What is the minimum size EGC allowed for a 3 hp motor when a 120/240-V panel is used with the minimum circuit conductors?

For a 3 hp motor operating at 240 volts, the minimum equipment grounding conductor (EGC) size is determined based on the National Electrical Code (NEC) guidelines, specifically found in NEC Section 250.122, which details the sizing requirements for EGCs.

In this case, for a motor rated at 3 horsepower, a common rule of thumb is to calculate the required EGC based on the motor’s ampacity and the size of the conductors supplying the motor. For motors, the size of the EGC is typically based on the size of the overcurrent protection device or the conductors supplying the motor.

When considering the conductors for a 3 hp motor, the usual operating current can be estimated at around 15 amps or higher; this would typically indicate that a 10 AWG wire is appropriate for feeding the motor. According to NEC guidelines, when using 10 AWG conductors, the minimum size for the EGC connected to the circuit would indeed be 10 AWG.

Therefore, the choice of 10 AWG as the minimum size EGC for a 3 hp motor under the specified conditions aligns with the NEC requirements, ensuring adequate grounding for safety and compliance in the electrical installation.