Journeyman Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsMedium
A marina service equipment is supplying power to a floating dock. The individual branch circuits for boat slips extend from the service equipment. According to NEC Article 555, what is the maximum permissible voltage for a single-phase branch circuit supplying power to a boat at a floating dock?
- A120 volts
- B240 volts
- C480 volts
- D250 volts
Show answer & explanationAnswer & explanation
Correct answer: D. 250 volts
NEC Section 555.5(A) states that the voltage for power supplied to a boat through a feeder or branch circuit shall not exceed 250 volts nominal for single-phase circuits. This limit is crucial for safety in the presence of water.
Why the other options are wrong
- A. While common, 120V is not the maximum permitted voltage for single-phase circuits at marinas.
- B. 240V is a common voltage, but the NEC allows up to 250V for single-phase marina circuits.
- C. 480V is too high and not permitted for single-phase circuits supplying boats at marinas.
Marina Branch Circuit Voltage Limit
The maximum nominal voltage allowed by the NEC for single-phase branch circuits supplying power to boats at floating docks or marinas.
- Applies to marinas and boatyards (NEC 555).
- Specific to single-phase circuits supplying boats.
- Limited to 250 volts nominal for safety.
Memory trick: Two-fifty is the voltage limit, for a single phase by the water's brim.