Running THHN vs UF-B To Barn Subpanel

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Old 05-19-16, 07:58 PM
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Running THHN vs UF-B To Barn Subpanel

I am re-running wire to a barn sub panel that was incorrectly wired in the past. My electrician friend walked me through it today and mentioned running 10-3 with ground UF Through the basement to a junction box then running THHN through wall and through a 1 inch PVC conduit buried 18inches in the ground.
My question is why transition to THHN, is there a benefit to just running the UF-B through the conduit?

Thanks!
 
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Old 05-19-16, 08:13 PM
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is there a benefit to just running the UF-B through the conduit?
UF-b will be a lot harder to pull but no advantage unless you skip the conduit and direct bury it. You can use NM-b in the basement. Easier to strip and maybe a bit cheaper.
 
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Old 05-19-16, 08:16 PM
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I was wondering why UF in the basement and not NM?
 
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Old 05-19-16, 08:35 PM
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I could run NM in the basement, I was just trying to simplify things by only running one type of wire. But it seems like it might be cheaper and and easier to go from NM to THHN
 
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Old 05-19-16, 09:25 PM
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But it seems like it might be cheaper and and easier to go from NM to THHN
Yes, that is correct.

Conduit is good for two reasons. You only need to dig 18" for PVC conduit not the 24" for direct burial. More importantly if you oversize the conduit you can easily up size if in the future if you need more power. With one inch you can go as large as #4 in the future.
 
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Old 05-19-16, 10:01 PM
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is there a benefit to just running the UF-B through the conduit?
10-3 UF thru conduit.

Yeah..... don't even entertain that thought.
 
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Old 05-20-16, 07:19 AM
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Nitpicking. For separate conductors, use THWN or combination THHN/THWN rather than THHN in the conduit.

Underground conduit must be regarded as a wet location no matter how well it is sealed.

If, logistically, you need to splice anyway where the cable enters either building, you might as well transition to THWN for the underground run rather than take the effort to pull cable through the conduit.
 
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Old 05-20-16, 10:46 AM
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It is my understanding that the THHN that Home Depot sells is THHN/THWN is this correct?

Southwire 100 ft. 10 White Stranded THHN Wire-22974037 - The Home Depot
 
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Old 05-20-16, 10:52 AM
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Very, very, very likely it is dual-rated THHN/THWN-2. Double check the printing on the wire to be sure before you buy.
 
 

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