[RE-wrenches] 310.15(A)(2) Exception

[Dave Click]

That's right, Drake. The long wire acts as a heat sink for that short 
section.


On 2011/8/17 17:58, Drake wrote:
> I think this answers a question I was pondering. If a conduit is run on
> standoffs over a roof, the temperature is cooler than on the roof, so
> the derating of the wire's ampacity is less. It would appear from
> 310.15(A)(2) Exception that it would _not_ be necessary to limit the
> ampacity of the wire to that of the hottest temperature zone, which is
> zero distance above the roof where the conductors penetrate.
>
> Is this a correct interpretation?
>
> Thanks,
>
> Drake
>
> At 01:51 PM 8/17/2011, you wrote:
>> As I read the rule, that 100' in the trench allows you to go 10' above
>> grade on each side while just worrying about the ampacity in the 100'
>> section (be sure to check that your terminals are OK). For 200' in the
>> trench, you're still looking at 10' above grade on each side. The rule
>> doesn't say that you can only use this exception once per circuit, so
>> it's fine that you use it once at each end.
>>
>>
>> On 2011/8/17 12:22, Brian Mehalic wrote:
>>> Question about the 10'/10% rule - the exception states "adjacent
>>> portions of a circuit." How does this apply to an underground conduit
>>> run, where there are two ends exposed to higher ambient temperatures
>>> than the length in the ground?
>>>
>>> For example, what if there is 100 feet in the trench, and 7 feet above
>>> grade on either side? Can the exception be applied? How about 200 feet
>>> in the trench and 7 feet above grade on either end?
>>>
>>> Thanks,
>>> Brian
>>>
>>> --
>>> ========================
>>> Brian Mehalic
>>> NABCEP Certified Solar PV Installer™ R031508-59
>>> IREC ISPQ Certified Affiliated Instructor/PV US-0132
>>> PV Curriculum Developer and Instructor
>>> Solar Energy International
>>> Carbondale, CO 81623
>>> http://www.solarenergy.org <http://www.solarenergy.org/>
>>>
>>>
>>>
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> Drake Chamberlin
> ATHENS ELECTRIC
> OH License 44810
> CO license 3773
> NABCEP Certified PV
>
>
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