What is the minimum size branch circuit equipment grounding conductor permitted for a 208 volt, 7 ½ horse power, three phase AC motor protected by 40 amp dual element fuses?

To determine the minimum size branch circuit equipment grounding conductor for a 208 volt, 7 ½ horsepower, three-phase AC motor protected by 40 amp dual element fuses, it's essential to reference the National Electrical Code (NEC) provisions. The NEC provides guidelines for grounding conductor sizes based on the size of the overcurrent protection device and the rating of the motor.

For three-phase motors, generally, the grounding conductor size is derived from the rules in NEC Article 250.122. Specifically, the size of the grounding conductor is based on the size of the overcurrent protection device. In this case, the 40 amp dual element fuses serve as the overcurrent protection.

According to NEC guidelines, for a 40 amp circuit, the minimum size of the grounding conductor would be 10 AWG for copper conductors. This size ensures adequate safety and is capable of handling potential fault currents without being compromised in terms of integrity.

Thus, the selection of 10 AWG as the minimum size equipment grounding conductor is appropriate, as it follows NEC requirements and ensures the safe operation of the electrical system for the specified motor.