# derating on roof



## ufcc (May 21, 2011)

need a little help when running conduit on the roodf i know i need to be 2 feet high on the roof, but if u only have 3 wires in conduit do u still have to derate ? my boss is telling me i do whitch i dissagree what does anyone think


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## tates1882 (Sep 3, 2010)

ufcc said:


> need a little help when running conduit on the roodf i know i need to be 2 feet high on the roof, but if u only have 3 wires in conduit do u still have to derate ? my boss is telling me i do whitch i dissagree what does anyone think


Well unless you are above 36" then you need to add the value out of table 310.15(b)(3)(c) to your average ambient temp then do the correction. 2011 code


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## don_resqcapt19 (Jul 18, 2010)

The adjustment factor for more than 3 current carrying conductors and the correction factor for ambient temperatures both have to be applied. In this case you only have 3 current carrying conductors so there is no adjustment factor, just a correction factor for ambient temperature.


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