A Little Help Please

[ptonsparky]

Tom -
Why is this? I don't recall any regulation or installation directions that would prevent putting pipe dope on say underground conduit threads. But this would only be the second one I have wrong on this subject:-?

AFAIK conduit threads, with pipe dope, wrench tight, are electrically connected.

carl

Doesn't have to do with grounding. Has to do with an explosion occuring inside an enclosure that is gas tight. The expanding gas could burst the enclosure allowing ignition of surroundiing gases. The idea of the 5 threads is to allow the gases to cool as they escape the enclosure or raceway, not contain the explosion. Pipe dope, silicone or whatever applied to the threads prior to installation would increase the internal pressures. Source is NEC 2002 Code Review by Appleton. Also what I was taught in school and various other seminars.

 

[coulter]

.... The idea of the 5 threads is to allow the gases to cool as they escape the enclosure or raceway, not contain the explosion. Pipe dope, silicone or whatever applied to the threads prior to installation would increase the internal pressures. ...

Yes, I was aware of that. And, of course, the prohibition of sealer on the milled surfaces for XP switch boxes - same reason, to let the hot gas cool as it escapes. I always figured they wer discusing the large diameter threads on screw-on caps, or the milled mating surfaces

I just had not remembered seeing anything in the equipment installations instructions that prohibited using sealer or lubrication on threads. In fact, Coruse-Hinds puts an anti-sieze compound on the aluminium cap for GUA series - have to, or they are one piece the next year.

carl

 

[coulter]

So, as long as I use Crouse-Hinds instead of Appleton - I'm okay

carl