bphgravity said:
1. Section 440.32
2. Section 334.80
3. Table 310.16
I would like to add article 240.4 which allows the asterik in Table 310.16 to be used.
If you consider the attic ambient to be 145F then we have to derate .58,
However there is much debate over what ambient temp. means. Is it the high temp of the year for one hour of the entire year or the temp. average for the hottest days, or the average for the summer months, or the average for the year.
We certainly know it is not 145F all day during the summer but it will peak there. I would love to know the answer to this question because I know that it is rarely considered on residential application. I don't believe I ever considered it except for the placement of transformers in the attic.
Anyway with VD and not using ambient I would say 12/2nm is good, however I would pull a 10/2.