Ambient temp.

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PCN

PCN

Senior Member
Location
New England
Is there anything in the code that clarifies ambient temperature?
On a current project the inspector claims we have not applied the proper correction factor when sizing conductors for rooftop equipment. (conduit routed on roof on 4" blocks). In 310.16 I used the 60c column with a 0.71 correction factor which is 105-113 degrees f. The inspector feels that with a black membrane flat roof the temperature will exceed that. While I don't completely disagree with him, I'm not really buying it 100%. I've worked on many a roof and know they get hot in the summer but what correction factor is well....correct?
Project is in New England.
 
Well then IMO you can not be forced to change what you have.

Under the 2008 you would have to put about a 30F adder on top of the ambient because of being on the roof.
 
The inspectors really shouldn't be winging it. In this case, the inspector should probably ask the engineer of record and/or the design professional whom put together the constuction documents to identify the size of the conductors needed for the circuits on the roof based on their calculations.

Otherwise, the inspectors SHOULD provide you something in writing that identifies how they determine ambient temperatures and when correction factors need to be applied.

While enforcement by "feel" is soemthing that occurs due to human nature, it is inappropriate and certainly not professional to make it up as you go...
 
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