2011 mike holt nec exam prep unit 6 practice questions, question 9 of 53

[joelbeach]

What is the ampacity of an 8 THHN conductor when installed in a walk-in cooler(dry location)if the ambient temp is 50 F?


A) 40A
B) 50A
C) 55A
D) 57A

By my calculations I have:
55A X 1.15=63.25
Code ref Table 310.15 B 2 a
Code ref Table 310.15 B 16


What am I missing here?

 

[charlie b]

I think the author of the test question would say that the correct answer is B (50 amps). You can calculate an ampacity using correction and adjustment factors, but you can't end up with a final answer that is higher than the value in the 75C column of table 310.15(B)(16). That is because we are also limited by the rating of the terminations, and there are no terminations rated for 90C. My reference on that is 110.14(C).

 

[joelbeach]

The answer is D according to the program and this is their calculation.

55 X 1.04=57

 

[infinity]

It's a correction here:http://www.mikeholt.com/documents/c...ook/11_ExamPrep_Textbook_Correx_Directory.pdf

16 Unit 6, Answer 31 Answer (d) should be changed to 63A, due to change in solution from ?55A x 1.04? to ?55A x 1.15.?

 

[joelbeach]

That's the link I've been looking for.