Common faults and treatment of industrial water chillers

High-pressure failure of industrial chillers: The compressor discharge pressure is too high, causing the high-pressure protection relay to operate. The compressor discharge pressure reflects the condensing pressure, the normal value should be 1.4~1.6MPa, and the protection value is set to 2.0MPa. If the pressure is too high for a long time, it will cause the compressor operating current to be too large, the motor is easy to burn, and it is easy to cause damage to the compressor exhaust valve. The reasons for the high voltage failure are as follows:

The cooling water temperature is too high and the condensation effect is poor. The rated working condition of the cooling water required by the chiller is 30~35℃. High water temperature and poor heat dissipation will inevitably lead to high condensing pressure. This phenomenon often occurs in high temperature seasons. The reason for the high water temperature may be: cooling tower failure, such as the fan is not turned on or even reversed, the water distributor does not turn, it is manifested as the cooling water temperature is very high, and it rises rapidly; the outside temperature is high, the water path is short, and the amount of water that can be circulated In this case, the temperature of the cooling water is generally maintained at a relatively high level, which can be solved by increasing the storage tank. The cooling water flow is insufficient, and the rated water flow cannot be reached. The main performance is that the pressure difference between the inlet and outlet water of the unit becomes smaller (compared with the pressure difference at the beginning of the system is put into operation), and the temperature difference becomes larger. The reason for the insufficient water flow is the lack of water in the system or the presence of air. The solution is to install an exhaust valve at the height of the pipeline to exhaust; the pipeline filter is blocked or the selection is too fine, and the water permeability is limited. You should choose a suitable filter and Clean the filter regularly; the water pump is small and does not match the system. The condenser is fouled or blocked. Condensate water is generally tap water. It is easy to scale when the temperature is above 30℃. Because the cooling tower is open, it is directly exposed to the air. Dust and foreign matter can easily enter the cooling water system, causing the condenser to be dirty and blocking and the heat exchange area is small. , The efficiency is low, and it also affects the water flow. The performance is that the pressure difference and temperature difference between the inlet and outlet water of the unit become larger, the upper and lower temperatures of the condenser are very high when the condenser is touched by hand, and the condenser outlet copper pipe is hot. The unit should be backwashed regularly, and chemical cleaning and descaling should be carried out if necessary. The refrigerant is overcharged. This situation generally occurs after maintenance, and it is manifested as high suction and exhaust pressure and balance pressure, and high compressor operating current. It should be vented according to the suction and discharge pressure, balance pressure and operating current under rated conditions until normal. Non-condensable gases such as air and nitrogen are mixed in the refrigerant. This situation generally occurs after maintenance, and the vacuum is not complete. It can only be drained, re-evacuated, and recharged with refrigerant. False alarms caused by electrical faults. Because the high-voltage protection relay is damp, poorly contacted or damaged, the unit electronic board is damp or damaged, and the communication failure causes a false alarm. This kind of false fault, often the HP fault indicator on the electronic board is not bright or slightly bright, the high-voltage protection relay manual reset is invalid, the computer displays "HPRESET", or disappears automatically, the running current of the compressor is normal, and the suction and discharge pressures are also normal. .

