USCG Exam PracticeSwitchboards and distribution systems
A vessel's emergency switchboard neutral bus-tie conductor to the main switchboard is found to have a circuit breaker installed in the neutral conductor. Under 46 CFR, this installation is:
- A. Acceptable provided the circuit breaker is rated for the full fault current of the system.
- B. Acceptable only if a fuse is used in place of the circuit breaker.
- ✓ A violation, because no switch or circuit breaker is permitted in the neutral conductor of the emergency-main switchboard bus-tie.Correct
- D. Acceptable if the circuit breaker simultaneously opens all ungrounded conductors.
Why C is correct
46 CFR §111.05-37(b) expressly prohibits a switch or circuit breaker in the neutral conductor of the emergency-main switchboard bus-tie. This prohibition is absolute and admits no exceptions based on rating or simultaneous operation.