USCG Exam PracticeSwitchboards and distribution systems
Regarding the neutral conductor of the bus-tie feeder connecting the emergency switchboard to the main switchboard, which statement is correct?
- A. It must have a circuit breaker rated for the full fault current of the emergency generator.
- B. It must be grounded directly at the emergency switchboard neutral bus.
- ✓ It must not have a switch, circuit breaker, or fuse installed in it.Correct
- D. It must have a fuse sized at 125 percent of the continuous load current.
Why C is correct
46 CFR §111.05-17(a)(3) and 46 CFR §111.05-37(b) both prohibit any switch, circuit breaker, or fuse in the neutral conductor of the emergency-main switchboard bus-tie. The neutral bus of the emergency system is permanently connected to the main switchboard neutral bus with no interrupting devices.