# PVC Permitted Uses



## 6506gary (Sep 20, 2010)

I have an installation that specs 2 inch PVC Sch 40 be installed outside on top of a retaining wall that is not subject to physical damage, is this permitted? The ambient temperature will not excede 122 degrees and the insulation will be THHN and will not be operated at a temperature higher than 122 degrees. The way I interpret Art 352, this is OK, however it seems I have read somewhere that it is not. What do you think?


----------



## McClary’s Electrical (Feb 21, 2009)

6506gary said:


> I have an installation that specs 2 inch PVC Sch 40 be installed outside on top of a retaining wall that is not subject to physical damage, is this permitted? The ambient temperature will not excede 122 degrees and the insulation will be THHN and will not be operated at a temperature higher than 122 degrees. The way I interpret Art 352, this is OK, however it seems I have read somewhere that it is not. What do you think?


 


Welcome to the forum. As described, it sounds compliant to me:thumbsup:


----------



## dawgs (Dec 1, 2007)

It is fine, but I would install expansion couplings.


----------



## Jlarson (Jun 28, 2009)

6506gary said:


> I have an installation that specs 2 inch PVC Sch 40 be installed outside on top of a retaining wall that is not subject to physical damage, is this permitted? The ambient temperature will not excede 122 degrees and the insulation will be THHN and will not be operated at a temperature higher than 122 degrees. The way I interpret Art 352, this is OK, however it seems I have read somewhere that it is not. What do you think?


Sounds go to me, I would have gone EMT though personally. You better paint the PVC cause the sun will bake it. The "sunlight resistant" rating is BS.


----------



## McClary’s Electrical (Feb 21, 2009)

Jlarson said:


> Sounds go to me, I would have gone EMT though personally. You better paint the PVC cause the sun will bake it. The "sunlight resistant" rating is BS.


 



He said, the job specs PVC,,,,how could you "go with" EMT??


----------



## Jlarson (Jun 28, 2009)

mcclary's electrical said:


> He said, the job specs PVC,,,,how could you "go with" EMT??


If the choice were mine it would be EMT. (read; I missed the spec. part)


----------



## voltz (Jun 2, 2010)

mcclary's electrical said:


> Welcome to the forum. As described, it sounds compliant to me:thumbsup:


are you sure?


----------



## voltz (Jun 2, 2010)

6506gary said:


> I have an installation that specs 2 inch PVC Sch 40 be* installed outside* on top of a retaining wall that is not subject to physical damage, is this permitted? The ambient temperature will not excede 122 degrees and the insulation will be *THHN* and will not be operated at a temperature higher than 122 degrees. The way I interpret Art 352, this is OK, however it seems I have read somewhere that it is not. What do you think?


highlighted portion of your post :no::no::no:


----------



## Jlarson (Jun 28, 2009)

voltz said:


> highlighted portion of your post :no::no::no:


At this point most almost if not all THHN is also rated THWN, THWN-2, and probably MTW and I think I saw some with AWM too once. Saying THHN is easier too.


----------



## jwjrw (Jan 14, 2010)

voltz said:


> highlighted portion of your post :no::no::no:





Are you saying pvc with thhn can not be ran outdoors?:blink:


----------



## Bob Badger (Apr 19, 2009)

jwjrw said:


> Are you saying pvc with thhn can not be ran outdoors?:blink:


You just have to be sure it is dual listed as THWN I _think_ all THHN is also THWN but I do not know that for sure.


----------



## jwjrw (Jan 14, 2010)

Bob Badger said:


> You just have to be sure it is dual listed as THWN I _think_ all THHN is also THWN but I do not know that for sure.




We must use the dual rated thhn. Its mostly what I see pulled here. I now realize it must have to do with the insulation being listed for a wet location.


----------



## raider1 (Jan 22, 2007)

jwjrw said:


> We must use the dual rated thhn. Its mostly what I see pulled here. I now realize it must have to do with the insulation being listed for a wet location.


Correct, THHN is not listed for use in a wet location, whereas THWN (Because of the W) is listed for use in a wet location therefore you would need to use a dual listed conductor.

Also remember that THWN (Not THWN-2) is only listed at 75 degrees C when used in a wet location. That is why when you look at Table 310.16 you will see that THWN is in the 75 degree column and THHN is in the 90 degree column.

THWN-2 is listed at 90 degrees C for wet locations.

Chris


----------



## Jsmit319 (Sep 23, 2010)

PVC is fine for that application, however the expansion coupler is a good idea. Your PVC will discolor and warp with the heat and sunshine, so like someone suggested earlier, paint it and you may want to add a couple of straps more than code requires. Don't forget your wiring has to be de-rated due to your max ambient temperature.


----------



## wayne g (Nov 28, 2010)

The conductors need a "w" in there.


----------



## raider1 (Jan 22, 2007)

wayne g said:


> The conductors need a "w" in there.


I think that has already been established in this thread.

Why are you resurrecting old threads?

Chris


----------



## Bkessler (Feb 14, 2007)

raider1 said:


> I think that has already been established in this thread.
> 
> Why are you resurrecting old threads?
> 
> Chris


For the fun of it, It thought all thhn was duel rated now?


----------



## raider1 (Jan 22, 2007)

Bkessler said:


> For the fun of it, It thought all thhn was duel rated now?


All the THHN that I have bought has be dual rated THWN-2 but that doesn't mean that they may not be some straight THHN out there.

Chris


----------



## Bkessler (Feb 14, 2007)

raider1 said:


> All the THHN that I have bought has be dual rated THWN-2 but that doesn't mean that they may not be some straight THHN out there.
> 
> Chris


I was told they don't make non duel rated wire anymore, by a pretty smart feller too.


----------



## raider1 (Jan 22, 2007)

Bkessler said:


> I was told they don't make non duel rated wire anymore, by a pretty smart feller too.


That could be.

Chris


----------

