Is chase nipple (+ bonding bush) proper way to mate RMC w/ sub-pa

fixizinFebruary 6, 2011

It seems that die-cast wet-location j-boxes have deep threaded channels--at least on the top and bottom--with nicely rounded entries, such that no bushing is required, just thread, say a 6" RIGID nipple, right into it, apply silicone sealant, done on that end...

But when bringing the other end of that RMC nipple into the knockout of a sheet-metal box, I'm guessing a simple pair of locknuts (inside/outside) is not adequate, as wires would be exposed to edges of nipple/conduit. I'm thinking put a chase nipple inside box, then (female) coupler to mate with the 6" nipple, yes/no/that's the only way/are you crazy? ;')

Also, are one or more BONDING bushings involved, to maintain GND? Wanna get it right-eous.

Thanks in advance, best practices always.

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fixizin

Today I looked into a similar setup w/ IMC coming in, and it did have 2 lock nuts--inside & outside--but then there was a red plastic bushing over the very end, to protect the insulation on the conductors.

Not sure if that's code-compliant, but it seems reasonable and adequate as far as providing a flared/beveled/soft transition zone for wires to enter conduit.

Only remaining question is, do the two locknuts constitute adequate GND bonding? Seems to do the job on EMT connectors.

    Bookmark   February 7, 2011 at 11:18PM
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fixizin

Don't everyone pipe up at once... you'll cause a "Denial-Of-Service" clog on my converted telegraph wire internet service, lol...

    Bookmark   February 9, 2011 at 7:22PM
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ontariojer

I don't know your local code on this, but here it is a question of wire size for bushing requirements, having said that, you can never go wrong putting on a plastic (or metal)bushing to protect the wire. A pair of nuts(inside/outside) PROPERLY tightened is adequate ground.

    Bookmark   February 9, 2011 at 7:54PM
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fixizin

Thanks, I've got the plastic bushing, and locknuts, and spanner thingy, and will go with that. (Not sure how I would tighten the chase nipple anyway, w/ box against wall, etc... UNnecessary complication.)

I'm just running two AWG12 THWN through a 1/2" nominal dia. RIGID nipple, to a single-gang wet-loc box w/ 20A GFCI--VERY short run... NOT in a seismic zone, lol.

    Bookmark   February 9, 2011 at 9:55PM
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