two nm cables through an fire chaulked hole derating

[JJWalecka]

i read somewhere that you didnt have to derate if the firechaulked hole has 80 percent of free space. Does anyone know where in the code it states that? thank you

 

[tom baker]

The 80% free space is not a code rule.

 

[don_resqcapt19]

The code does not say anything like that.

334.80....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 ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1) and 310.14(A)(2), Exception, shall not apply. ...

However if you are using NM cables for circuits 30 amps or less, there is no real world impact until you have more than 4 cables in the caulked hole.

 

[JJWalecka]

The 80% free space is not a code rule

thx