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Definition: Return liquid refers to the liquid refrigerant that has not completely evaporated and enters the compressor along with the return gas. This may cause liquid impact in the compressor, poor lubrication, and even mechanical damage.
1. Expansion valve factors
Excessive selection
The expansion valve capacity is far greater than the system requirements, resulting in excessive liquid supply.
Incorrect overheat setting
If the overheat setting is too low (close to 0°C), it indicates insufficient evaporation and the liquid refrigerant is prone to reflux.
Incorrect installation of the temperature sensing bulb or insulation damage
If the temperature sensing bulb is not tightly attached to the return gas pipe or the insulation fails, it will misjudge the return gas temperature, causing the expansion valve to open too wide.
Expansion valve failure
If the valve core is stuck or the diaphragm is aged, it will cause the expansion valve to fail to function properly.
2. Liquid addition control (for capillary system)
The capillary has no regulating capability, and the system is extremely sensitive to the filling volume.
Excessive fluorine addition
→ The evaporator cannot fully vaporize → The liquid refrigerant returns to the compressor → Return of liquid.
3. Evaporator and Fan Issues
The evaporator is severely frosty.
The frost layer hinders heat exchange, preventing the refrigerant from absorbing heat and evaporating.
Fan failure/insufficient airflow
Poor air circulation, reduced heat transfer efficiency → Incomplete evaporation → Return of liquid.
4. Temperature fluctuations (especially in cold storage)
Frequent start-stop or significant temperature fluctuations in the cold storage → Frequent adjustment of the expansion valve → Control lag or incorrect operation → Uncontrolled liquid supply → Return of liquid.
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