For a 400-A circuit with two parallel raceways, the copper EGC arrangement required is two of which gauge, one in each raceway?

For a 400-A circuit with two parallel raceways, the copper EGC arrangement required is two of which gauge, one in each raceway?

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

Answer: (B)

When conductors are run in parallel, each parallel path must have its own equipment grounding conductor sized for the current carried by that path. In a 400 A circuit split into two parallel paths, you effectively have two 200 A circuits. For copper EGCs, the size that corresponds to a 200 A per-path rating is 3 AWG. Therefore, you place a copper equipment grounding conductor of 3 AWG in each raceway, giving one EGC in each parallel path. This setup ensures a proper grounding path for faults regardless of which raceway the fault occurs in and adheres to the per-path sizing requirement. Installing only one EGC in a single raceway would not provide a grounding path for the other parallel path, and using a larger single conductor wouldn’t satisfy the per-path protection rule.

When conductors are run in parallel, each parallel path must have its own equipment grounding conductor sized for the current carried by that path. In a 400 A circuit split into two parallel paths, you effectively have two 200 A circuits. For copper EGCs, the size that corresponds to a 200 A per-path rating is 3 AWG. Therefore, you place a copper equipment grounding conductor of 3 AWG in each raceway, giving one EGC in each parallel path.

This setup ensures a proper grounding path for faults regardless of which raceway the fault occurs in and adheres to the per-path sizing requirement. Installing only one EGC in a single raceway would not provide a grounding path for the other parallel path, and using a larger single conductor wouldn’t satisfy the per-path protection rule.