Putting electric in my shed, what size wire?

115339 Views 16 Replies 12 Participants Last post by jisco43, Aug 30, 2020

jdean0003

Discussion Starter · Jul 15, 2004 (Edited by Moderator)

Hello,

I saw another thread about burying wiring on here, but it did not answer all my questions so I thought I would list exactly what I am doing in hopes of getting some much-needed advice.

I have a storage/lawnmower shed behind my house. It is about 50 feet outdoors and about 50 feet indoors(including going up the walls etc.) from my breaker box to the shed. I plan to use Direct Burial Romex and run a phone wire to the shed. The shed is about 13' X 20'.

I am planning on using one set of wires for lighting. I will have two double-light fluorescent shop lights and four 75W spot-style lights.
Can I use 12-2 wiring for this on a 20 amp breaker?

For my other wiring, I want to be able to use a 115 Volt 5,000 BTU window unit A/C and have enough juice for a table saw or another type of power tool equipment and maybe a shop-vac running for dust collection at the same time. What size wiring and breaker do I need for this?

Or would it be wise to put a small breaker box in the shed for all of this instead? If so, how do I go about getting the wire to that? Can I break off of my breaker box on a larger breaker and run a large gauge wire out to the shed? IF so, what size? Would it be cheaper to run 6 or 8 gauge once than running two or three lines of 10 gauge?

I will not be using any type of 220 equipment out there ever.

Thanks for your time in advance. I am fairly new to household wiring when it comes to sizing and such. I am a fast learner, however.

Thanks again!!!

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1 - 17 of 17 Posts

fordy

· #2 · Jul 15, 2004

...................Go to Home depot or equivalent and BUY the necessary footage of #8 direct bury cable. It should contain 2 runs of #8 stranded with a #8 SOLID copper for the ground. Also pickup a breaker box that will hold a Double 20 amp breaker switch. This will give you a 20 amp breaker for each 120 volt HOT leg to hook to the Stranded #8 wires Too. On the House end go to the master panel and install a Double 20 amp breaker just like you did for the Shed end of the cable. Hook each #8 stranded wire to a 20 amp breaker and then run the solid ground\neutral to the common tie point inside your master panel. #8 direct bury with a ground is good for up to 50 amps as long as the Run is less than 100 feet. Now all you have to do is run a lenth of #12 ga. romex for your window unit and 14 ga. romex for the lights with switches in the appropriate locations...####Note the point for running 2-120 volt power legs to the shed is that ONE 120 volt leg will run your window unit.....and the other will run your lights and other tools . If you anticipate hooking up an aircompressor then run #12 for the lights and the aircompressor. DIVIDE the heavy Loads UP between the 2 -120 volt supply legs.....fordy.....

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G

· #3 · Jul 15, 2004

jdean0003 said:
Or would it be wise to put a small breaker box in the shed for all of this instead? If so, how do I go about getting wire to that? Can I break off of my breaker box on a larger breaker and run a large gauge wire out to the shed? IF so, what size? Would it be cheaper to run 6 or 8 gauge once than running two or three lines of 10 gauge?

Thanks again!!!

This is the _only_ way to do it. As the other reply says as well.

Get a 220 breaker from your basement box, run the bigger cable to your shed, and install a small breaker box there, split up into your different runs.

220v is really just a pair of 120 lines that added together make 220, but split apart will give you 2 seperate independent 120 lines. It is much much better to run the 220 and then split it into seperate 120 runs in your little shed. It is also not up to code to run 2 seperate 120 lines to your shed - not legal. You probably want to run a 30 amp (or 50 is better) wire to your shed, and then run smaller breakers in a box of 120 from there to your lights & outlets.

It will be _so_ much better to have the air conditioner on 1/2 of the 220, and the other power tools on the other 1/2 of the 220. Otherwise all you will have is popping breakers....

You are going to get into grounding issues, isolating the ground bar or bonding it. This conversation quickly gets into legal & NEC code jargin. I would strongly, strongly suggest getting a little booklet called 'Wiring Simplified" and study it, follow it. It shows you how to do this sort of thing legally & to code & safely. You probably need to run a 6 or 8 (I'm not sure, didn't look it up, but the booklet will have charts) cable with the 2 hots, a neutral, and a ground. It is real confusing as to why, but it is real important to not ever connect the neutral & ground together anywhere except at your master circut box in the basement. All other grounding busses need to be openned, not connecting the 2 - otherwise you defeat the whole point of the ground wire.

The breakers only protect the wire from heating up and melting, so you will need a big breaker in your basement, which protects the bigger wire heading out to the shed. Then the smaller breakers you use in the shed box protect each run of smaller wire from there.

