Code Change Summary: The title to table 310.15(B)(3)(c) has been modified to make it clear that the table now applies to more than just circular raceways on or above a roof.

In the 2011 NEC^®, Table 310.15(B)(3)(c) only applied to circular raceways exposed to sunlight on or above the rooftop. Now, in the 2014 NEC^®, this table applies to any raceway or cable exposed to sunlight on or above the rooftop.

Table 310.15(B)(3)(c) provides temperature adders to be added to the ambient temperature correction factors in Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b). These temperature adders are based on how close a rooftop wiring method is located to the hot roof surface. The further away the wiring method is from the hot roof surface, the lower the temperature adder is.

Example: PVC coated, sunlight resistant MC cable containing THWN (75°C conductors) installed 4 in. above the rooftop in a location where the ambient temperature is 100°F.

• First, Table 310.15(B)(3)(c) requires a temperature adder of 30°F to be added to the 100°F ambient temperature for a total of 130°F ambient temperature correction factor.

• Next, use the 75°C column of Table 310.15(B)(2)(a), and the 130°F overall ambient to obtain a .67 correction factor.

• Basically, this MC cable can now only carry 67% of its normal value because of its close proximity to the hot roof surface.

See image for an example of Table 310.15(B)(3)(c).