On Sun, 17 Dec 2006 01:17:49 GMT, (Doug Miller)
wrote:

In article , wrote:
To connect a welder about 15 feet from breaker box. The welder says
primary amps 40. A wire chart on a website shows #6 as 37.5 amps.

Wow, I wonder where they came up with that. The National Electrical Code shows
#6 copper at 55 amps.


Here's the site: I thought it shoul be higher than that....
http://www.interfacebus.com/Copper_Wire_AWG_SIze.html
It seems to me like the old cable type service entrances for 60A
service were #6-3 plus ground (wrapped around the bundle).


Will #6 be close enough or should I use #4?

Neither -- #8 copper is quite sufficient for 40 amps. If you're using
aluminum, then you need #6. But in no case do you need #4 for a load of only
40 amps.

Thanks