Wire Sizing

[ken44]

I have 4 each of 400 Amp CB's that are located in a UPS, there are 2 CB's at each end of the UPS; I will be sizing the wire for these CB's from the 75 degree column of 310-16 per the terminal temperature rating of the CB's, Do I have to use 600 KCMIL (420 Amps@75 degrees)or does the NEC allow me to use 500 KCMIL (380 Amps@75 degrees) per the "next size up" rule?

 

[raider1]

You can use 500 Kcmil conductors and the next size up rule provided that the calculated load on the feeder does not exceed 380 amps.

Chris