Journeyman Electrician Practice Exam

What is the minimum size equipment grounding conductor required for a 5 hp, 3-phase, 208-volt motor?

1. 12 AWG

2. 10 AWG

3. 8 AWG

4. 6 AWG

The correct answer is: 10 AWG

The minimum size equipment grounding conductor for a motor is determined based on its full-load current and the requirements set forth in the National Electrical Code (NEC). For a 5 hp, 3-phase motor operating at 208 volts, the full-load current can be calculated using specific guidelines available in NEC tables. According to NEC Table 430.250, the full-load current for a 5 hp, 3-phase motor at 208 volts is approximately 14.5 amperes. When sizing the equipment grounding conductor, the NEC requires it to be sized according to NEC Table 250.122, which lists the minimum equipment grounding conductor sizes based on the overcurrent protection device rating. For a full-load current of 14.5 amps, the 10 AWG copper grounding conductor is sufficient, as it is the minimum size required for circuits rated up to 20 amps. Thus, selecting a 10 AWG copper equipment grounding conductor meets the code requirements while providing adequate ground fault protection for the motor and its associated equipment. Therefore, based on NEC requirements, the correct answer is indeed 10 AWG. The other sizes would either be too large or incorrect for the specific application of a 5 hp motor at the given voltage and