Doug Miller wrote:
In article .com, wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison