour simulated-use test, [deg]F([deg]C).
[rho](Tmax,1) = the density of the stored hot water 
evaluated at the maximum measured mean tank temperature after cut-
out following the first draw of the 24-hour simulated-use test 
(Tmax,1), lb/gal (kg/L).
Cp(Tmax,1) = the specific heat of the stored 
hot water, evaluated at Tmax,1, Btu/(lb[middot][deg]F) 
(kJ/(kg[middot][deg]C)).
[rho](125 [deg]F) = the density of the stored hot water at 125 
[deg]F, lb/gal (kg/L).
Cp(125 [deg]F) = the specific heat of the stored hot 
water at 125 [deg]F, Btu/(lb[middot][deg]F) (kJ/(kg[middot][deg]C)).
125 [deg]F (51.7 [deg]C) = the nominal maximum mean tank temperature 
for a storage tank that does not utilize a mixing valve to achieve a 
125 [deg]F delivery temperature.
    67.5 [deg]F (19.7 [deg]C) = the nominal average ambient air 
temperature.

    6.3.2 Mass of Water Removed. Determine the mass of water removed 
during each draw of the 24-hour simulated-use test 
(Mdel,i) as:

    If the mass of water removed is measured, use the measured 
value, or, if the volume of water removed is being measured,

    Mdel,i = Vdel,i * Pdel,i

Where:

Vdel,i = volume of water removed during the ith draw of 
the 24-hour simulated-use test, gal (L).
[rho]del,i = density of the water removed, evaluated at 
the average outlet water temperature measured during the ith draw of 
the 24-hour simulated-use test, (Tdel,i), lb/gal (kg/L).

or, if the volume of water entering the water heater is measured,
    Mdel,i = Vin,i * [rho]in,i

Where:

Vin,i = volume of water entering the water heater during 
draw ith draw of the 24-hour simulated-use test, gal (L).
[rho]in,i = density of the water entering the water 
heater, evaluated at the average inlet water temperature measured 
during the ith draw of the 24-hour simulated-use test, 
(Tin,i), lb/gal (kg/L).
or, if the mass of water entering the water heater is measured,
    Mdel,i = Min,i

Where:
Min,i = mass of water entering the water heater during 
draw ith draw of the 24-hour simulated-use test, lb (kg).
    6.3.3 Recovery Efficiency. The recovery efficiency for gas, oil, 
and heat pump water heaters with a rated storage volume greater than 
or equal to 2 gallons, [eta]r, is computed as:

[[Page 40486]]

[GRAPHIC] [TIFF OMITTED] TR21JN23.021

Where:

Vst = as defined in section 6.3.1 of this appendix.
[rho]1 = density of stored hot water evaluated at 
(Tmax,1 + T0)/2, lb/gal (kg/L).
Cp1 = specific heat of the stored hot water, evaluated at 
(Tmax,1 + T0)/2, Btu/(lb[middot][deg]F) (kJ/
(kg[middot][deg]C).
Tmax,1 = maximum mean tank temperature recorded after the 
first recovery period as defined in section 5.4.2 of this appendix, 
[deg]F ([deg]C).
T0 = mean tank temperature recorded at the beginning of 
the 24-hour simulated-use test as determined in section 5.4.2 of 
this appendix, [deg]F ([deg]C).
Qr = the total energy used by the water heater during the 
first recovery period as defined in section 5.4.2 of this appendix, 
including auxiliary energy such as pilot lights, pumps, fans, etc., 
Btu (kJ). (Electrical auxiliary energy shall be converted to thermal 
energy using the following conversion: 1 kWh = 3412 Btu).
Nr = number of draws from the start of the 24-hour 
simulated-use test to the end to the first recovery period as 
described in section 5.4.2.
Mdel,i = mass of water removed as calculated in section 
6.3.2 of this appendix during the ith draw of the first recovery 
period as described in section 5.4.2, lb (kg).
Cpi = specific heat of the withdrawn water during the ith 
draw of the first recovery period as described in section 5.4.2, 
evaluated at (Tdel,i + Tin,i)/2, Btu/
(lb[middot] [deg]F) (kJ/(kg[middot] [deg]C)).
Tdel,i = average water outlet temperature measured during 
the ith draw of the first recovery period as described in section 
5.4.2, [deg]F ([deg]C).
Tin,i = average water inlet temperature measured during 
the ith draw of the first recovery period as described in section 
5.4.2, [deg]F ([deg]C).

