Low Pressure Lockout + High Pressure Fault Codes: No Heat Pump


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Old 01-23-23, 12:35 PM
T
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Low Pressure Lockout + High Pressure Fault Codes: No Heat Pump

My electric bill is very high and found that my heat pump system is using Aux heat full time.
I have a 7 year old Lennox 14HPX-036-230-19 outdoor unit; the manual is ** Here **

(1) The compressor/condenser, the red/green lights showed a Low Pressure Lockout.
(2) After I turned the breakers off and back on for both indoor and outdoor units, the compressor+fan started running while showing (green/red lights) a High Pressure Fault code. Then it shut down and gave the code for Low Pressure Lockout again.
(3) My indoor filter is super clean, has no indoor air flow restrictions, and the outdoor unit is super clean.
(4) The compressor sounds a little weird - like a rattling tin can or something, not terribly loud though.

Q: Could someone let me know what the highest probability problem it could be? Low refrigerant?
Q: How can there be a low pressure fault AND a high pressure fault? Not a big deal, I may not understand why anyway.

I will probably call a tech on this one, but wanted to be educated so I don't get taken advantage of. Thank you!!
 
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Old 01-24-23, 08:57 PM
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So you saw green off and red flashing slowly initially when it was locked out then green flashing slowly and red off after resetting power?

Q: How can there be a low pressure fault AND a high pressure fault? Not a big deal, I may not understand why anyway.
A restricted metering device can cause a high high side and a low low side reading.

Like a dam on a river.

TXV failure.

I would still take an Ohm reading across the outdoor temperature sensors and compare to a 10K thermistor chart.
 
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Old 01-24-23, 11:13 PM
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Thank you for the reply Houston.

Actually, when the unit was not running when I first looked at it, the green was off and the red was steady on (Low Press Lockout). Then after resetting power, the green was flashing slowly and the red was off (High Pressure fault).

I'll look at the TXV tomorrow to see if anything looks bad. I still have Aux heat, but my electric bill was double last month!
 
 

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