PVC

[grosonke]

I am thinking of running PVC from a pole to a garage and using THHN but I have notice in many PVC installations that there has been water in the existing PVC can THHN stand this? Is this common to have water in PVC if so whats the answer.

 

[slicer]

Re: PVC

If you look at the wire, you will see that there are usually multiple listings. Most THHN is also THWN and MTW rated. According to Table 310.13, THHN may be used in dry and damp locations, THWN om dry and wet, and MTW in dry and wet.

Water in underground electrical conduits is a given. There is no way to avoid it. The pvc glue doesn't seal at the joints well enough to keep out ground water. You also have condensation that will build up.

Your alternative is to go arial with your feed. But that may not appeal to the visual senses. :roll:

 

[pierre]

Re: PVC

THHN/THWN conductors can be used in dry or wet locations, hence the dual rating. If you use it as THHN (dry location), you can use the 90 degree column for derating purposes. If you use it as THWN (wet location), you use the 75 degree column for derating purposes.
Regardless THHN (if not dual rated) cannot be used for wet locations, and underground installations are considered wet locations.

Pierre