eprosenx
Active Member
This is a great table that I reference all the time, but do understand that it is a dummed down version.
The actual source of record is NEC Table 310.15(B)(16) for many of the use cases we talk about on this forum.
It differs in important ways for 10 gauge conductors and smaller. There are other rules on the books that cause these fixed "15, 20, 30" amp ratings for the smaller gauge wires, but the real numbers are equal to or greater than what is in that table and you need those "raw" numbers in order to calculate proper derating like in this case with many current carrying conductors in a raceway.