For a single-pole breaker in a 120/240-V panel supplying a 1 hp motor, what is the minimum size EGC if the largest permitted DETD fuses are used?

In this situation, the minimum size Equipment Grounding Conductor (EGC) for a single-pole breaker supplying a 1 horsepower (hp) motor is determined according to the requirements set forth in the National Electrical Code (NEC).

For a motor rated at 1 hp, the circuit is generally protected by fuses or circuit breakers, and the size of the EGC should be based on the largest overcurrent device (in this case, the DETD fuses). The NEC provides guidelines for determining the appropriate size of the EGC based on the size of the feeder conductors and the type of overcurrent protection.

When using the largest permitted DETD fuses for a 1 hp motor, the minimum EGC size is typically required to be a certain percentage of the feeder conductor size. According to NEC Table 250.122, for overcurrent protection devices rated at 15 to 30 amps, which aligns with the requirements for a residential or similar application with a 1 hp motor, a 14 AWG copper grounding conductor is the minimum allowable size.

Using a 14 AWG wire for the EGC ensures that it is sufficient to handle any ground fault currents that may occur without losing its ability to provide adequate grounding