panels in firewall

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
why cant I install a new panel in a firewall but j-boxes are ok ?
1. Are you sure they are? Even if mounted back to back?
2. J-boxes typically are not full depth in the wall while panels often are. That leaves an insulating space between the inside of the box and the wallboard or whatever is behind it.
3. Panels are a lot bigger. More area = more heat exposure and chance of flame transmission.
 

infinity

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Location
New Jersey
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Journeyman Electrician
Off of the top of my head, I believe that for a box in firewall the penetrations are limited to 16 square inches.
 

roger

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Location
Fl
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Electrician
To go along with Infinity's post


From the UL Fire Resistance Directory



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.

Metallic boxes located on opposite sides of walls or partitions shall be seperated by a minimum horizontal distance of 24in. This minimum seperation distance between metallic boxes may be reduced when "Wall Opening Protective Materials" (CLIV) are installed according to the requirements of their Classification.
Roger
 

mwm1752

Senior Member
Location
Aspen, Colo
If the penetration of the box is greater than 16" you must firerate around it -- putty pads, 5/8 X sheetrock - check with the building dept & proposed a solution -- there are 3 basic rules for electrical boxes - penetration lgreater than 16" -- through penetration (boxes facing opposite directions) with in 2' horizontally -- 100 sq in of combined penetrations (IE: 13 - 1gang openings)within 100 sq ft of wall
 
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cowboyjwc

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Location
Simi Valley, CA
If the penetration of the box is greater than 16" you must firerate around it -- putty pads, 5/8 X sheetrock - check with the building dept & proposed a solution -- there are 3 basic rules for electrical boxes - penetration lgreater than 16" -- through penetration (boxes facing opposite directions) with in 2' horizontally -- 100 sq in of combined penetrations (IE: 13 - 1gang openings)within 100 sq ft of wall
The thing about wrapping it is that you wont find a "listed" or "approved" method. Always best to check with the AHJ and see what they allow.
 

roger

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Location
Fl
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Electrician
I have done this (Wrap it with 3M fire pads) many times and has passed inspection without any problem. View attachment 9359

But check with your AHJ first.
The inspectors need to read the listing information on the pads, and to follow mgookins post, why would you do it in the first place in that wall assembly?


Roger
 

roger

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Location
Fl
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Electrician

mwm1752

Senior Member
Location
Aspen, Colo
Read sections #2 "Applications" and #6 "Installation Techniques" and note the sizes of boxes they can be used on.

Wrapping a load center with them is beyond their limits.

Roger
For larger applications, pads can be molded together by hand. section 2 -- pretty strong statement --

 

edward

Senior Member
Not as strong as the information here and a load center is not mentioned.

Roger
The way I read that it is a "installation suggestion" for electrical boxes and it will not include panels. If the instruction allows the pads to be molded together for larger surfaces then i don't see it as a violation. Unless i am missing something else.



Suggested Installation for

3M? Fire Barrier Moldable Putty+
on Electrical Outlet Boxes
 
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