Temperature Limitations

[jumpinjohnny]

In reference to Art. 110-14 (C)(1)(b). Have new 1200A panelboard in old location. 75*C rating. S.E.C's are 500 mcm THW 380Amps 3 sets 1140Amps. To increase this to 1200Amps according to Art.310-16 Using THHN would you have to use 500 mcm or 600mcm

 

[bob]

Re: Temperature Limitations

You would use the 75C rating of the conductor ampacity in 310.16. 500kcm 4 x 380 = 1520
or 600 kcm 3 x 420 = 1260. 3 ckts of 500 kcm would be 3 x 380 = 1140 amps which would not be adequate for the 1200 amp main breaker.