# Derating feeder ampacity in sunshine



## BBQ (Nov 16, 2010)

105 in the shade?

Anyway I would probably look at 2008 Table 310.15(B)(2)(c) or 2011 Table 310.15(B)(3)(c) for guidance.


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## B4T (Feb 10, 2009)

BBQ said:


> 105 in the shade?
> .


That has to be a typo.. it might get that hot once in (30) years in the shade..

The record is 110 degrees back in 1936..

http://www.infoplease.com/ipa/A0001416.html


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## Shorty Circuit (Jun 26, 2010)

BBQ said:


> 105 in the shade?
> 
> Anyway I would probably look at 2008 Table 310.15(B)(2)(c) or 2011 Table 310.15(B)(3)(c) for guidance.


Thanks for the advice but....this is 1200 amps 3 phase 480 volts with a full neutral. 310.15B doesn't apply.


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## Dennis Alwon (May 9, 2009)

I would not worry about maximum temp unless it was constant. It seems there is little direction as to what ambient temp. means. Is it the average? or what?


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## BBQ (Nov 16, 2010)

Shorty Circuit said:


> Thanks for the advice but....this is 1200 amps 3 phase 480 volts with a full neutral. 310.15B doesn't apply.



You are either looking at the wrong table or you are speaking a language I do not understand.


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> I would not worry about maximum temp unless it was constant. It seems there is little direction as to what ambient temp. means. Is it the average? or what?


Somewhere someone posted a link to the recommended design temps for different areas.

I think the list came from NEMA or a conductor manufacturer.


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## BBQ (Nov 16, 2010)

Shorty Circuit said:


> Thanks for the advice but....this is 1200 amps 3 phase 480 volts with a full neutral. 310.15B doesn't apply.


If this feeder ran across a roof this table would apply. I am suggesting you could use it as a guide for your wall application if you wanted to.


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## Dennis Alwon (May 9, 2009)

BBQ said:


> Somewhere someone posted a link to the recommended design temps for different areas.
> 
> I think the list came from NEMA or a conductor manufacturer.


This is what you mean. Click Here


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> This is what you mean. Click Here



Thanks. :thumbsup:


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## Shorty Circuit (Jun 26, 2010)

Dennis Alwon said:


> This is what you mean. Click Here


Thanks. I was looking at the wrong table. That's the one I need.


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## Dennis Alwon (May 9, 2009)

You are welcome. The problem I still have is this doesn't help much with temp. In attics- some houses are in the shade some in sunlight. So what is the design temp used there. Quite frankly I have never heard of anyone even mentioning ambient temp derating for nm cable. Maybe that is why NM is rated 60C even though it has 90C wire.


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## RePhase277 (Feb 5, 2008)

The Code used to have a map of the U.S. showing the the temperature of different areas in different seasons. That was deleted sometime in the 70's I think. If someone could find it, it may be a useful starting point.


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## nitro71 (Sep 17, 2009)

I got sunshine.. on a cloudy day..


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