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Thread: Attaching sub-panel in outbuilding

  1. #1

    Default Attaching sub-panel in outbuilding

    I'm attaching a 100A sub-panel in a garage that is 150 feet from the house. The main panel is on the outside of the house. I plan to run the wire in PVC conduit. What gauge and type wire would I need to run? What size an schedule conduit should I use?

  2. #2
    Join Date
    Dec 2003
    Kent, WA


    How many amps do you really need in that garage? I doubt you need 100, but nothing wrong with putting in a 100A panel. You can feed it with less.

    You should use sch80 PVC for the vertical rise out of the ground. You can use sch 40 in the ground buried at 18" down. Conduit diameter will depend on wire size, but never push conduit fill on a long run.

    You will need to run 4 wires from the house to the detached garage. I'd recommend a 60A breaker in the house feeding #2 aluminum (hot, hot, neutral) with a #8 copper grounding wire in that conduit. This would require a 1.25" conduit, but I'd put in 1.5". You could use three #4 copper wires too, but that will cost more. If you won't need 60A at 240V, then the wires could be smaller. But because of the long distance, you should use wires sized one size larger than required to make up for voltage drop.

    Since this is a buried conduit, it is considered a wet area. Wire type should be THWN individual conductors. That should be easy to buy at home depot.

    Does your garage panel have a main breaker? If not, you're limited to 6 breaker handles in that panel. Garage will require 2 ground rods unless you have some other legal electrode there (like a UFER rebar foundation ground).
    Kent, WA

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