Jessica Dragoo
Member
Minimum size conductors in a raceway are based on actual load ampacity, ajustment factors for more than 3 current-carrying conductors [Table 310.15(B)(2)(a)], and correction factors to Table 310.16. If ampacity is adjusted requiring a larger conductor size, is voltage drop calculated based on the new larger conductor size? Or is voltage drop still calculated at the minimum size conductor? Are these two corrections for conductor size additive?
For example, if we bundle (16) #10 THHN current-carrying conductors in a single raceway, based on adjustment factor of .50 and the 90 degree C column of table 310.16, #10 THHN is good for 20A. If the voltage drop calculated on that circuit required an increase from #12 to #10 without accounting for the current-carrying adjustment, should the conductors be then sized as a #8 to account for both ampacity adjustment and voltage drop?
For example, if we bundle (16) #10 THHN current-carrying conductors in a single raceway, based on adjustment factor of .50 and the 90 degree C column of table 310.16, #10 THHN is good for 20A. If the voltage drop calculated on that circuit required an increase from #12 to #10 without accounting for the current-carrying adjustment, should the conductors be then sized as a #8 to account for both ampacity adjustment and voltage drop?
