polyeurothane foam over elec wiring
To install electrical wiring behind sheetrock walls in my basement, I removed the spun glass insulation, installed the wiring circuits, outlets, and so forth. Rather than re-install the spun glass insulation, I was thinking of spraying in the new foam insulation, then re-installing the sheetrock. Since the electrical wiring is now neatly routed between the 2 X 4 studs with the individual wires located at least one inch back from the leading edge of the studs, will it matter if the sprayed insulation covers the wiring? If that is against code, how do you prevent the expanding foam from covering the wiring? Many thanks. Walther
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The only objection my electricians have is when they need to pull more wire someday in the future, LOL
Theoretically, there could be more heat held by wire in the foam, but have never heard of it being a problem or against code.
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15 years ago or so, we had discussions related to foaming the wire entrances to J boxes and light fixtures and such re: the compatibility of e.g. urethane spray foam with the NM sheathing on e.g. standard Romex. Does it e.g. void the U-L listing of the box or device? It's not really any different if you fill the entire cavity and that in turn seals the entrance to the box. It may make a difference depending on the type of insulation you use (e.g. urethane, icynene, etc.).
Never heard if this was a violation of NEC or not. But I frequently see people still do it ... most commonly the holes penetrating the top plate of walls are sealed w/ insulation foam. Inspectors see it ... it 'must be OK'. Your inspector should give you an idea if he knows of a compatibility problem. Ask him. Assuming he is level headed and not big headed.
The wires are 1" back ....with metal protection plates, right? 1" isn't deep enough to protect the cable from a screw and is not up to code.
...that's not a mistake, it's rustic
typically needs to be back 1 1/4 " or use a plate.
let's see - half inch sheetrock hung with 1-5/8" screw plus penetration dimpling the SR = 1-1/8"+ into the stud with that pointy tip
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metal nail plate is a code requirement for cable that close to the sheetrock. The code even requires a minimum thickness for the nail plate ( I cant remember off-hand which it is, but ask the electrician at your home center when you go to buy them). There is no NEC code specific to spray foam insulation that I can recall in the 2005 edition. Check your local codes, the electrical inspector in your area has final say.........period. You could just call your local building inspection department and they will point you in the right direction. Regardless of whether or not you are having this particular project inspected by the building department, if you or your client ever go to resell the building, your building department will require any code violations to be fixed at your expense.
"Check your local codes, the electrical inspector in your area has final say.........period. "Not really. They can only require what is written in the codes.Now there are areas that are subject to interpretation. And if challenged they are start being real nitpicking.But they can't require anything that is not written in the code."if you or your client ever go to resell the building, your building department will require any code violations to be fixed at your expense."Highly unlikely. Few places have any kind of inspections on sale and even when they do it is usually limited to items like smoke detectors and maybe broken glass.And how would they know what the code was when the work was done?And how how deep a hole is in stud covered by DW?.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
This is an interesting issue. Most people know about derating multiple conductors bundled together through stud holes. In that case the conductors are somewhat free to "unbundle" between studs and cool a bit. But if you add foam insulation to the mix the wires are likely to remain in close proximity and moreover they are thermally insulated. No cooling there. Could this be a case where the code hasn't caught up?Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.â€
I haven seen any engineering reports of such, but I am not in a loop to see them.But cable in insulation isn't anything new. You have the dense pack cels and BIPS.But it can still dispate, just much less.Not like being in the middle of bundle of 6 active wires.And they play enough games with the ratings on #14, 12, and 10 and in general and while the wire in NM-B is rated to 90C you can only use the 60C column..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The foam can be in contact with the wire but you need to put extra care in the stapling esp with low voltage stuff like speaker, phone, t-stat, and E-net because the expanding foam can get behind the wire and push it out towards the room and if you need to shave the foam to install the drywall you can nip those wires. Mostly we have problems with the signal wires that are not installed by the electricians.
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