In a home-run conduit with four branch circuits, what is the minimum size of the aluminum equipment ground when there is a 40-amp protection circuit?

The correct answer is based on the requirements set forth in the National Electrical Code (NEC) regarding grounding conductors for branch circuits. Specifically, when dealing with a circuit that has a 40-amp breaker, the size of the equipment ground must be adequately sized to ensure safety and compliance with electrical standards.

According to NEC guidelines, the minimum size of the equipment grounding conductor for aluminum conductors is determined by the size of the overcurrent protection device. For a 40-amp circuit, the NEC typically specifies that the grounding conductor should be no smaller than 8 AWG when using aluminum. This requirement ensures that in the event of a fault condition, the grounding conductor can effectively carry the fault current back to the ground source, minimizing electrical shock hazards and potential fire risks.

Larger sizes of grounding conductors are required for circuits with higher amperages, but for a circuit with a 40-amp breaker, 8 AWG aluminum is the appropriate minimum size to provide effective grounding while ensuring compliance with safety regulations. This highlights the importance of following the NEC to ensure installations are both safe and effective.