I was down at the boat last week end and am having trouble with the reverse cycle heat on the A/C unit. When you first turn the unit on it seems to run well everything sounds normal. After an hour to an hour and a half of running we start ot here a low rumble or humming kind of sound. When the temp gets to 60f the compressor shuts off even though the the thermostat is set at 65f. After about 3-4 minutes the compressor starts up again and heats the cabin up 62f then the compressor shurts off again. This goes on for a hour or so then the breaker on the AC panel pops. If you give it a few minutes and reset the breaker the whole things repeats but it takes less time for the breaker to pop. It seem to be getting enough cooling water and I get no alarms or warnings on the control unit (thermostat panel). The hum seems to be comming from one of the isolation transformers but it's hard to tell. The boat has two shore power connections and changing the A/C unit to the other connection dosen't fix the problem. Thought it might be low voltage or Amps from the marina but no one else on my dock is having problems. Anyone have any ideas?