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!
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>>>
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>
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?
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.