Wire size to run 200' to a shed

Question

I want to run a 60 amp sub panel to my shed 200'+ out back. This will only run a few lights, an outlet and run to a chicken coop for a heat lamp in the winter. What size wire would get it done? I will be putting it below ground in conduit. Thank you for any help or guidance you can give.

Answer 1

The capacity of the sub-panel isn't what's important, you could put in a 200 amp panel configured as a sub-panel and feed it with 14 ga wire on a 15 amp breaker. Not a good idea at all, but it could be done. The wire size all depends upon the maximum load and distance. in your case #6 ga copper would provide you with about 50-55 amps, depending upon temp derating. Are you planning on a 240v sub-panel? If so, that would require 2 hots, a neutral and a ground. If only 120, it would need 1 hot, 1 neutral and a ground. Running large copper that far would be expensive, you might consider aluminum #4gauge for that distance. Don't forget the "goop" (NOALOX) compound if you go AL. You could get by with smaller wires, but like I said, it's all about the maximum load and distance. There's tons of info here at SE on installing sub-panels. I suggest you do a search and you'll be inundated with answers!

EDIT: In reviewing my answer I find it somewhat incomplete, so here goes with the EDIT: The panel must be rated for AT LEAST the maximum power supplied to it. There is nothing wrong with installing a sub-panel with a capacity LARGER than the supply to it. That is commonly done. I have a 200 amp panel in my shop fed by a 100 amp breaker. I did that just so I'd have enough breaker spaces for my tools.

For us to better help you, add up all the loads you can think of that might be running at the same time. Going big on sub-panels isn't very expensive...going big on wire (esp. copper) on a long run can really run up the $$$, so a reasonable assessment of the loads is important. So get back to us with the info for perhaps better advice.

Answer 2

The lights are rounding error.

The outlet is 12.5 amps "worst case to plan for".

The heat lamp is 1 amp @ 120V, maybe 2 amps worst case.

So a 20A/120V circuit is adequate. 60A/240V is wild overkill, and I'd guess you said that because it's something you heard somewhere, or because that's the panel you saw in the store that seemed just right. But hold that thought.

On the panel, as George says it's an absolute maximum like the 112 mph speed rating on your car tires... not a mandatory. The important thing is the number of breaker spaces needed to serve your current and future needs. You never want to run out of breaker spaces. It creates unnecessary trouble and expense that is easily avoided when you are buying the panel. Panel spaces are cheap.

By the time you get a panel with plenty of spaces, you are usually at 100A bus rating or higher. But that's just a rating like tires.

Voltage drop

The problem is, carrying 120V long distances, "voltage drop" is painful. 10 AWG x 2 conductors + ground ($1.08/foot) , you're still at 4.55% voltage drop running one plug-in circular saw alone.

But going to the next size up, 8 AWG x 2 conductors plus ground ($1.91/ft), makes no sense whatsoever because that wire would cost more money than 2-2-2-4 MH feeder.

2-2-2-4 is at a pricing "sweet spot" because they use a LOT of it.

If we re-factor this thing for 2-2-2-4 MH feeder ($1.20/foot), then your "worst case" 120V 12.5A load comes in at 1.27% voltage drop. That's very acceptable.

You will be able to circuit-breaker this 2-2-2-4 at 90A at the panel (75A in Canada) but only plan to use 72A at most.

That's gonna work :)

There's nothing wrong with aluminum at these large sizes. Now, you could go backwards on the aluminum track and try #6 aluminum at 240V (80 cents a foot for all 4 wires). You can breaker that at 50A (30A in Canada) and plan to use more like 30A.

Canada numbers are lower because they are militant on voltage drop. NEC gives you the freedom to make that call for yourself.

240V at even 50A is gross overkill for your requirements, but this is how the costs are working out. Using smaller wire is more expensive (paradoxically) and I don't recommend aluminum smaller than #6 because home-buyers have prejudices against it.