bhernandez
Member
- Location
- Florida
I recently failed a rough inspection becuase the inspector rejected the use of 9 #12 THWN Cu conductors in 3/4" ENMT that will be be on 20A breakers. He is basing his decision on using 20 amps as the starting point of the 70% derating. I explained that for derating purposes you can use the 30 amp listed in 310-16 for 90C #12 THHN CU (20 amp being the maximum overcurrent protection allowed). 70% of 30a is 21 amps and ok for use with 20a breakers. Am I right or wrong?