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#216752 - 02/11/16 03:55 PM NMC in contact with spray foam insulation?
sparkync Offline
Member

Registered: 10/17/02
Posts: 811
Loc: NC
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...

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#216754 - 02/11/16 05:39 PM Re: NMC in contact with spray foam insulation? [Re: sparkync]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
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.

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#216756 - 02/11/16 06:21 PM Re: NMC in contact with spray foam insulation? [Re: sparkync]
sparkync Offline
Member

Registered: 10/17/02
Posts: 811
Loc: NC
Ok. Thanks for info..

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#216758 - 02/11/16 10:18 PM Re: NMC in contact with spray foam insulation? [Re: sparkync]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
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

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#216760 - 02/12/16 04:24 AM Re: NMC in contact with spray foam insulation? [Re: sparkync]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
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!

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#216762 - 02/13/16 11:09 PM Re: NMC in contact with spray foam insulation? [Re: sparkync]
dougwells Offline

Member

Registered: 05/03/03
Posts: 1228
Loc: kamloops BC Canada
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/default/...0Form%20Ins.pdf


Edited by dougwells (02/13/16 11:45 PM)
Edit Reason: to add link

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#216763 - 02/14/16 09:47 AM Re: NMC in contact with spray foam insulation? [Re: sparkync]
HotLine1 Online   content

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
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
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John

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#216774 - 02/16/16 09:25 PM Re: NMC in contact with spray foam insulation? [Re: gfretwell]
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
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~


Edited by sparky (02/16/16 09:26 PM)

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#216775 - 02/16/16 09:29 PM Re: NMC in contact with spray foam insulation? [Re: dougwells]
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
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/default/...0Form%20Ins.pdf


But they are talking about mechanical strain, not thermal damage

~S~

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#216777 - 02/16/16 11:00 PM Re: NMC in contact with spray foam insulation? [Re: sparkync]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
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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