# Running 240 to outbuilding



## Ditchmonkey (Oct 19, 2016)

I have a 100SF cottage that I want to run power to. My initial idea was to put a 30 amp breaker in the garage and run wires to the cottage. The run would be about 170 feet, and calculators state I would probably need a 6 or even 4 gauge wire, and my eyeballs just about popped out of my head when I priced that wiring.

I talked with a local electrician about it and he said I should run 240 to a subpanel at the cottage, and run 2 20 amp circuits in the cottage. This would let me get away with running 10 gauge wire. Sounds good to me!

However, I'm a complete newbie when it comes to electricity. Can someone fill in the details for me on how/why this works? It seems counter intuitive that I am doubling the voltage, but reducing the gauge of the wires. Can someone explain the basics of how this works?


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## Sparky617 (Oct 19, 2016)

Even 12/2 is rated at 600 volts.  The rating you need to worry about is the amperage not the voltage.  Each leg is only going to be carrying a nominal 120 VAC.  To get nominal 240 VAC you need to connect to both hots.


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## nealtw (Oct 19, 2016)

I think the first question is what you want to do with it. A couple lights, a heater? Look at all possible uses because doing it once is bad enough, replacing it because it wasn't big enough is a lot more expensive.


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## Snoonyb (Oct 19, 2016)

Ditchmonkey said:


> I have a 100SF cottage that I want to run power to. My initial idea was to put a 30 amp breaker in the garage and run wires to the cottage. The run would be about 170 feet, and calculators state I would probably need a 6 or even 4 gauge wire, and my eyeballs just about popped out of my head when I priced that wiring.



Current caring derates at each 100', so a 120V 30amp @ 170' would be near it's safe limit with 8ga stranded conductors.



Ditchmonkey said:


> I talked with a local electrician about it and he said I should run 240 to a subpanel at the cottage, and run 2 20 amp circuits in the cottage. This would let me get away with running 10 gauge wire. Sounds good to me!



You've received some competent advise. Did you by chance discuss the code in your area regarding direct burial, or conduit and the depth, as well as grounding for the subpanel?

A subpanel allows you greater flexibility for distribution, as opposed to a large "J"box.


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## Ditchmonkey (Oct 19, 2016)

Snoonyb said:


> You've received some competent advise. Did you by chance discuss the code in your area regarding direct burial, or conduit and the depth, as well as grounding for the subpanel?
> "J"box.



I live in the country and I don't plan to get inspected, however I am concerned with safety. I plan to run conduit, but probably at just 12 inch depth so I can run in the same trench as existing PVC water piping. I figure I know it's there so the depth should be fine. Already doing better than the non-conduit line the previous owner ran across the property to the well.

I plan on having an electrician hook all this up. I just want to buy the wire and get the wire/conduit in place myself. Just wanting to make sure I get the right stuff.


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## Ditchmonkey (Oct 19, 2016)

nealtw said:


> I think the first question is what you want to do with it. A couple lights, a heater? Look at all possible uses because doing it once is bad enough, replacing it because it wasn't big enough is a lot more expensive.



Not much. 3 lights, 2 outlets, and maybe a 4amp convection heater (or maybe propane), but nothing bigger than that in terms of heat. The biggest load it will see is on occasion I'll turn everything off and run my circular saw off one of the outlets.


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## nealtw (Oct 19, 2016)

Ditchmonkey said:


> Not much. 3 lights, 2 outlets, and maybe a 4amp convection heater (or maybe propane), but nothing bigger than that in terms of heat. The biggest load it will see is on occasion I'll turn everything off and run my circular saw off one of the outlets.



The saw would be 10 to 13 amps and pulls the limit when doing a long deep rip in wet lumber.

I would go with as much as I could that makes you comfortable with the budget.
Something like a range.
Pvc conduit should be at 18" and for the extra work I would go that deep and water pipe above it will protect it from someone digging in the wrong place.:nono:
Others here no better about sub panels.


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## Snoonyb (Oct 19, 2016)

Ditchmonkey said:


> I plan on having an electrician hook all this up. I just want to buy the wire and get the wire/conduit in place myself. Just wanting to make sure I get the right stuff.



!8 too 24" depth is safe because there a few casual implements that will attain that depth.

Ask the electrician if they are willing to accomplish the connection for you, without a permit, as some will not, because of the liability. They should also make a visit prior to the start to advise you about specific equipment you may need for the service and subpanel entry.


