Complex Imaginary Exam 1 Prob 26- overcurrent protection

[ElecPwrPEOct11]

For 300kcmil, TW, 60 degree cable the question asks what's the largest allowable overcurrent device:

A) 150A

B ) 180A

C) 200A

D) 225A

The allowable ampacity of the conductor is 190A from the NEC. However this is not a standard ampere rating per 240.6. NEC 240.4 (B ) allows you to round up to the next highest standard size 200A, except in a couple of very specific instances. Due to this, 200A is the correct answer. Can someone explain why the given solution of 180A is instead correct? Thanks.

 

[Wildsoldier PE]

I think you are right...200Amp shall be the over current protection. article 240.6(A) gives the standard breaker sizes and since the feeder is less than 800 amps you are allowed to use a higher breaker on a lower rating wire. For the people that don't know the wire specified in the problem is aluminum wire.

 

[TFT]

I also agree with your answer. I've submitted it as an errata but it has not been corrected yet.

 

[ElecPwrPEOct11]

^^ cool, thanks for confirming that I didn't miss something critical with this basic question.