Panel and Plywood

tonype

Senior Member
Location
New Jersey
I frequently see panels mounted to plywood bases. However, I have never seen it where the panel is behind the plywood and the cover installed on top. Is this a fire concern?
DSCF6681.JPG
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
It's 1/4" for non-combustible materials like wall board, tile, etc. Wood and other combustibles need to have the edge of the cabinet flush with the wood surface.

312.3 Position in Wall. In walls of concrete, tile, or other noncombustible material, cabinets shall be installed so that
the front edge of the cabinet is not set back of the finished surface more than 6 mm ( 1 ⁄ 4 in.). In walls constructed of
wood or other combustible material, cabinets shall be flush with the finished surface or project therefrom.
 

MTW

Senior Member
Location
SE Michigan
Looks like a violation to me, combustible material exposed to the interior of the load center when the cover is installed.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Looks like a violation to me, combustible material exposed to the interior of the load center when the cover is installed.
If the cover is a flush cover, there is an issue, but if you install a surface cover, there will be no exposed wood. However that doesn't change the code violation issue cited in post #4.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
So 312.3 references what the wall is constructed of, not what the finish surface is. Meaning the picture would be a violation even if the plywood were gypsum board? That seems a bit strange.

314.20, in contrast, references the finish material.

Cheers, Wayne
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
If the cover is a flush cover, there is an issue, but if you install a surface cover, there will be no exposed wood. However that doesn't change the code violation issue cited in post #4.
I agree, but if I had one of my inspectors cite me for that (presuming I at least used a surface cover) lets just say I might go to jail for however I respond to it.:censored:
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
So 312.3 references what the wall is constructed of, not what the finish surface is. Meaning the picture would be a violation even if the plywood were gypsum board? That seems a bit strange.
Sounds like a verbiage problem but the requirements should be the same.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
If we assume for the moment that 312.3 is supposed to be referencing the wall surface material, rather than the whole wall, I would think the condition in the OP could be easily addressed by adding some metal over the exposed plywood corners around the opening. That would make the wall finish noncombustible in the vicinity of the panel. Is there a minimum thickness specified anywhere in the NEC, or could one just use aluminum tape, such as that used for connecting rigid air ducts?

Cheers, Wayne
 

kwired

Electron manager
Location
NE Nebraska
If we assume for the moment that 312.3 is supposed to be referencing the wall surface material, rather than the whole wall, I would think the condition in the OP could be easily addressed by adding some metal over the exposed plywood corners around the opening. That would make the wall finish noncombustible in the vicinity of the panel. Is there a minimum thickness specified anywhere in the NEC, or could one just use aluminum tape, such as that used for connecting rigid air ducts?

Cheers, Wayne
Just says non combustible. Shouldn't even need to be metal. That said most anything can burn if you get it hot enough.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Sure, but seems like metal on wood is combustible if the metal is thin enough (e.g. gold leaf), or non-combustible if the metal is thick enough. Just looking for some guidance on how thick it would need to be. 312.10(B) says a sheet metal cabinet should be at least 1.35mm thick. So certainly a field constructed flange of 1.35mm thick angle would suffice to cover the plywood edges. But is there a simpler/thinner solution?

Cheers, Wayne
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
So 312.3 references what the wall is constructed of, not what the finish surface is. Meaning the picture would be a violation even if the plywood were gypsum board? That seems a bit strange.

314.20, in contrast, references the finish material.
Perhaps 312.3 requires that the wall (and not just the surface finish) be noncombustible to allow the 1/4" set back because cabinets often contain service conductors, feeders, etc. with higher current levels than the boxes for outlets, etc. described in 314.20. In other words, maybe the intent was to provide an extra margin of safety for cabinets beyond what's specified by 314.20, even though as you mention it's hard to rationalize the distinction when looking at the details of what's involved. Just speculation on my part ...
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I see it as a direct violation. The panel is set back in the wall too far. (Post #4)
Which came first? The panel or the plywood wall covering?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I don't think there is any question that what we have is a violation however, what Wayne is saying is that the intent of the section may be the wall material not what material is used to build the wall. I am certain a code proposal would be accepted if you just change it to wall covering.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The intent of 312.3 is to address both the construction and finish of the wall, and the intent of 314.20 is to only address the finish of the wall.
 

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Engineer
... Is this a fire concern?
If the steel cabinet of a circuit-breaker (?) panel approaches the ignition temperature of plywood, you have more-important concerns to address first.

If the cover is a flush cover, there is an issue, ...
That might depend on how securely the panel's mounted. If it moves forward enough when the cover screws are tightened, (and/or the plywood moves back) no clearance-to-combustibles violation.
 
Top