Sparky302
Member
- Location
- Rock Port, Missouri
With foarm insulation istalled in new construction do you need to derate NM-B wire or is the 80% rule O.K.
With foarm insulation istalled in new construction do you need to derate NM-B wire or is the 80% rule O.K.
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.
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)With foarm insulation istalled in new construction do you need to derate NM-B wire or is the 80% rule O.K.
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?
Yea, that stuff:
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