USCG Exam PracticeMotor controllers and remote control
Under 46 CFR §111.70-7, when a control, interlock, or indicator circuit cannot be powered from the load side of the disconnect device and its voltage exceeds 24 volts, one acceptable alternative is to use a disconnect device actuated by the opening of the controller door. Which additional requirement applies when this arrangement is used for a vital auxiliary circuit?
- A. A fixed sign warning to open both disconnect devices must be posted on the exterior of the main disconnect door
- ✓ The disconnect device and its connections must have no electrically uninsulated or unshielded surface, and a nameplate warning that opening the door will trip the vital auxiliary off-line must be affixed to the doorCorrect
- C. The control circuit voltage must be reduced to 24 volts or less before the door-actuated disconnect is permitted
- D. An independent overcurrent device rated at not more than 300 percent of conductor capacity must be installed in each side of the control circuit
Why B is correct
46 CFR §111.70-7(d)(2) requires that when a door-actuated disconnect is used, the disconnect device and its connections including terminal blocks must have no electrically uninsulated or unshielded surface. Additionally, when used for vital auxiliary circuits, a nameplate warning that opening the door will trip the vital auxiliary off-line must be affixed to the controller door. Option A describes the alternative method in §111.70-7(d)(1), not (d)(2).
Cited:46 CFR §111.70-7