Service 400A

[Leonan]

Hello everyone, I have a question at work. To provide a 400A service for 6 units, I will use only one pipe and leave the wires in parallel. So will I have to apply table 310.25 C1? Which would be 400A/80%: 500A/2: 250A per phase. Would it have to be a 350 kmil aluminum parallel?

 

[infinity]

Are you asking about the derating or ampacity adjustment table? Youve got a misprint that's T310.15(C)(1). If so your calculations are correct.

 

[Leonan]

Yes it is the table 310.15 C1

 

[infinity]

Yes it is the table 310.15 C1

With a 90° C conductor:
350kcmil aluminum is rated at 280 amp @ 90° C.
300 kcmil aluminum is rate at 260 amps @ 90° C.
260*2*80%=416 amps so 300 kcmil would work.