wire thhn

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butcher

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i have an electrical inspector in another city that says that thhn can not be used in conduit in the underground but,will let you install it(thhn) in conduit along the side of a building in conduit or as service riser.i would like to know if thhn can be installed in the underground in conduit.what is the difference?
thank you for your time in this matter.

butch hass
 
Re: wire thhn

Wouldn't it need to be THWN or any other variant with a "w"? (310.8 (A) - (C) Locations)

See 100 (definitions):
Location, Damp.
Location, Dry.
Location, Wet.
The differences are explained there.


Some THHN is labeled as THHN/THWN/THWN-2 and can be used underground as per 310.8 (A) - (C).

Wire labeled as ONLY THHN cannot be underground.

What kind of inspector are you? Elec., plumbing, fire, home?
 
Re: wire thhn

Originally posted by triphase:
T= thermoplastic H= 75c HH= 90c N= nylon W= moisture resistant
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In wet locations it is only 75deg.

Roger
 
Re: wire thhn

Originally posted by don_resqcapt19:
Has anyone ever seen any THHN that was not also marked as THWN? I never have.
Don
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I actually went and physically checked a roll, also...mine also was marked -2.

Someone may be still using the first roll of THHN ever made - w/o the other types listed :D

[ January 11, 2006, 04:58 PM: Message edited by: celtic ]
 
Re: wire thhn

I believe that any outdoor location, whether above or below grade, is 'wet' unless the under-canopy, -roof, etc. exception applies. Inside a conduit is not considered any drier than outside it.
 
Re: wire thhn

I too, have never seen any THHN that did not say THWN on it somewhere.

Maybe I better keep looking.
 
Re: wire thhn

Originally posted by don_resqcapt19:
Has anyone ever seen any THHN that was not also marked as THWN? I never have.
Don
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I haven't either; it's usually THHN/THWN/MTW and most are now appended "-2."

Edit: corrected the designators from lower to upper case

[ January 12, 2006, 03:28 AM: Message edited by: rbalex ]
 
Re: wire thhn

Well, If memory serves me correctly, they didn't make any THWN until they found out that the THHN would not hold up under water. It would keep blowing holes through the insulation. Some how the water in conduits was too impure and provided a good ground path.

:D :D What are you guys? A bunch of newbies? :D :D
 
Re: wire thhn

Nope! Not a "nubie" yeah dirty water makes a good ground path and been in the trade for 18 years and have pulled out a lot of THHN "Old Stuff from the 70's" out of pipe that failed. "Good Point" However, the new designations / use need to be addressed.
 
Re: wire thhn

Originally posted by dlhoule:


:D :D What are you guys? A bunch of newbies? :D :D
Click to expand...
Anyone got a washcloth...I feel a little dampness behind my ears
sporty.gif
 
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