What is the recommended wire thickness to run between 125-150ft to a detached shed (home office)? I was thinking 60 amp breaker, 4/3 thwn-2 (2 hot, 1 neutral, 1 ground). Do I need more?

  • How many square feet is said shed, and how is it heated/cooled? What size is the service you're trying to run this off of? Dec 27 '20 at 0:10
  • Stating 4/3 with ground ? But then thwn-2 would require conduit a 4 wire feed will be needed unless in metallic conduit allowed to be used as the ground. you don’t provide a load so providing the correct wire size other than the feeder breaker that you have. Check out south wire and there voltage drop calculator.
    – Ed Beal
    Dec 27 '20 at 0:17
  • @ThreePhaseEel - 120 sqft, 200amp main, no heating or cooling.
    – Merkd
    Dec 27 '20 at 0:38
  • What are you running the THWN in, by the way? Dec 27 '20 at 2:18

#4 THWN aluminum is exactly what I'd use.

As far as voltage drop, 150' isn't far enough for voltage drop to become a concern. I don't even run the numbers until 180' :)

#4 THWN aluminum breakers at 70A (it's rated for 65A but you round up to the next breaker size which exists).

Because it's capable of 70A, you need a 70A ground wire, which is #8 copper or #6 aluminum. If aluminum, it must be insulated. You're allowed to use #4 aluminum, and the benefit is that you get to use black wire and mark it green with phase tape. #8 or #6 ground would need to be actually green or bare.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.