In article 1120098843.355098.302240
@g47g2000cwa.googlegroups.com, says...
There are several types of circuit breakers. One type is a thermal
circuit breaker. You would not want to use a 90a thermal circuit
breaker with 10 gauge wire.

Copied from Electronic Design article on circuit breakers.

"Appropriate for equipment where high-surge currents accompany the
start of motors, thermal circuit breakers use bimetal technology to
discriminate between safe switch-on currents/transients and prolonged
overloads. A typical thermal breaker must trip within one hour at 140%
of its rating. A latching mechanism makes these devices highly tolerant
of shock and vibration."

lets see 140 percent of 90 amps is 126 amps. So you think it might be
alright to run 126 amps through 10 gauge wire for an hour? Granted
most circuit breakers are not thermal breakers, but without knowing the
breaker type, I would not recommend sizing the breaker for more current
than the wire is rated for. I have no problem recommending using a
welder on a circuit with wire that can not handle the input current of
a welder on a 100 % duty cycle.


The circuit breakers described in that article are not
permitted for branch circuit protection. In fact, if you
look at the catalogs published by Cutler-Hammer, SquareD,
Siemens, etc., they avoid "circuit breaker" when talking
about these devices and refer to them as "supplementary
protectors," and reserve the term "circuit breaker" for
devices that can be used as branch circuit protection.

The 90A number for #10 wire that's been bandied about is
incorrect, at least for the more common insulation classes.
There's an additional provision in the NEC section on
welders that says that the overcurrent device must be set
to no more than twice the conductor rating, so 70A(for 75C
insulation - romex) or 80A(for 90C - THHN) is a more
realistic high end.

Ned Simmons