4

I need to run some wires 235 feet in conduit.

Given the distance, I believe the sizes I need are three 3/0 AWG (000 AWG) and one 1 AWG for ground. I'm assuming all copper, and this is for 200 amps.

Can you confirm what size wire do I need? Can I run these wires that far?

Is 2 inch pipe enough room to pull these wires through?

isherwood
  • 137,324
  • 8
  • 170
  • 404
Christina Lewis
  • 41
  • 1
  • 3

1 Answers1

10

First, on wire this large, you should avoid using copper wire. Some people have heard some myths about aluminum wire - there was a grain of truth to that, but it only related to very small wire sizes - used in the smallest circuits in a home. However these heavy feeders are very large, and such large aluminum wires have always been reliable. We have 60 years of hard data on that.

Costly copper is so foolish that I'll proceed presuming you listened to the above advice.

For aluminum wire sizes for 200A service and for your 235 foot distance, the conductors should be a size called "250 MCM". For the ground you are OK at "1 AWG".

Those will just fit in 2" conduit. For easier pulling, consider larger conduit.

EMT metal conduit is not allowed underground at all but it is allowed outdoors above ground, and indoors obviously. You can use PVC conduit at 18" of burial depth (or rather of cover), or you can use rather costly RMC or IMC metal conduit at 6" of cover, except 12" under vehicle pathways.

Harper - Reinstate Monica
  • 300,628
  • 26
  • 286
  • 734
  • 3
    As an added bonus, the cash saved on buying AL instead of CU will probably cover the cost of the conduit and rental of a trenching machine to bury it. And maybe even a cold beverage when the job is done. – FreeMan Sep 28 '22 at 11:24
  • Harp, I gotta disagree that EMT is not allowed AT ALL to be buried. The 2017 code changed that. Below is a link that specifies it. That said, I'd never bury it and was surprised the NEC was revised to allow it. It's too thin and will rust out, probably to the extent the wires would be "glued in" by rust making them impossible to replace. Bottom line: It may be allowed now, but I wouldn't do it. https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=273.0 – George Anderson Sep 28 '22 at 11:52
  • 1
    I agree that 2" conduit is minimal for your application, 2.5" would be better, but the price of conduit is so ridiculously high right now that 235' run would cost you $1,700 (current price at home depot) JUST FOR THE CONDUIT. 2" would cost about $840. At this point, I'd consider running direct burial aluminum and dig a deep enough trench to make it code legal. Yeah, ppl here will snip me for suggesting not using conduit, it's just a comment, not an answer. Do go with AL in any case, you'd have to rob Fort Knox to pay for that amount of copper wiring. – George Anderson Sep 28 '22 at 12:04
  • Well worth shopping "real electrical supply" rather than home cheapo. Some things at home cheapo are absurdly priced, and they also simply don't carry stuff (no Sch 80 PVC in my area, for example). At least worth checking elsewhere. Also, considering that this is described (in a deleted answer that should have been an edit, but was not edited into the question) as a subpanel, not service, the service derate doesn't apply. – Ecnerwal Sep 28 '22 at 16:40
  • @Ecnerwal yeah, not sure why they call it Home Cheapo since it's not. The addendum in the deleted answer was simply a cut-paste of the question title, which I reworked when trying to turn it into an answerable question. – Harper - Reinstate Monica Sep 28 '22 at 22:08
  • @George that requires corrosion protection of some kind, and I'm not sure how you apply corrosion protection on the inside. Anyway that seems to apply only to the stub-up since that is the area subject to physical damage. – Harper - Reinstate Monica Sep 28 '22 at 22:15