How should equipment grounding conductors for motor branch circuits be sized?

Sizing equipment grounding conductors for motor branch circuits is crucial for safety and compliance with electrical standards. The correct method for determining the appropriate size of these conductors is by using Table 250.122, which is found in the National Electrical Code (NEC). This table correlates the size of the grounding conductor to the rating of the overcurrent protection device protecting the motor.

By basing the size of the equipment grounding conductor on the rating of the device, you ensure that the conductor is capable of carrying the fault current that may occur, thus reducing the risk of injury or fire. It's essential that the grounding conductor is adequately sized to provide a low-resistance path back to the source in the event of a fault, facilitating the operation of overcurrent protective devices.

Other options, such as determining the size based on the appliance type or local municipal codes, may not provide a standardized or sufficiently safe approach in all circumstances. Additionally, the length of the circuit run does not directly impact the size of the grounding conductor, as the primary concern is to ensure adequate fault current capacity regardless of run length. This standardization promotes safety and efficacy in grounding practices across installations.