Expert: cleggsan - 12/21/2006

Question
Hi
It might seems like I am gonna ask to do my homework but it is not.Currently I am studying NEC calculations and I found an question which's answer does not match with mine.
Q) what size wireway is required if it contains               4 No#3/0, 6 No#6 and 20 No#12 THWN conductors?
Autors Answer)
#3/0 ---- 0.4151 sq. in.  x  4    =1.66 sq. in.
#6   ---- 0.1238 sq. in.  x  6    =0.74 sq. in.
#12  ---- 0.0384 sq. in.  x  20   =0.77 sq. in.

1.66+0.74+0.77=3.17 sq. in. total conductor filling area

(max 20% allowed by the NEC to fill wireway)
3.17 x 5 = 15.9 sq. in.
so 16 sq in. wireway required.

this is the answer from the author. but I looked the Table 5, chapter 9 for the each conductors area I could not find any of the numbers he gave me.
do you think is this answer is correct?if not what it should be?
thank you
evrim

Answer
Sorry, I can't help on this one. I don't have the National Electric Code requirements handy and I am overloaded with questions from my other expert categories just now so I don't have time to make the calculations.

BUT: Authors and professors do make mistakes sometimes  - not usually, though.

Why don't you go back to the author and inquire of the methodology employed.
Cleggsan