Why is the refrigeration unit not working well? What are the common reasons?

Why is the refrigeration unit not working well? What are the common reasons?

1. Refrigerant leakage

【 Fault Analysis 】 After refrigerant leakage in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and the intermittent "squeaking" airflow sound can be heard at the expansion valve, which is much larger than usual. The evaporator does not have frost or a small amount of floating frost. If the expansion valve hole is enlarged, the suction pressure still does not change significantly. After shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.

【 Troubleshooting 】 After refrigerant leakage, do not rush to fill the system with refrigerant. Instead, immediately identify the leakage point and repair it before filling with refrigerant.

2. Excessive refrigerant filling after maintenance

【 Fault Analysis 】 If the amount of refrigerant filled in the repaired refrigeration system 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 will not frost properly, and the cooling in the warehouse will be slow.

【 Troubleshooting 】 According to the operating procedure, it is necessary to shut down for a few minutes before releasing excess refrigerant at the high-pressure shut-off valve. At this time, residual air in the system can also be released together.

3. There is air in the refrigeration system

[Fault analysis] The air in the refrigeration system will reduce the refrigeration efficiency. The prominent phenomenon is that the suction and discharge pressures increase (but the discharge 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 discharge pressure and the discharge temperature increase. This article is sourced from the refrigeration encyclopedia WeChat official account.

【 Troubleshooting 】 After a few minutes of shutdown, air can be continuously released from the high-pressure shut-off valve several times, and some refrigerant can be filled appropriately according to the actual situation.

4. Low compressor efficiency

【 Fault Analysis 】 Low efficiency of refrigeration compressors refers to the decrease in actual exhaust volume, resulting in a responsive decrease in refrigeration capacity, under constant operating conditions. This phenomenon often occurs on compressors that have been used for a long time, with significant wear, large clearances between various components, and a decrease in the sealing performance of the air valve, resulting in a decrease in actual displacement.

【 Troubleshooting 】 Check if the cylinder head paper gasket has been punctured and caused leakage; Check if the high and low pressure exhaust valve plates are not tightly closed; Check the fit clearance between the piston and cylinder

5. Excessive frost on the surface of the evaporator

【 Fault Analysis 】 Long term use of cold storage evaporators should be defrosted at regular intervals. If not defrosted, the frost layer on the evaporator pipeline will accumulate thicker and thicker. When the entire pipeline is wrapped in a transparent ice layer, it will seriously affect heat transfer, causing the temperature inside the warehouse to not drop within the required range.

【 Troubleshooting 】 Stop defrosting, open the warehouse door to allow air circulation, or use fans or other devices to accelerate circulation and reduce defrosting time.

6. There is refrigerant oil in the evaporator pipeline

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

【 Troubleshooting 】 Remove the refrigerant oil from the evaporator. Remove the evaporator, blow it clean, and then dry it. Not easy to disassemble, it can be compressed from the evaporator inlet and then dried with a spray lamp.

7. The refrigeration system is not smooth

【 Fault Analysis 】 Due to poor cleaning of the refrigeration system, after several periods of use, dirt gradually accumulates in the filter, and some mesh holes are blocked, resulting in a decrease in refrigerant flow rate and affecting the refrigeration effect. The filter screen at the expansion valve and compressor suction port in the system also shows slight blockage.

【 Troubleshooting 】 The micro blocking components can be removed, cleaned, dried, and then reinstalled.

8. Filter blockage

Fault analysis: The desiccant has been used for a long time and forms a paste to seal the filter, or dirt gradually accumulates inside the filter, causing blockage.

【 Troubleshooting 】 Remove the filter, clean and dry it, replace it with a new desiccant, and install it into the system.

9. Refrigerant leakage inside the expansion valve temperature sensing package

【 Fault Analysis 】 After the leakage of the temperature sensing agent in the expansion valve temperature sensing package, the two forces below the membrane push the membrane upwards, causing the valve hole to close and the refrigerant in the system to not pass through, resulting in non cooling. 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 】 Stop the machine and close the shut-off valve. Remove the expansion valve to check if the filter is blocked. If not, use a nozzle to blow the inlet of the expansion valve to see if it is ventilated. It can also be visually inspected or disassembled for inspection, and replaced if damaged.

10. The cooling effect of the cold air cooled condenser in the cold storage is poor

Fault Analysis

① The fan is not turned on.
② The fan motor is damaged.
③ Fan reverse direction.
④ The ambient temperature is high (above 40 ℃).
⑤ The heat sink of the condenser is blocked by oil and dust, and the air is not circulating.

【 Troubleshooting 】 Use a wire brush to remove surface dust, or clean.

11. The cooling effect of water-cooled condensers in cold storage is poor

Fault Analysis

① Cooling water valve not opened or opened too small, inlet water pressure too low
② The water volume control valve is malfunctioning.
③ The scale on the condenser tube wall is relatively thick.

【 Troubleshooting 】 Check the cooling water volume. Remove scale.

12. There is residual air in the system

[Fault Analysis] There is air circulation in the system, which can cause high exhaust pressure, high exhaust temperature, hot exhaust pipes, poor cooling effect, compressor running for a short time, and exhaust pressure exceeding normal values.

【 Troubleshooting 】 Stop the machine and release air at the exhaust valve hole.

13. Shutdown caused by 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 act and cut off the power supply.

【 Troubleshooting 】 1. Refrigerant leakage. 2. The system is blocked.

14. Temperature controller out of control

Fault analysis: The temperature controller fails to adjust or the temperature sensing package is improperly installed.

【 Troubleshooting 】 Remove the temperature controller to inspect its contacts, adjust them, and adjust the position of the temperature sensing bulb

15. Sudden shutdown caused by other reasons

Fault Analysis

【 Troubleshooting 】 Stop the machine immediately to prevent danger.