In article , wrote:
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

Below the table, it does say "The National Electrical Code [NEC] requires
their own cable sizing for premises wiring. Refer to the NEC rules to
determine building wiring, as this page relates to electronic equipment
wiring."

This is then followed by a sample list of wire guages and supposedly
NEC-permissible ampacities, which I will *not* reproduce here because it's
wrong.

It seems to me like the old cable type service entrances for 60A
service were #6-3 plus ground (wrapped around the bundle).

Sounds about right.


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

Good luck, and stay safe.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.