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## nealtw (Oct 19, 2016)

I did some work on a farm and I saw a hook screwed into the barn just above the foundation. Not heavy enough to hold a dog so I asked.
It turned out he had a hook on every building where the power cables were so he could just pull a string between buildings to mark where the cables were. He said it came in handy when they had to put drainage around the barn.


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## kok328 (Oct 20, 2016)

Before you go out and purchase anything or dig anything, find an electrician that is willing to work with you on this project.  Speak with him about your plans and what HE wants to see.  Otherwise, nobody is going to wire up anything because they will be liable and were not the person that installed EVERYTHING start to finish and don't know if it was done correctly to code.  You'll also have problems finding and electrician that will not pull a permint and have a final inspection, their license is on the line and not worth losing everything because somebody else did something wrong.


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## afjes_2016 (Oct 21, 2016)

Once you decide exactly how many amps you want in the cottage then the size of the conductor/s is determined along with the length of the run. At that point the type of conductor/conduit (if used) is determined. Then the bury depth is regulated by this chart HERE.

Also be sure that there are 4 conductors sent to the cottage. Two hots, one neutral and a ground wire. Since the cottage is detached a ground wire (of sufficient size by code) should run from the sub panel to a ground rod (preferrably two ground rods at least 6 feet from each other and the ground wire continuous from panel to the last ground rod without a break or splice) Also since it is a sub panel the ground and neutrals should be separate from each other. The ground bar is bonded to the panel while the neutral is isolated from the panel.


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## Mastercarpenty (Oct 21, 2016)

When you double the voltage it takes half of the current-carrying capability in the wire so you can use a smaller size wire (Ohm's law) Code calls for a subpanel and earth grounding at the remote location (safety), and that's not expensive for only a few circuits there.  I agree on the burial depth being proper. If you haven't dug yet just go that deep then fill over the conduit till you reach the water line level. And you should do permits and inspections to cover your butt when the property gets sold and to allow for insurance coverage.

You'll have to ask but most electricians will probably let you run the conduit, maybe pull the wires through it, plus drive the ground rods in- that's the hard part of the work which helpers usually do and that will save you money. They may also let you mount the panel and boxes and maybe even rough in the wiring in the building if you know what you're doing, But that's going to be an individual thing because in the end they have their license on the line for the entire job plus they want to make a little profit like we all do.

Phil


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## Ditchmonkey (Oct 27, 2016)

kok328 said:


> Before you go out and purchase anything or dig anything, find an electrician that is willing to work with you on this project.  Speak with him about your plans and what HE wants to see.  Otherwise, nobody is going to wire up anything because they will be liable and were not the person that installed EVERYTHING start to finish and don't know if it was done correctly to code.  You'll also have problems finding and electrician that will not pull a permint and have a final inspection, their license is on the line and not worth losing everything because somebody else did something wrong.



I had an electrician out and got some good info. I have a question now regarding the subpanel on the outbuilding. Does it matter where it is placed on the outbuilding? I have a spot about 2 feet off the ground that would be ideal and sheltered from the weather.


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## Snoonyb (Oct 27, 2016)

Inside would be the Ideal location.


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## JoeD (Oct 27, 2016)

It needs to have proper working clearances the same as a main panel. 2 feet off the ground would not meet that criteria.


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## Ditchmonkey (Oct 27, 2016)

Snoonyb said:


> Inside would be the Ideal location.



Heh yeah now that you say that - obvious really. :facepalm:


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## Kabris (Oct 28, 2016)

Generally the sub panel is installed inside wherever your feeders meet the building, and installing it in a location with sufficient working space. Joe is right about the 2 feet. I will normally measure the top of the sub to around 6 feet.


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## afjes_2016 (Oct 28, 2016)

Ditchmonkey said:


> I had an electrician out and got some good info. I have a question now regarding the subpanel on the outbuilding. Does it matter where it is placed on the outbuilding? I have a spot about 2 feet off the ground that would be ideal and sheltered from the weather.



Where did the electrician suggest that the sub panel be placed?

Again, inside is ideal and following the space clearance code for the panel would be good also. I would hope that the electrician did not suggest placing it only two feet off the ground.

I don't know what part of the country you are in but if in a snow-belt or something like that snow can pile up against it and block entry to it when needed.

Is there any particular reason why you would not want it on the inside of the cottage?


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## JoeD (Oct 28, 2016)

They do make exterior panels but you still need the clearances.


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