    The recovery efficiency for electric water heaters with immersed 
heating elements, not including heat pump water heaters with 
immersed heating elements, is assumed to be 98 percent.
    6.3.4 Hourly Standby Losses. The energy consumed as part of the 
standby loss test of the 24-hour simulated-use test, 
Qstby, is computed as:

Qstby = Qsu,f - Qsu,o

Where:

Qsu,0 = cumulative energy consumption, including all 
fossil fuel and electrical energy use, of the water heater from the 
start of the 24-hour simulated-use test to the start of the standby 
period as determined in section 5.4.2 of this appendix, Btu (kJ).
Qsu,f = cumulative energy consumption, including all 
fossil fuel and electrical energy use, of the water heater from the 
start of the 24-hour simulated-use test to the end of the standby 
period as determined in section 5.4.2 of this appendix, Btu (kJ).

    The hourly standby energy losses are computed as:
    [GRAPHIC] [TIFF OMITTED] TR21JN23.022
    
Where:

Qhr = the hourly standby energy losses of the water 
heater, Btu/h (kJ/h).
Vst = as defined in section 6.3.1 of this appendix.
[rho] = density of the stored hot water, evaluated at 
(Tsu,f + Tsu,0)/2, lb/gal (kg/L).
Cp = specific heat of the stored water, evaluated at 
(Tsu,f + Tsu,0)/2, Btu/(lb[middot][deg]F), 
(kJ/(kg[middot]K)).
Tsu,f = the mean tank temperature measured at the end of 
the standby period as determined in section 5.4.2 of this appendix, 
[deg]F ([deg]C).
Tsu,0 = the maximum mean tank temperature measured at the 
beginning of the standby period as determined in section 5.4.2 of 
this appendix, [deg]F ([deg]C).
[eta]r = as defined in section 6.3.3 of this appendix.
[tau]stby,1 = elapsed time between the start and end of 
the standby period as determined in section 5.4.2 of this appendix, 
h.

    The standby heat loss coefficient for the tank is computed as:
    [GRAPHIC] [TIFF OMITTED] TR21JN23.023
    
Where:

UA = standby heat loss coefficient of the storage tank, Btu/
(h[middot] [deg]F), (kJ/(h[middot] [deg]C).
Tt,stby,1 = overall average mean tank temperature between 
the start and end of the standby period as determined in section 
5.4.2 of this appendix, [deg]F ([deg]C).
Ta,stby,1 = overall average ambient temperature between 
the start and end of the standby period as determined in section 
5.4.2 of this appendix, [deg]F ([deg]C).

6.3.5 Daily Water Heating Energy Consumption. The total energy used 
by the water heater during the 24-hour simulated-use test (Q) is as 
measured in section 5.4.2 of this appendix, or,

Q = Qf + Qe = total energy used by the water 
heater during the 24-hour simulated-use test, including auxiliary 
energy such as pilot lights, pumps, fans, etc., Btu (kJ).
Qf = total fossil fuel energy used by the water heater 
during the 24-hour simulated-use test, Btu (kJ).
Qe = total electrical energy used during the 24-hour 
simulated-use test, Btu (kJ). (Electrical energy shall be converted 
to thermal energy using the following conversion: 1kWh = 3412 Btu.)

    The daily water heating energy consumption, Qd, is 
computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.024

Where:

Vst = as defined in section 6.3.1 of this appendix.
[rho] = density of the stored hot water, evaluated at 
(T24 + T0)/2, lb/gal (kg/L).
Cp = specific heat of the stored water, evaluated at 
(T24 + T0)/2, Btu/(lb[middot][deg]F), (kJ/
(kg[middot]K)).
T24 = mean tank temperature at the end of the 24-hour 
simulated-use test as determined in section 5.4.2 of this appendix, 
[deg]F ([deg]C).
T0 = mean tank temperature recorded at the beginning of 
the 24-hour simulated-use test as determined in section 5.4.2 of 
this appendix, [deg]F ([deg]C).
[eta]r = as defined in section 6.3.3 of this appendix.

