not wet area wire in wet area -- what happens?

[lakee911]

Other than the code/permit inspection police hauling you away to electrical violation jail, what happens when wire that isn't rated for wet use is used in a wet area?

I've seen NM hold up outside (even buried!) or in damp locations just fine, but if THHN or other non-W wire, is used in an underground raceway that fills with water (which I'd consider worst case), will it cause problems?

Thx,
Jason

 

[sameguy]

over time yes it will degrade,could take a long time on soil make up before it corrodes or shorts out.

 

[al hildenbrand]

. . . what happens when wire that isn't rated for wet use is used in a wet area?

The material, the insulation is made of, isn't NRTL evaluated for the wet area. Depending upon the weirdness of the manufacturer's choice of the actual material that is on wire that you actually bought and installed, the insulation may, or may not, age prematurely and fail to act as insulation.

If the wire doesn't have a W rating, the manufacturer has a wider choice of insulation to choose from, and will most likely choose the material with the better profit margin. If it happens that the material chosen is a W capable material, but is not submitted by the manufacturer for the NRTL approval of that manufacturer's wire, then the wire will age well in a wet area. But its a crap shoot.

The NRTL approval, and the wire type (W), turn the crap shoot into a certainty.

 

[tom baker]

THHN has PVC insulation a bit of a nick in the jacket, water gets in and starts corroding the conductor. Nearly all UG conduits will be full of water.
I have seen XHHW fail in a water filled conduit.

 

[renosteinke]

In reality? It all depends on three things: the specific insulation, how wet it gets, and how heavily loadedthe circuit is.

So, in most cases, you can get away with it- at least, these days, with the most common wire types. Try it with the old tar-soaked cotton insulated wire, though, and things could get very interesting.

I caution against trusting your own common sense, though. For example, most folks assume thatboth "Bell" boxes and outdoor extension cords are just fine for use in contact with the soil - yet (at least in Reno) simple soil contact will eat the aluminum and rot the rubber in no time flat. For some reason, "direct burial" materials do not have this problem.

 

[juptonstone]

Not Just Nevada!

Not Just Nevada!

Florida too! The soil is acidic and eats everything. Never use aluminum wire... only copper - and avoid USE if possible. Make sure that you glue every joint and use THHN/THWN dual-purpose wire, or just THWN. It seems to hold up well in acid soil conditions with lots of water intrusion.