Section 310.15(B)(2) includes two tables of correction factors, one for a 30° C ambient and the other based on 40° C.

The 30° C correction factors are used for a conductor installed in an ambient temperature different than the 30° C that is assumed in Table 301.15(B)(16) and Table 301.15(B)(17).

The 40° C correction factors are used for a conductor installed in an ambient different than the 40° C ambient that is assumed in some other tables, such as Tables 310.15(B)(18) through (21).