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Heat Pump Troubleshooting
5. Symptom: Compressor loses oil
Possible Causes
Compressor short cycling
Liquid refrigerant
6. Symptom: Low refrigeration suction pressure
Possible Causes
Lack of refrigerant
Evaporator dirty
Suction line blockage
Condensing temperature too low
Low water temperature
Low discharge pressure
Improper expansion valve settings
Mis-adjusted or defective TXV
Clogged liquid line filter-drier
Excessive glycol concentration
Liquid line solenoid restricted or faulty
Insufficient chilled water
Restricted water/glycol line
Water/glycol mixture contaminated
Evaporator clogged or fouled
LP alarm: Heating to defrost
LP alarm: at the end of defrost
LP alarm: start at low ambient in heating mode
Incorrect fan speed
7. Symptom: High refrigeration suction pressure
Possible Causes
Incorrect fan speed in heating mode
Leakage refrigeration through solenoid bypass (from receiver to evaporator
entrance in cooling mode)
High water temperature in heating mode
8. Symptom: Low refrigerant discharge pressure
Possible Causes
Insufficient refrigerant in heat pump ; Improper charge
Faulty compressor
Low ambient conditions in cooling mode
66
Potential Solutions
Adjust proper control settings for Min. ON/OFF runtime.
Check compressor superheat. Superheat at the compressor suction should be
approximately 12°F.
Potential Solutions
Check for leaks. repair and add charge.
Clean with chemical.
Check suction line for any obstacle.
Check fan settings.
Raise set point; Check design specification.
Refrigerant charge; Replace compressor; check fan settings.
Check EXV functionality and settings.
Adjust or replace valve.
Replace filter drier or cartridges.
Charge to proper glycol concentration.
Replace solenoid valve, coil, or internals as necessary.
Adjust flow rate through heat exchanger.
Clean strainers; check manual and electronic valves.
Intensive cleanup effort needed to identify source of contamination; external
filter may be required.
Reverse flush with appropriate chemical solutions.
Check solenoid valve; check EXV startup position settings on HMI (80%).
Check fan settings at defrost mode.
Checking EXV startup delay (needs to be set at 12s).
Check fan settings.
Potential Solutions
Check fan settings.
Check bypass solenoid valve to be close completely when system gets stable
in cooling mode.
Check refrigerant charge, excessive load, and design specification.
Potential Solutions
Check for leaks, repair, and add refrigerant as needed.
Check compressor.
Check design condition.
ARTC-SVX009A-EN
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