Why is the refrigeration unit not effective? What are the common reasons?

1. Refrigerant leakage

[Fault analysis] After the refrigerant leaks in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and a much louder intermittent "squeaking" airflow sound can be heard at the expansion valve than usual. The evaporator is not frosted or has a small amount of floating frost. If the expansion valve hole is increased, the suction pressure will not change much. After shutdown, the balance pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.

[Troubleshooting method] After the refrigerant leaks, do not rush to fill the system with refrigerant, but immediately find the leakage point and refill it after repair.

2. Too much refrigerant after maintenance

[Fault analysis] If the amount of refrigerant filled in the refrigeration system after maintenance exceeds the capacity of the system, the refrigerant will occupy a certain volume of the condenser, reduce the heat dissipation area, and reduce its refrigeration efficiency. The suction and exhaust pressures are generally higher than the normal pressure values, the evaporator is not frosted, and the temperature in the warehouse drops slowly.

【Troubleshooting method】According to the operating procedure, the excess refrigerant must be released from the high-pressure stop valve after the machine is shut down for a few minutes. At this time, the residual air in the system can also be released.

3. There is air in the refrigeration system

[Fault analysis] Air in the refrigeration system will reduce the refrigeration efficiency. The prominent phenomenon is that the suction and exhaust pressures increase (but the exhaust pressure has not exceeded the rated value), and the temperature from the compressor outlet to the condenser inlet increases significantly. Because there is air in the system, the exhaust pressure and exhaust temperature increase. This article comes from the WeChat public account of Refrigeration Encyclopedia.

[Troubleshooting method] You can release air from the high-pressure stop valve several times in a row after the machine is shut down for a few minutes, and you can also fill some refrigerant appropriately according to the actual situation.

4. Low compressor efficiency

[Fault analysis] Low efficiency of refrigeration compressor means that when the working conditions remain unchanged, the actual exhaust volume decreases, resulting in a corresponding decrease in cooling capacity. This phenomenon often occurs on compressors that have been used for a long time, with large wear, large clearance between components, and reduced sealing performance of the air valve, resulting in a decrease in actual exhaust volume.

【Troubleshooting method】 Check whether the cylinder head paper gasket is punctured and causes leakage; check whether the high and low pressure exhaust valves are not closed tightly; check the clearance between the piston and the cylinder

5. The frost on the evaporator surface is too thick

【Fault analysis】 The cold storage evaporator used for a long time should be defrosted regularly. If it is not defrosted, the frost layer on the evaporator pipeline will become thicker and thicker. When the entire pipeline is wrapped into a transparent ice layer, it will seriously affect the heat transfer, causing the temperature in the warehouse to fall below the required range.

【Troubleshooting method】 Stop the machine for defrosting, open the warehouse door to allow air circulation, and use fans to accelerate circulation to reduce defrosting time.

6. There is refrigeration oil in the evaporator pipeline

【Fault analysis】 During the refrigeration cycle, some refrigeration oil remains in the evaporator pipeline. After a long period of use, when there is more residual oil in the evaporator, it will seriously affect its heat transfer effect and cause poor refrigeration.

【Troubleshooting method】 Clear the refrigeration oil in the evaporator. Remove the evaporator, blow it, and then dry it. If it is not easy to disassemble, you can use a compressor to inflate the evaporator inlet, and then use a blowtorch to dry it.

7. The refrigeration system is not smooth

[Fault analysis] Because the refrigeration system is not cleaned properly, after a period of use, dirt gradually accumulates in the filter, and some mesh holes are blocked, resulting in a reduction in the refrigerant flow, affecting the refrigeration effect. The filter screen at the expansion valve and the compressor suction port in the system is also slightly blocked.

[Troubleshooting method] The slightly blocked parts can be removed, cleaned, dried, and then installed

8. Filter blockage

[Fault analysis] The desiccant has been used for a long time and has become a paste that seals the filter, or dirt gradually accumulates in the filter and causes blockage.

[Troubleshooting method] Remove the filter, clean and dry it, replace it with a new desiccant, and install it in the system.

9. Refrigerant leakage in the expansion valve temperature sensing package

[Fault analysis] After the temperature sensing agent in the expansion valve temperature sensing package leaks, the two forces under the diaphragm push the diaphragm upward, the valve hole is closed, and the refrigerant in the system cannot pass through, resulting in no refrigeration. At this time, the expansion valve does not frost, the low pressure is vacuum, and no airflow sound can be heard in the evaporator.

[Troubleshooting method] Shut down and close the stop valve, remove the expansion valve to check whether the filter is blocked. If not, you can blow the expansion valve inlet with your mouth to see if it is ventilated. It can also be visually inspected or disassembled for inspection, and replaced when damaged.

10. The cold storage of the cold air cooling condenser has poor heat dissipation effect

[Fault analysis] ① The fan is not turned on. ② The fan motor is damaged. ③ The fan is reversed. ④ The ambient temperature is high (above 40°C). ⑤ The condenser heat sink is blocked by oil and dust and the air does not circulate.

[Troubleshooting method] Use a wire brush to remove surface dust, or clean it.

11. The cold storage of water-cooled condenser has poor heat dissipation effect

[Fault analysis] ① The cooling water valve is not opened or opened too small, and the water inlet pressure is too low ② The water volume regulating valve fails. ③ The scale on the condenser tube wall is thick.

[Troubleshooting method] Check the cooling water volume. Remove the scale.

12. There is residual air in the system

[Fault analysis] There is air circulation in the system, which will cause the exhaust pressure to be too high, the exhaust temperature to be high, the exhaust pipe to be hot, the refrigeration effect to be poor, and the exhaust pressure to exceed the normal value after the compressor has been running for a short time. [Troubleshooting method] Shut down and release air at the exhaust valve hole.

13. Shutdown caused by too low suction pressure

[Fault analysis] When the suction pressure in the system is lower than the set value of the pressure relay, its contacts will operate and cut off the power supply.

[Troubleshooting method] 1. Refrigerant leakage. 2. The system is blocked.

14. The temperature controller is out of control

[Fault analysis] The thermostat adjustment fails or the temperature sensor is improperly installed.

[Troubleshooting method] Remove the thermostat to inspect its contacts, adjust, and adjust the position of the temperature sensor.

15. Sudden shutdown caused by other reasons

[Troubleshooting method] Shut down immediately to prevent danger