A few things about B.310.11.

In general under the NEC we can not use B.310.11 unless we are engineers.

310.15(A) tells us we have to either follow 310.15(B) or 310.15(C)

310.15(B) requires we use Tables 310.16 through Table 310.19 and Ampacity Table 310.20 through 310.23 as modified by (1) through (6).

310.15(C)Allows us to use engineering supervision which is the only way under the NEC to use Table B.310.11.

I say under the NEC as for us here in MA we do use Table B.310.11 all the time without even knowing it.

The MA amendments modify 310.15(B)(2)(a) into B.310.11. [Linked Image]

Bob Badger
Construction & Maintenance Electrician
Massachusetts