"Matthew" wrote in message
...

"Keith Carlson" wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
Ground). The "3-wire" terminology was confusing. Hence 3-wire with
ground is common, if a bit of a mouthful.

Yeah, this is what I was talking about: 2 hot wires, 1 neutral, 1 grounding
wire. In my HP Richter book, they called it a "3-wire" or "split-wire"
circuit. "3-wire" sounded less confusing to me. Don't know how common that
term is in sparky-land.

Even if the startup surge would cause the current to exceed the breaker
rating, the breaker probably would not open. Circuit breakers have what
is called a time-current curve, which tells you how long a circuit breaker
can carry excess current before it opens. Most breakers will carry 2x or
3x their rated current (ex: 30 or 45A on a 15A breaker) for ten seconds or
so before they open; even short time delay models will do it for a second
or so, which covers the startup surge. Google on "circuit breaker time
current curve" to check it out for yourself.

Once you go above this level, the breaker will trip very quickly. For
example, when a hot wire shorts to the neutral or ground, a current of
many time the rated current occurs (10x? 20x?), and the breaker trips
within milliseconds.

The general idea is that larger overcurrents trip quickly, but that 2x or
3x currents can run for a long time. This protects the wiring, which is
one of the reasons for circuit breakers; a "shorted curcuit" level of
overcurrent would damage wires quickly, but lower overcurrents would take
a long time to overheat the wiring.

Hmm. I do have trouble tripping the breaker on the current (present) 15A
circuit. Could be that the breaker is old and trips easier? From what you're
saying, starting up a TS or planer shouldn't draw a high current long enough
to trip the breaker.