Heat Pump Problem


Old 11-23-02, 08:39 AM
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Carrier Heat Pump

Hi All,
I have a Carrier heat pump that is acting funny and I think I can fix it if I had some more info. The problem is the compressor and all related functions ie outside fan etc cycle rapidly. It does this intermittantly with the only common clue being it only seems to happen right when the thermostat is close to shutting the pump off. Being an auto technician I liken it to a relay failing. The thermostat and heat pump were replaced about 8 years ago and the problem seems to have started then but I can't say for sure. The thermostat has 2 leds; one green for aux heat and 1 red for em heat, when the problem is occuring the green led flashes in time with the compressor cycling. If I turn the thermostat temp setting down the led stops flashing but the compressor still cycles. If I turn the setting up the cycling stops and the led stays on. With the intermittant nature of the problem I can't see calling in a service tech as it may well not happen while they are here. The inside unit is 20 plus years old and the number is almost illegible but this is what it appears to be:540A-0030-300BB The outside units #'s are Serial 0894E18699 &
Model 38YCA024340 Any help will be greatly appreciated.
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Old 11-23-02, 12:44 PM
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,815
Cool sizing

You MAY have a mismatched unit. It appears from first sight the air handler is 2-1/2 ton (AUG 1994) and the condensing unit is 2 ton. Sometimes they are OK within a 1/2 ton but maybe not in this case. If there is an expansion valve on it, no big deal but if you see the fixed orifice plastic bag still stuck to the unit outside, the tech may not have replaced it.
Your problem almost sounds like a loose connectin or bad anticipator. The thermostat may not be compatable for the unit. I'd talk to the Carrier dealer nearest for this one, but check the connections first , and make sure that both coils are very clean and the air filer is new. The only way to know is to measure the voltage signal to the contactor. Measure the line voltage to the condensing unit and make sure the transformer is set on the matching voltage. This gets overlooked on many installations. Good luck.

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