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
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options& settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules& etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
Drake Chamberlin
ATHENS ELECTRIC
OH License 44810
CO license 3773
NABCEP Certified PV
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