6.3.6 Adjusted Daily Water Heating Energy Consumption. The adjusted 
daily water

[[Page 40487]]

heating energy consumption, Qda, takes into account that 
the ambient temperature may differ from the nominal value of 67.5 
[deg]F (19.7 [deg]C) due to the allowable variation in surrounding 
ambient temperature of 65 [deg]F (18.3 [deg]C) to 70 [deg]C (21.1 
[deg]C). The adjusted daily water heating energy consumption is 
computed as:

Qda = Qd - (67.5[deg]C - Ta,stby,2) 
UA [tau]stby,2

or,

Qda = Qd - (19.7[deg]C - Ta,stby,2) 
UA [tau]stby,2

Where:

Qda = the adjusted daily water heating energy 
consumption, Btu (kJ).
Qd = as defined in section 6.3.4 of this appendix.
Ta,stby,2 = the average ambient temperature during the 
total standby portion, [tau]stby,2, of the 24-hour 
simulated-use test, [deg]F ([deg]C).
UA = as defined in section 6.3.4 of this appendix.
[tau]stby,2 = the number of hours during the 24-hour 
simulated-use test when water is not being withdrawn from the water 
heater.
    A modification is also needed to take into account that the 
temperature difference between the outlet water temperature and 
supply water temperature may not be equivalent to the nominal value 
of 67 [deg]F (125 [deg]F-58 [deg]F) or 37.3 [deg]C (51.7 [deg]C-14.4 
[deg]C). The following equations adjust the experimental data to a 
nominal 67 [deg]F (37.3 [deg]C) temperature rise.
    The energy used to heat water, Btu/day (kJ/day), may be computed 
as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.025

Where:

N = total number of draws in the 24-hour simulated-use test.
Mdel,i = the mass of water removed during the ith draw (i 
= 1 to N) as calculated in section 6.3.2 of this appendix, lb (kg).
Cpi = the specific heat of the water withdrawn during the 
ith draw of the 24-hour simulated-use test, evaluated at 
(Tdel,i + Tin,i)/2, Btu/(lb[middot] [deg]F) 
(kJ/(kg[middot][deg]C)).
Tdel,i = the average water outlet temperature measured 
during the ith draw (i = 1 to N), [deg]F ([deg]C).
Tin,i = the average water inlet temperature measured 
during the ith draw (i = 1 to N), [deg]F ([deg]C).
[eta]r = as defined in section 6.3.3 of this appendix.

    The energy required to heat the same quantity of water over a 67 
[deg]F (37.3 [deg]C) temperature rise, Btu/day (kJ/day), is:
[GRAPHIC] [TIFF OMITTED] TR21JN23.026

or,
[GRAPHIC] [TIFF OMITTED] TR21JN23.027

The difference between these two values is:

QHWD = QHW,67.[deg]F - QHW

or,

QHWD = QHW,37.3[deg]C - QHW

    This difference (QHWD) must be added to the adjusted 
daily water heating energy consumption value. Thus, the daily energy 
consumption value, which takes into account that the ambient 
temperature may not be 67.5 [deg]F (19.7 [deg]C) and that the 
temperature rise across the storage tank may not be 67 [deg]F (37.3 
[deg]C) is:

Qdm = Qda - QHWD

    6.3.7 Estimated Mean Tank Temperature for Water Heaters with 
Rated Storage Volumes Greater Than or Equal to 2 Gallons. If testing 
is conducted in accordance with section 5.4.2.2 of this appendix, 
calculate the mean tank temperature immediately prior to the 
internal tank temperature determination draw using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR21JN23.028

Where:

Tst = the estimated average internal storage tank 
temperature, [deg]F ([deg]C).
Tp = the average of the inlet and the outlet water 
temperatures at the end of the period defined by [tau]p, 
[deg]F ([deg]C).
vout,p = the average flow rate during the period, gal/min 
(L/min).
Vst = the rated storage volume of the water heater, gal 
(L).
[tau]p = the number of minutes in the duration of the 
period, determined by the length of time taken for the outlet water 
temperature to be within 2 [deg]F of the inlet water temperature for 
15 consecutive seconds and including the 15-second stabilization 
period.
Tin,p = the average of the inlet water temperatures 
during the period, [deg]F ([deg]C).
Tout,p = the average of the outlet water temperatures 
during the period, [deg]F ([deg]C).

