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#185485 - 03/16/09 07:10 PM Bonding of metal studs
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
Could someone please direct me to a written code requirement outlining the bonding of metal studs when non-metallic electrical boxes and wiring are installed within the walls?

I don't think that 250.104 [C] or D, [2] applies here, since these metal studs are partitions, they are not really structural and are also normally faced with drywall so are not exposed.

I remember this subject being brought up at a code seminar several years ago, and it was recommended that if NM boxes were used, a tail should be extended from a branch circuit equipment grounding conductor in one of the boxes and attached to one metal stud in the wall with a lug or machine screw, but I can't recall if there was an actual reference to this in the NEC though. Obviously this is less of an issue when metal boxes are used.

Thanks


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#185488 - 03/16/09 07:53 PM Re: Bonding of metal studs [Re: KJay]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
It has not made the NEC as far as I know unless you want to get fast and loose with "metal that may become energized" but the Florida building code addresses it directly.

Quote:
SECTION E3302 BONDING METAL FRAMING MEMBERS

E3302.1 Metal framing members. Metal framing members shall be bonded to the equipment grounding conductor for the circuit that may energize the framing and be sized in accordance with Table 250.122 of the National Electric Code. For the purpose of this section, a grounded metal outlet box attached to the framing shall be permitted.



This is one of the few additions to the NEC they have.
_________________________
Greg Fretwell

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#185491 - 03/16/09 08:29 PM Re: Bonding of metal studs [Re: gfretwell]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
The issue is a timely one ...

At the Home Inspector forums, they're asserting that such 'light steel framing' MUST be bonded, and tell all manner of tales.

I agree that the NEC does NOT require such to be bonded. To me, ?structural steel' has a red primer and is at least 1/4" thick.

My experience has shown this type of framing to be something used only in commercial settings - where, oddly enough, practice has been to not use NM or plastic boxes.

Otherwise, as with suspended ceilings, I've always doubted it was possible to make one without it somehow being bonded.

On balance, I suppose it'snot such a bad idea to have some manner of bonding; I just don't want someone to go overboard, and require listed bonding jumpers all over the place! The last thing wer need is someone worrying about 'sheet metal screws being used ... to connect sheet metal!

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#185493 - 03/16/09 08:43 PM Re: Bonding of metal studs [Re: renosteinke]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
Interesting topic john (oops I mean Reno smile )

Last years code revue/con-ED, we discussed the need to bond 'Victolic' fittings on the sprinkler systems (and others).

PS: On those HI forums,do they always argue like that? what a bunch of.....Lack of suitable word.


Edited by leland (03/16/09 08:45 PM)
Edit Reason: HI forum note

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#185498 - 03/16/09 09:18 PM Re: Bonding of metal studs [Re: leland]
Bigplanz Offline
Member

Registered: 03/06/09
Posts: 72
Loc: Louisville, Kentucky
This may be why Florida has a specific requirement for bonding metal studs.

http://www.clickorlando.com/money/7302637/detail.html

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#185499 - 03/16/09 10:06 PM Re: Bonding of metal studs [Re: Bigplanz]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
Sad article Big.
But a few questions remain; What are the wiring standards there? Metal boxes,MC etc? Wood frame metal studs?

Here in the Northeast,I find it hard to find any metal framed wall not to be bonded.Not that it can't happen (as this article shows) But in proper construction,accidental bonding is far better than I could provide.

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#185505 - 03/17/09 01:05 AM Re: Bonding of metal studs [Re: leland]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
The typical 1 & 2 family here is wired with Romex in plastic boxes with steel framing unless it is a load bearing wall. All plastic piping for water and DWV.
They avoid wood because in our wet climate it is hard to find a straight 2x4 and these days mold is also a big issue.
If the structural inspector sees a moldy 2x4 on the FEPAC you are not hanging drywall tomorrow, you are getting a mold mitigation certification. It was so bad my wife was just getting her trusses sprayed and certified as soon as the roof was black, whether they needed or not. It is not a cheap sticker to get.

I said long before the guy got killed up there that they should use at least one steel box in each isolated wall section. I have even heard of a plastic box with a bonding screw to the metal mounting strap. That would work too.
In most houses, if you bonded the wall in the kitchen with the range box, the laundry with the dryer box and got the bathrooms with a metal box you would have most of the hazards covered. That is where that metal framing might get connected to something you could touch. In the case of the guy up north it was the dryer vent box. It could also easily be the medicine cabinet in the bathroom.
I also think metal sinks should be bonded but that may just be me. Usually, I suppose the disposal does that but I haven't seen anything in the listing to prove it.
_________________________
Greg Fretwell

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#185519 - 03/17/09 11:10 AM Re: Bonding of metal studs [Re: gfretwell]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
This is similar to what I see around here as well, especially when a basement get finished off.
Sometimes when the metal stud wall is attached to the concrete floor with PAT fasteners, that is as close to grounding as they will get without any metal boxes being used.
At least your state has addressed the issue, I'm not sure that my state's building code has any reference to this at all yet, but I will continue to look.

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#185523 - 03/17/09 06:12 PM Re: Bonding of metal studs [Re: KJay]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
I have seen alot of what you describe Kjay, I always use metal boxes on the metal studs. Perhaps just my Industrial/commercial background. Habit more than anything else.

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#185531 - 03/17/09 09:35 PM Re: Bonding of metal studs [Re: leland]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
Originally Posted By: leland
I have seen alot of what you describe Kjay, I always use metal boxes on the metal studs. Perhaps just my Industrial/commercial background. Habit more than anything else.

Lee, do you recall seeing anything regarding bonding metal stud walls in the MA building Code? I was at a seminar several years back and this came up, but I haven't heard anything about it since.

TKX

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