[Title 29 CFR 1910.303]
[Code of Federal Regulations (annual edition) - July 1, 2002 Edition]
[Title 29 - LABOR]
[Subtitle B - Regulations Relating to Labor (Continued)]
[Chapter Xvii - OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT]
[Part 1910 - OCCUPATIONAL SAFETY AND HEALTH STANDARDS]
[Subpart S - Electrical]
[Sec. 1910.303 - General requirements.]
[From the U.S. Government Printing Office]
29LABOR52002-07-012002-07-01falseGeneral requirements.1910.303Sec. 1910.303LABORRegulations Relating to Labor (Continued)OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENTOCCUPATIONAL SAFETY AND HEALTH STANDARDSElectrical
Sec. 1910.303 General requirements.
(a) Approval. The conductors and equipment required or permitted by
this subpart shall be acceptable only if approved.
(b) Examination, installation, and use of equipment--(1)
Examination. Electrical equipment shall be free from recognized hazards
that are likely to cause death or serious physical harm to employees.
Safety of equipment shall be determined using the following
considerations:
(i) Suitability for installation and use in conformity with the
provisions of this subpart. Suitability of equipment for an identified
purpose may be evidenced by listing or labeling for that identified
purpose.
(ii) Mechanical strength and durability, including, for parts
designed to enclose and protect other equipment, the adequacy of the
protection thus provided.
(iii) Electrical insulation.
(iv) Heating effects under conditions of use.
(v) Arcing effects.
(vi) Classification by type, size, voltage, current capacity,
specific use.
(vii) Other factors which contribute to the practical safeguarding
of employees using or likely to come in contact with the equipment.
(2) Installation and use. Listed or labeled equipment shall be used
or installed in accordance with any instructions included in the listing
or labeling.
(c) Splices. Conductors shall be spliced or joined with splicing
devices suitable for the use or by brazing, welding, or soldering with a
fusible metal or alloy. Soldered splices shall first be so spliced or
joined as to be mechanically and electrically secure without solder and
then soldered. All splices and joints and the free ends of conductors
shall be covered with an insulation equivalent to that of the conductors
or with an insulating device suitable for the purpose.
(d) Arcing parts. Parts of electric equipment which in ordinary
operation produce arcs, sparks, flames, or molten metal shall be
enclosed or separated and isolated from all combustible material.
(e) Marking. Electrical equipment may not be used unless the
manufacturer's name, trademark, or other descriptive marking by which
the organization responsible for the product may be identified is placed
on the equipment. Other markings shall be provided giving voltage,
current, wattage, or other ratings as necessary. The marking shall be of
sufficient durability to withstand the environment involved.
(f) Identification of disconnecting means and circuits. Each
disconnecting means required by this subpart for motors and appliances
shall be legibly marked to indicate its purpose, unless located and
arranged so the purpose is evident. Each service, feeder, and branch
circuit, at its disconnecting means or overcurrent device, shall be
legibly marked to indicate its purpose, unless located and arranged so
the purpose is evident. These markings shall be of sufficient durability
to withstand the environment involved.
(g) 600 Volts, nominal, or less--(1) Working space about electric
equipment. Sufficient access and working space
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shall be provided and maintained about all electric equipment to permit
ready and safe operation and maintenance of such equipment.
(i) Working clearances. Except as required or permitted elsewhere in
this subpart, the dimension of the working space in the direction of
access to live parts operating at 600 volts or less and likely to
require examination, adjustment, servicing, or maintenance while alive
may not be less than indicated in Table S-1. In addition to the
dimensions shown in Table S-1, workspace may not be less than 30 inches
wide in front of the electric equipment. Distances shall be measured
from the live parts if they are exposed, or from the enclosure front or
opening if the live parts are enclosed. Concrete, brick, or tile walls
are considered to be grounded. Working space is not required in back of
assemblies such as dead-front switchboards or motor control centers
where there are no renewable or adjustable parts such as fuses or
switches on the back and where all connections are accessible from
locations other than the back.
Table S-1--Working Clearances
------------------------------------------------------------------------
Minimum clear distance
for condition\2\ (ft)
Nominal voltage to ground --------------------------
(a) (b) (c)
------------------------------------------------------------------------
0-150........................................ \1\ 3 \1\ 3 3
151-600...................................... \1\ 3 3\1/2\ 4
------------------------------------------------------------------------
\1\ Minimum clear distances may be 2 feet 6 inches for installations
built prior to April 16, 1981.
