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What Problems Can Be Caused by Low Pressure Failure of Chillers?

Jul. 09, 2022

The low pressure fault of chiller is that the compressor inlet pressure is too low, which causes the low pressure protection relay to operate. The normal compressor suction pressure of room temperature chiller should be 0.3~0.45Mpa, and the protection value is set to 0.2Mpa.


The danger of low pressure fault of chiller

A common cause of low pressure alarm in industrial chillers is refrigerant system leakage. If the leakage point happens to be located in the water tank or evaporator and other locations where water will be contacted, it is likely to lead to water ingress. Refrigeration compression system, resulting in damage to the compressor. Therefore, when we find a low-pressure fault alarm in the unit, we must determine the cause of the fault as soon as possible and make treatment.

 Water Cooled Scroll Chiller

Water Cooled Scroll Chiller          

What are the causes of low chiller pressure? How to solve?

1. Insufficient refrigerant or leakage

Insufficient refrigerant will lead to system pressure failure, resulting in lower suction pressure. The chiller will issue a low pressure alarm and the unit will stop.

Solution: The refrigerant leakage part can be diagnosed from the piping connection of compressor, condenser, filter, expansion valve, evaporator and other accessories. After troubleshooting, charging the right amount of refrigerant can solve the problem.

2. Low ambient temperature

When the outside temperature is low, the temperature of cooling water and compressor oil will also be low. If you start the chiller at this time, it will issue a low pressure fault alarm.

Solution: If the cooling water temperature is too low, close the cooling tower fan or throttle the cooling water to raise the cooling water temperature. If the compressor oil temperature is too low, extend the chiller preheating time, the refrigeration oil temperature will return to normal.

Air Cooled Screw Chiller

 Air Cooled Screw Chiller   

3. System pipe blockage

When the chiller is installed, it is inevitable that impurities will penetrate into the system, and after using it for a long time, various impurities will also enter the system. When there are too many impurities, the filter will be blocked, so that the refrigerant channel and return air will be reduced, and low pressure failure will occur.

Solution: Clean the filter, condenser and evaporator.

4. Expansion valve opening is too small or damaged

Expansion valve is the throttling device of the refrigeration system. Too little expansion valve opening will allow less refrigerant vapor to pass through. Too little refrigerant vapor will make the compressor inlet pressure too low, resulting in low pressure failure.

Solution: Increase the expansion valve opening appropriately or replace the damaged expansion valve.

Air Cooled Chiller

 Air-Cooled Chiller

5. Relay failure, electrical system false alarm

Relays play the role of indirect protection devices, compressor normal suction pressure is generally 0.4 ~ 0. 6MPa, when the suction pressure is lower than 0. 2MPa, will lead to low pressure protection relay action, the chiller stopped running. Sometimes the low-pressure relay will not work properly due to moisture, circuit breakage and other faults.

Solution: Check the low pressure relay and repair or replace it. Non-technical personnel can contact the manufacturer for help to solve the problem.

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