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Old 05-25-2012, 12:57 PM   #1
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Electricity for Shed


I have a 12/2 wire in a junction box in my crawl space that currently powers two 20amp receptacles. These are both outdoors and are not used very frequently.

I just got a new shed and I'm looking to have two receptacles and one light in.

1. Can my current junction box handle this? Assuming I would run one 12/2 wire out to the shed and then daisy chain from that to the two receptacles and the light?

2. What is the best type of wire to use for running underground?

3. What is the best material (PVC, rubber etc) to encase the wire in?

4. Do I need a junction box on the outside of the shed?

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Old 05-25-2012, 01:59 PM   #2
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Electricity for Shed


Many of your questions can be answered using the search function and the terms shed and subpanel.

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Old 05-25-2012, 06:38 PM   #3
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Electricity for Shed


Quote:
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Many of your questions can be answered using the search function and the terms shed and subpanel.
Ahh, so THAT'S how you are able to make 4,430 posts
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Old 05-25-2012, 06:48 PM   #4
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Ahh, so THAT'S how you are able to make 4,430 posts
Jim Port is one of the most informed and helpful people on this forum. I suggest you listen to him and not make snide remarks.
You don't have the cred for your comment.
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Old 05-25-2012, 07:58 PM   #5
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Ahh, so THAT'S how you are able to make 4,430 posts
This from a guy who asked why the screws are so long....
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Old 05-25-2012, 08:52 PM   #6
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Electricity for Shed


Be nice---I suggest you put that shed circuit on a gfi from inside the house===any break in the wire under the ground should trip the GFCI--
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Old 05-26-2012, 06:24 AM   #7
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Electricity for Shed


I'm not a professional but here's my idea:

1. Can my current junction box handle this? Assuming I would run one 12/2 wire out to the shed and then daisy chain from that to the two receptacles and the light? Absolutely. if your shed is 50 feet out a 12/2 will handle up to 15 amps. http://www.csgnetwork.com/wiresizecalc.html
2. What is the best type of wire to use for running underground? It's all waterproof.
3. What is the best material (PVC, rubber etc) to encase the wire in? Some say the gray PVC, so future diggers will recognize it as electrical, not water.
4. Do I need a junction box on the outside of the shed? Every junction box is just another chance for something to go wrong.

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Old 05-26-2012, 06:38 AM   #8
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Electricity for Shed


Underground conduits are not waterproof. They will fill with water. This is why the insulation on the conductors needs a W in its' rating.

The use of a listed material is required so using hose or plumbing pipe would not be acceptable. Electrical PVC conduit is the easiest for a homeowner to work with but other options are available.

You could use type UF cable and protect it with a conduit sleeve. The sleeve would need to go from 18" below grade, 12" if GFI protected and 20 amps or less, to a point where it is no longer subject to damage above ground.

You will be fine with a 50' length of #12 at 20 amps. Some circuits in a house are longer than this.
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Old 05-26-2012, 06:47 AM   #9
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Quote:
Originally Posted by puttster View Post
I'm not a professional but here's my idea:

1. Can my current junction box handle this? Assuming I would run one 12/2 wire out to the shed and then daisy chain from that to the two receptacles and the light? Absolutely. if your shed is 50 feet out a 12/2 will handle up to 15 amps. http://www.csgnetwork.com/wiresizecalc.html
2. What is the best type of wire to use for running underground? It's all waterproof.
3. What is the best material (PVC, rubber etc) to encase the wire in? Some say the gray PVC, so future diggers will recognize it as electrical, not water.
4. Do I need a junction box on the outside of the shed? Every junction box is just another chance for something to go wrong.

Puttster
Puttster

You should stop giving advise. You are just confusing posters. Read alot more and post a lot less.
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Old 05-26-2012, 08:14 AM   #10
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Electricity for Shed


TB,

i did this project and here is what i would advise

1. your existing jb can handle another 12-2 only if there is sufficient room. if it currently has 3 cables in it, and you would be adding a 4th, that would require a box of at least 20.25 cu inch (4 black wires, 4 white wires, 1 ground) * 2.25 cu in per conductor

2. as Jim noted you can use UF cable sleeved when it is above ground or run thhn/thwn wire in conduit the whole way. i used 1/2 inch pvc. big mistake. use 3/4.

