ECN Forum Forums Code Related Discussion NEC & other Code issues Bonding of metal studs

George, that is true. In Florida the code "reacted" to a dead guy.
There is nothing that prevents a contractor from bonding steel studs. In fact it may even be implied if you have a wide view of what is "structural" or "likely to be energized".
This would not even be a question if the family sued the box manufacturer for not providing a bonding means on the box.
They would all have one as soon as the line could be turned around. Then it would be a 110.3(B)

John, until there was a fault path there was no arc to detect. AFCIs look for current anomalies. Even if the wall did provide a significant load, a power driven screw may have made a clean "make" of that circuit. Your best hope would be that it was a 30ma or greater ground fault. If this was tapconned/shot pinned into a concrete slab, tied to the Ufer, it probably would trip a AFCI or GFCI but if it was on a wood deck, maybe not so much. You might not even get a trip if this was stem wall construction with a floating slab, sitting on visqueen. Usually it is on notched block and poured with the stem wall cell pour tho, in Fla, so it would be integral with the Ufer.

There are several ways to approach this.

The first is to say 'too bad' and moveon. You can't prevent everything.

Then there's the old practice of megger testing your circuits before you fire them up.

If you believe that there is a need for some 'common sense' to enter the code, where to start? Romex in metal studs seems to be, well, wrong (and I don't care that they sell bushings for the openings!). I'd like to see how the stuff is stapled! Add to this using plastic boxes - I don't see how those boxes were mounted securely - well, I guess I've lived a sheltered life. Must be from growing up in Chicago At any rate, here's an ideal opening for local amendments to simply say: No Romex in metal framing."

GFCI breakers? AFCI breakers? Once again, we're using technology to try to accomodate an inadequate wiring method.

Reno, they have plastic boxes meant for steel studs (why I think the bonding lug could be integrated quite easily).
It has a metal mounting tab. The grommet provides the horizontal support, just like Romex in a bored hole. The vertical support and within 12" of the box, is usually a tywrap.
You can get mad about plastic boxes but they are cheap and fast to install (no Romex clamp screw to tighten) so I think they are just a fact now.
I am not an engineer but it only took me a minute to come up with several ways to get from the EGC to the metal mounting strap. It could be as complicated/expensive as a green ground screw in a tab that comes in the bottom of the box to a spring stab or just a metal lip over the edge of the box you could drive a ground clip on.

I do think there is already a plastic box with a bonding means but I don't have a link to it. I think I saw it mentioned on the Fl IAEI BB when this first came up but I may be wrong about that.

At any rate, here's an ideal opening for local amendments to simply say: "No Romex in metal framing."

That's a good idea, functionally, but financially doesn't that add significant cost? I assume AC/MC/BX whatever would be the alternative, which is more expensive and problematic to use with plastic boxes.

I agree though, Romex and metal steel studs just seem...wrong. I did a walk through with a senior inspector one afternoon last summer and it was weird seeing all that yellow wire snaking through a metal stud wall.

Greg, if there are boxes intended for mounting to steel, then I am simply astounded that ther is no 'idiot proof' bonding already incorporated.

Cost? As the AFCI advocates will point out, cost is not a consideration. Any wiring method has to be suitable for it's use ... and perhaps we have to re-think this expanding acceptance of Romex. With Romex being expanded in scope to commercial buildings, there will be many more opportunities for it to encounter metal studs.

Heck, with all the fuss AFCI's have caused, perhaps we ought to re-think Romex alltogether. After all, there's all that concern about the 'errant staple.'

I'm not being critical here; rather, I'm showing my ignorance. I just can't see Romex in either metal studs or commercial uses.

I guess the issue here is metal studs are very popular for 1 & 2 family in Florida and nobody wants to make MC cable or pipe necessary there.
I tend to agree that RX may not be particularly appropriate for most commercial

Metal studs absolutely must be bonded for safety. It's no different than I-beams in a commercial building. If the manufacturer has them UL listed for screws providing adequate bonding, that's great, that's easy, just bond each section to the highest ampacity circuit it's likely to be energized with.

Regardless of what's done for safety, the metal studs in a house should be grounded for lightning protection. Not so much to protect against a lighting strike, but to prevent one; ungrounded metal can become charged during an electrical storm and attract lightning bolts. Proper grounding of electrical systems and metal building components is a lot of why homes are only very rarely struck.

Steel studs are not, and have never been, considered in the same category as structural iron - at least as it pertains to bonding.

Nor should they! The last thing we want os for somone to take the next step, and deliberately use them as a grounding conductor - as we already do when we bond a transformer to structural iron.

I think you have an 'apples and oranges' situation here, as bonding a metal stud to provide a safety ground back to the service panel in the event of a short is hardly the equivalant to using a metal stud to bond a transformer.

Bigplanz ... I agree completely. I am just at a loss trying to write code that differentiates between "structural steel" and "steel framing."