double derating of conductors?

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Electron_Sam78

Electron_Sam78

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Palm Bay, FL
I have a project I'm planning and was wondering if I have 3 circuits (9 current carrying conductors) in a trench together (not separated) and ambient, summertime temperatures of 96-104 F do I need to derate for both factors or just the highest factor? The circuits separate once emerged from the trench. What's the NEC reference to answer this question?
 
The number of current carrying conductions and ambient both stack on top of each other. I don't have the code book on me.

Do you really think the conduit will be exposed to 96 degrees in a trench?
 
If the pipes are in the ground and covered by earth, i see no reason to derate on that. But once the pipes come through the earth, will they be exposed to sunlight? and what is the location of the exposed pipes to sunlight? on a roof? on the side of a wall? what size wire?
 
Any derating required must be done.

If both T310.15(B)(2)(a) and the ambient temp on the bottom of T310 apply, then both are calculated. It's not a smorgasboard.
 
These are direct buried conductors not in conduit. There are 9 total conductors in the trench where T315(B)(2)(a) [more than 4 conductors deration factor] applies. Then when emerging from the trench they are in coduit and separated from each other by circuit (one cicuit to a conduit). But, when the conductors are not in the trench the summertime ambient air temps can reach around 100 degrees here. It's kind of a strange situation as far as applying deration factors that's why I'm a bit cornfused. These circuits are in an open area that receives direct sun. The conductors are 4/0 aluminum
 
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if the conductors are buried per 300.5, I'd not think ambient would be a problem in the ditch (opinion) and exception 4 to 310.15(b)(2) would exclude up to 10 ft of conductor after it leaves the trench. With that in mind, you may not have a derating issue as far as ambient.
 
active1 said:
Are you sure your not over estimating the tempiture?

It averages 89 F in the summer there:
http://www.climate-charts.com/Locations/u/US72000001159431.php
The record temp was 95 F in 2002 today in Mt. Vernon, IL.
The next day the record temp was 95 F again in 1999.

http://www.wunderground.com/cgi-bin/findweather/getForecast?query=62864
Click to expand...

That's the "official" average and record. Those are usually a bit lower than it really is. We hit 97 F 2 weeks ago. Besides If it gets to 95 at least a few days a year it should be planned for right
 
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