\2\ Conditions (a), (b), and (c), are as follows: (a) Exposed live parts
on one side and no live or grounded parts on the other side of the
working space, or exposed live parts on both sides effectively guarded
by suitable wood or other insulating material. Insulated wire or
insulated busbars operating at not over 300 volts are not considered
live parts. (b) Exposed live parts on one side and grounded parts on
the other side. (c) Exposed live parts on both sides of the workspace
[not guarded as provided in Condition (a)] with the operator between.
(ii) Clear spaces. Working space required by this subpart may not be
used for storage. When normally enclosed live parts are exposed for
inspection or servicing, the working space, if in a passageway or
general open space, shall be suitably guarded.
(iii) Access and entrance to working space. At least one entrance of
sufficient area shall be provided to give access to the working space
about electric equipment.
(iv) Front working space. Where there are live parts normally
exposed on the front of switchboards or motor control centers, the
working space in front of such equipment may not be less than 3 feet.
(v) Illumination. Illumination shall be provided for all working
spaces about service equipment, switchboards, panelboards, and motor
control centers installed indoors.
(vi) Headroom. The minimum headroom of working spaces about service
equipment, switchboards, panel-boards, or motor control centers shall be
6 feet 3 inches.
Note: As used in this section a motor control center is an assembly
of one or more enclosed sections having a common power bus and
principally containing motor control units.
(2) Guarding of live parts. (i) Except as required or permitted
elsewhere in this subpart, live parts of electric equipment operating at
50 volts or more shall be guarded against accidental contact by approved
cabinets or other forms of approved enclosures, or by any of the
following means:
(A) By location in a room, vault, or similar enclosure that is
accessible only to qualified persons.
(B) By suitable permanent, substantial partitions or screens so
arranged that only qualified persons will have access to the space
within reach of the live parts. Any openings in such partitions or
screens shall be so sized and located that persons are not likely to
come into accidental contact with the live parts or to bring conducting
objects into contact with them.
(C) By location on a suitable balcony, gallery, or platform so
elevated and arranged as to exclude unqualified persons.
(D) By elevation of 8 feet or more above the floor or other working
surface.
(ii) In locations where electric equipment would be exposed to
physical damage, enclosures or guards shall be so arranged and of such
strength as to prevent such damage.
(iii) Entrances to rooms and other guarded locations containing
exposed live parts shall be marked with conspicuous warning signs
forbidding unqualified persons to enter.
(h) Over 600 volts, nominal--(1) General. Conductors and equipment
used on circuits exceeding 600 volts, nominal,
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shall comply with all applicable provisions of paragraphs (a) through
(g) of this section and with the following provisions which supplement
or modify those requirements. The provisions of paragraphs (h)(2),
(h)(3), and (h)(4) of this section do not apply to equipment on the
supply side of the service conductors.
(2) Enclosure for electrical installations. Electrical installations
in a vault, room, closet or in an area surrounded by a wall, screen, or
fence, access to which is controlled by lock and key or other approved
means, are considered to be accessible to qualified persons only. A
wall, screen, or fence less than 8 feet in height is not considered to
prevent access unless it has other features that provide a degree of
isolation equivalent to an 8 foot fence. The entrances to all buildings,
rooms, or enclosures containing exposed live parts or exposed conductors
operating at over 600 volts, nominal, shall be kept locked or shall be
under the observation of a qualified person at all times.
(i) Installations accessible to qualified persons only. Electrical
installations having exposed live parts shall be accessible to qualified
persons only and shall comply with the applicable provisions of
paragraph (h)(3) of this section.
(ii) Installations accessible to unqualified persons. Electrical
installations that are open to unqualified persons shall be made with
metal-enclosed equipment or shall be enclosed in a vault or in an area,
access to which is controlled by a lock. If metal-enclosed equipment is
installed so that the bottom of the enclosure is less than 8 feet above
the floor, the door or cover shall be kept locked. Metal-enclosed
switchgear, unit substations, transformers, pull boxes, connection
boxes, and other similar associated equipment shall be marked with
appropriate caution signs. If equipment is exposed to physical damage
from vehicular traffic, suitable guards shall be provided to prevent
such damage. Ventilating or similar openings in metal-enclosed equipment
shall be designed so that foreign objects inserted through these
openings will be deflected from energized parts.
