On Tue, 4 Sep 2007 20:03:48 -0700, "42etus"
wrote:

I think you guys missed my point. The OP seemed to be concerned that he was
going to have a cord rated at 25 amps protected by a 50 amp breaker. What I
meant to point out is that it is very common and allowed by the NEC to have
cords supplying appliances that are rated less than the breaker supplying
the circuit.

Exactly. The welder has 12-3 SO Cable on it, and you have to
remember that the "20 Amps for 12-AWG wire" rule is artificially
imposed - in reality it's good for quite a bit more depending on the
temperature rating of the cable insulation and the ambient temperature
around it, especially in free air.

The reason you would not use 12-3 for the welder extension cord is
voltage drop. 10-3 would work fine for a 25' to 50' welder or plasma
cutter extension cord - that's what I use.

If you want that cord to go 100' or more, when you run across a coil
of 8-3 or 8-4 SO cord at a good price, grab it.

Most household appliances, toasters, lamps, radios, computers etc all
have power supply cords that are not rated for the 20 amps that wall outlets
are capable of supplying. Can you imagine your electric razor having a 12/3
SJO cord just because your outlet in the bathroom was on a circuit protected
by a 20 amp breaker? That would make shaving each morning a real PITA.

That was why they invented the cordless razor. Of course, you had
to hold it upright so the battery acid from the open tank cells didn't
get spilled in your beard... ;-P

But this kind of stupidity still exists in certain instances - they
have a rule for Commercial Track Lighting that if the track and the
dimmer are rated for 20A (2400W), they have to figure the actual load
at 2400W - even if you are only going to connect 400W of lights...

To get around this, they came up with permanent small breakers
between the power source and track to "derate" the track to 4A (480W),
thus allowing them to reduce the overall building load calculations.

-- Bruce --