Panel and Plywood

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tonype

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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?
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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.
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Looks like a violation to me, combustible material exposed to the interior of the load center when the cover is installed.
 
MTW said:
Looks like a violation to me, combustible material exposed to the interior of the load center when the cover is installed.
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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.
 
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
 
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don_resqcapt19 said:
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.
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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:
 
wwhitney said:
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.
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Sounds like a verbiage problem but the requirements should be the same.
 
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
 
wwhitney said:
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
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Just says non combustible. Shouldn't even need to be metal. That said most anything can burn if you get it hot enough.
 
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
 
wwhitney said:
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.
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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 ...
 
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?
 
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.
 
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.
 
don_resqcapt19 said:
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.
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Seems 312.3 covers panels, cabinets, meter socket enclosures, and 314.20 covers outlet boxes, junction boxes device boxes, etc.
 
tonype said:
... Is this a fire concern?
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If the steel cabinet of a circuit-breaker (?) panel approaches the ignition temperature of plywood, you have more-important concerns to address first.

don_resqcapt19 said:
If the cover is a flush cover, there is an issue, ...
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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.
 
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