Derating PV conductors on roofs.

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wwhitney

Senior Member
Location
Berkeley, CA
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Is the insulation on your conductors rated 90C, 105C, or 125C?

If 105C or 125C, you may use tables 690.31(A)(3)(1) and (2). If 90C, then Article 310 as usual.

Cheers, Wayne
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
electrofelon said:
90c, THWN-2. Alsoi 2017 NEC.
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Ah, 2017 NEC.

I don't see anything in 690.31(A) that gives relief from the requirement in 310.15(B)(3)(c), so that still applies. As for the tables, the values agree with each other, so it doesn't matter which one you use.

[Other than the fact that Table 690.31(A) goes to 10C wide bands starting at 61C, but that's just a stupid difference. You don't have to use the tables anyway, you can use Formula 310.15(B)(2), which may provide a marginal benefit if the ambient temperature is not a multiple of 5C.]

Cheers, Wayne
 
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