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Heating, Air Conditioning, Fridge, HVAC/Air Handler banging, Heat Pump line freezing


I have a 9-year-old Rheem heat pump (PKB series) and its air handler (located in garage attic). Three weeks ago, the air handler would bang several times when the cooling cycle began. The sound was like a short but powerful burst of air. A metallic sound also came from the air handler. The company that serviced it found nothing wrong with the handler; they said their readings indicated a slight restriction in the return flow. They said the refrigerant was on the low side of "normal." They took no actions other than offer their maintenance plan about a dozen times.

I called a second company to check it the next day. Still found nothing amiss with the handler. The heat pump at first looked low 2 lbs--he rechecked it five minutes later and it was okay. The next day the liquid line froze. He added 1 lbs. And today, the line is frozen again.

Any clues on causes? Are the handler banging and the frozen liquid line related?

The only thing I can think of to cause the sounds from the air handler are a loose belt if it is belt driven or bad bearings in the motor or blower, but either of these should have been obvious. I recommend turning the thermostat to off and have someone turn just the fan on while you are at the fan. If you can safely remove the access door, remove it and watch it start to see if something moves that should not. It also could be the duct expanding with air when it first starts, that is common also. The lines icing is caused by either a low refrigerant charge or lack of air flow. Check the fan first to ensure it is running correctly and you feel good air flow at the supply vents. If you remove the access door, there will ususally be a micro switch that has to be depressed to make the fan run. The door pushes this switch when it is in place. Thanks and let me know. J

Heating, Air Conditioning, Fridge, HVAC

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J Cook


With 25+ years experience, I am familiar with residential, commercial, and industrial HVAC equipment including but not limited to boilers, chillers, reciprocating and screw compressors. I am trained in all manners of control wiring.


I currently have three HVAC licenses and Refrigeration license by the State of North Carolina. I have been in this field for over twenty years. I have been a service technician for a contractor and also worked at a state college in the repair and maintenance of steam lines and equipment. I am currently the Building Maintenance Superintendent for a municipality.

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