ECN Forum Forums Code Related Discussion NEC & other Code issues Romex in pipe

Al,

I think if you look closely at the wire you will see that it says both THHN and THWN meaning it is approved as both.

Bill

Bill:
Is Romex rated both thhn and thwn ? I know stranded wire is rated both but I think Romex is only rated for dry locations. Ergo, pvc under ground would be considered a Wet-location. No ?

Where do you find that this is allowed?

-T

>>Is Romex rated both thhn and thwn ? I know stranded wire is rated both but I think Romex is only rated for dry locations. Ergo, pvc under ground would be considered a Wet-location. No ?<<

You're correct. I think we're talking about 2 different things here at the same time. I was saying to Al, that, what we commonly call THHN is also (always?) labelled and rated THWN if you look at the wire. Maybe that was why He thought THHN would be allowed in conduit outside and underground.

Bill

[This message has been edited by Bill Addiss (edited 12-12-2001).]

Isn't it the clear plastic coating on THHN/THWN that makes the W possible in THWN?.

BTW,
Does a conduit installed above ground outdoors require wiring rated for wet locations? I say yes. Supply house man says no.

[This message has been edited by Redsy (edited 12-13-2001).]

Redsy,

I don't know about the plastic covering, but I read in an NEC Handbook that the intent was that the interior of a conduit (outside) be considered a wet location. I've also heard that from a UL rep when it was brought up at a local meeting.

Bill

Responding to Nick,
Why wouldn't THHN be allowed underground, if it is completely weatherproof. How else would you run circuits underground not using UF?

THWN is allowed... And I'm betting dollars to donuts that your THHN is also marked THWN and therefore compliant...



[This message has been edited by sparky66wv (edited 12-13-2001).]

aldav53,
There is no such thing as a dry underground conduit. You must us a wet location wire. Air moves in and out of the conduit carrying with it water vapor. When the air cools in the conduit the water vapor condenses out leaving water in the conduit. Over a period of time the conduit will fill with water.
Don(resqcapt19)

aldav,

The whole point is, underground conduits are not weatherproof at all. The "W" is required in the designation if it is to be installed in a wet location. Look at table 310.13 and notice that all (except MI) conductors allowed in wet locations have a "W" in the (Type Letter) column.