Say I feed a multiple gang box with a single 14/2 cable fed by a 15 amp cb, wire-nut seven neutrals, pigtail the hot to 6 switches, then feed six 14/2 cables up the wall and through a single bored hole in the top plate. These six cables continue on to six individual recessed luminaires.
According to code, I have 12 current carrying conductors through this hole. Building code requires me to draft stop this hole, and 334.80 requires me to derate these conductors per 310.15(B)(2)(a).
But, because I feed all six cables from a single 15 amp breaker, am I exempted from the derating requirement? (after all, I am limited to 15 amps shared among all cables)