Quote Originally Posted by shadow738 View Post
... I work in a hardware store and we sell big, 240-volt air compressors; if you try to run them on 120 the thermal breaker in the motor will trip--that's the good news. The motor is trying to draw twice times the amps resulting in four times the heat.
Uh... not exactly. Power (wattage) equals IČR or VČ/R. Halve the voltage and you get 1/4 the power. What is probably happening is that the motor has a starting circuit (which has much less resistance, resulting in higher amps during starting until a centrifugal switch cuts out the start circuit), and the lower voltage can't get the motor up to speed to get it off the starting circuit, so it quickly overheats.