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#62647 02/23/06 04:54 PM
Joined: Jul 2002
Posts: 680
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I don't see many metal studs up here but aren't they structural steel and thereby have to bonded?? Why would you use plastic boxes on steel studs, do they use a nail on like box with tech screws??

#62648 02/23/06 11:32 PM
Joined: Jul 2004
Posts: 9,923
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The argument against bonding goes that they are not "exposed" steel members.
It is clear anything attached to them like the dryer vent can or the medicine cabinet is exposed.
They use plastic boxes because they are a few cents cheaper and faster to install.
Yup they just screw the mounting flange to the steel framing with drill screws.
If they used a steel box for the dryer, the stove and the bathroom vanity outlets they would have most of the steel bonded.


Greg Fretwell
#62649 02/23/06 11:37 PM
Joined: Apr 2002
Posts: 7,381
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WALRUS:
Here in NJ there is some metal stud in resi, mostly remodel, or basement finishing. These are lightweight studs, 2x3 & 2x4 are common.

I have seen pieces of wood 2x4 inserted in the metal stud, screwed, and a nail-on plastic box into the wood. There are plastic boxes with a front flange to tec screw to the metal, and some have a bond screw and 'clip' to 'bond' the studs.

Now, IMHO, metal studs, metal boxes. As an EC, we do comm, metal studs MC cable, or EMT. Yes, in some instances, I could use NMC, but I choose not to.

As an AHJ, if it's NEC compliant, I have to accept it, personal opinions, or preferences don't count.

John


John
#62650 02/24/06 09:52 AM
Joined: Aug 2001
Posts: 7,520
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I had a job some time ago in a prefab unit, one of the "Arcon" units erected here just after WWII as temporary housing intended to last 10 years (and still with us 60 years later).

The roofing on those was asbestos sheets fitted over a steel truss system of small girders and tubes. Apparently the plumber had been crawling around up there doing some work, got shocked when he reached across a strut, and had no intention of going back up there until it had been checked it out (a wise decision!).

It turned out to be a T&E (Romex-type) cable which had been slung loosely across the base girders and then had a ton of junk stacked on top so that the sheath had been damaged.

After taking care of the obvious repair and rerouting of the cable, I also installed bonding on the metalwork.

#62651 02/24/06 09:24 PM
Joined: May 2003
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Years ago, I had a simular situation... (Rather than tell the story all over again, I'll see if I can find the last time I told it here...)

Oh I cant find it... Anyway, troubleshooting at a resturaunt, that the dish washers had been getting shocked at for years, a screw that held the sheet metal to the wall, that the sinks were mounted to went through cable and conduit behind. Seperate ones, seperate phases, so if you touched one sink you got 120, if both 240. On top of that the manager did not want to fix it, so I shut off the service....

Funny part, metal walls, metal pipes to metal sinks, nothing tripped - nothing grounded.


Mark Heller
"Well - I oughta....." -Jackie Gleason
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