ECN Forum Forums General Topics of the Trade General Discussion Area Customer Installed PVC

Bob, you can call me an MOB anytime. Showing off can be a good thing when you are right. 300.5(D)(5) is a good point to remember also.

Al

The difference of the "THHN or THWN" type conductor is the temperature rating of the conductor for ampacity rating.
If you use the "THHN or THWN" conductor (dual rated conductor) for underground, you can only use the THWN using the 75*C column of table 310.16, even for ampacity adjustment.
Example: 2 AWG THHN is rated for 130 amps at 90*C, 2AWG THWN is rated for 115 amps at 75*C.

Bob and Roger are actually College students who room together,and hatch this stuff up.

I think they learned it from two other guys named Ed and Bennie,who went to the same College.

(Ducking for cover)

Russell

Russell, no need to duck, being put in the same post with these three guys is quite the honor.

BTW, Bob keeps his side of the dorm room pretty neat.

Roger

Per PCBelarge' comments:
don't forget that the "weakest link" in the circuit governs. The terminals at equipment usually are rated at 60oC or 75oC, so that is the limitation on ampacity. i.e. Column to use in Tbl 310-16ff.
(310.15(B)FPN1

Very true energy7, luckily very few items are not marked as 75 C.

Bob

One time a customer did not want to wait for us so he ran 1 1/4 plumbling pvc. Nothing was glued together. He used plumbing elbows for bends. Under a new brick patio and 1/2 wall.

Tom

The "plumbing pipe" thing happens to me all the time. Customers call me after they have poured the patio and tell me they already installed the pipe for the hot tub to make things "easy" for me. It's usually 1/2 inch plumbing pipe and fittings no where close to where I need them. Thanks for the help!