What is the smallest size copper wire allowed as a grounding electrode conductor (GEC) for building steel from a 200 A main breaker?

For a 200 A main breaker, the grounding electrode conductor (GEC) needs to be appropriately sized to ensure safety and compliance with the National Electrical Code (NEC) requirements. According to NEC guidelines, the minimum size for a copper GEC connected to a grounding electrode such as building steel is determined by the size of the service disconnect and the type of electrode used.

In this scenario, a 200 A service requires a minimum size of 4 AWG copper wire for grounding. This is specified in NEC Article 250.66, which outlines the minimum sizes based on the largest ungrounded conductor or derived from specific grounding electrodes.

Choosing 4 AWG for a 200 A service ensures that the grounding system can handle potential fault currents effectively, reducing the risk of electrical shock and fire hazards. By using the correct size, you maintain the integrity of the grounding system, enhancing the safety of the electrical installation. The other wire sizes (2 AWG, 6 AWG, and 8 AWG) do not meet the minimum requirement for grounding electrode conductors for a 200 A service, as they are either too large or too small, thus failing to comply with safety regulations.