What is the minimum size Grounding Electrode Conductor (GEC) required for a service with a 400-amp main breaker and specified conductors?

To determine the minimum size Grounding Electrode Conductor (GEC) required for a service with a 400-amp main breaker, one must refer to the National Electrical Code (NEC), which provides guidelines for grounding and bonding systems. According to the NEC, the size of the GEC is mainly based on the size of the service entrance conductors and the rating of the overcurrent device, such as the main breaker.

In the case of a 400-amp service, the NEC specifies a certain minimum size for the GEC. For a 400-amp service, the requirement typically outlines that a 1/0 copper conductor is the minimum size required as the grounding electrode conductor. This sizing is critical because it ensures the safety and effectiveness of the grounding system, enabling it to adequately conduct fault current safely to the ground.

Although larger conductors like 2 or 4/0 could be used for enhanced conductivity or to account for other factors in larger installations, the minimum required size according to NEC guidelines specifically defines 1/0 as the appropriate minimum for a 400-amp service. Therefore, the selection of 1/0 as the answer aligns perfectly with the standards set forth in the electrical code.