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installing electric to an outside shed

Posted by doityourselfer_2010 (My Page) on
Fri, Jun 18, 10 at 13:51

Would appreciate any assistance in getting electricty hooked up to an outside shed, that I occasionally use power tools in, such as band saw, table saw and the like.

I would like to know what size breaker I would need to install at the pole where the home power is hooked up.

what type/size wire

what else is needed.

I am going to run in underground plastic conduit about 18 inches, distance to shed is about 75 feet, would like to have 2 or 3 outlets as well as an overhead light.
I currently have a 15 amp breaker and 14/2 wire, don't think this is enough as I've had it hooked up before and when the light came on, I turned it off and the breaker kept tripping. Any assistance would be greatly appreciated. thanks


Follow-Up Postings:

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RE: installing electric to an outside shed

You can only have a single circuit to a detached building without putting in a sub-panel in the detached building.

The single circuit CAN be a multi-wire circuit, providing 120/240 V or a pair of 120 V legs without the panel.

A sub-panel in a separate building has special rules about grounding electrodes depending on if there is ANY metallic connection between the buildings (like water lines, phone, etc.)

"I turned it off and the breaker kept tripping"

Something is wrong with the setup.
Was this a GFCI breaker or a regular breaker?


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RE: installing electric to an outside shed

Southwire 14-2 Romex SIMpull NM-B- this is the wire I purchased, I hooked one end to the breaker in the box provided by the electic co. Hotwire attached to breaker, nuetral wire and wire connected to the neutral pole. I installed a light fixture, light switch and regular outlets in the shed, hot wire to hot side, ground to ground, nuetral to nuetral. From the pole, I attached the lead to the light switch from there I fed it to the light, which fed to the outlets. I turned the power one, doesn't matter what position the light switch was on, the light came on, once I turned it off, it would trip the breaker. At this point, after trying to figure out what was wrong, I removed the line from the pole, but still have everything wired as previously described in the shed. Is that where my mistake is or is it something other. Thanks for the assist.


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RE: installing electric to an outside shed

As stated, it sounds like your switch turns off the light and the outlets. Is this correct?
Is the breaker panel the main panel, i.e. the first point of disconnect after the meter? If not, then it's a subpanel and neutrals and grounds may not be connected together.
Also, as a 'potentially wet location', the outlets in the shed must be GFCI protected.
All of that said, I don't see how turning the light switch OFF would trip the breaker if it doesn't matter which position it was in when the breaker was turned ON. Was anything, like perhaps a motor or microwave, plugged into the outlets at that time? Have you tested the voltage at the outlets?
I would use 12/3 cable and a 20 amp double pole breaker with the most heavily used outlet on one leg and the light and other outlet(s) on the other. (JMHO)


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RE: installing electric to an outside shed

... the light was on, and when he flipped the switch to turn it off, the breaker tripped.

Fairly common mistake made by people who don't understand what they're doing. He wired the switch in parallel with the light, not series. He is concluding that "it didn't matter" because the switch clearly said OFF but the light was quite clearly ON. Obviously it DID matter, or else 'off' would not have existed, and it would be impossible for him to have tripped the breaker.

NM-B is also very much NOT the right wire to be using underground, but that will not cause the breaker to trip until several years from now when the wire insulation finally disintegrates enough to short.


He talks about a panel on a pole, so I'm guessing his main panel is outdoors, under the meter, and the house itself is a subpanel of that. In this configuration, a simple branch circuit off the panel under the meter would, in fact, have neutral and ground tied together... so at least he did one thing right.


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RE: installing electric to an outside shed/Clarity

Out of the wire that I can purchase from home depot/lowes what should I get. Breaker 15 or 20 Amp, conncected to the panel under the meter, running through, plastic conduit, connecting to a shed 100' away, wishing to run 2 or 3 outlets, and a light. will use for table and various drills and saws, no heat or air. What recommendations can anyone make that will facilitate my needs. Thanks in advance for your reply


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RE: installing electric to an outside shed

12/2 UF, 100 feet is $73.71 locally. 20A.

Using sheathed (NM, UF, etc) cable inside conduit gets weird, but you're allowed to do it where protection from damage is required/desired, and, if you ask me, any spot underground fits that condition.

On the shed end, wire all your outlets first, ignoring the light for now. Aim to make a loop around the shed, with the last outlet being the one closest to the switch. You apparently know how to wire outlets since you mistakenly wired your switch the same way. All in parallel. Black to black, white to white, etc., around the whole shed. Black goes to the side with the small slot, white to the other, connect your grounds together and pigtail to the green screw.

After you've wired up all your outlets, add another piece of 12/2 coming off the one closest to the switch. Run it TO the switch. Run another piece from the switch to the light. Inside the switch box, wirenut the two white wires together and connect/pigtail your grounds as well. When you've done this you'll have two black conductors remaining. One goes to each screw on the switch. If the switch has a ground screw, attach it.

You connected the panel end correctly: hot to screw on breaker, both other wires to neutral/ground bar.


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RE: installing electric to an outside shed

" if you ask me, any spot underground fits that condition. "

Except that UF (Underground Feeder) was designed and developed for direct burial.

It may require protection when it enters and exits the ground.

As noted, while switches have two screws, they do not use a neutral wire.
The switch is in the hot lines, so hot in , and hot out.


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RE: installing electric to an outside shed

NM cable isn't suitable for wet locations, and inside a buried conduit is (practically speaking) usually a wet location.

DIY: I suggest you buy a copy of Wiring Simplified and read it. Don't skip the chapter on basic electrical circuits.

Here is a link that might be useful: Wiring Simplified


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RE: installing electric to an outside shed

"inside a buried conduit is (practically speaking) usually a wet location. "

Inside a buried conduit is DEFINED as a wet location by the NEC.


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