derating for foam insulation

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brother said:
Check out NEC 2008 334.80 the last paragraph shows the changes concerning thermal insulation where 2 or more NM cables are installed without maintaining spacing.
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Also, as a reminder: NM-B can be derated from the 90? column. If you have 9 CCCs or less (current carrying conductors) it won't really affect anything.

edit to add: Welcome to the forum!
 
Sparky302 said:
With foarm insulation istalled in new construction do you need to derate NM-B wire or is the 80% rule O.K.
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You do not derate for foam unless you have bundled more than four 2 wire cables. 334.80 says to derate for more than two nm cables but nm has 90C conductors so you are not affected by this until you have more than four 2 wire cables. Table 310.15(B)(2)(a)
 
Are we talking about that ungodly spray on stuff that makes it impossible to work in a previously nice, open basement or attic?

The stuff that makes a 12AWG wire look like a 3" drain pipe?

The stuff that fills in all the nicely drilled holes for wires?
 
ArcNSpark said:
Are we talking about that ungodly spray on stuff that makes it impossible to work in a previously nice, open basement or attic?

The stuff that makes a 12AWG wire look like a 3" drain pipe?

The stuff that fills in all the nicely drilled holes for wires?
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Yea, that stuff:

DSC04024a.jpg
 
480sparky said:
Yea, that stuff:

DSC04024a.jpg
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I would be mad if I had paid for that install. Looks like they did a crappy job of spraying toward the ridge on the back wall. If nor done correctyly, that stuff can be a real problem. Once sprayed, the attic is actually only 10 degrees or so higher than the living space.

c2500
 
c2500 said:
I would be mad if I had paid for that install. Looks like they did a crappy job of spraying toward the ridge on the back wall. If nor done correctyly, that stuff can be a real problem. Once sprayed, the attic is actually only 10 degrees or so higher than the living space.

c2500
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This was not an attic. It's a loft.
 
What aboat IC rated can light I was thinking about rapping them with friction fit to make them accessable to the J-box. That foam stuff looks like it will make the can unable to slide out of the ceiling.
 
I saw a presentation by a wire manufacturer with reguard to 2008 code changes
and table 310.15 b 2 c . but in addition to that he showed 1 nm cable installed in fiberglass, sprayed insulation , and something else, and the circuit is loaded to 16amp and the results were amazing (even if I don't remember the numbers) the spray insulation dosen't allow heat to disapate. I'm sure someone else can be more specific.
 
The only thing I like is that this does seem to suggest that NM cables that pass through wood framing together NOT filled with foam don't have to be derated. Which is something that has been suggested in the past.
 
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