Metal romex two screw clamps into plastic boxes

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JoeNorm

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Is it permitted to use metal romex clamps in a plastic(say, PVC) without bonding them somehow? I had never really thought about it until an apprentice asked me the other day and I didn't know the answer. Thanks.
 
Definitely could use a bonding bushing, but sticking with plastic sounds like the best option. Thanks.
 
I answered basically this same question the other day. Guy wanted to run 6/3NM into a PVC box and wanted to use a plastic "push-in" connector. I didn't like it and said I would like to see a two-screw connector. But I had questioned whether it would have to be bonded. I suggested a bonding bushing.

Another guy want's to use a PVC box to house the contactors for an Ansul system. I asked how he was going to handle bonding the conduits and MC cables going into the box.

Knuckle Dragger said:
I understand that. :) Just saying I haven't had a reason to have to do it.
It doesn't seem natural ;).
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Doesn't seem natural to me either. You see PVC boxes on the shelves of all the big boxes. Never screw cover, hinged cover or rain tight metal boxes. So which ones do you think people are going to try and use?

-Hal
 
hbiss said:
I answered basically this same question the other day. Guy wanted to run 6/3NM into a PVC box and wanted to use a plastic "push-in" connector. I didn't like it and said I would like to see a two-screw connector. But I had questioned whether it would have to be bonded. I suggested a bonding bushing.

Another guy want's to use a PVC box to house the contactors for an Ansul system. I asked how he was going to handle bonding the conduits and MC cables going into the box.



Doesn't seem natural to me either. You see PVC boxes on the shelves of all the big boxes. Never screw cover, hinged cover or rain tight metal boxes. So which ones do you think people are going to try and use?

-Hal
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Funny, I just saw a This Old House segment where a homeowner wanted power at his shed. The electrician used two-screw clamps in plastic boxes to make the splices from THWN in underground PVC to Romex for the indoor sections. No bonding bushings anywhere. Looked quite "hack." It looked like he just went shopping at Home Depot for the segment. We've discussed the quality of the electrical work on TOH before...

If I absolutely HAD to run something like 6-3 Romex into a plastic box, I'd probably use a domenut / plastic cable gland. They're pricy in those sizes, though.

As for your question regarding bonding multiple cables entering a nonmetallic box, I had to do that once. I had our CNC department laser cut me a plate from 14ga steel with about a dozen 1/2" KO's staggered across its face. That plate was fastened to the inside of the fiberglass enclosure, and any time we needed a KO in the box, it was drilled to match the "cheesegrater" panel on the inside. The connectors' locknuts bit through the thin layer of Krylon spraypaint I put on the plate to prevent rusting, and bonded the connectors and MC cable armor effectively. We bonded the plate to the EGC that fed the enclosure. Worked a treat, and the inspector was impressed. I realize that not everyone has a CNC department though :)



SceneryDriver
 
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make sure to thread a hole on the back of the box for the green ground screw while your at it ..

bond bushings really ... ok ...to be sincere here, why or how should any plastic ( non ) conductive box even be considered to become grounded.
 
The metallic raceways can be bonded at the other ends of their runs, and EGCs can be added to maintain continuity if needed.
 
LarryFine said:
The metallic raceways can be bonded at the other ends of their runs, and EGCs can be added to maintain continuity if needed.
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I see your point Larry, but isn't the whole purpose of a bonding busing to assure solid continuity when using a concentric knock out, to assure the grounded metallic pipe and its grounding conductor within maintain the same integrity.
 
Another C10 said:
I see your point Larry, but isn't the whole purpose of a bonding busing to assure solid continuity when using a concentric knock out, to assure the grounded metallic pipe and its grounding conductor within maintain the same integrity.
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For GECs, yes, because of choke effects at lightning-induced currents and frequencies.

And we're discussing plastic boxes here, not metallic; concentric issues involve services.
 
LarryFine said:
And we're discussing plastic boxes here, not metallic
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but with due respect .. were talking about ground bushings, besides when is an MC sheathing utilized as a grounding path , isn't it more so for protection and yes at the same time, tends to maintain grounding capabilities. The MC ground wire is truly the intended fault path. .. right ?
 
SceneryDriver said:
Funny, I just saw a This Old House segment where a homeowner wanted power at his shed. The electrician used two-screw clamps in plastic boxes to make the splices from THWN in underground PVC to Romex for the indoor sections. No bonding bushings anywhere. Looked quite "hack." It looked like he just went shopping at Home Depot for the segment.

SceneryDriver
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Reminds me of a time Bob Villa was knocking plaster off a lathe wall with a spade, you see a blue flash on camera when he hit a receptacle! He kept on banging like nothing had happened! LOL!
 
Years ago did some work in a office building built in 1979, wiring was NM cable with suspended ceilings, now prohibited, but whoever wired it ran NM cable to one & two gang nail on plastic boxes on the trusses to supply the lights, they then ran 1/2" steel flex from the boxes to the 2X4 troffers, which each suite had 8 of, with 4-F40 lamps in each, the biggest problem was they did not run a grounding conductor so anyone in contact with the T-bar & then touching a gas line got rather unpleasant tingle, from the leakage of 16 ballasts. Some boxes were replaced with metal but I would be on pretty firm ground to say most is still as built today. :(
 
Another C10 said:
but with due respect .. were talking about ground bushings, besides when is an MC sheathing utilized as a grounding path , isn't it more so for protection and yes at the same time, tends to maintain grounding capabilities. The MC ground wire is truly the intended fault path. .. right ?
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OP was talking about NM cable and a metallic connector in a plastic box, you still need to bond that metallic fitting, grounding bushing would work great for that. Other option is to avoid using a metallic fitting. Nylon cable gland should work, larger ones can be a little pricey, but grounding bushing has a cost as well that at least offsets the difference some.
 
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