Determine the ampacity (current-carrying capacity) of four (4) size 1/0 AWG THW copper current-carrying conductors installed in a common raceway with an ambient temperature of 86 degrees F.
First locate the wire size on the left side of Table 310.16 and look to the right under the copper THW column, with a temperature rating of 75ºC, and note the ampacity of the wire is 150 amperes. The table is based on an ambient temperature of 86ºC and not more than three current-carrying conductors in the raceway. This question states four (4) current-carrying conductors are in the raceway so we must apply the adjustment factor as shown in Table 310.15(C)(1)(a) as follows: Size 1/0 AWG THW ampacity = 150 amperes before adjusting 150 amperes x 80% (adjustment factor) = 120 amperes
