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I would like to run two new outdoor electric lines to two locations in my yard.

I would like to run two new outdoor electric lines to two locations in my yard.

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  #1  
Old 05-26-19, 01:37 PM
Ninarina's Avatar
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I would like to run two new outdoor electric lines to two locations in my yard.

One location is a 3 vehicle carport which I just need some lights, 2 ceiling fans and some receptacles. Nothing too fancy except it might be nice to be able to run a compressor in there for working on vehicles or woodworking things. The builder already put a 50 amp service on the side of the house anticipating this project. It's 75' from the house.

The other location is where there is a concrete pad from an old mobile home. I would like to put a 12 x 20 shed on that slab and use the building mostly for storage and maybe small stuff like running a drill. Having a 6000 btu window AC would be a dream if possible. It's 75' in the attic and then 100' outdoors to the shed location.

Because of the mobile home having been there, I found the ground rod when I was doing irrigation, so I ran my trench to that location for the shed electric assuming it would be useful.

Please look at my drawing and photo. You can almost make out the concrete slab on the right in the photo.

I happen to have a 100' roll of 8/2 romex which I would love to be able to use in the attic portion of the shed electric project before transitioning to the UF cable outside.

Because it's heading into the hottest part of the year, I just want to put the UF cable in the ground until fall when the rest of the project will be completed. I did the trenching for this electric when doing the irrigation project.

Please advise me what kind of electrical "box" subpanel etc. I should get and what kind of UF cable to buy and lay in my trenches.
 
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Last edited by Ninarina; 05-26-19 at 02:01 PM.
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  #2  
Old 05-26-19, 03:41 PM
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If you want the full 50 amps to the carport you would need 6/3 UF with ground. The panel size in the carport can be anything rated 50 amps or more.

The 8/2 will get you 40 amps max but it will only be 120 volts as you need 4 wires for 120/240 volts service. That would still have no problem running an A/C if you wanted. However, since you are going through the trouble, I would recommend running a 3 wire cable (with ground) out the shed as well. Again, the panel you put in the shed needs to be rated the same or higher than the breaker feeding it. 8/3 will get you 40 amps, 6/3 will get you 60 amps.
 
  #3  
Old 05-26-19, 05:25 PM
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Thanks so much for your reply. The question I'm concerned about is the distance vs the wire size.

If I have to run the shed electric wire through the attic for 75' and then through the yard for another 100' to the actual place where the ground rod is, can I still do 30 amps with a 8-3 awg at the distance of 175 feet? I was reading about voltage drop etc.
 
  #4  
Old 05-26-19, 06:20 PM
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Just an FYI voltage drop will vary depending on the load on the circuit, not the breaker rating.

At a 30 amp load @ 120 volts @ 175' run your voltage drop would be 5.5% using #8 copper. A little bit higher than recommended, but still in the +/- 10%.
 
  #5  
Old 05-27-19, 11:17 AM
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I would have recommended #6 for the run to the shed/trailer pad to get the voltage drop down under 4%.

Do a load calculation (sample rules at the back of the NEC book). Include the equipment you propose to use e.g. compressor, air conditioner, electric car charger. It is possible that for a project this size you may need to upgrade the service from the meter in order to pass code.
 
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