The phase conductors of a 400-amp circuit are divided into two parallel raceways. The NEC requires which of the following copper EGCs?

• A. Single 3 AWG in either raceway
• B. Two 3 AWG, one in each raceway
• C. Single 1 AWG in either raceway
• D. Two 1 AWG, one in each raceway

Answer: (B)

When you run a circuit in parallel and place the current-carrying conductors in separate raceways, each raceway must carry an equipment grounding conductor back to the service. This guarantees a reliable fault path in every raceway that carries part of the circuit.

For a 400-amp circuit, the copper equipment grounding conductor must be sized according to Table 250.122, based on the overcurrent protection device rating. That sizing calls for a 3 AWG copper EGC. Because the phase conductors are split into two raceways, you need an EGC in each raceway, both sized to meet the same requirement. So you place two copper EGCs, each 3 AWG, one in each raceway.

This setup ensures that any fault current has a proper grounding path in both raceways, complying with the NEC. A single EGC in only one raceway would leave the other raceway without a grounding path, and larger conductors in both raceways are possible but not the minimal code-compliant size.