Flexible Conduit Connection to Outdoor Metal Single Gang Box

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jsclancy

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Apologies if this seems like a silly question, but...

When one is using a flex-conduit fitting (like shown in the picture below) to connect to a metal single-gang outdoor box (also shown below), what keeps the threaded fitting secured inside the metal box threads? Is it just a friction fit against the rubber O-ring or is there a backing nut as shown on the fitting? The threads on the fitting do not look long enough to extend inside the box to accommodate a backing nut.


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Welcome to the forum.

The box has threaded holes, so the lock-nut is not needed.

Some here will debate whether that is an approved use.
 
Uh oh. So, the lack of a backing nut would disqualify it? I'm not sure what other type of box would be useful with flex conduit. A standard gang box doesn't seem like it would be water-tight enough for outdoor use.

Alternatively, what kind of conduit would be used with the box that I've shown? I thought flex would be a natural fit.
 
jsclancy said:
Uh oh. So, the lack of a backing nut would disqualify it? I'm not sure what other type of box would be useful with flex conduit.
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The issue is the threads. It's a straight vs. tapered thread issue. Technically those threaded hubs are intended only to be used with RMC or IMC which is ridiculous.
 
well one would hope once box is mounted and conduit is strap that it won't have any means to twist out of the threads. I would take the locknut off and it threads in fine if feeding from top. if side or bottom I would just remove the rubber also, serves no purpose on back and bottom.
 
jsclancy said:
Uh oh. So, the lack of a backing nut would disqualify it? I'm not sure what other type of box would be useful with flex conduit. A standard gang box doesn't seem like it would be water-tight enough for outdoor use.
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In my opinion, no, lack of the lock-nut with a threaded opening would not disqualify it.

I personally would use that connector with that box, with the O-ring and no lock-nut.

Alternatively, what kind of conduit would be used with the box that I've shown? I thought flex would be a natural fit.
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In theory, rigid conduit. I'm still with you. Ask for your inspector's oinion if you're really concerned.
 
LarryFine said:
I personally would use that connector with that box, with the O-ring and no lock-nut.
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Me too. The connection to the box is still required to be suitable for wet locations so the gasket should remain on the fitting.
 
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