Wiring my shed with 10-3

Discussion in 'Electrical Forum discussion & Blog' started by jpmaddog, Mar 7, 2010.

  1. jpmaddog

    jpmaddog New Member

    Mar 4, 2010
    Hi, I have 80 feet of 10-3 underground wire and would like a light and an outlet in my shed that is 40 feet from my 200amp box. What is the simplest way to do this? (My level of experience is that I've run wiring for my Washer, Dryer, stove, microwave and bathroom.) Code wants me to buy a $15 permit and burry the cable 18" deep or 12" deep in conduit.

    What breaker do I use in my box?
    Must I have a subpanel box in the shed?
  2. drick

    drick In the Trades

    May 16, 2008
    10-3? How many rooms does you shed have?

    Well you can do a couple of things. You could put in a 20 Amp breaker, abandon one side of the 10-3 (ie don't use the red wire) and have a 20 amp circuit for a light and an outlet and not worry about the subpanel. You cannot run more than 1 circuit to an outbuilding without a subpanel in that building so this is basically the max configuration without a subpanel and is fine for what you said you need.

    OR you could put a 2 pole 30 Amp breaker in your panel and install a subpanel in your shed with the needed 15 and 20 amp breakers for outlets, lights, beer fridge , entertainment center, etc. You will also need ground rods for the sub panel. I would not go this route unless you like to spend money or have a reason to need that much power in the shed.

    Also your not supposed to run UF inside buried conduit. You can use it for physical protection for the wire when exiting the house down into the ground and back up out of the ground into the shed.

    Last edited: Mar 7, 2010
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  4. Lightwave

    Lightwave New Member

    Aug 20, 2007
    Vancouver, BC
    Unfortunately you've backed yourself into a problem. NEC requirements dictate using a subpanel if you want more than one circuit. The NEC also requires that outbuilding subpanels be connected to the main service ground via an insulated grounding conductor. For this, you need to run four wires--i.e. 10-4 cable or something similar.

    I don't know if it's acceptable to run a 110V-only panel and use the red wire as a grounding conductor.

    The most straightforward thing for you to do at this point is run the 10-3, leave the red wire unused, and feed the shed via a 20A GFCI breaker. Be sure to pigtale your 10ga wires with 12ga before connecting to outlets unless they're rated for use with 10ga wiring.

    If you need more than 20A, then you'll need to run a separate, insulated, grounding conductor, install a subpanel, and drive a few ground rods.
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Jan 5, 2008
    Test, Don't Guess!
    Land of Cheese
    UF needs to be 18" deep & rigid conduit only 6" if not run under a driveway.

    You can only run one circuit without installing a subpanel, which sounds like all you need. With the single branch circuit you are required to have a ground coming from the main panel. There must also be a disconnect in the shed, which can be regular snap switch.
  6. Jim Port

    Jim Port Electrical Contractor

    Aug 22, 2009
    Electrical Contractor
    I don't know how or where you came to this conclusion. Would you like to post the Article from the NEC?

    The grounding conductor can be bare like it is in the 10-3, or green. 10-3 UF has the required 4 conductors, black, red, white and the bare grounding conductor.
  7. codeone

    codeone Code Enforcement

    Sep 5, 2008
    Code Enforcement, Instructor
    North Carolina
    Maybe he was thinking about a subpanel feeding swimming pool equipment or a panel or disconnect feeding equipment on artificial or natural bodies of water, which does require an insulated ground in the 2008 nec. Articles 680 and 682 respectively.
  8. jpmaddog

    jpmaddog New Member

    Mar 4, 2010

    I called the permit guy and here's what he said:

    I need:
    A sub panel box with a main shutoff switch in the shed
    A 8' grounding rod at the shed
    To keep neutral and ground separate
    A 12" trench (which he must see)(and he recommends conduit)
    GFI protected outlets

    Now I have 3 questions:

    1. If I run the wire out the block wall to the outside, it will have to travel 4' down the outside wall to the ground. Does the UF cable need to be inside conduit and what keeps the top waterproof.

    2. The 10-3 UF wire is about 3/4 wide, should I use 1" conduit or would 1 1/2" or even 2" be better? (the trench will only be 40' long and it costs between $1 and $2.50 per 10 feet depending on size.)

    3. what does he mean by keeping the neutral and ground separate?
  9. drick

    drick In the Trades

    May 16, 2008
    This is not very useful without knowing what you asked him. But again I think a subpanel in the shed is overkill unless for some reason you need more than 1 20A circuit. You are potentially making this more expensive then it needs to be.

    The conduit should terminate inside the house. You need an 90 degree LB connector to go into the shed and into the house. And UF and THHN is waterproof. Underground conduit almost always ends up with water in it no matter how hard you try to keep it out. Just assume the inside of outdoor conduit will be wet and you'll be fine.

    The inspector should fail your install for installing UF in underground conduit. UF is rated for direct burial. It is not rated for installation in conduit. You should use single conductor THHN if this is the route you are going to go and you are having it inspected. With UF you can use a short piece of conduit for physical protection where it travels above ground into the shed and into the house but thats it. If you want to use the piece of UF you have start diggin.

    Way back when dinosaurs roamed the earth you could run just three wires, 2 hots and a neutral to the subpanel. That is illegal now. You must run 4 wires 2 hots, a neutral and a separate ground.

    Last edited: Mar 12, 2010
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