I'm wanting to run wires underground to my shed from the house.

  • Run is 85 feet
  • I have a 30amp breaker in the house for the shed.
  • I'll have need for one 240v outlet and several others for 120.

I've dug the trench which is 3 ft deep. Will be putting in 1 1/4 inch conduit, will this be big enough? I'm looking at using 10 gauge wire, but should I go to 8 gauge? Will I need a breaker box for the shed?


Yes, you will either need a subpanel for the shed, or you will need to serve only one circuit of each voltage.

All the receptacles attached to a 30A breaker must be 30A. You cannot hang a bunch of 15 and 20A receptacles off a 30A circuit, except by having the 30A circuit feed a subpanel.

So for instance you could run a single 120V 20A circuit, say, on two 12 or 10 AWG wires. Then a single 240V 30A circuit on 10 or 8 AWG wires, plus one ground wire for all. Those will fit in a 1-1/4 conduit just fine, and be easy to pull. I've pulled 12 12/10AWG wires 100 feet in a 1" conduit and that was easy.

Or you could run four 10 or 8 AWG wires and serve off the 30A breaker to a subpanel. The subpanel can be any size (larger then 30A obviously). It will need to have a main breaker in it, because you need a local shutoff switch and that's the easiest way to do it. You will need to keep ground and neutral separate inside the subpanel, and add a local grounding rod at the shed. I myself would run 4 AWG Aluminum because it will leave lots of headroom to 50A, and the lugs on the panels are aluminum anyway.

Also I'd get a fairly big panel. Panel space is cheap, I'd go at least 20. Some of them even throw in free breakers.

Adding an Image of Sub Panel Service Diagram with notes.. Borrowed from here > Link

 Sub Panel Service Diagram

  • your third paragraph - sub panel route is probably his best option - just a lot easier to work with later on. – Ken May 9 '17 at 2:19

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