I have an older model electric motor driven compressor that causes my electrical circuit breaker to trip when the motor kicks in to "refill" a low pressurized tank. In other words, when the tank is empty and I plug it in, it starts and works fine, filling up the tank, then stops automatically when full. After use or when the tank's pressure becomes low, the motor attempts to start the compressor again, but is not able to. The motor hums for a short while, then trips the breaker. The circuit is one a 15 amp breaker, the motor draws less than 11 amps. Any ideas?