What is the minimum size copper equipment grounding conductor for a 15-ampere branch circuit supplying a swimming pool pump motor?

In the context of grounding conductors for branch circuits, the National Electrical Code (NEC) provides specifications for the sizing of equipment grounding conductors to ensure safety and proper functioning of electrical installations. For a 15-ampere branch circuit, especially one that supplies a swimming pool pump motor, the NEC requires a minimum size for the copper equipment grounding conductor to effectively handle potential fault currents.

The minimum size for a copper equipment grounding conductor serving a circuit that supplies motor loads, such as a swimming pool pump, typically derives from Table 250.122 in the NEC. For a circuit rated at 15 amperes, the minimum size equipment grounding conductor is determined by the rating of the circuit and the specific requirements related to motor applications.

In this case, 12 AWG copper wire meets the necessary criteria outlined in the code for grounding conductors for this type of application. The use of 12 AWG ensures that, in the event of a fault, the grounding conductor can safely carry the fault current back to the source, allowing protective devices to operate as intended and ensuring the system's safety.

Choosing a larger or smaller gauge would either exceed the requirements or fail to provide adequate protection, which is why 12 AWG stands as the correct answer