What is the minimum size equipment-grounding conductor for a branch circuit protected by a 40-ampere overcurrent device?

The minimum size equipment-grounding conductor for a branch circuit is determined based on the rating of the overcurrent protective device, in this case, a 40-ampere device. According to the National Electrical Code (NEC), the size of the equipment-grounding conductor must be adequate to ensure safety and functionality.

For a circuit protected by a 40-ampere overcurrent device, the NEC stipulates that the minimum grounding conductor should be a specific gauge to prevent overheating and ensure effective grounding in the event of a fault condition. In this instance, the standard dictates that a 10 AWG copper grounding conductor is required for circuits protected by a 40-ampere breaker. This size is chosen to provide enough capacity to handle fault currents that could arise in the circuit.

Utilizing a 10 AWG copper conductor ensures that the grounding system is robust enough to maintain equipment safety and compliance with electrical codes. Smaller gauges, like 12 AWG or 14 AWG, do not meet the requirement for a 40-amp circuit, as they may not effectively conduct any fault current and could potentially overheat, leading to unsafe conditions.