Fkohestani
Member
- Location
- Boston MA
I am trying to size low voltage (480V) cables for 4000A load in 50 degree C ambient temperature routed in ladder cable tray.
As per NEC 392.80(2) I used table 310.15(B)(17) 90 degree ampacity rating for 500 kcmil copper cables 700A.
using a 65% ampacity per 392.80(2)(b) and 0.82 temperature correction factor from table 310.15(B)(2)(a) I get
700*0.65*0.82=373.1.
The equipment is rated 75 degree C, and Since the 373A does not exceed the 380A from table 310.15(B)(16) for 75 degree C, I assume that
4000A/373A=10.72=11 set of cables should be fine.
I know that when you size cables, you have to take the equipment termination temperature rating into consideration, which is why I compared the 373A to the 380A from table 310.15(B)(17) 90 degree C.
My question is, do I need to apply ambient temperature correction factors for the termination point as well? based on NEC 310.15(B) and NEC 110.14(C), I don't think I need to do that.
As per NEC 392.80(2) I used table 310.15(B)(17) 90 degree ampacity rating for 500 kcmil copper cables 700A.
using a 65% ampacity per 392.80(2)(b) and 0.82 temperature correction factor from table 310.15(B)(2)(a) I get
700*0.65*0.82=373.1.
The equipment is rated 75 degree C, and Since the 373A does not exceed the 380A from table 310.15(B)(16) for 75 degree C, I assume that
4000A/373A=10.72=11 set of cables should be fine.
I know that when you size cables, you have to take the equipment termination temperature rating into consideration, which is why I compared the 373A to the 380A from table 310.15(B)(17) 90 degree C.
My question is, do I need to apply ambient temperature correction factors for the termination point as well? based on NEC 310.15(B) and NEC 110.14(C), I don't think I need to do that.