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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)? 

Question asked by Andrew Rogers on Sep 15, 2016
Latest reply on Dec 10, 2016 by Joseph Hren

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)?

 

 

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