According to NEC®, what cannot be smaller than the grounding electrode conductor?

The importance of grounding electrode conductors (GEC) is emphasized in the National Electrical Code (NEC) for safety and reliability in electrical systems. The grounded conductor, commonly referred to as the neutral, is essential for completing the electrical circuit. According to the NEC, the size of the grounded conductor must be adequate to handle the maximum fault current that may occur during a fault condition.

The grounded conductor cannot be smaller than the grounding electrode conductor because it needs to provide a low-resistance path back to the source of power in the event of a fault. If the grounded conductor is too small, there is a risk that it could overheat and possibly lead to a hazardous situation. This requirement helps ensure that the electrical system is safe and that both the grounding and neutral systems work effectively to protect against electrical faults.

In contrast, the ungrounded conductor does not have the same sizing requirements relative to the grounding electrode conductor since it carries the supply voltage without a direct return path to the ground. Therefore, the neutral is specifically governed by the NEC's guidelines to ensure it is properly sized for safety.