[Code of Federal Regulations]
[Title 46, Volume 4]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR111.70-7]

[Page 237-238]
 
                           TITLE 46--SHIPPING
 
    CHAPTER I--COAST GUARD, DEPARTMENT OF TRANSPORTATION (CONTINUED)
 
PART 111--ELECTRIC SYSTEMS--GENERAL REQUIREMENTS--Table of Contents
 
       Subpart 111.70--Motor Circuits, Controllers, and Protection
 
Sec. 111.70-7  Remote control, interlock, and indicator circuits.

    (a) Overcurrent protection. A conductor of a control, interlock, or 
indicator circuit of a motor controller must be protected against 
overcurrent unless:

[[Page 238]]

    (1) The conductor is wholly within the controller enclosure;
    (2) The rating or setting of the branch circuit overcurrent device 
is not more than 300 percent of the current-carrying capacity of the 
control, interlock, or indicator circuit conductor;
    (3) There is an overcurrent device in each side of the line that has 
a rating or setting of not more than 300 percent of the current-carrying 
capacity of the control, electrical interlock, or indicator circuit 
conductor, except if under operating conditions there is no appreciable 
difference in potential between the external conductors, overcurrent 
protection need only be at the supply of that side of the line; or
    (4) The opening of the control, interlock, or indicator circuit 
creates a hazard.
    Note: For overcurrent protection of steering gear control and 
indicator circuits, see Subpart 111.93 of this chapter.
    (b) Accidental ground. The controller must be designed to prevent an 
accidental ground in a remote control circuit from causing the stop 
switches to fail to operate or causing the motor to start.
    (c) Source of potential. The potential for a control, interlock, or 
indicator circuit must be derived from the load side of the motor and 
controller disconnect device, except if the control functions require 
circuits that must be common to two or more controllers, the switching 
arrangement in paragraph (d) of this section must be met.
    (d) Switching. In the design of a control, interlock, or indicator 
circuit, all practicable steps must be taken to eliminate all but one 
source of power in an enclosure. If the control functions make it 
impracticable to energize a control interlock or indicator circuit from 
the load side of a motor and controller disconnect device and the 
voltage of the control, interlock, or indicator circuit is more than 24 
volts, there must be one of the following alternative methods of 
switching:
    (1) Each conductor of a control, interlock, or indicator circuit 
must be disconnected from all sources of potential by a disconnect 
device independent of the motor and controller disconnect device. The 
two independent devices must be adjacent to each other, and a fixed 
sign, warning the operator to open both devices to disconnect completely 
the motor and controller, must be on the exterior of the door of the 
main disconnect device.
    (2) Each conductor of a control, interlock, or indicator circuit 
must be disconnected from all sources of power by a disconnect device 
actuated by the opening of the controller door, or the power must first 
be disconnected to allow opening of the door. The disconnect device and 
its connections, including each terminal block for terminating the 
vessel's wiring, must have no electrically uninsulated or unshielded 
surface. When this type of disconnect device is used for vital auxiliary 
circuits, a nameplate must be affixed to the vital auxiliary motor 
controller door that warns that opening the door will trip a vital 
auxiliary off-line.

[CGD 74-125A, 47 FR 15236, Apr. 8, 1982, as amended by CGD 94-108, 61 FR 
28282, June 4, 1996; 62 FR 23909, May 1, 1997]