(3) Workspace about equipment. Sufficient space shall be provided
and maintained about electric equipment to permit ready and safe
operation and maintenance of such equipment. Where energized parts are
exposed, the minimum clear workspace may not be less than 6 feet 6
inches high (measured vertically from the floor or platform), or less
than 3 feet wide (measured parallel to the equipment). The depth shall
be as required in Table S-2. The workspace shall be adequate to permit
at least a 90-degree opening of doors or hinged panels.
(i) Working space. The minimum clear working space in front of
electric equipment such as switchboards, control panels, switches,
circuit breakers, motor controllers, relays, and similar equipment may
not be less than specified in Table S-2 unless otherwise specified in
this subpart. Distances shall be measured from the live parts if they
are exposed, or from the enclosure front or opening if the live parts
are enclosed. However, working space is not required in back of
equipment such as deadfront switchboards or control assemblies where
there are no renewable or adjustable parts (such as fuses or switches)
on the back and where all connections are accessible from locations
other than the back. Where rear access is required to work on de-
energized parts on the back of enclosed equipment, a minimum working
space of 30 inches horizontally shall be provided.
Table S-2--Minimum Depth of Clear Working Space in Front of Electric
Equipment
------------------------------------------------------------------------
Conditions \2\ (ft)
Nominal voltage to ground --------------------------
(a) (b) (c)
------------------------------------------------------------------------
601 to 2,500................................. 3 4 5
2,501 to 9,000............................... 4 5 6
9,001 to 25,000.............................. 5 6 9
25,001 to 75kV \1\........................... 6 8 10
Above 75kV \1\............................... 8 10 12
------------------------------------------------------------------------
\1\ Minimum depth of clear working space in front of electric equipment
with a nominal voltage to ground above 25,000 volts may be the same as
for 25,000 volts under Conditions (a), (b), and (c) for installations
built prior to April 16, 1981.
\2\ Conditions (a), (b), and (c) are as follows: (a) Exposed live parts
on one side and no live or grounded parts on the other side of the
working space, or exposed live parts on both sides effectively guarded
by suitable wood or other insulating materials. Insulated wire or
insulated busbars operating at not over 300 volts are not considered
live parts. (b) Exposed live parts on one side and grounded parts on
the other side. Concrete, brick, or tile walls will be considered as
grounded surfaces. (c) Exposed live parts on both sides of the
workspace not guarded as provided in Condition (a) with the operator
between.
[[Page 840]]
(ii) Illumination. Adequate illumination shall be provided for all
working spaces about electric equipment. The lighting outlets shall be
so arranged that persons changing lamps or making repairs on the
lighting system will not be endangered by live parts or other equipment.
The points of control shall be so located that persons are not likely to
come in contact with any live part or moving part of the equipment while
turning on the lights.
(iii) Elevation of unguarded live parts. Unguarded live parts above
working space shall be maintained at elevations not less than specified
in Table S-3.
Table S-3--Elevation of Unguarded Energized Parts Above Working Space
------------------------------------------------------------------------
Nominal voltage between phases Minimum elevation
------------------------------------------------------------------------
601 to 7,500.............................. *8 feet 6 inches.
7,501 to 35,000........................... 9 feet.
Over 35kV................................. 9 feet + 0.37 inches per kV
above 35kV.
------------------------------------------------------------------------
*Note.--Minimum elevation may be 8 feet 0 inches for installations built
prior to April 16, 1981 if the nominal voltage between phases is in
the range of 601-6600 volts.
(4) Entrance and access to workspace. (See Sec. 1910.302(b)(3).)
(i) At least one entrance not less than 24 inches wide and 6 feet 6
inches high shall be provided to give access to the working space about
electric equipment. On switchboard and control panels exceeding 48
inches in width, there shall be one entrance at each end of such board
where practicable. Where bare energized parts at any voltage or
insulated energized parts above 600 volts are located adjacent to such
entrance, they shall be suitably guarded.
(ii) Permanent ladders or stairways shall be provided to give safe
access to the working space around electric equipment installed on
platforms, balconies, mezzanine floors, or in attic or roof rooms or
spaces.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7, 1981]