Primary service on roof..

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mike0w

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When placing primary service conduits on the roof to a substation located in a penthouse on the roof, I need to calcuate for derating conductors (and) for the area located on the roof (higher heat). Does it matter what one is completed first derating then heat loss or heat loss then derating? thanks for the help,,
 
Re: Primary service on roof..

Do you mean you need to consider an adjustment factor and a correction factor for the same group or groups of conductors? If so, it does not matter which factor you use first.
 
Re: Primary service on roof..

Mike - If I understand the question correctly - you have multiple conductors in a conduit in a higher temperature area. A derate for mulitple conductors in a single conduit is required and a derate for higher ambient temperature is required.

It does not matter which derate is applied first, since both are percentage multipliers. You should get the same answer.

Remember you can tart derating from the 90C rating.
 
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