With a 200-Amp branch circuit using a 6 AWG EGC, if 12 AWG wire is used instead, how will this affect the circuit breaker response time during a ground fault?

Using a 12 AWG wire instead of a 6 AWG Equipment Grounding Conductor (EGC) in a 200-Amp branch circuit will lead to a longer response time of the circuit breaker during a ground fault. This is because the size of the grounding conductor affects the current-carrying capability and the effectiveness of the fault current path to trip the circuit breaker effectively.

A smaller conductor like 12 AWG has a higher resistance compared to a larger conductor like 6 AWG. When a ground fault occurs, the fault current must travel through the EGC to get back to the ground and help the circuit breaker detect the fault. The higher resistance of the 12 AWG wire can result in a lower magnitude of fault current, which may not be sufficient to trip the breaker instantaneously. Thus, the circuit breaker response time increases, posing a safety risk as it could allow more time for potential damage or hazard before the breaker actuates.

In essence, using a smaller gauge wire for the EGC compromises the performance of the grounding system and impacts how quickly the circuit breaker reacts, which is critical for safety in electrical installations.