2. Overfilling of refrigerant after maintenance
【Fault Analysis】If the refrigerant charge in the system after maintenance exceeds the system's capacity, the refrigerant will take up space in the condenser, reducing the heat transfer area and lowering refrigeration efficiency. This results in suction and discharge pressures being generally higher than normal, improper frost formation on the evaporator, and slow cooling in the storage.
【Solution】According to the operating procedure, stop the system for a few minutes and then release the excess refrigerant at the high-pressure shut-off valve. This will also help to release any remaining air in the system.
3. Air in the refrigeration system
【Fault Analysis】Air in the system reduces refrigeration efficiency, with obvious signs including increased suction and discharge pressures (though discharge pressure has not exceeded the rated value) and a noticeable rise in temperature from the compressor outlet to the condenser inlet. Due to the presence of air, both the discharge pressure and temperature increase.
【Solution】After stopping the system for a few minutes, release air several times from the high-pressure shut-off valve, and top up with a suitable amount of refrigerant as needed.
4. Low compressor efficiency
【Fault Analysis】Low compressor efficiency means that under unchanged working conditions, the actual discharge volume decreases, leading to a reduced cooling capacity. This often occurs in compressors that have been used for a long time, with significant wear, large clearance between parts, and reduced valve sealing performance, resulting in lower actual discharge volume.
【Solution】Check if the cylinder head gasket is damaged and leaking; check if the high and low-pressure valve plates are not closing properly; inspect the piston and cylinder clearances.
5. Excessive frost on the evaporator surface
【Fault Analysis】Evaporators in cold storage that are used for a long time need regular defrosting. If not defrosted, the frost layer on the evaporator pipes will thicken over time, and when the entire pipe is coated in a transparent ice layer, it will seriously affect heat transfer, causing the temperature in the storage to not reach the required range.
【Solution】Stop the machine to defrost, open the storage door to allow air circulation, or use a fan to speed up air movement and reduce defrosting time.
6. Refrigeration oil in the evaporator pipe
【Fault Analysis】During the refrigeration cycle, some refrigerant oil may remain in the evaporator pipes. After prolonged use, if there is a significant amount of residual oil in the evaporator, it will severely impact heat transfer and cause poor refrigeration performance.
【Solution】Remove the refrigerant oil from the evaporator. Take the evaporator apart, blow-clean it and dry it. If it is difficult to dismantle, use compressed air from the evaporator inlet and then heat with a blowtorch.
7. Refrigeration system not circulating properly
【Fault Analysis】If the refrigeration system is not cleaned properly, over time debris gradually builds up in the filter, blocking some mesh holes and reducing the flow of refrigerant, thereby affecting the cooling effect. The filters at the expansion valve and the compressor suction might also get slightly blocked.
【Solution】Remove the slightly blocked components, clean them, dry them and reinstall.
8. Filter Blocking
[Fault Analysis] The desiccant has been used for a long time and becomes paste-like, blocking the filter, or dirt gradually accumulates inside the filter causing blockage.
[Troubleshooting] Remove the filter for cleaning and drying, replace with new desiccant, and reinstall in the system.
9. Refrigerant Leak in Expansion Valve Sensing Bulb
[Fault Analysis] If refrigerant leaks from the sensing fluid inside the expansion valve bulb, the force under the diaphragm pushes it upwards, closing the valve hole. This prevents refrigerant flow in the system, causing no cooling. At this time, the expansion valve will not frost, the low pressure will be in a vacuum, and no airflow sound is heard in the evaporator.
[Troubleshooting] Shut down the system and close the stop valve, remove the expansion valve and check if the filter screen is blocked. If not, blow into the expansion valve inlet with your mouth to see if air passes through. You can also inspect visually or by disassembly, and replace it if damaged.
10. Poor Cooling Performance of Air-Cooled Condenser
[Fault Analysis] 1. Fan is not on.
2. Fan motor is damaged.
3. Fan is rotating in the wrong direction.
4. Surrounding ambient temperature is high (above 40°C).
5. Condenser fins are blocked by oil and dust, preventing airflow.
[Troubleshooting] Use a wire brush to remove surface dust, or wash the condenser.
11. Poor Cooling Performance of Water-Cooled Condenser
[Fault Analysis] 1. Cooling water valve is not open or is only slightly open, causing low inlet pressure.
2. Water flow regulating valve is malfunctioning.
3. Scale has built up on the condenser tube walls.
[Troubleshooting] Check the cooling water flow. Remove the scale.
12. Residual air in the system
[Fault Analysis] If there is air circulation in the system, it can cause high exhaust pressure, high exhaust temperature, hot exhaust pipes, poor cooling performance, short compressor operation, and exhaust pressure exceeding the normal value.
[Remedy] Stop the machine and release the air at the exhaust valve.
13. Shutdown caused by low suction pressure
[Fault Analysis] When the suction pressure in the system falls below the set value of the pressure relay, its contacts operate and cut off the power supply.
[Remedy] 1. Refrigerant leakage. 2. System blockage.
14. Temperature controller out of control
[Fault Analysis] Temperature controller adjustment failure or improper installation of the sensing bulb.
[Remedy] Remove the temperature controller to check and adjust its contacts; adjust the position of the sensing bulb.
15. Sudden shutdown caused by other reasons
[Fault Analysis]
[Remedy] Stop the machine immediately to prevent danger.
