Fire rating of plastic cut in boxes

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Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I was wondering how a Carlon blue cut in box B114r can claim 2 hour fire rating. I thought you cannot float a box on the drywall in a rated wall.
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
I don't know much about fire code, but the way that I look at this: Just because the box has 2 hour rating does not mean we can cut into a fire rated wall.

Yet, what is the difference between a cut in box and the nail on box, unless the nail on box has fire padding before sheetrock. They both do penetrate the sheetrock. :? I don't know.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Difference is a nail on box is fastened to a framing member either wood or steel.

How can it be listed as such if it is only secured by drywall.
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
Difference is a
nail on box is fastened to a framing member either wood or steel
. YES I know that

How can it be listed as such if it is only secured by drywall.

But how does nailing it to 2x4 make that penetration fire rated. It is still the same box material except one is mounted to the 2x4 with sheetrock around it one is mounted on the sheetrock.

This is a good homework for me to ask my local AHJ and see what they have to say.
 

alive wire

Member
Location
Phoenix, AZ US
In all honesty I just run add on circuits on fire rated walls in wire mold so I don't have to worry about it, new construction I follow code for spacing

Sent from my SM-N900V using Tapatalk
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
But how does nailing it to 2x4 make that penetration fire rated. It is still the same box material except one is mounted to the 2x4 with sheetrock around it one is mounted on the sheetrock.


As much as there is logic to your question, it is not applicable to the issue. Wall assemblies are listed. In order to achieve a listing they are assembled in certain ways and they are intensively tested. The listing is only good for that assembly, not that assembly as modified. There are sure to be many wall assemblies that would hold up to fire as well or better than the listed assembly, but until they are specifically tested, they are not listed. Boxes receive a separate testing, so two different boxes that receive their test regiment can be used in the same "listed wall assembly". If the local Authority requires a listed rated wall assembly then it must be just that. At some point it isn't our's to question why. As far as a nail on box vs a cut in though, here is a speculation... The box is subject to being blown out by the varying pressures in the cavity and out, or on the other side. The open hole is then subject to loss of integrity and a quicker compromise of the barrier. I don't know this, just idle speculation.
 

luckylerado

Senior Member
I was wondering how a Carlon blue cut in box B114r can claim 2 hour fire rating. I thought you cannot float a box on the drywall in a rated wall.

The exception in IBC 713.3.2 addresses this.

Membrane penetrations by listed electrical boxes
of any material, provided such boxes have been
tested for use in fire-resistance-rated assemblies
and are installed in accordance with the instructions included in the listing.
The annular space between the wall membrane and the box shall not exceed l/S inch (3.1 mm) unless listed otherwise. Such boxes on opposite sides of the wall or partition shall be separated by one of the following:
2.1. By the horizontal distance specified in the listing of the electrical boxes;
2.2. By solid fire blocking in accordance with Section 717.2.1;2009 INTERNATIONAL BUILDING CODE®FIRE AND SMOKE PROTECTION FEATURES
2.3. By protecting both boxes with listed putty pads; or
2.4. By other listed materials and methods.
 

mwm1752

Senior Member
Location
Aspen, Colo
If the cut in box is rated for 2 hrs then there should be no problem in installing it in a rated wall or ceiling assembly. Gennerally, in a nut shell the issues of extra protection are based upon - through penetrations within 24" - openings greater than 16 sq in - & openings adding up to > 100 sq in In 100 sq ft.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
I don't have time to look anything up as far as non metallic boxes are concerned at the moment, but here is what UL says about Metallic boxes in rated walls.

