Flexible Conduit Connection to Outdoor Metal Single Gang Box

[jsclancy]

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.

 

[LarryFine]

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.

 

[jsclancy]

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.

 

[infinity]

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.

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.

 

[AC\DC]

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.

 

[LarryFine]

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.

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.

In theory, rigid conduit. I'm still with you. Ask for your inspector's oinion if you're really concerned.

 

[infinity]

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

Me too. The connection to the box is still required to be suitable for wet locations so the gasket should remain on the fitting.

 

[BarryO]

Some here will debate whether that is an approved use.

"Hubs accept all threaded fittings and threaded conduit"

https://hubbellcdn.com/specsheet/5320-0.pdf