Per the Exception noted at Table 310.15(B)(3)(c), XHHW-2 insulated conductors "shall not be subject to the ampacity adjustment" noted in the Table.
Yet, in the application example provided in the 2014 National Electrical Code Handbook, XHHW-2 is used to demonstrate the impact of applying the adjustment factor noted in the Table which results in an "18% loss of usable conductor ampacity."
Is this an oversight? Or are we misunderstanding the Exception. Can Type XHHW-2 insulated conductors be ran in conduit on the roof without being subject to the Adjustment Factors for Ambient Temperature noted in Table 310.15(B)(3)(c)?
Inquiring minds want to know....