   Low-pressure failure of industrial chiller: The suction pressure of the compressor is too low, which causes the low-pressure protection relay to operate. The suction pressure of the compressor reflects the evaporation pressure, the normal value should be 0.4~0.6MPa, and the protection value is set to 0.2MPa. If the suction pressure is low, the return air volume is small, and the refrigeration capacity is insufficient, resulting in a waste of electric energy. For the return air cooling compressor motor, the heat dissipation is poor and the motor is easily damaged. The reasons for the low pressure failure are as follows: insufficient refrigerant or leakage. If the refrigerant is insufficient and only partially leaked, the equilibrium pressure may be higher when the machine is stopped, and the suction pressure is lower after the start-up, the discharge pressure is also lower, the compressor operating current is small, and the operating time is short, and a low pressure fault will be reported. The computer displays "LPCURRENT", and the unit electronic board LP fault indicator lights at the same time. After a few seconds, the computer displays "LPRESET" and the unit electronic board LP fault indicator turns off. If most of the refrigerant leaks, the balance pressure is very low, and a low pressure fault will be reported when the machine is turned on. If the suction pressure is lower than 0.2MPa, the machine cannot be turned on, the computer displays "LPCURRENT", and the unit electronic board LP fault indicator is on. Another possibility is that the refrigerant is sufficient, but the expansion valve is too small or blocked (or the refrigerant pipeline is not smooth), which may also cause a low-pressure failure. In this case, the equilibrium pressure is often high, but the suction pressure is very low during operation, the discharge pressure is high, the compressor operating current is also very large, and the valve temperature is also very low, the expansion valve is frosted, and the pressure is long after shutdown To restore balance. This situation generally occurs during low-temperature operation or at the beginning of each year, and it can return to normal after a period of operation. The refrigerant water flow is insufficient, the absorbed heat is small, the refrigerant evaporation effect is poor, and it is supercooled and supersaturated steam, which is prone to wet compression. The performance is that the pressure difference between the inlet and outlet water of the unit becomes smaller, the temperature difference becomes larger, the suction temperature is low, and the suction There is frosting in the mouth. The reason for the insufficient water flow is: there is air or lack of water in the system, the solution is to install an exhaust valve at the height of the pipeline to exhaust; the pipeline filter is blocked or the selection is too fine, and the water permeability is limited, so a suitable filter should be selected And clean the filter regularly; the water pump is small, and it is not compatible with the system, and a larger water pump should be selected, or a spare water pump should be activated. The evaporator is blocked, the heat exchange is poor, and the refrigerant cannot evaporate. The harm is the same as the lack of water. The difference is that the pressure difference between the inlet and outlet water becomes larger, and the suction port will also appear frost. Therefore, the unit should be backwashed regularly. Electrical failure caused false alarms. Because the low-voltage protection relay is damp short-circuit, poor contact or damaged, the unit electronic board is damp or damaged, and the false alarm caused by communication failure. When the outside air temperature is low and the cooling water temperature is very low, low pressure failure will also occur when the cooling water temperature is low. When the unit is running, because there is not enough preheating, the temperature of the refrigerating oil is low, and the refrigerant is not sufficiently separated, low pressure failure will also occur. In the former case, measures such as shutting down the cooling tower and throttling the cooling water can be taken to increase the temperature of the cooling water. In the latter case, extend the preheating time, and the refrigerating oil temperature can generally return to normal after the temperature rises.

    Low valve temperature failure of industrial chillers: The outlet temperature of the expansion valve reflects the evaporation temperature, which is a factor that affects the heat exchange. Generally, the difference between it and the outlet temperature of the refrigerant water is 5~6°C. When a low valve temperature failure occurs, the compressor will stop, and when the valve temperature rises, it will automatically resume operation with a protection value of -2°C. The reasons for the low valve temperature failure are as follows: a small amount of refrigerant leaks, which generally manifests as a low valve temperature failure rather than a low pressure failure. Insufficient refrigerant will evaporate at the outlet of the expansion valve, causing cooling, which is manifested as frosting at the outlet of the expansion valve, and at the same time, the temperature of the suction port is higher (superheated steam), and the cooling capacity decreases and the temperature drops slowly. The expansion valve is blocked or the opening degree is too small, and the system is not clean. For example, the refrigerant pipeline is not cleaned after maintenance, and the refrigerant is impure or contains moisture. Insufficient refrigerant water flow or blockage of the evaporator, poor heat exchange results in low evaporation temperature and low suction temperature, and the opening of the expansion valve is adjusted according to the suction temperature, and low temperature results in a small opening, resulting in low valve temperature malfunction. False alarms caused by electrical faults, such as poor contact of the valve temperature line, cause the computer to display -5°C unchanged.