30 ccc's

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Section 376 states that over 30ccc's it is mandatory to use section 310.15(B)(2)(a). I understand where section 310.15(A)(2) excp can be used but IMO not for wireways.
 
SEO said:
...I understand where section 310.15(A)(2) excp can be used but IMO not for wireways.
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Please cite the code reference which says we cannot. I certainly don't see it anywhere in Article 376.

We are not disregarding the 30 CCC rule. We simply apply it, then use 315(A)(2) Exception to override it. We are permitted to because the exception states we can use the higher adjacent ampacity as long as the 10% up to 10' stipulation is met.
 
Back in the 2005 NEC an ampacity adjustment was added regarding NM cables use through fire stopped or draft stopped holes. The requirement was to derate those cables. Problem was that 310.15(A)(2)Ex made that new requirement unenforceable. In the 2008 NEC, 334.80 contains new wording that explicitly prohibits applying the 310.15(A)(2)exception to this type of installation. Until they add similar wording to Article 376, 310.15(A)(2)Ex can be applied to wireways with more than 30 CCC's.
 
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