Al,
Motor loads can have a very high inrush current when first turned on. A motor that only uses say, 10 amps can draw 60 or 100 for a short time when first turned on. So, it is sometimes necessary to use a larger breaker to allow the Motor to start, and the wire is basically sized to the running load of the motor.
Take a look at 430-52 and Table 430-152 in the 1999 NEC
Bill