3. i agree with Jim on the 20 amps. my shed is only 30 feet from the house (40 total from the main box) and some of my other circuits are further from the box than that

4. whether its conduit or UF, bury to depth as required by local code

5. you dont have to have a junction box on the outside. there are many different ways to terminate the conduit run (we can elaborate when you get more specfic about your plans)

6. I used conduit for all wiring inside the shed as well (I didnt even check to see if it was required, i just did it)

Some considerations:
1. receptacles outside need to be weather resistant and gfci protected (the first receptacle in the shed can GFCI be or you can reconfigure some of the stuff inside your house) [do receptacles inside the shed need to be WR? i took the position that the shed was an outside location and put WR on both the receptacles inside the shed and on the outside]
2. In addition to a light in the shed controlled by a switch inside the door, I also put a light on the outside of the shed, over the door, controlled by a switch inside the house. this meant adding a switch box inside and running one more hot conductor in the conduit.
3. for all this work, consider future needs. if its just a storage shed, this is probably okay (that was my case). however, if you are thinking future workshop, adding A/C etc, consider a dedicated circuit or a MWBC. you cant run more than a MWBC unless you add a subpanel and the requirements for that are more complicated.

I am happy to post pics of any of this if you like

Last edited by kevinp22; 05-26-2012 at 09:34 AM.
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Old 05-26-2012, 08:21 AM   #11
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Electricity for Shed


You wouldn't have to install type WR devices inside the shed. Think about it this way? Kevin...you said you installed WR receptacles inside your shed, if so, did you install WP covers on all your devices?

One more thing to add to your list...the outlets in the shed...they need to be tamper-proof.
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Old 05-26-2012, 08:31 AM   #12
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no, they dont have covers on the inside. my usual overkill, i guess.

the good thing is that all WR rec (at least the ones at the HD here) are also tamper resistant
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Old 05-27-2012, 03:32 PM   #13
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Electricity for Shed


Quote:
Originally Posted by kevinp22
TB,

i did this project and here is what i would advise

1. your existing jb can handle another 12-2 only if there is sufficient room. if it currently has 3 cables in it, and you would be adding a 4th, that would require a box of at least 20.25 cu inch (4 black wires, 4 white wires, 1 ground) * 2.25 cu in per conductor

2. as Jim noted you can use UF cable sleeved when it is above ground or run thhn/thwn wire in conduit the whole way. i used 1/2 inch pvc. big mistake. use 3/4.

3. i agree with Jim on the 20 amps. my shed is only 30 feet from the house (40 total from the main box) and some of my other circuits are further from the box than that

4. whether its conduit or UF, bury to depth as required by local code

5. you dont have to have a junction box on the outside. there are many different ways to terminate the conduit run (we can elaborate when you get more specfic about your plans)

6. I used conduit for all wiring inside the shed as well (I didnt even check to see if it was required, i just did it)

Some considerations:
1. receptacles outside need to be weather resistant and gfci protected (the first receptacle in the shed can GFCI be or you can reconfigure some of the stuff inside your house) [do receptacles inside the shed need to be WR? i took the position that the shed was an outside location and put WR on both the receptacles inside the shed and on the outside]
2. In addition to a light in the shed controlled by a switch inside the door, I also put a light on the outside of the shed, over the door, controlled by a switch inside the house. this meant adding a switch box inside and running one more hot conductor in the conduit.
3. for all this work, consider future needs. if its just a storage shed, this is probably okay (that was my case). however, if you are thinking future workshop, adding A/C etc, consider a dedicated circuit or a MWBC. you cant run more than a MWBC unless you add a subpanel and the requirements for that are more complicated.

I am happy to post pics of any of this if you like
Thanks, my shed is about 160ft from the outside of the house where I would likely come out of the crawl space. What wire would a length such as that require?
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Old 05-27-2012, 05:49 PM   #14
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Electricity for Shed


The most you can draw from the junction box fed by 12 gauge wiring is 20 amps.

You would need 8-2 cable to get 15 amps @ 120 volts out to the shed with no more than 3% additional voltage drop from the junction box on out the 160 feet.

To avoid having two different feeds going to the shed and have a light at the shed controlled by a switch at the house, it is suggested you run a 14-3 cable, powered out at the shed, back to the house and directly to the switch box. This may share the conduit that has the feed to the shed. This provides unswitched hot, switched hot, and neutral to the switch box.
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Last edited by AllanJ; 05-27-2012 at 06:35 PM.
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Old 05-27-2012, 06:03 PM   #15
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Electricity for Shed


Quote:
Originally Posted by AllanJ
The most you can draw from the junction box fed by 12 gauge wiring is 20 amps.

You would need 8-2 cable to get 15 amps @ 120 volts out to the shed with no more than 3% additional voltage drop from the junction box on out the 160 feet.
Thanks, 8/2 wire enought to run two junction boxes in the shed and a light + switch?

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