[Title 46 CFR 111.50]
[Code of Federal Regulations (annual edition) - October 1, 1996 Edition]
[Title 46 - SHIPPING]
[Chapter I - COAST GUARD, DEPARTMENT OF]
[Subchapter J - ELECTRICAL ENGINEERING]
[Part 111 - ELECTRIC SYSTEMS--GENERAL REQUIREMENTS]
[Subpart 111.50 - Overcurrent Protection]
[From the U.S. Government Publishing Office]




  46
  SHIPPING
  4
  1996-10-01
  1996-10-01
  false
  
  111.50
  Subpart 111.50
  
    SHIPPING
    COAST GUARD, DEPARTMENT OF
    ELECTRICAL ENGINEERING
    ELECTRIC SYSTEMS--GENERAL REQUIREMENTS
  


                 Subpart 111.50--Overcurrent Protection



Sec. 111.50-1  Protection of equipment.

    Overcurrent protection of electric equipment must meet the following 
listed subparts of this chapter:
    (a) Appliances, Subpart 111.77.
    (b) Generators, Subpart 111.12.
    (c) Motors, motor circuits, and controllers, Subpart 111.70.
    (d) Transformers, Subpart 111.20.



Sec. 111.50-2  Systems integration.

    The electrical characteristics of each overcurrent protective device 
must be compatible with other devices and its coordination must be 
considered in the design of the entire protective system.

    Note to Sec. 111.50-2: The electrical characteristics of overcurrent 
protective devices may differ between standards. The interchangeability 
and compatibility of components complying with differing standards 
cannot be assumed.

[CGD 94-108, 61 FR 28279, June 4, 1996]



Sec. 111.50-3  Protection of conductors.

    (a) Purpose. The purpose of overcurrent protection for conductors is 
to open the electric circuit if the current reaches a value that will 
cause an excessive or dangerous temperature in the conductor or 
conductor insulation. A grounded conductor is protected from overcurrent 
if a protective device of a suitable rating or setting is in each 
ungrounded conductor of the same circuit.
    (b) Overcurrent protection of conductors. Each conductor must be 
protected in accordance with its current carrying capacity, except a 
conductor for the following circuits which must meet the following 
listed subparts of this chapter:
    (1) Propulsion circuits, Subpart 111.35.
    (2) Steering circuits, Subpart 111.93.
    (3) Motor circuits, Subpart 111.70.
    (4) Flexible cord and fixture wire for lighting circuits, Subpart 
111.75.
    (5) Switchboard circuits, Subpart 111.30.
    (c) Fuses and circuit breakers. If the allowable current carrying 
capacity of the conductor does not correspond to a standard fuse or 
circuit breaker rating

[[Page 237]]

which meets article 240-6 of the NEC or IEC 92-202 and the next larger 
standard fuse or circuit breaker rating is used, it must not be larger 
than 150 percent of the current carrying capacity of the conductor. The 
effect of temperature on the operation of fuses and thermally controlled 
circuit breakers must be taken into consideration.
    (d) Parallel overcurrent protective devices. An overcurrent 
protective device must not be connected in parallel with another 
overcurrent protective device.
    (e) Thermal devices. A thermal cutout, thermal relay, or other 
device not designed to open a short circuit, must not be used for 
protection of a conductor against overcurrent due to a short circuit or 
ground, except in a motor circuit as described in Article 430 of the 
National Electrical Code or in IEC 92-202.
    (f) Ungrounded conductors. A fuse or overcurrent trip unit of a 
circuit breaker must be in each ungrounded conductor. A branch switch or 
circuit breaker must open all conductors of the circuit, except grounded 
conductors.
    (g) Grounded conductor. An overcurrent device must not be in a 
permanently grounded conductor, except:
    (1) An overcurrent device that simultaneously opens all conductors 
of the circuit, unless prohibited by Sec. 111.05-17 for the bus-tie 
feeder connecting the emergency and main switchboards; and
    (2) For motor-running protection described in Article 430 of the 
National Electrical Code or in IEC 92-202.

[CGD 74-125A, 47 FR 15236, Apr. 8, 1982, as amended by CGD 94-108, 61 FR 
28279, June 4, 1996]



Sec. 111.50-5  Location of overcurrent protective devices.

    (a) Location in circuit. Overcurrent devices must be at the point 
where the conductor to be protected receives its supply, except as 
follows:
    (1) The generator overcurrent protective device must be on the 
ship's service generator switchboard. (See Sec. 111.12-11(g) for 
additional requirements.)
    (2) The overcurrent protection for the shore connection conductors 
must meet Sec. 111.30-25.
    (3) If the overcurrent device that protects the larger conductors 
also protects the smaller conductors, an overcurrent device is not 
required at the supply to the smaller conductors.
    (4) If the overcurrent device protecting the primary side of a 
single phase transformer (two wire with single-voltage secondary) also 
protects the conductors connected to the secondary side, as determined 
by multiplying the current-carrying capacity of the secondary conductor 
by the secondary to primary transformer voltage ratio, and this 
protection meets Sec. 111.20-15 of this chapter, an overcurrent device 
is not required at the supply to the secondary side conductors.
    (b) Location on vessel. Each overcurrent device:
    (1) Must be:
    (i) Readily accessible; and
    (ii) In a distribution panelboard, switchboard, motor controller, or 
similar enclosure; and
    (2) Must not be:
    (i) Exposed to mechanical damage; and
    (ii) Near an easily ignitable material or where explosive gas or 
vapor may accumulate.



Sec. 111.50-7  Enclosures.

    (a) Each enclosure of an overcurrent protective device must meet 
Sections 240-30 and 240-33 of the National Electrical Code.
    (b) No enclosure may be exposed to the weather unless accepted by 
the Commandant.



Sec. 111.50-9  Disconnecting and guarding.

    Disconnecting and guarding of overcurrent protective devices must 
meet Part D of Article 240 of the National Electrical Code.