I’m running some EMT conduit across my roof for some conductors for a PV system. It is supposed to be a ” water tight installation”. The EMT conpression couplings I bought to connect the pipe say they are water tight – no problem. My question is about the EMT conector that screws into the threaded junction box. Is that connection considered “water tight” just by screwing in the threads, or does it need some sealant , teflon tape, etc. to be “water tight”.
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The code making panel forgot anything outside will never be water tight. That is why you need "wet location" wire and weather proof devices. A little later in that article they say conduits are required to be arranged to drain. Even if you could keep the rain out you still have condensation. It would be a violation to put caulk or teflon tape on the threads (grounding issues).
edit
One thing you do have to consider is heat on the roof and derating of the conductors
Edited 7/20/2009 9:58 pm ET by gfretwell
"It would be a violation to put caulk or teflon tape on the threads (grounding issues)."There's no reason that an o-ring could not be put on the threaded end of the connector before inserting it into the box. The ground path will still be there through the threads and the nut biting into the metal inside the box.BruceT
If the connector is listed with an O ring you can use it but if that is not the way it is listed to be installed it is a 110.3(B) violation.
I usually only see them on PVC "liquid-tite" connectors.
caulk/sealant or an "O" ring...
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