Single circuit for a shed using 10-2?

Old 06-07-06, 07:19 AM
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Single circuit for a shed using 10-2?

I'm writing with one more "how to wire my outbuilding" question.
I've read the other posts, `and I'm getting it -- but still need some clarification.

I built a small personal workshop/toolshed/bikeshop -- 12x16' -- and want to run a couple of outlets for small power tools and pancake compressor and 3 lights. No welder, no HVAC, no fans. While building, I've been using one 100' 12g extension cord pugged into an outlet on a 20a breaker with no problems. In the future, I'll never exceed these requirements.

I built a 200 sq' addition and wired that myself -- I run the wire and my father-in-law does all the connections. He's competent but not an actual electrician, but his work impressed my building inspector.

I own a 250' coil of 10-2 wire that is the kind you can bury in a trench.

My question -- I'd really like to run the 10-2 straight from an appropriate and conservatively sized breaker in the house panel to the shed. Distance would be about 130' -- 90' across the crawlspace and 40' across the gravel driveway in a trench.

I really don't care about having to go back to the house if I trip a breaker, but I do want this to be safe on both ends. If I use GFCI outlets in the shed and a 30 amp breaker at the house, can I get away without wiring a subpanel and sinking additional grounding rods into my rocky, mountain ground?

Thanks for any advice!
Old 06-07-06, 07:48 AM
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Yes, you can use UF rated cable as long as it has a ground. However, you cannot use a 30 amp breaker in your main panel. The maximum allowed is 20 amps.

My recommendation is to run 10-3, and make this a multi wire circuit. Yes, that means not using the 10-2 you have, but I think you'll someday appreciate the extra capacity the multi wire circuit provides. A multi wire circuit will still limit you to a 20 amp breaker, but it will be a 240 volt breaker, meaning you will have double the capacity of the single 120 volt circuit.
Old 06-07-06, 07:52 AM
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Assuming you are correct about the direct burial cable (type UF-B), you can run the 10/2 the entire way. For protection, put the cable in conduit from the point it exits or enters the building through an LB fitting down to the bottom of the trench, and use a sweep fitting to transition from vertical to horizonal. I would also sleeve the cable in a piece of conduit under the driveway so the vehicle weight doesn't push a rock through the cable.

Fire up the ditch witch, the cable should be buried 18" deep. If the soil is rocky, you should also backfill a few inches of sand or peastone to protect the cable from damage by underground rocks.

Use only a 20A breaker in the house. While it's true that #10 wire can handle 30A, general purpose receptacles are restricted to 20A. Therefore, you can only use a 20A breaker without installing a subpanel. Install a switch for use as a disconnect as the first thing in the shed. Your receptacles in the shed must be GFCI protected, but lighting does not.

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