Doug Miller wrote:
In article et, HorneTD wrote:

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.


OK, fine -- doesn't change the fact that the previous poster was undersizing
the job.


I agree. I just didn't want to leave anyone with the impression that a
ninety degree column ampacity would ever be the ending point for an
ampacity question.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.