[Code of Federal Regulations]

[Title 46, Volume 4]

[Revised as of October 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 46CFR111.50-3]



[Page 228]

 

                            TITLE 46_SHIPPING



                  (This book contains parts 90 to 139)

 

   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)

 

PART 111_ELECTRIC SYSTEMS_GENERAL REQUIREMENTS--Table of Contents

 

                  Subpart 111.50_Overcurrent Protection

 

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, subchapter F of this chapter.

    (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 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; CGD 97-057, 62 FR 51047, Sept. 30, 1997]