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Problem: Heat pump is burning up transformers and has high amp draw on low voltage wiring?

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Problem: I have found your web page to be very informative and have it saved in my favorites.   I have a Tech Support Question if you feel like helping. I have been troubleshooting a 2 stage all electric heat, AC heat pump.   Sometimes I blow the transformer during the troubleshooting.   I measure the amp draw on the secondary wire (24V), was getting 7.9. Changed relay and seq. Now when i turn on the breaker to the air handler, nothing on except transformer (hums but not loud-ok), I am getting 5 amp draw on the secondary wire.I dont think this is normal, but I am not sure.  Do you know why I would be getting this 5 amp with nothing on except the power to air handler, I.e. ‘no calls’? Could it be all the way back to the main breaker box? Thanks, Gary


Hi Gary! Thanks so much for your kind words, interest in our website and the opportunity to do business with you! All that I can guess on the high low voltage amp draw with everything off would maybe be the solenoid on the reversing valve. Many of the heat pump reversing valve solenoids are constantly energized in the cooling mode. Try turning your thermostat to heating or off and see if the amp draw is still there. The windings in the solenoid valve might be shorted, or you might have a slight short in the thermostat wires that might cause this high amp draw and cause the transformer to blow. I would suggest if you have not already to check the thermostat wires closely especially outside where animals might chew through the wires or where sun light can damage the insulation over time. Also check sharp corners where the thermostat wires go into the air handler or outdoor unit. These are the places where I would find thermostat wires shorted most often when I was doing HVAC service work. No, I would not think this would have anything to do with the main breaker box. This sounds like the problem is in your secondary low voltage wiring and not the primary. Please click here if you are interested in the low voltage transformers we sell.  Best of luck in finding the problem. I hope that you have a great day!

Steve Arnold, 

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