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Old 10-18-2008, 01:10 PM   #1
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wire size suggestions


I apologise in advance if this information is posted elsewhere, but sorting through all the posts here would take me a month.

I need to run 3 - 20 amp electrical lines to my shed:

1 for my lathe (small 120 volt/ 3/4 HP motor)
1 for other power equipment (never using more than 1 tool at a time)
1 for 6 48 inch florescent shop lights

I know the correct thing to do would be add a sub panel, but I rent this house and although the land lord would be thrilled to allow me to upgrade HIS electrical service, I am opting to add a few breakers from the main panel to get the juice where I need it. In other words, very long extension cords.

These runs will be about 70 to 80 feet long so my major concern is loss of voltage. I would appreciate recommendations on the size wire I should use.

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Old 10-18-2008, 01:43 PM   #2
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Well, you're likely to get many comments on this.

The main one is going to be DO NOT touch anything electrical in a place that you rent. This would be my first advice.

Second, you cannot legally run three circuits to a detached structure. Compounding the first advice, it would be even worse if you create a bunch of violations in doing so.

Sorry, that's all I've got on this one.

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Answers based on the 2008 & 2011 NEC.
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Old 10-18-2008, 02:07 PM   #3
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Thanks for the input Speedy Petey but the first thing about the renting is a non issue. The owner and I have discussed this situation and he will have one of his guys do the work if I will buy the materials. I'm just trying to make sure I get the right size wire so I don't burn a motor up due to low voltage issues.

That being said, I can work around the part about not being able to legally run three circuits to a detached structure by continuing to use an outlet that already exists on the side of the house to run the lights - assuming of course that you can run 1 circuit to a detached structure. Its inconvenient, but I can live with it. I would still like to run a single line from the breaker box for my lathe and other power tools.

Any additional thoughts would be appreciated much.
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Old 10-18-2008, 03:46 PM   #4
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wire size suggestions


Well, for the motor you could have 10 awg ran, how much does your motor pull? To keep the price for materials down, id use a ##/3 wire for the motor and outlet to share and 12/2 for the lights.

That would be 3 20 ampere circuits, and should be fine.

You cannot use extension cords like that, its a fire hazard and a nec violation.
I would have your landlord have somebody do it, and you pay for it. Be sure this guy is a REAL electrician!

Last edited by rgsgww; 10-18-2008 at 03:49 PM.
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Old 10-18-2008, 03:50 PM   #5
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Originally Posted by dkennedy View Post
Thanks for the input Speedy Petey but the first thing about the renting is a non issue.

Oh yes it is...
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Old 10-18-2008, 05:15 PM   #6
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wire size suggestions


You'd probably be better off running a 10/3 with ground UF to the detached structure with a 30 amp breaker feeding a small sub panel. It would be code-compliant with the no more than 1 circuit rule, and would provide the 3 circuits you are looking for with a little room to spare. You could get 2 good 20 amp circuits, with 10 amps each leg left over (more than enough for lighting). You could easily do 4 circuits at 15 amps each, or 2 circuits at 20 amps, and 2 circuits at 15 amps or any combination. Just put your two "heavy load" circuits on opposite legs of the panel to balance it out, and pick one for your lights on a 15 amp breaker.
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Old 10-18-2008, 05:28 PM   #7
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Perhaps I muddied the waters a bit with too many details and my own ignorance. The original idea has since been scrapped. Now that I think about it, it makes perfect sense that 3 individual lines from a breaker box to my shed would be illegal.

No more electricity than I use it just doesn't make sense to pay for a sub panel and all the assorted materials that involves, so I will opt for having 2 GFI outlets installed on the same side of the house that the shed is on and get a couple of 10 ft. heavy duty extension cords to plug into when I'm working on a project.

I know nothing about electricity so I'll leave the actual installation of the outlets to whomever the guy I rent from is sending to do it, but I want to make sure that his/her installation will suit my needs once everything is done.

The new and improved solution still requires that 120 volts and at least 15 amps of electricity be moved 70 or 80 feet, underground, from point A to point B. What would the recommended size and type of wire to make this transmission possible while keeping lost power to a minimum?
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Old 10-18-2008, 06:25 PM   #8
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Quote:
Originally Posted by dkennedy View Post
The new and improved solution still requires that 120 volts and at least 15 amps of electricity be moved 70 or 80 feet, underground, from point A to point B. What would the recommended size and type of wire to make this transmission possible while keeping lost power to a minimum?