This is just a little info, please don't rely upon it when it comes to playing with electricity, get good info from the booklet.

--->Paul

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Tractorman

· #4 · Jul 16, 2004

Hey I agree with Paul #8-4 conductor with a 50 amp breaker in the main panel and you will have capability of anything you will need. I am an licensed electrician so if you have specific questions let me know but sounds like Paul gave some good advice.

JWH123

· #5 · Jul 16, 2004

I just want to elaborate a little on what Paul says about keeping the neutral and ground separate. What he's saying is right on the money.

So you will need a wire with 2 hots (black and red), white, and ground.

http://www.homewiringandmore.com shows exactly what you need to do.

You cannot have the neutrals and grounds connected anywhere but in your main breaker panel, and there are some cases (outside the main disconnect, I believe is one of the cases), where they aren't even connected in your main breaker panel.

Anyhow, when you buy your small subpanel to put in the shed, make sure it either has two neutral/grounding busses (a bare aluminum bar with several holes to stick your neutral or ground wires and hold them in place with setscrews), or you will often need to buy the second ground bus. If you have to buy a separate one, this will be the grounding bus bar, and it will be attached directly (or at least have a strap electrically connecting it) to the metal of your sub panel. The original aluminum bar will now be your NEUTRAL bus bar. There should be a (probably green) screw that is called the 'bonding screw'. You do NOT want to screw this into the case of your panel. You will put the white wires all in the NEUTRAL bus bar (the one that is not electrically connected to the case). You will put all the bare copper ground conductors in the GROUNDING bus bar.

I'd recommend getting a "Main Lug" type of panel that doesn't have a main breaker handle. As long as you have less than 6 breakers in that panel, you don't need a main. You probably won't have much luck finding a sub panel with less than 4/8 spaces. 4 spaces if you use full-size breakers, 8 spaces if you use the 'tandem' breakers that fit 2 breakers in the space of one normal one. Of course, if you ever end up with a 220V need in this shed, a 220V breaker will take up two of those spaces. If the 'Main Breaker' type of panel is close in cost, I'd just as soon get that so you can have a main disconnect in your shed, it will save you a few steps if you ever do more wiring work in that shed.

PS a good source of information for further help that I like is www.handymanwire.com

Good luck!
John

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G

· #6 · Jul 18, 2004

uf direct burial cable is 60 c rated so # 8 wire is rated 40 amps not 50amps
needs to be 18" deep in the ground and protected with conduit where it comes out of the ground and is exposed on outside of buildings.
suggest you get black and deckers book on home electrical--- good book with great pictures and info.

after you finish take a picture and make a simple drawing where the trench with the wires are, measure from points you know will be there in the future, then if you do work in the area in years to come you'll know where not to dig.

ground all metal parts so that fault current has a path back to source.

kurt

aaatraker

· #7 · Jul 29, 2004

Unregistered said:
uf direct burial cable is 60 c rated so # 8 wire is rated 40 amps not 50amps
needs to be 18"deep in the ground and protected with conduit where it comes out of the ground and is exposed on outside of buildings.
suggest you get black and deckers book on home electrical--- good book with great pictures and info.

after you finish take a picture and make a simple drawing where the trench with the wires are, measure from points you know will be there in the future, then if you do work in the area in years to come you'll know where not to dig.

ground all metal parts so that fault current has a path back to source.

kurt

deepth should be 24" >>>>>>>>>>>>>>>>>>>kurt

agmantoo

· #8 · Jul 29, 2004

Here is a nice litle calculator for determining the wire size to run
http://www.stanselectric.com/vdrop.html

South of Forty

· #9 · Jul 31, 2004

A similar question is- If I want to run an electrical line from my pump house to a shed, ( about a 100 foot run), would it over load the main breaker box back at the house or the other wire? From the house to the pump house is about 200 feet.

Ross

· #10 · Jul 31, 2004

Your line and breaker to the pump house are likely sized to suit the job already being done. If the pump house has it's own breaker panel then you might be able to tap into it there. You'd need to know the wire size servicing the pump house and how many amps you need there.

deviator12000

· #11 · Aug 8, 2004

Breaker...........................Wire Gauge.........Description

7 amp.............................18 GA................lamp cords, door chimes
10 amp...........................16 Ga...............Fixture wires, extension cords
15 amp............................14 Ga...............Lighting circuit, Extension cords
20 amp............................12 Ga...............Recepticles, lighting circuits,
Fridge, pumps
30 amp............................10 Ga...............Clothes dryer, 240 V.A.C air
conditioner
55 amp...........................06 Ga................Electric Range, Central Air-Heat
Pump
Non-metalic cable (UF), "underground Feeder, is allowed in wet places, which means it can be buried.

