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NMC in contact with spray foam insulation? #216752 02/11/16 07:55 PM
Joined: Oct 2002
Posts: 830
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sparkync Offline OP
Member
Anyone heard the the affect that spray foam has on romex?
Have a customer that had her whole walk in attic sprayed full of it. Romex cable, etc...

Thanks...

Work Gear for Electricians and the Trades
Re: NMC in contact with spray foam insulation? [Re: sparkync] #216754 02/11/16 09:39 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
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NEMA issues a "white paper" some time ago on the topic. The short version? No need to change anything .... the foam will not harm the cable, and derating remains the same.

Re: NMC in contact with spray foam insulation? [Re: sparkync] #216756 02/11/16 10:21 PM
Joined: Oct 2002
Posts: 830
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sparkync Offline OP
Member
Ok. Thanks for info..

Re: NMC in contact with spray foam insulation? [Re: sparkync] #216758 02/12/16 02:18 AM
Joined: Jul 2004
Posts: 9,382
G
gfretwell Offline
Member
The only time it becomes an issue is if a couple cables are bundled in the foam or going through a penetration sealed with foam. You treat it like a raceway at that point. (you derate)
334.80


Greg Fretwell
Re: NMC in contact with spray foam insulation? [Re: sparkync] #216760 02/12/16 08:24 AM
Joined: Dec 2001
Posts: 2,454
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Texas_Ranger Offline
Member
I've seen PVC react with foam but AFAIK it affects the foam rather than the PVC. The end result is that both stick together. Probably plasticisers from the PVC soften the foam and make it sticky. That's why you should never store vintage equipment in its original box without separating any cords from the foam. Now that I think of it the RF cable of the Commodore C-16 I sold some time ago did have melted spots from the packaging!

Re: NMC in contact with spray foam insulation? [Re: sparkync] #216762 02/14/16 03:09 AM
Joined: May 2003
Posts: 1,154
dougwells Offline
Member
Apparently Canada had a bad run with spray foam and romex about 10 years ago.. it was destroying the jacket on the romex.

http://safetyauthority.ca/sites/def...%20Polyurethane%20Spray%20Form%20Ins.pdf

Last edited by dougwells; 02/14/16 03:45 AM. Reason: to add link
Re: NMC in contact with spray foam insulation? [Re: sparkync] #216763 02/14/16 01:47 PM
Joined: Apr 2002
Posts: 7,105
HotLine1 Offline
Member
There were some issues with foam related to the chemical contained in the product that I recall from time past.

NM jacket becoming soft and 'melting', similar to what happens with a non-latex base primer used in fire restoration jobs.

Time to check out Dougs link


John
Re: NMC in contact with spray foam insulation? [Re: gfretwell] #216774 02/17/16 01:25 AM
Joined: Oct 2000
Posts: 5,373
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sparky Offline
Member
Originally Posted by gfretwell
The only time it becomes an issue is if a couple cables are bundled in the foam or going through a penetration sealed with foam. You treat it like a raceway at that point. (you derate)
334.80


Yes but i am confused Greg....

334.80 forbids 310.15 A 2 EX. & requires 310.15 B 3>>>

Quote
Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a).


338.80 in part reads>
Quote
Where more than two NM cables containing two or
more current-carrying conductors are installed, without
maintaining spacing between the cables, through the same
opening in wood framing that is to be sealed with thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 31 0.15(B)(3)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.


Most of our installs are required to have fire caulk between floors and/or units. These holes might be 4-5" in length, not 24" , so can i take it the 24" is relevant here?

I ask , because local code 'lore' seems to think otherwise, or perhaps said firecaulk does not work well for mutli-wires?


~S~

Last edited by sparky; 02/17/16 01:26 AM.
Re: NMC in contact with spray foam insulation? [Re: dougwells] #216775 02/17/16 01:29 AM
Joined: Oct 2000
Posts: 5,373
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sparky Offline
Member
Originally Posted by dougwells
Apparently Canada had a bad run with spray foam and romex about 10 years ago.. it was destroying the jacket on the romex.

http://safetyauthority.ca/sites/def...%20Polyurethane%20Spray%20Form%20Ins.pdf


But they are talking about mechanical strain, not thermal damage

~S~

Re: NMC in contact with spray foam insulation? [Re: sparkync] #216777 02/17/16 03:00 AM
Joined: Jul 2004
Posts: 9,382
G
gfretwell Offline
Member
Sparky, I agree the fairly new 334.80 does not really make a lot of sense.
The NEMA, study often cited, even makes it more confusing since it really just refers to the foam not damaging the jacket. I see nothing that indicates short sections in foam would overheat.

http://gfretwell.com/electrical/NEMA%20Romex%20in%20foam%20study.pdf

But rulz is rulz.


Greg Fretwell
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