A homeowner has an air compressor he would like installed on the backside of a remote building near his house. I will install an 8x8x4 can containing a relay, with the relay control switch located in the garage. There is already a 50A 240V circuit running to the building, but it is supplying the AC unit, and not the building itself. There are no electrical items associated with the remote building whatsoever. There is no room for another breaker in the main panel, so running a second circuit to the air compressor is not an option, at least not from the main panel itself. I'm trying to do this as economical as possible for the homeowner, and obviously meet code at the same time.
Should I:
A) Turn the 50A AC circuit into a sub-panel feed with sub-panel located on exterior of remote building and drive a ground rod?
B) Turn the 50A AC circuit into a sub-panel feed with sub-panel located immedietely to the left or right of main panel. Install one conduit, containing two circuits, to junction box located on exterior of remote building. Branch out to disconnects for each unit. Wait, wouldn't I still need a ground rod, as the Exception to 250.32(A) would not apply, would it?
Is there a scenario where I won't have to drive a ground rod?
Thanks.
