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AC unit continues to randomly trip the breaker

Posted by ajay1967 (My Page) on
Mon, Jul 11, 11 at 9:32

My AC continues to trip the breaker, it has been doing this for years. It trips the breaker randomly, It may go a whole month with no problem then do it 2 or 3 times in one day. I have had professionals look at it and I have changed the breaker, and we put a hard start kit on the unit. It is a Ruud 5 ton 10 seer and is about 10 yrs old. But this problem started years ago. Any help with this would be greatly appreciated.


Follow-Up Postings:

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RE: AC unit continues to randomly trip the breaker

Have the resistance checked between the windings and the case.

All it takes is a tiny defect in the winding insulation on the motor inside the hermetic case to cause a problem.

It is generally only repairable by replacing the compressor.


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RE: AC unit continues to randomly trip the breaker

Intermittent problems are the hardest to pinpoint, especially when the occurrences are as far apart as those you experience. I've seen this happen when the thermostat shuts the unit off and then calls for cooling again before the 3 minute time period the refrigerant needs to equalize in the system. The mercury bulb and bi-metal strip type thermostats are likely to do that. Rapid changes in the air strata near the thermostat can cause that too, someone walking by, and even slight vibrations would trip the thermostat back on or, even off, if those things happen when the temperature is very close to either trip point. If a home is configured where the thermostat is located on the wall across the hall from a bathroom which has a supply, I see this happen. Keeping the bathroom door half closed helps. Another cause can be brown out conditions or even a slight surge in incoming supply. I've found surges to be common in areas where the power distribution station performs a switching operation. It's like a roulette wheel and happens far enough apart it is difficult to catch it when it happens. When I run into one of these rare situations, I connect monitoring and recording equipment on incoming power, low voltage power, temperature, time etc. The problem doing that in your situation would tie the equipment up for too long.

I suggest things you might try is making sure the thermostat base is perfectly level and kept free of dust. If you have fans operating, make sure they don't direct air toward the thermostat. If a room is across the hall from where the thermostat is located, keep the door half closed. Monitor if this seems to stop the problem or not.


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