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In the field of air conditioning and refrigeration, common refrigeration equipment is mainly divided into two categories: cold units and water-cooled units. Among them, the fan system mainly achieves cooling or heating effects by directly introducing fresh air and utilizing the exchange between fresh air and indoor air. Water-cooled units first cool or heat the heat medium water, then transport the treated heat medium water to the fan coil air conditioning system. Finally, fresh air or mixed air precisely delivers the heat or cold energy to the designated area at the end, meeting the heating and cooling needs of different Spaces.
The chiller, a device widely used in industrial and commercial fields, is also known as a freezer, refrigeration unit, ice water unit or cooling equipment, etc. Due to the significant differences in usage scenarios and demands across various industries, the requirements for water chillers also vary. Generally speaking, a chiller mainly consists of four core components: the compressor, evaporator, condenser and expansion valve. These four parts work in coordination to jointly achieve the cooling and heating functions of the unit.
High-pressure faults are a relatively common problem during the operation of water chillers. The so-called high-pressure fault of the chiller refers to the situation where the exhaust pressure of the compressor is too high, triggering the action of the high-pressure protection relay. The exhaust pressure of the compressor actually reflects the condensing pressure. Its normal value should be maintained between 1.4 and 1.8MPa, while the setting of the protection value is recommended not to exceed 2.0MPa. If the compressor is in a state of excessively high pressure for a long time, it will cause the operating current to be too large, which in turn is likely to burn out the motor and cause damage to the compressor.
So, what are the main causes of high-voltage faults?
Excessive refrigerant charge is a common cause. This situation usually occurs after equipment maintenance, characterized by high suction and exhaust pressures, as well as high equilibrium pressure, and at the same time, the operating current of the compressor is also high. To address this issue, the solution is to discharge the refrigerant in appropriate amounts under rated working conditions based on the suction and exhaust pressures, equilibrium pressure, and operating current until all indicators return to normal.
2. Excessively high cooling water temperature can also lead to poor condensation effect. The rated working condition of the cooling water required by the chiller is 30 to 35℃. If the water temperature is too high and the heat dissipation is poor, it will inevitably lead to an increase in the condensing pressure. This phenomenon is particularly common in hot seasons. The solutions include checking whether the cooling tower is faulty, such as whether the fan is turned on, whether it is reversed, and whether the water distributor is rotating, etc. Meanwhile, in view of the high external temperature, short waterways and small amount of recyclable water, the method of adding water storage tanks can be adopted to lower the water temperature.
3. Insufficient cooling water flow is also an important reason. This is mainly manifested as a decrease in the pressure difference between the inlet and outlet water of the unit (compared with the pressure difference at the beginning of the system's operation), and an increase in the temperature difference. The solution is to check whether the pipeline filter is clogged or too fine, which limits the water permeability. A suitable filter should be selected and the filter screen should be cleaned regularly. In addition, it is necessary to check whether the water pump is selected too small and does not match the system.
4. Scaling or clogging of the condenser should not be ignored either. Since the condensate water usually uses tap water, it is prone to scaling when the temperature is above 30℃. Moreover, the cooling tower is open and directly exposed to the air, making it easy for dust and foreign objects to enter the cooling water system, causing the condenser to be clogged, reducing the heat exchange area, lowering efficiency, and simultaneously affecting the water flow rate. It is manifested as an increase in the pressure difference and temperature difference between the inlet and outlet water of the unit. When touched by hand, the temperature at the top and bottom of the condenser is very high, and the copper tube at the outlet of the condenser is hot to the touch. The solution is to regularly backwash the unit and, if necessary, carry out chemical cleaning to remove scale.
5. Electrical faults may also cause false alarms. False alarms may occur due to reasons such as moisture, poor contact or damage to the high-voltage protection relay, moisture or damage to the unit electronic board, as well as communication failures. The characteristics of this false fault are that the fault indicator light on the electronic board does not light up or is slightly lit, manual reset of the high-voltage protection relay is ineffective, the operating current of the compressor is normal when measured, and the suction and exhaust pressures are also normal. The solution is to inspect and replace the damp or damaged parts.
6. The presence of non-condensable gases such as air and nitrogen in the refrigerant is also a reason. When there is air in the refrigeration system, many times the pointer of the high-pressure gauge will shake very violently. This situation usually occurs after maintenance when the vacuuming is not thorough. The solution is to empty the condenser at the highest point after the machine stops or to re-evacuate and add refrigerant.
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