If you have outlets on the side of the house, just get a heavy duty 12 (10 for least power lost)awg extension cord for your motor and drills, and just roll it up when your done.
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Old 10-19-2008, 03:33 AM   #9
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wire size suggestions


If you only want a 15 amp circuit run 70-80 feet underground with little power loss, you would probably be best off with running at least one size larger and going with 12gauge. You could do a 20 amp circuit underground and go with 10 gauge, which would probably be your better solution, get your lights on that circuit and a few good outlets.

One thing you might be able to do, (I'd wait for the electricians to chime in on this one) is to run like 12/3 with ground UF or 10/3 with ground UF on a double pole breaker in the main panel to 2 separate circuits in the shed. It would be a multi-wire branch circuit over one run of cable. I don't know if this would comply with the one circuit rule (technically its 2 circuits). Could get 2 20 amp circuits this way if it is allowed.
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Old 10-19-2008, 09:29 AM   #10
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Originally Posted by theatretch85 View Post
It would be a multi-wire branch circuit over one run of cable. I don't know if this would comply with the one circuit rule (technically its 2 circuits). Could get 2 20 amp circuits this way if it is allowed.

The NEC considers a multi-wire branch circuit as ONE circuit, but you still need a disconnect, but no GES is required, (aka: ground rods)
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Old 10-19-2008, 09:52 AM   #11
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If the cord is unplugged after use, and he uses GFCI quad, wouldn't that fall under temporary application?
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Old 10-19-2008, 12:13 PM   #12
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Quote:
Originally Posted by chris75 View Post
The NEC considers a multi-wire branch circuit as ONE circuit, but you still need a disconnect, but no GES is required, (aka: ground rods)
So there ya go, just install a double pole switch as your disconnect in the shed, finding one rated for 20 amps shouldn't be that hard to do. Install the switch as the first thing the wire runs into in the shed and then it would turn off both branch circuits. Might be able to get away with this also serving as your light switch, though it would turn off all your outlets at the same time too.
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Old 10-19-2008, 12:49 PM   #13
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Quote:
Originally Posted by theatretch85 View Post
So there ya go, just install a double pole switch as your disconnect in the shed, finding one rated for 20 amps shouldn't be that hard to do. Install the switch as the first thing the wire runs into in the shed and then it would turn off both branch circuits. Might be able to get away with this also serving as your light switch, though it would turn off all your outlets at the same time too.
Your supposed to have a means of disconnecting the entire multiwire circuit at once, so you go with a double pole breaker as an easy way of doing so.

Not to mention the requirement of physical protection of the wire and how you have to dig 24" deep if you go the romex way, 18" if you go with conduit.

Last edited by rgsgww; 10-19-2008 at 12:53 PM.
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Old 10-19-2008, 12:53 PM   #14
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Originally Posted by rgsgww View Post
Your supposed to have a means of disconnecting the entire multiwire circuit at once, so you go with a double pole disconnect.
Yes, and a double pole switch would satisfy that requirement, it would break both hot wires running into the detached structure. I was simply saying he may be able to use the disconnect switch as his light switch as well. There would be no reason to need a heavy duty disconnect for a MWBC rated at 20 amps or less. They make double pole switches rated at 20 amps, I know this because I have purchased them before.

The op (or the electrician) would simply have to clearly indicate on the switch plate that it is the service disconnect.
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Old 10-19-2008, 01:01 PM   #15
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Not to mention the requirement of physical protection of the wire and how you have to dig 24" deep if you go the romex way, 18" if you go with conduit.

Romex would be illegal to run underground, even if it is run in conduit. You must run UF (underground feeder) or conduit the entire run with individual THWN wires in the conduit.

The cheapest solution though would probably to just direct bury the UF cable, rather than running the conduit. The conduit would be required for protection where the UF cable exits the ground and enters the building (on both ends of the run). Direct burying UF cable however would require it to be buried deeper (24") than just conduit (18"), so that would be something to consider. You can still run UF in conduit, just make sure the conduit is sized correctly for the UF cable.

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