deviator12000

· #12 · Aug 8, 2004

agmantoo said:
Here is a nice litle calculator for determining the wire size to run
http://www.stanselectric.com/vdrop.html

I went to the site, and copied it to my documents folder for future use. Thanks.

deviator12000

· #13 · Aug 8, 2004

South of Forty said:
A similar question is- If I want to run an electrical line from my pump house to a shed, ( about a 100 foot run), would it over load the main breaker box back at the house or the other wire? From the house to the pump house is about 200 feet.

you'd are still pulling your current from the house. Seems to me you'd need a heavy wire to the shed, and also a heavy wire to the pump. Resistance builds heat. The heavier the wire, the less resistance. Course, when I'm unsure, I always like to go overkill just to be safe, and you're running about 300'. "I" would think about the main breaker at the house. However, I would think that any resistance would start from the pump house backwards to the first breaker box. Makes sense. However I am not an electrician. Just food for thought.

morrowsmowers

· #14 · Aug 13, 2004

If you are burying wire it would be much easier to run conduit. You can then pull out wire if a repair is needed without digging up the yard again. Also, if you use large conduit now you can easily run larger wire later if your needs increase. Also, you mentioned running a phone line to the shed, that will have to be run seperately from the electrical lines and should be in its own conduit. I'm in the midst of running power to my shop/shed now and lines are going in conduit and topped with concrete for protection. I'm running a 60A feed from the house to the shed, feeding a subpanel with 80A capacity but not using it fully, and then tapping off my 120V lines from the subpanel at the shed.

Ken in Glassboro

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[email protected]

· #15 · Aug 4, 2020

Tractorman said:
Hey I agree with Paul #8-4 conductor with a 50 amp breaker in the main panel and you will have capability of anything you will need. I am an licensed electrician so if you have specific questions let me know but sounds like Paul gave some good advice.

Hey I have similar questions. I'm running electrical to two sheds that have a 100 amp breaker box installed. Will be installing seven outlets for small power tools and possible 110 air conditioner. With overhead light and porch light. Could you please explain to me exactly what wiring I will need to properly do this. And what type breaker needed to wire to house breaker box. Tia

[email protected]

· #16 · Aug 4, 2020

deviator12000 said:
Breaker...........................Wire Gauge.........Description

7 amp.............................18 GA................lamp cords, door chimes
10 amp...........................16 Ga...............Fixture wires, extension cords
15 amp............................14 Ga...............Lighting circuit, Extension cords
20 amp............................12 Ga...............Recepticles, lighting circuits,
Fridge, pumps
30 amp............................10 Ga...............Clothes dryer, 240 V.A.C air
conditioner
55 amp...........................06 Ga................Electric Range, Central Air-Heat
Pump
Non-metalic cable (UF), "underground Feeder, is allowed in wet places, which means it can be buried.

I'm running electrical to two sheds that have a 100 amp breaker box installed. Will be installing seven outlets for small power tools and possible 110 air conditioner. With overhead light and porch light. Could you please explain to me exactly what wiring I will need to properly do this. And what type breaker needed to wire to house breaker box. Tia

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jisco43

· #17 · Aug 30, 2020

jdean0003 said:
Hello,

I saw another thread about burying wiring on here, but it did not answer all my questions so I thought I would list exactly what I am doing in hopes of getting some much needed advice.

I have a storage/lawnmower shed behind my house. It is about 50 feet outdoors and about 50 feet indoors(including going up the walls etc.) from my breaker box to the shed. I plan to use Direct Burial Romex and to run a phone wire to the shed. The shed is about 13' X 20'.

I am planning on using one set of wires for lighting. I will have two double light flourescent shoplights and four 75W spot style lights.
Can I use 12-2 wiring for this on a 20 amp breaker?

For my other wiring, I want to be able to use a 115 Volt 5,000 BTU window unit A/C and have enough juice for a table saw or other type of power tool equipment and maybe a shop-vac running for dust collection at the same time. What size wiring and breaker do I need for this?

Or would it be wise to put a small breaker box in the shed for all of this instead? If so, how do I go about getting wire to that? Can I break off of my breaker box on a larger breaker and run a large gauge wire out to the shed? IF so, what size? Would it be cheaper to run 6 or 8 gauge once than running two or three lines of 10 gauge?

I will not be using any type of 220 equipment out there ever.

Thanks for your time in advance. I am fairly new to household wiring when it comes to sizing and such. I am a fast learner however.

Thanks again!!!

12 - 2 URD which is direct burial. The 20 amp breaker will be plenty. Most people buy and install small 30 amd Disconnect boxes. They are more or less mini breaker boxes and would mount inside the shed. You could add two, 15 amp breakers and put lights on one and use the other for 3 or 4 outlets.

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