    6.3.8 Uniform Energy Factor. The uniform energy factor, UEF, is 
computed as:

[[Page 40488]]

[GRAPHIC] [TIFF OMITTED] TR21JN23.029

Where:

N = total number of draws in the 24-hour simulated-use test.
Qdm = the modified daily water heating energy consumption 
as computed in accordance with section 6.3.6 of this appendix, Btu 
(kJ).
Mdel,i = the mass of water removed during the ith draw (i 
= 1 to N) as calculated in section 6.3.2 of this appendix, lb (kg).
Cpi = the specific heat of the water withdrawn during the 
ith draw of the 24-hour simulated-use test, evaluated at (125 [deg]F 
+ 58 [deg]F)/2 = 91.5 [deg]F ((51.7 [deg]C + 14.4 [deg]C)/2 = 33 
[deg]C), Btu/(lb[middot][deg]F) (kJ/(kg[middot][deg]C)).

    6.3.9 Annual Energy Consumption. The annual energy consumption 
for water heaters with rated storage volumes greater than or equal 
to 2 gallons is computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.030

Where:

UEF = the uniform energy factor as computed in accordance with 
section 6.3.88 of this appendix.
365 = the number of days in a year.
V = the volume of hot water drawn during the applicable draw 
pattern, gallons.
= 10 for the very-small-usage draw pattern.
= 38 for the low-usage draw pattern.
= 55 for the medium-usage draw pattern.
= 84 for high-usage draw pattern.
[rho] = 8.24 lb/gallon, the density of water at 125 [deg]F.
Cp = 1.00 Btu/(lb [deg]F), the specific heat of water at 
91.5 [deg]F.
67 = the nominal temperature difference between inlet and outlet 
water

    6.3.10 Annual Electrical Energy Consumption. The annual 
electrical energy consumption in kilowatt-hours for water heaters 
with rated storage volumes greater than or equal to 2 gallons, 
Eannual,e, is computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.031

Where:

Eannual = the annual energy consumption as determined in 
accordance with section 6.3.99 of this appendix, Btu (kJ).
Qe = the daily electrical energy consumption as defined 
in section 6.3.5 of this appendix, Btu (kJ).
Q = total energy used by the water heater during the 24-hour 
simulated-use test in accordance with section 6.3.5 of this 
appendix, Btu (kJ).
3412 = conversion factor from Btu to kWh.

    6.3.11 Annual Fossil Fuel Energy Consumption. The annual fossil 
fuel energy consumption for water heaters with rated storage volumes 
greater than or equal to 2 gallons, Eannual,f, is 
computed as:

Eannual,f = Eannual-(Eannual,e * 3412)

Where:

Eannual = the annual energy consumption as determined in 
accordance with section 6.3.9 of this appendix, Btu (kJ).
Eannual,e = the annual electrical energy consumption as 
determined in accordance with section 6.3.10 of this appendix, kWh.
3412 = conversion factor from kWh to Btu.

    6.4 Computations for Water Heaters with a Rated Storage Volume 
Less Than 2 Gallons.
    6.4.1 Mass of Water Removed
    Calculate the mass of water removed using the calculations in 
section 6.3.2 of this appendix.
    6.4.2 Recovery Efficiency. The recovery efficiency, 
[eta]r, is computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.032

Where:

M1 = mass of water removed during the first draw of the 
24-hour simulated-use test, lb (kg).
Cp1 = specific heat of the withdrawn water during the 
first draw of the 24-hour simulated-use test, evaluated at 
(Tdel,1 + Tin,1)/2, Btu/(lb[middot][deg]F) 
(kJ/(kg[middot][deg]C)).
Tdel,1 = average water outlet temperature measured during 
the first draw of the 24-hour simulated-use test, [deg]F ([deg]C).
Tin,1 = average water inlet temperature measured during 
the first draw of the 24-hour simulated-use test, [deg]F ([deg]C).
Qr = the total energy used by the water heater during the 
first recovery period as defined in section 5.4.3 of this appendix, 
including auxiliary energy such as pilot lights, pumps, fans, etc., 
Btu (kJ). (Electrical auxiliary energy shall be converted to thermal 
energy using the following conversion: 1 kWh = 3412 Btu.)

