Here's an example if the neutral is considered a current-carrying conductor: Ampacity 3/0 THHN is 225A [Table 310.16 at 90°C) Adjustment factor [Table 310.15 (B) (2) (a)] = 0.70 Adjusted ampacity = ...

Q. What is the allowable ampacity of any one of the current-carrying 12 AWG THHN insulated conductors installed in a cellular concrete floor raceway with 29 other current-carrying 12 AWG THHN ...