Put NM connector with screw side inside box????

[Zeke]

Exactly right. But who hasn't had an old work box in lath and plaster where the wings won't grab? So you run screws from the inside.

There are pages of debates on this on Mike Holt and others. Seems as screws can be tricky business.

 

[dave*99]

Screws can certainly cause issues. The gist of the codes are to prevent energizing screws that venture outside a box. For a plastic box, it's easy to see how a live conductor could energize a metal screw that exits the box.

A properly grounded metal box will not be susceptible to this phenomenon.

I'm not advocating for steel NM clamps to be installed with the clamp screws inside the box, but if it's done on a grounded steel box, any faulted wire will trip the breaker.

A ungrounded steel NM clamp is not permitted on a plastic box.

 

[Zeke]

A steel NM clamp is not permitted on a plastic box.

I'm sure not. There is no provision to mount one unless you make the hole. I suppose that's covered in a code somewhere. The code I cited doesn't differentiate plastic boxes from metal. So you could construe that a field fabricated hole would be permitted. Then you'd have to bond the clamp. I should do that sometime for giggles and see what an inspector does.

Like MC into a plastic box.

 

[kaffine]

I'm sure not. There is no provision to mount one unless you make the hole. I suppose that's covered in a code somewhere. The code I cited doesn't differentiate plastic boxes from metal. So you could construe that a field fabricated hole would be permitted. Then you'd have to bond the clamp. I should do that sometime for giggles and see what an inspector does.

Like MC into a plastic box.

I've seen plastic boxes with conduit knockouts. Normally used for ENT but a NM-B clamp would fit.

https://www.homedepot.com/p/Carlon-...ew-Work-ENT-Electrical-Box-A122-CAR/202077343

I've never really thought about it before guess there is a bit of an issue with ungrounded metal. I guess there is a reason I prefer metal boxes.

 

[Zeke]

Come to think of it I have seen those too. Never used the KO.

 

[sparky 1971]

I've seen plastic boxes with conduit knockouts. Normally used for ENT but a NM-B clamp would fit.

https://www.homedepot.com/p/Carlon-...ew-Work-ENT-Electrical-Box-A122-CAR/202077343

I've never really thought about it before guess there is a bit of an issue with ungrounded metal. I guess there is a reason I prefer metal boxes.

If a metal romex connector is used in a non metallic box, a grounding bushing should probably be installed on it. A 1/2" grounding bushing is a *****. Also, a metal connector may not be listed for use in a non metallic box, I don't care enough to research this trivial GJ stuff.

And, being the rebel that I am, I have used metal clamps on plastic boxes because some times ya gotta do what ya gotta do to gir 'r done.

 

[kaffine]

Now I'm trying to remember if I was dumb enough to use a plastic box with a metal cable clamp.

 

[Norcal]

Now I'm trying to remember if I was dumb enough to use a plastic box with a metal cable clamp.

I avoid plastic boxes whenever I can, metal outperforms plastic.

 

[cmandp]

I've used metal NM clamps on a plastic box once.

I believe I ended up bringing a ground to each one and wire nutting it into the rest in the box

 

[kaffine]

I avoid plastic boxes whenever I can, metal outperforms plastic.

I typically use metal but found some plastic rework boxes that I liked the mount better than the metal ones I can find. I checked I didn't use metal NM clamps on them.

 

[wyliesdiesels]

I've used metal NM clamps on a plastic box once.

I believe I ended up bringing a ground to each one and wire nutting it into the rest in the box

How did you attach the bonds to the clamps?

 

[billconner]

I used these. Vapor barrier seals so well around them and so easily. Nothing like it in metal. Not sure how metal would ever "out perform" these. Best built in clamp I've used - much better than a lot of plastic boxes.

 

[acer66]

I used these. Vapor barrier seals so well around them and so easily. Nothing like it in metal. Not sure how metal would ever "out perform" these. Best built in clamp I've used - much better than a lot of plastic boxes.

Who makes these?

 

[sparky 1971]

Who makes these?

Arlington makes all of the cool things...

https://southernele.com/arlington-fn101fx-non-gasketed-nail-on-vapor-box/

 

[billconner]

Those are Arlington. My local electric supply got them. Vapor barrier boxes are expensive but Arlington seems to be the lowest price. I had trouble even finding any of them on line. Amazon wanted like $15 or 18 a pop for Raco's s.g. box. Ace around $6. I got these for under $5, all thanks to vendor, not me. And no one had them in stock.

 

[wyliesdiesels]

I used these. Vapor barrier seals so well around them and so easily. Nothing like it in metal. Not sure how metal would ever "out perform" these. Best built in clamp I've used - much better than a lot of plastic boxes.

wow never seen those here

 

[cmandp]

How did you attach the bonds to the clamps?

I looped ground wire cutoffs around one of the clamp screws and ran it next to the NM through the clamp into the box.

Admittedly I knew it was questionable when I did it but needed to get it done with the box ENT box I had.

 

[wyliesdiesels]

I looped ground wire cutoffs around one of the clamp screws and ran it next to the NM through the clamp into the box.

Admittedly I knew it was questionable when I did it but needed to get it done with the box ENT box I had.

yeah not listed for that

 

[BreeStephany]

Is it common practice?... No. Should it be used for new work... No. Have I done it before?... yes.

Mostly done it when I had to fish wire down to the panel and then installed a snap-in connector with the screws on the inside of the enclosure so that I could tighten it down without having to cut the sheetrock above the panel.

With that said, per NEC and UL listing, following manufacturer's instructions / direction for correct installation.