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Queens, NY

4 edits
reply to John Galt

Re: Gang box recommendation

said by frroo:

Gang box recommendation

FYI, froo - the photo above is generally referred to as a gang box (a tool box for a gang of workers). You are looking for a low-voltage 'outlet box'. Where the word 'gang' is used, is for the size of the electrical box, as in 'single-gang', two-gang', etc., meaning the quantity of wiring device yokes it allows mounting of.

said by John Galt:

Although it probably does not matter in your particular instance, but the low-voltage "frames" you mention cannot be used in rated firewalls.

John is generally correct. However, the great majority of home's generally don't have fire-resistance-rated walls (except between an interior garage or boiler room and the rest of the home). Regardless of what boxes are used, if they are being placed in fire-resistance-rated walls, the integrity of the fire-resistance rating must be maintained. So, what does that mean?

- If one were to use an open-frame type low-voltage box, they would likely have to build a 'compartment' around the frame within the wall and submit the sketch of the box to the AJH. The AHJ could actually require testing in a lab if they feel its not suitable. This is one of the reasons that you don't often find these in commercial buildings, and instead, steel boxes are used with conduit stub-ups into the plenum ceiling compartment. However, and open-frame box can be used in such walls is these steps are taken. But its simply a lot easier and quicker to use a large, deep enclosed metal box with a 'mud-plate' on the front.

- Where enclosed boxes are used in such walls, they normally provide adequate protection and maintain the rating, except where the wall requires over a 2-hour fire-resistance-rating and the wall is constructed of gypsum board - or where boxes are placed on both side of the wall, back-to-back in the same cavity; the latter situation generally being avoided at all costs (and is not recommended in homes, regardless if the walls have no fire-resistance rating). The solution for these situations is usually placing an intumescent 'mat' of the proper thickness behind the boxes. This technique is also used where floor boxes or ceiling boxes are placed in concrete slabs reducing the thickness of the concrete at that point.

Regardless of what method is employed, any box - open or closed - can be used in a fire-resistance-rated wall, provided the rating of the wall is maintained.

John Galt
Forward, March
Happy Camp

1 recommendation

said by whizkid3:

FYI, froo - the photo above is generally referred to as a gang box (a tool box for a gang of workers).

I thought the same thing when I saw the subject line. I was thinking "get the wheel kit for it!"

Rated firewalls are also found in MDU / condo buildings. The methods of maintaining the fire rating that whizkid3 See Profile discusses is the proper way to maintain that rating.
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