    6.4.3 Daily Water Heating Energy Consumption. The daily water 
heating energy consumption, Qd, is computed as:

Qd = Q

Where:

Q = Qf + Qe = the energy used by the water 
heater during the 24-hour simulated-use test.
Qf = total fossil fuel energy used by the water heater 
during the 24-hour simulated-use test, Btu (kJ).
Qe = total electrical energy used during the 24-hour 
simulated-use test, Btu (kJ).

[[Page 40489]]

(Electrical auxiliary energy shall be converted to thermal energy 
using the following conversion: 1 kWh = 3412 Btu.)

    A modification is needed to take into account that the 
temperature difference between the outlet water temperature and 
supply water temperature may not be equivalent to the nominal value 
of 67 [deg]F (125 [deg]F-58 [deg]F) or 37.3 [deg]C (51.7 [deg]C-14.4 
[deg]C). The following equations adjust the experimental data to a 
nominal 67 [deg]F (37.3 [deg]C) temperature rise.
    The energy used to heat water may be computed as:
    [GRAPHIC] [TIFF OMITTED] TR21JN23.033
    
Where:

N = total number of draws in the 24-hour simulated-use test.
Mdel,i = the mass of water removed during the ith draw (i 
= 1 to N) as calculated in section 6.4.1 of this appendix, lb (kg).
Cpi = the specific heat of the water withdrawn during the 
ith draw of the 24-hour simulated-use test, evaluated at 
(Tdel,i + Tin,i)/2, Btu/(lb[middot][deg]F) 
(kJ/(kg[middot][deg]C)).
Tdel,i = the average water outlet temperature measured 
during the ith draw (i = 1 to N), [deg]F ([deg]C).
Tin,i = the average water inlet temperature measured 
during the ith draw (i = 1 to N), [deg]F ([deg]C).
[eta]r = as defined in section 6.4.2 of this appendix.

    The energy required to heat the same quantity of water over a 67 
[deg]F (37.3 [deg]C) temperature rise is:
[GRAPHIC] [TIFF OMITTED] TR21JN23.034

Where:

N = total number of draws in the 24-hour simulated-use test.
Mdel,i = the mass of water removed during the ith draw (i 
= 1 to N) as calculated in section 6.4.1 of this appendix, lb (kg).
Cpi = the specific heat of the water withdrawn during the 
ith draw of the 24-hour simulated-use test, evaluated at 
(Tdel,i + Tin,i)/2, Btu/(lb[middot][deg]F) 
(kJ/(kg[middot][deg]C)).
[eta]r = as defined in section 6.4.2 of this appendix.

    The difference between these two values is:

QHWD = QHW,67[deg]F-QHW

or,

QHWD = QHW,37.3[deg]C-QHW

    This difference (QHWD) must be added to the daily 
water heating energy consumption value. Thus, the daily energy 
consumption value, which takes into account that the temperature 
rise across the water heater may not be 67 [deg]F (37.3 [deg]C), is:
Qdm = Qda + QHWD

    6.4.4 Uniform Energy Factor. The uniform energy factor, UEF, is 
computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.035

Where:

N = total number of draws in the 24-hour simulated-use test.
Qdm = the modified daily water heating energy consumption 
as computed in accordance with section 6.4.3 of this appendix, Btu 
(kJ).
Mdel,i = the mass of water removed during the ith draw (i 
= 1 to N) as calculated in section 6.4.1 of this appendix, lb (kg).
Cpi = the specific heat of the water withdrawn during the 
ith draw of the 24-hour simulated-use test, evaluated at (125 [deg]F 
+ 58 [deg]F)/2 = 91.5 [deg]F ((51.7 [deg]C + 14.4 [deg]C)/2 = 33.1 
[deg]C), Btu/(lb[middot][deg]F) (kJ/(kg[middot][deg]C)).

