What is the minimum requirement for service grounding electrode size?

The minimum requirement for service grounding electrode size is based on the National Electrical Code (NEC) standards that aim to ensure adequate grounding to protect both people and property from electrical faults. The correct answer specifies that a grounding electrode conductor must be at least #6 AWG (American Wire Gauge) when using copper, and #4 AWG when using aluminum.

This size is established to provide a sufficient path to safely carry fault current to the ground, thereby minimizing the risk of electric shock or fire that could result from a ground fault condition. The resistance of the grounding path must be low enough to allow protective devices to operate during a fault condition, and the larger wire sizes (as indicated in the correct answer) help to achieve that necessary conductivity.

Grounding electrodes must effectively dissipate electrical energy, and using the specified wire sizes for copper and aluminum ensures that the conductor can handle the expected fault currents without overheating or degrading over time. The other options present smaller gauge wires, which may not meet the NEC requirements for effective grounding, decreasing safety and reliability in electrical installations.