detached building sub-panel

[Kidd6488]

Because NEC says the earth shouldn't be used as a ground return path, I need to run a 4th wire out to our detached barn, correct? And I should drive a ground rod out at the barn? The phase conductors and neutral are #2 Al, and on a 100A breaker. So what guage shall the grounding conductor be?

~Jonathon Reinhart

[HayZee518]

They say not to consider ground as a return path because of the resistivity of the ground. It changes within the earth cover. For an earthing conductor run a #3 aluminum or #4 copper thw. Drving a ground rod at the remote location is ok, just bond all equipment grounds at the sub. Keep the neutral isolated above ground (no bonding jumper) Look at my diagram for sub-panels in the "sticky"