old work box in fire rock

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I recently was failed for fishing mc cable down inside a 1 hour fire rated wall in which I installed a metal cutin box, I fire caulked around my box and mc entry into the fire rock. The inspector said this was an NEC code vialation that I could not use the fire rock as support of the box it had to be fasten to the metal studs. This would constitute removing sections of fire rock to install supports for the boxes im having trouble finding this in the code and could use a little help !
 

roger

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You won't find it in the NEC, it is in the UL Orange Books.


WALL AND PARTITION ASSEMBLIES

Metallic Eletrical Outlet Boxes

Listed single and double gang metallic outlet and switch boxes with metallic or nonmetalliccover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2h. These walls shall have gypsum wallboard facings similar to those shown in Design Nos. U301,U411, and U425. The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall be cut so that the clearance between the box and the wallboard does not exceed 1/8 in. The surface area of individual metallic outlet or switch boxes shall not exceed 16 sq in. The aggregate surface area of the boxes shall not exceed 100 sq in per 100 sq ft of wall surface.


Roger
 

PetrosA

Senior Member
You won't find it in the NEC, it is in the UL Orange Books.


...


Roger

I haven't come up against this, but I'm trying to understand. Is there a listed single gang old work metal box that can be fastened to a stud, metal or wood, with no more than 1/8" play around the edges? I can imagine that it would be possible to cut in a two gang wall case and somehow get enough of an angle to screw into the stud (as long as you're lucky enough to hit the solid side of a metal stud) but I can't think of how it's possible with a regular 1 gang wall case. Is an old work box even possible here?

Thanks
 

roger

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I haven't come up against this, but I'm trying to understand. Is there a listed single gang old work metal box that can be fastened to a stud, metal or wood, with no more than 1/8" play around the edges? I can imagine that it would be possible to cut in a two gang wall case and somehow get enough of an angle to screw into the stud (as long as you're lucky enough to hit the solid side of a metal stud) but I can't think of how it's possible with a regular 1 gang wall case. Is an old work box even possible here?

Thanks

It boils down to the fact that whatever box is used, it must be fastened to a structural component, this may involve opening the wall enough to fasten the box properly and then repairing the membrane to the 1/8" limitation.

Roger
 

chris kennedy

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Miami Fla.
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60 yr old tool twisting electrician
You won't find it in the NEC, it is in the UL Orange Book Roger

Roger, do you have a section/article number for that? I would like to look that up in the Florida Building Code as I am currently putting many openings in 1hr firewalls at

'the school'.:mad:

Thanks
 

roger

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Roger, do you have a section/article number for that? I would like to look that up in the Florida Building Code as I am currently putting many openings in 1hr firewalls at

'the school'.:mad:

Thanks

Chris, I think I have something at work, I'll see if I can find it.

The reality is that if you have a UL wall assembly the penetrations or what have you has to be compatible with the wall assembly to maintain the rating and that is where the UL orange books come into play.

My earlier quote came out of the first few pages of volume 1 of the UL Fire Resistance Directory (the Orange book set)

Roger
 
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mpd

Senior Member
look in the UL white book also under metallic outlet boxes, has the same info roger posted, for use in a rated assembly
 

M. D.

Senior Member
Is there any chance that NM-b could be used? there are boxes that could easily be installed


http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073991686&sequence=1


USE IN FIRE-RATED ASSEMBLIES

Listed single- and double-gang metallic outlet and switch boxes with metallic or nonmetallic cover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2 h. These walls have gypsum wallboard facings similar to those shown in Design Nos. U301, U411 and U425, as covered under Fire Resistance Ratings - ANSI/UL 263 (BXUV). The boxes are intended to be fastened to the studs with the openings in the wallboard facing cut so that the clearance between the boxes and the wallboard does not exceed 1/8 in. The boxes are intended to be installed so that the surface area of individual boxes does not exceed 16 sq in, and the aggregate surface area of the boxes does not exceed 100 sq in per 100 sq ft of wall surface.
 
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