bonding metal studs , holts states no only if exposed !

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Ray G.

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How about a drywall screw, thru the stud + nicks a rx or imc + the breaker does not trip making the studs hot. Now a potential hazard . see informational note 250-116 + the definition article 100 of eqpt.a general term, including fittings, devices . appliances, luminaires , apparatus, machinery , + the like like used as a part of ,or in connection with, an elect. installation. Would you not consider the metal studs equipt? The box could not be installed . There are exceptions as with all old work. All it comes down to is using 1 metal box as not plastic. /// Also see definition of effective ground -fault current path. Structures get remodeled, + what was covered can be exposed . ANY THOUGHTS ?Ray G.
 
The parts of a building are not equipment.

The NEC does not require metal studs to be bonded, but I believe there are areas with amendments that do require such bonding.
 
I have witnessed a couple of times a faulted 120v and 277v on sections of metal stud walls that was for all purposes "Floating" and didn't cause the overcurrent device to trip. Damn near killed the restaurant owner with a shock on one of the incidents I got called in to correct, the installer ran thhn without conduit from a j-box down thru a smashed hole (where the wire nicked) in a top plate to a receptacle outlet. No ground wire. So yeah it isn't a bad idea, but not sure it should be added to the NEC due to rarity of it .
 
What about metal siding, roofing whether they be something that looks like conventional wood siding or shingles or just corrugated sheet metal?

We don't bond those. Have seen them become energized by mishaps on occasion.

Unless the typical metal stud for drywall is heavy enough to be a structural member they pretty much need to be covered or they have no strength.
 
macmikeman said:
I have witnessed a couple of times a faulted 120v and 277v on sections of metal stud walls that was for all purposes "Floating" and didn't cause the overcurrent device to trip. Damn near killed the restaurant owner with a shock on one of the incidents I got called in to correct, the installer ran thhn without conduit from a j-box down thru a smashed hole (where the wire nicked) in a top plate to a receptacle outlet. No ground wire. So yeah it isn't a bad idea, but not sure it should be added to the NEC due to rarity of it .
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With an install that bad, I don't think a rule about bonding the studs would've helped. The dude before you clearly didn't feel the need to read the code book. :)

SceneryDriver
 
We could come up with all types of hypotheticals on our route to doing this Do you need to bond to every single stud or do you rely on the screws and with what size wire? Do you size it like a ground wire for a pool or do you need to size it based on the overcurrent protective device, in which case in a high-rise you might need to accommodate a 400 amp or bigger circuit that someone might someday decide to put through there? And then can the studs handle fault current themselves or do they need to be sistered with a wire attached to the stud every, maybe 12 inches? Do you need to tell the drywall installer that they can’t use self tapping screws? Can we just 3-D print the entire house out of copper instead?

I think in most cases where there is a potential for them to be energized they end up being connected anyway. If there’s a metal box that’s properly grounded it’s also going to be secured to the stud.

I one time saw a bathroom in a high-rise building that was under construction where the walls had been painted but at every location where there was a screw underneath the drywall there was metal fragments. Most likely, someone did something that tripped the breaker but before it did, it magnetized the metal parts on its way down.
 
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