Cutting boxes in a fire rated partition.

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hbiss

hbiss

EC, New York NEC: 2017
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Little Falls, New York NEC: 2017
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EC
Not really an NEC question but does anybody know where I can find details for installing boxes in an existing fire rated partition? These will be used for telephone and data.

-Hal
 
Threads like this remind me why I really want to get a UL orange book set. Time to visit my friendly neighborhood fire chief. Fire chiefs get the UL books for free, and are good candidates for electrician's to hit up for free old copies.
 
A lil more info in what your trying to accomplish would be helpfull. Commercial, Residential?

Well, I am talking about sheetrock on metal studs. That could be multi-unit resi or commercial. Fire rated assemblies are the same in either case- 30 minute, 90 minute, etc. One layer each side of 5/8" sheetrock, 2 layers, etc.

I'm wondering when I should be cutting the sheetrock out, installing a bracket box to a stud like in new work then putting fire putty on the back of the box. Rockers or tapers will then have to patch. Or when will a cut-in box suffice?

-Hal
 
hbiss said:
. Or when will a cut-in box suffice?
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Is there such a thing as a rated cut-in box? I haven't run into one yet, as far as I know, but I've certainly cut in my share of metal rated boxes supported with Madison's in rated assemblies.
 
I've certainly cut in my share of metal rated boxes supported with Madison's in rated assemblies.

Me too. Just wondering when (or if) that's acceptable. Never been called on it but that doesn't mean its right in all cases. Not all inspectors are going to be able to look at a partition and know what the fire rating is.

-Hal
 
Cut in boxes are fine, madison straps aren't.

From 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.
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Roger
 
Some people would argue that not all fire rated walls are found in the orange book. Many are from the gypsum manual, or from Chapter 7 of the IBC. A safer thing to hang your hat on could be the UL White book, which governs electrical product listings. You could then cite 110.3(B). Here is the applicable passage, from the 2006 UL White Book, product category QCIT:

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 rating 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 do not exceed 1/8 in. The boxes are intended to be
installed so that the surface area of individual boxes do not exceed 16 sq in,
and the aggregate surface area of the boxes do not exceed 100 sq in per 100
sq ft of wall surface.
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I've been using SmartBoxes for a good while not for old work when using NM or with low voltage cables. I'm pretty sure they're okay'ed for rated assemblies. They attach to the stud, even metal, in any event.

SB1G.jpg
 
hbiss said:
I'm pretty sure they're okay'ed for rated assemblies...

MD, I think "Listed single and double gang metallic outlet and switch boxes" would not allow them.

-Hal
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OH....:grin:

Yes, very few plastic boxes are of metallic construction. But there are rated plastic boxes. I wonder where they fit in?
 
hbiss said:
I'm pretty sure they're okay'ed for rated assemblies...

MD, I think "Listed single and double gang metallic outlet and switch boxes" would not allow them.

-Hal
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Hal, the section that I quoted only applies to metallic boxes. For nonmetallic boxes, category QBWY applies. It requires the box to be marked with the UL symbol, plus "Class * hr, F, W and/or C".
where * indicates hourly rating such as 1 hr or 2 hr and F = Floor, W =
Wall and C = Ceiling.

I don't think you will find a cut-in with those markings.
 
By the way, the 2006 edition of the UL white book has a new feature that allows you to search for a product based on the code rule you are trying to address. For example, for this problem, I would search for 300.21, then find out which of the products meets what you need. I absolutley love the 2006 white book. :)
 
I just completed (N.J.)a resteraunt last week in a "strip mall". It was all new construction with the exception of the partition walls wich were double 5/8" rock. I used deep ,metal ,old work MC boxes with the mad. bars. Where the MC cable was fished from the top I had to seal with fire rated foam. Other than that I had no problem with AHJ's.
 
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