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#100764 01/02/07 08:34 PM
Joined: Jan 2007
Posts: 7
F
Junior Member
our inspector requires panels mounted in basements to be seperated from the concreate wall by plywood. Does anyone know in the code where it requires this? Also, If the wall is studed and the panels are mounted to the studs with the concrete behind them, would this still require the plywood?

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#100765 01/02/07 08:37 PM
Joined: Jan 2003
Posts: 4,391
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Not an NEC requirement.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#100766 01/02/07 09:08 PM
Joined: Jun 2005
Posts: 821
S
Member
I would ask the AHJ wich article in the NEC he is referring to if he's requiring you to do this. I did some looking around at article 408, and from there one of the articles referred me to 312.2 (A). As long as the panel is elevated 1/4" off the concrete wall I don't believe there is a violation. However, unless a panel is mounted between two studs I ALWAYS use a sheet a plywood as a barrier from the concrete wall. Think corrosion.

#100767 01/02/07 09:45 PM
Joined: Jan 2007
Posts: 7
F
Junior Member
thanks alot, It's probably just a local requirement due to the corrosion like you stated.

I have seen the 1/4" rule before, I guess with no studs the plywood gives the 1/4" and the corrosion.

#100768 01/02/07 10:11 PM
Joined: Jun 2005
Posts: 821
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Member
I had an inspector once who wanted sheet metal placed behind the plywood!

Anyone have any idea why?

#100769 01/02/07 10:37 PM
Joined: Dec 2004
Posts: 209
H
Member
Termite shield...you wouldn't want those termites to eat the plywood and get corrosion on their little bodies would you!

#100770 01/02/07 10:45 PM
Joined: Jul 2004
Posts: 9,959
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G
Member
The sheet metal protects the plywood (vapor barrier) and the plywood protects the panel?
I would think VisQueen would do the same thing. If the basement walls are damp you can make the 312.2 (1/4") rule work.


Greg Fretwell
#100771 01/02/07 10:54 PM
Joined: Jun 2005
Posts: 821
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Member
I figured the sheetmetal was for some sort of protection for corrosion, but why isn't it in the code somewhere?

Or maybe the AHJ was using 300.6 as his justification.

Anyway, I only did it a few times and no one has enforced it since.

Gfretwell, you're an inspector, right? Do you enforce this?

#100772 01/02/07 10:59 PM
Joined: Jul 2004
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I didn't do that much residential. In commercial the enclosures were usually on strut. Also we don't have basements. [Linked Image]


Greg Fretwell
#100773 01/02/07 11:23 PM
Joined: Jun 2005
Posts: 821
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Member
I forgot that basements are non-existant in some areas of the country. I just got back from the Carolina's and they didn't have any down there either. I've become so accustomed to them that I could not imagine not having one. Where would I store all my crap? LOL.

By the way, isn't all concrete considered to be a damp location? And why don't inspectors enforce 4x4 metal boxes on concrete walls be mounted on some sort of wood? If we do it for panels, we should also do it for any metal electrical box.

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