    6.4.5 Annual Energy Consumption. The annual energy consumption 
for water heaters with rated storage volumes less than 2 gallons, 
Eannual, is computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.036


[[Page 40490]]


Where:

UEF = the uniform energy factor as computed in accordance with 
section 6.4.4 of this appendix.
365 = the number of days in a year.
V = the volume of hot water drawn during the applicable draw 
pattern, gallons.
= 10 for the very-small-usage draw pattern.
= 38 for the low-usage draw pattern.
= 55 for the medium-usage draw pattern.
= 84 for high-usage draw pattern.
[rho] = 8.24 lb/gallon, the density of water at 125 [deg]F.
Cp = 1.00 Btu/(lb [deg]F), the specific heat of water at 
91.5 [deg]F.
67 = the nominal temperature difference between inlet and outlet 
water.

    6.4.6 Annual Electrical Energy Consumption. The annual 
electrical energy consumption in kilowatt-hours for water heaters 
with rated storage volumes less than 2 gallons, 
Eannual,e, is computed as:
[GRAPHIC] [TIFF OMITTED] TR21JN23.037

Where:

Qe = the daily electrical energy consumption as defined 
in section 6.4.3 of this appendix, Btu (kJ).
Eannual = the annual energy consumption as determined in 
accordance with section 6.4.5 of this appendix, Btu (kJ).
Q = total energy used by the water heater during the 24-hour 
simulated-use test in accordance with section 6.4.3 of this 
appendix, Btu (kJ).
Qdm = the modified daily water heating energy consumption 
as computed in accordance with section 6.4.3 of this appendix, Btu 
(kJ).
3412 = conversion factor from Btu to kWh.

    6.4.7 Annual Fossil Fuel Energy Consumption. The annual fossil 
fuel energy consumption for water heaters with rated storage volumes 
less than 2 gallons, Eannual,f, is computed as:

Where:

Eannual = the annual energy consumption as defined in 
section 6.4.5 of this appendix, Btu (kJ).
Eannual,e = the annual electrical energy consumption as 
defined in section 6.4.6 of this appendix, kWh.
3412 = conversion factor from kWh to Btu.

    6.5 Energy Efficiency at Optional Test Conditions. If testing is 
conducted at optional test conditions in accordance with section 5.6 
of this appendix, calculate the energy efficiency at the test 
condition, EX, using the formulas in sections 6.3 or 6.4 
of this appendix (as applicable), except substituting the applicable 
ambient temperature and supply water temperature used for testing 
(as specified in section 2.8 of this appendix) for the nominal 
ambient temperature and supply water temperature conditions used in 
the equations for determining UEF (i.e., 67.5 [deg]F and 58 [deg]F).
    7. Test Set-Up Diagrams
BILLING CODE 6450-01-P

[[Page 40491]]

[GRAPHIC] [TIFF OMITTED] TR21JN23.038


[[Page 40492]]


[GRAPHIC] [TIFF OMITTED] TR21JN23.039


[[Page 40493]]


[GRAPHIC] [TIFF OMITTED] TR21JN23.040


[[Page 40494]]


[GRAPHIC] [TIFF OMITTED] TR21JN23.041

PART 431--ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND 
INDUSTRIAL EQUIPMENT

0
8. The authority citation for part 431 continues to read as follows:

    Authority: 42 U.S.C. 6291-6317; 28 U.S.C. 2461 note.


0
9. Amend Sec.  431.102 by revising the definition for ``Commercial heat 
pump water heater (CHPWH)'' to read as follows:


Sec.  431.102  Definitions concerning commercial water heaters, hot 
water supply boilers, unfired hot water storage tanks, and commercial 
heat pump water heaters.

* * * * *
    Commercial heat pump water heater (CHPWH) means a water heater 
(including all ancillary equipment such as fans, blowers, pumps, 
storage tanks, piping, and controls, as applicable) that uses a 
refrigeration cycle, such as vapor compression, to transfer heat from a 
low-temperature source to a higher-temperature sink for the purpose of 
heating potable water, and operates with a current rating greater than 
24 amperes or a voltage greater than 250 volts. Such equipment 
includes, but is not limited to, air-source heat pump water heaters, 
water-source heat pump water heaters, and direct geo-exchange heat pump 
water heaters.
* * * * *
[FR Doc. 2023-11429 Filed 6-20-23; 8:45 am]
BILLING CODE 6450-01-C