Ambient Temp Correction

[fossil112]

Hello all,
I've seen both types of PV designs - those that include ambient temp correction and those that don't. I can see it indoors where you have a steady state ambient temp, but I'm curious if others use it for outdoor conductors (AC specifically). It'd be tough to quantify ambient temp qualification, besides ASHRAE's 2% value.

 

[augie47]

(I misread the post and deleted my irrelevant answer. sorry)

 

[augie47]

I inspecting, I require the 310.15(B) (3)(c) & (B)(2)(a) Tables be taken into account on PV.

 

[ggunn]

Hello all,
I've seen both types of PV designs - those that include ambient temp correction and those that don't. I can see it indoors where you have a steady state ambient temp, but I'm curious if others use it for outdoor conductors (AC specifically). It'd be tough to quantify ambient temp qualification, besides ASHRAE's 2% value.

Temperature derating should be used in all conductors using the ASHAE tables. I use the 2% numbers for all outdoor conductors with the NEC specified heat adder for rooftop conductors in conduit per the 2014 code. Under 2017 I hear that the heat adder is going away, though.

 

[fossil112]

I inspecting, I require the 310.15(B) (3)(c) & (B)(2)(a) Tables be taken into account on PV.

How do you determine ambient temp?

 

[ggunn]

How do you determine ambient temp?

As you said, from the 2% average high temperature number on the ASHRAE tables. I use this website: http://www.solarabcs.org/about/publications/reports/expedited-permit/map/index.html

 

[fossil112]

As you said, from the 2% average high temperature number on the ASHRAE tables. I use this website: http://www.solarabcs.org/about/publications/reports/expedited-permit/map/index.html

Yup, that's also what I use.

 

[jaggedben]

Note the NEC doesn't specify where you get the temperature value, and only gives ASHRAE as a suggestion. Whatever your AHJ approves is okay.

But thanks for the link ggunn!