brother
Senior Member
A friend of mine sent this calculation question to me from their electrical article. I did not get the same answer as the author, especially about the 75 degree rating equipment.
answer they gave is 1080 amperes ? 2008 NEC 400.5(A), 400.2.
The only way I can see how they even come close to that is they used column E2 in the 90 degree section. 361 X 3=1083, but even then that's still not exactly right. But how can they use E2 since its only for 2 conductor cables and other cables when only 2 are current carrying?
In addition to that, I thought when you had 75 degree equipment that you had to still derate for that even for cables. Let me know what I am missing here.
article said:What is the ampacity of three parallel 4/0 Type W portable power cables with a
temperature rating of 90⁰C connected to equipment terminals having a
temperature rating of 75⁰C? - See correct answer on Page 2.
answer they gave is 1080 amperes ? 2008 NEC 400.5(A), 400.2.
The only way I can see how they even come close to that is they used column E2 in the 90 degree section. 361 X 3=1083, but even then that's still not exactly right. But how can they use E2 since its only for 2 conductor cables and other cables when only 2 are current carrying?
In addition to that, I thought when you had 75 degree equipment that you had to still derate for that even for cables. Let me know what I am missing here.