Complex Imaginary, Vol 1, Q19 (NEC Conductor selection)

[Silkworm]

The question asks you to determine the appropriate size UF Al (60 degC) conductor using NEC for a 3HP continuous duty motor. I understand the load amperage is 25x1.25=31.3A. Using table 310.15, an 8AWG conductor can carry 35A, which is what I selected since its greater than FLAx25%.

However, the answer in the book selects 6AWG which is capable of 40A. Isn't the minimum size conductor the 8AWG?

Please help.

Thanks.

 

[katag]

I worked this test out today and got the same answer. I am using the 2011 NEC code and it seems that they may have changed that value from the 2008 NEC code because it is highlighted. This could be the answer with the 2008 version but I don't have it to verify. Either way I agree with your answer.

 

[knight1fox3]

What voltage is the motor operating at?

 

[soma]

Which version of CI tests you are using ? I have the latest one and answer is 8 AWG, so your solution is correct.