cmelguet
Electrical
- Jul 19, 2009
- 64
Hi,
I am trying to figure out the following:
- NEC article 392.80(A)(2)(c)state that for single conductors installed in a trifoil formation with separation of 1 diameter between individual conductors we should use table 310.15(B)(17) for ampacity. This table for example gives you an ampacity of 620 A for a 500MCM, 75 C conductor at 30 C ambient temp.
-NEC article 392.80(A)(2)(d)state that for single conductors installed in a trifoil formation with separation of 2.15 diameter between conductors we should use table 310.15(B)(20) for ampacity. This table gives you an ampacity of 496 A for a 500 MCM, 75 C conductor at 40 C ambient temp, or 560 Amp at 30 C ambient temperatura (using the corection factors of table 310.15(B)(2)(B).
My question is: Why if i separate the conductors 2.15 diameters, which is more than 1 diameter, the ampacity of the table i have to use is less? This make no sense to me, if this is the case, it will be better to separate conductors just 1 diameter and not 2.15.
Regards,
Cmed.
I am trying to figure out the following:
- NEC article 392.80(A)(2)(c)state that for single conductors installed in a trifoil formation with separation of 1 diameter between individual conductors we should use table 310.15(B)(17) for ampacity. This table for example gives you an ampacity of 620 A for a 500MCM, 75 C conductor at 30 C ambient temp.
-NEC article 392.80(A)(2)(d)state that for single conductors installed in a trifoil formation with separation of 2.15 diameter between conductors we should use table 310.15(B)(20) for ampacity. This table gives you an ampacity of 496 A for a 500 MCM, 75 C conductor at 40 C ambient temp, or 560 Amp at 30 C ambient temperatura (using the corection factors of table 310.15(B)(2)(B).
My question is: Why if i separate the conductors 2.15 diameters, which is more than 1 diameter, the ampacity of the table i have to use is less? This make no sense to me, if this is the case, it will be better to separate conductors just 1 diameter and not 2.15.
Regards,
Cmed.