From the UL Fire Resistance Directory


WALL AND PARTITION ASSEMBLIES

Metallic Electrical Outlet Boxes

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 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
 

mwm1752

Senior Member
Location
Aspen, Colo
I don't have time to look anything up as far as non metallic boxes are concerned at the moment, but here is what UL says about Metallic boxes in rated walls.
Roger

Ther is quite a bit of info but it follows suit with the metallic boxes -- I could not find anywhere in the UL directory that allows non metallic boxes to be supported by drywall -- are you sure the cut in is rated for 2 hrs
 

JFletcher

Senior Member
Location
Williamsburg, VA
You could use an inside-box putty pad, something like this:

http://www.firetherm.com/pictures/82/20091125181321522297366.pdf

I've had to do a ton of boxes in rated walls, but never a cut in box. Is one also allowed to fish wire in a rated wall? If so, how would you fire stop a vertical penetration?

I honestly dont believe that every cut-in box installed in a rated wall involved the removal of substantial amounts of drywall... not saying that's right, or code, just saying...

If you cut it in right next to a stud, you can screw the box to the stud, then it's not 'floating' in the drywall. Problem solved, yes?
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Ther is quite a bit of info but it follows suit with the metallic boxes -- I could not find anywhere in the UL directory that allows non metallic boxes to be supported by drywall -- are you sure the cut in is rated for 2 hrs

Yes it is stamped in the back of the box classified 2 hr -w


In any case what do you folks use to cut in a box in a fire separation wall.
In the past I have used a regular box and screwed it to the stud. I understand that may be improper.
 

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sandsnow

Senior Member
Only UL and or Carlon can truly answer your question.
If you do a Google search for Carlton b114r you will come across a carlon faq which includes this.....http://www.carlonsales.com/oldworknmbox.php

Hi could you please tell me your box rating on 4 sq. plastic boxes, also on single gang box? If you are discussing fire classification, most of Carlon's blue nonmetallic outlet boxes, with the exception of old work boxes, are fire classified for two-hour fire rated walls or less.

Why is the Old work box stamped with a rating? I'm guessing factory error.
Should UL catch this in their periodic factory visits? Yes. Nobody is perfect.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
The exception in IBC 713.3.2 addresses this.

Membrane penetrations by listed electrical boxes
of any material, provided such boxes have been
tested for use in fire-resistance-rated assemblies
and are installed in accordance with the instructions included in the listing.

I think this answers how the box can be rated, even though it isn't attached to the stud.

Although it could also be a labeling mistake as Sandsnow mentioned, because Carlton's website says this:

The majority of Carlon outlet boxes have a two-hour rating. We choice not to rate our old work boxes for two-hour assemblies for liability reasons. An easy well to tell if a box is rated for firewall construction is to look at the UL logo in the box (or in the area of the UL logo). If the box is marked with a 2-HR-* (* = W, C, F or WC) it is classified for two fire resistive assemblies.

That's from this: http://www.carlonsales.com/techinfo/faqs/FAQ-ZipBoxes.pdf

If you really want to learn about fire ratings, they also refer to this: http://www.carlonsales.com/techinfo/codesstandards/CS-Fire_PVC_Building_Codes.pdf

which could take a while to digest, and may not provide any more useful info on old work boxes.
 

sandsnow

Senior Member
I forgot your other question. Since cut-in boxes are not an option for existing walls, we would require a larger than the box opening next to a stud and patch in a piece of drywall using this Gypsum Assoc document. Do a Google search for repair of fire resistive walls and select a pdf entitled...

REPAIR OF FIRE-RATED GYPSUM PANEL PRODUCT SYSTEMS


The document above is the only guide to repair I ever found. You'll find all kinds of stuff on "repair to original rating" or "repair with listed products". Those documents or explanations never point you to resources.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I forgot your other question. Since cut-in boxes are not an option for existing walls, we would require a larger than the box opening next to a stud and patch in a piece of drywall using this Gypsum Assoc document. Do a Google search for repair of fire resistive walls and select a pdf entitled...

REPAIR OF FIRE-RATED GYPSUM PANEL PRODUCT SYSTEMS


The document above is the only guide to repair I ever found. You'll find all kinds of stuff on "repair to original rating" or "repair with listed products". Those documents or explanations never point you to resources.

What if you secure the cut in box to the stud, if you are good you can cut in tight. no gap.
 
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