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Components of a condensing unit
It plays the role of compressing and driving the refrigerant in the refrigerant circuit. The compressor extracts and compresses the refrigerant from the low pressure area, sends it to the high pressure area for cooling and condensation, and dissipates the heat to the air through the heat sink, and the refrigerant changes from the gaseous state to the liquid state.
It is one of the main heat exchange equipment in the cold storage refrigeration system, and its role is to cool and condense the high temperature refrigerant superheated vapor discharged from the assembled cold storage compressor into high pressure liquid.
It sucks away the heat from the cold storage, so that the liquid refrigerant evaporates at low pressure and temperatures, and evaporates into gaseous refrigerant. The gaseous refrigerant is sucked into the compressor and compressed, then discharged into the condenser to exhaust heat.
4. Storage tank
It’s used to ensure that the refrigerant is always saturated.
5. Solenoid valve
On one hand, it prevents high pressure refrigerant liquid from entering into the evaporator when the compressor stops. On the other hand, when the temperature of the condensing unit reaches the set value, the thermostat acts, and the solenoid valve loses power. When the temperature in the cold storage rises to the set value, the thermostat acts, and the solenoid valve gains power.
6. High and low voltage protector
It protects the compressor from being at too high voltage or too low voltage.
It is equivalent to the brain of cold storage that controls the starting and stopping of cold storage refrigeration and fan.
8. Dry filter
It filters impurities and water from the system.
9. Oil pressure protector
It ensures that the compressor has sufficient lubricant.
10. Expansion valve
Also known as throttle valve, it can make the high and low voltages form a huge pressure difference, so that high pressure refrigeration liquid at the expansion valve outlet will quickly evaporate.
11. Oil separator
Its function is to separate the lubricating oil in the high-pressure steam discharged from the refrigeration compressor in order to ensure safe and efficient operation of the condensing unit.
12. Evaporator regulating valve
It prevents the the pressure and evaporation temperature) of the evaporator from dropping below a specified value.
13. Fan speed controller
This series of fan speed controller is mainly used to control the speed of outdoor air-cooled condenser fan of refrigeration equipment, or the speed of chiller fan of cold storage.
Common faults and troubleshooting procedures
1. Refrigerant leakage
Due to the refrigerant leakage in the system, the cooling capacity will be insufficient, the suction and discharge pressure will become low, and the intermittent “squeak” airflow sound can be heard at the expansion valve which is much larger than usual. If there’s no obvious change in the suction pressure after the expansion valve hole is adjusted, the equilibrium pressure in the system after stopping is generally lower than the saturation pressure corresponding to the same ambient temperature.
Troubleshooting procedure: In case of refrigerant leakage, you should immediately find the leakage point and fill the refrigerant after the repair. The cold storage cooling system with open compressor has many joints and sealing surfaces, so there are more potential leakage points. You should pay attention to every link where refrigerant leakage is easy to occur and check the main leakage points for oil leakage, pipe break, or loose joint based on your experience.
2. Excessive refrigerant charge after repair
The amount of refrigerant charged in the refrigeration system after repair exceeds the capacity of the system, the refrigerant will take up a certain volume of the condenser and reduce the heat dissipation area, so that its cooling effect decreases, the suction and discharge pressure is generally higher than the normal pressure value, and the temperature in the cold storage is slow to cool down.
Troubleshooting procedure: The excess refrigerant must be released at the high pressure shut-off valve after a few minutes of shutdown, when the residual air in the system can also be released together.
3. Air left in the refrigeration system
Air in the refrigeration system will reduce the refrigeration efficiency, increase the suction and discharge pressure (but the discharge pressure has not exceeded the rated value), and significantly increase the temperature from the compressor outlet to the condenser inlet.
Troubleshooting procedure: You can release the air from the high pressure shut-off valve several times after a few minutes of shutdown, and you can also charge some refrigerant appropriately according to the actual situation.
4. Low compressor efficiency
Low refrigeration compressor efficiency means that the actual exhaust volume decreases and cooling capacity reduces when working conditions remain unchanged.
Troubleshooting procedure: (1) Check whether the cylinder head paper gasket is pierced, and replace it if so; (2) check whether the high and low pressure exhaust valve pieces is closed properly, and replace it if not properly; (3) check the fit clearance between piston and cylinder, and replace them if the clearance is too large.
5. Too thick frost on the evaporator surface
When the thick frost on the evaporator pipeline warps the whole pipeline into a transparent ice layer, the heat transfer will be seriously affected, resulting in the temperature of the storage can not fall within the required range.
Troubleshooting procedure: Stop the condensing unit and defrost, open the door for air circulation, and use a fan to accelerate the circulation, to shorten the defrosting time. Do not use iron or wooden stick to knock the frost layer, to prevent damage to the evaporator pipeline.
6. Refrigeration oil in the evaporator pipeline
In the refrigeration cycle process, some refrigeration oil is left in the evaporator pipeline, and much oil will be generated after a long time of use, which will seriously affect its heat transfer effect and lead to poor refrigeration.
Troubleshooting procedure: Remove the refrigerant oil inside the evaporator. Take down the evaporator, blow, wash it and then dry it.
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