Double Derating

[infinity]

Okay! Thank you!

I put it back for you.

 

[HEYDOG]

I put it back for you.

Thank you!

 

[Strathead]

So if 2 days out of the year the outside temp reaches 100 degrees you would base the calculation on that? There are so many variables. I wire a house that is under trees so the temp in the attic is not very hot but then some trees get removed.... I think they need to come up with a better term or at least a good way to determine ambient temp. I think there is some chart somewhere for this...

From the NEC, which is better than nothing. I agree that it is a pain, but some sort of accounting needs to exist for hot days and conductor ampacity. This is also very true for expansion of PVC, which is rarely addressed.

Informational Note: One source for the ambient temperatures
in various locations is the ASHRAE Handbook — Fundamentals.

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