I have a question concerning whether or not you need to derate conductor sizes base on ambient air temperature if the conductors are run underground in a ductbank. I have an inspector that is saying because the conductors come out of the ground and connect to an outdoor panel, I need to derate the conductors based on ambient air temperature at the panel. I say the majority of the conductor length is installed underground and have no direct sunlight contact, therefore, ambient temperature derating is not required. Any thoughts?
Underground conductor derating based on temperature
- Thread starter thomrk
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- Lockport, IL
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- Retired Electrical Engineer
This is a more complex question than you might think. But I will start by asking how long the conductors are, and what is the distance from the point of their passing above grade level to the point they terminate within the panel. I am thinking in terms of the exception to 310.15(A)(2).
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