A low-pressure alarm for industrial chillers is a common problem. There are seven causes and solutions for low-pressure alarms of the industrial chiller.

How can you accurately and quickly diagnose the cause of the low-pressure alarm?

How can you solve the problem after a low-pressure failure is identified?





The working principle of an industrial chiller

Let’s first understand how an industrial chiller works?

Industrial chillers are operated by 3 interrelated systems: refrigerant circulation, water circulation, and electrical automatic control. The refrigerant absorbs the heat of the cooled object in the evaporator and vaporizes into steam, the compressor continuously draws the generated steam from the evaporator and compresses it, and the compressed high temperature, high-pressure steam is sent to the condenser and condensed into a high-pressure liquid by exothermic cooling medium (such as water, air, etc.), which enters the evaporator after being depressurized by the throttling mechanism and vaporizes again to absorb the heat of the cooled object. So on and so forth in a cycle.


What is a chiller low-pressure alarm fault?

A low-pressure fault in a chiller plant means that the inlet pressure of the compressor is too low, causing the low-pressure protection relay to act. The normal compressor suction pressure of a room temperature chiller should be 0.3~0.45 Mpa and the protection value is set at 0.2 Mpa.


The dangers of low-pressure faults in chiller systems

A common cause of low-pressure alarm in industrial chillers is system leakage of refrigerant, and if the leakage point happens to be located in the water tank or evaporator and other locations that will come into contact with water, it is likely to cause water in the refrigeration compression system, resulting in damage to the compressor. Therefore, when we find that the unit has a low-pressure fault alarm, we must determine the cause of the fault as soon as possible and make treatment.


Chiller System


Seven Causes and Solutions for Low-Pressure Alarm of Industrial Chiller are as follows.

1. Dirty blockage of the filter drier or oil blockage of the copper pipe in the chiller refrigeration system.

2. The low-pressure protector in the chiller refrigeration system is faulty.

3. The chiller refrigeration system in the solenoid valve can not open.

4. Failure of the expansion valve in the chiller refrigeration system.

5. Refrigerant leakage in the chiller refrigeration system.

6. The condenser of the chiller cooling system dissipates heat too well.

7. The liquid return pipe in the chiller refrigeration system is flattened resulting in poor liquid return.


The following is an analysis of the Industrial Chiller Low-Pressure Alarm

1. Filter drier dirty plug or copper pipe oil plug.

Copper pipe connections need to be burned, some copper slag can not be completely clean by blowing dirt, the spoils in the refrigeration system will collect in the filter drier, air conditioning, and refrigeration system operation process, the two ends of the filter will have a temperature difference.

If the filter is clogged due to a dirty system, it will only cause a drop in the cooling capacity of the unit if it is minor, and you will not even feel the impact. When the “filter” is slightly blocked, there will be a temperature difference between the inlet and outlet of the “filter”, which can be felt by holding the inlet and outlet in your hand. In severe cases, the filter will become dewy or frosty. If the filter becomes dewy or frosty (when the machine is running, dewy is not considered when it is stopped), the filter can be judged to be blocked.

Solution: If the filter is particularly dirty, the refrigeration system needs to be re-blown or cleaned, and the general treatment is to replace the filter drier with the same type and specification.


Filter drier


2. Low-pressure protector faults in the refrigeration system.

We use a meter to detect the industrial chiller system, if the pressure is normal, use a multimeter to measure the low-pressure protector line, or short the low-pressure protector, turn on the compressor, if the system is normal on the low-pressure protector failure.

Solution: Replace the low-pressure protector with the same specification and model.


Low-pressure protector


3. The solenoid valve in the industrial chiller system is no open.

During the industrial chiller working, you can hear the sound of the solenoid valve open; if the solenoid valve is not open, the low-pressure will gradually drop until the low-pressure alarm is generated; in the air conditioning control panel for alarm reset, low pressure will not rise again, at this time the solenoid valve coil measurement, there is resistance value indicates normal, infinity indicates that the coil has been burned.

Solution: Replace the solenoid valve coil with the same specification and model


solenoid valve


4. Failure of the expansion valve in the industrial chiller system.

If the expansion valve failure, in the operation of the industrial chiller system, low pressure can not come up, high-pressure pressure can not go up, additional refrigerant low pressure can not rise.

Solution: first adjust the expansion valve opening degree, such as still no effect, you need to replace the expansion valve with the same specification and the same model.

(Note: need to exclude whether the expansion valve is a dirty plug or ice plug).


Expansion valve


5. Refrigerant leaks in the industrial chiller system.


First of all, use a meter to detect and show no pressure, indicating that the refrigerant in the industrial chiller system has leaked out; if there is still pressure at this time, the chiller system can barely run, additional refrigerant, the pressure immediately rises, also indicates that the refrigerant leakage.

Solution: Firstly, test the chiller system at various locations to detect any signs of oil leakage, use detergent to focus on the location of oil leakage; if necessary, carry out segmentation of the chiller system to maintain pressure, and then carry out an investigation. After the leak is identified, the leak is welded and the industrial chiller system is recommissioned.


Refrigerant leaks

Refrigerant leaks


6. Industrial chiller system evaporator heat dissipation effect is not good.

Cause evaporator heat exchange insufficient probably have the following two points:

A. evaporator water flow is insufficient.
B. evaporator foreign body blockage.


Evaporator water flow is insufficient:

the main factors causing this phenomenon, there are bad water pump or pump impeller inside the foreign body, or pump into the water pipe has a gas leak phenomenon (more difficult to check, need to carefully analyze) caused by insufficient water flow.

Solution: replace the water pump, or the water pump disassembled clear impeller within the foreign body, you can remove the fault.

To determine whether the evaporator is blocked or the evaporation tube is scaled, the pump must first be ruled out and only after ensuring that the pump and the inlet piping are in order. There is a common and very obvious characteristic of a blocked evaporator or structure (for medium temperature units only): there is no significant condensation or frost or ice on the surface of the compressor when the unit is normally normal. When you see a lot of condensation or frost and ice on the surface of the compressor, you can basically decide that the evaporator is blocked.

Solution:  If the evaporator is blocked or the evaporation tube is scaled, dismantle the evaporator, remove the evaporation tube and flush it with a high-pressure water gun or clean it with a special liquid dip.





7. Flattened return lines in the industrial chiller system resulting in a poor return.

The chances of this occurring are small and the copper pipework needs to be investigated to find the location of the flattening.

Solution: Find the location of the flattened copper pipe and replace it with the same size copper pipe.


copper pipe

copper pipe



Here is another article about – Troubleshooting Common Chiller Problems and Solutions Guide to know more.



Lando industrial chillers are equipped with a low-pressure alarm system and compressor delayed start protection features.  Kindly contact us if any other questions.