In the process of using the screw chiller, some common faults that friends will encounter are high-pressure fault, low-pressure fault, low valve temperature fault, compressor overheating fault, communication fault, etc., but it is necessary to effectively solve these fault problems. The main working principle of the screw chiller is first linked, and the four processes of the refrigeration cycle are among the most important. After adiabatic compression by the compressor, it becomes a high temperature and high pressure state. The compressed gas refrigerant is cooled and condensed by isobaric cooling in the condenser, and then transformed into a liquid refrigerant after condensing, and then expanded to a low pressure through a throttle valve to become a gas-liquid mixture. Among them, the liquid refrigerant at low temperature and low pressure absorbs the heat of the cooled material in the evaporator and turns into a gaseous refrigerant again. The gaseous refrigerant re-enters the compressor through the pipeline to start a new cycle.
01. High voltage fault
The compressor discharge pressure is too high, causing the high pressure protection relay to act. The compressor discharge pressure reflects the condensing pressure, the normal value should be 1.40~1.60MPa, and the protection value is set to 2.00MPa. If the long-term pressure is too high, it will cause the compressor running current to be too large, which will easily burn the motor and cause damage to the valve plate of the compressor discharge port. What should be done is naturally to control the compressor discharge pressure within a safe range. Inside!
02. Low voltage fault
The suction pressure of the compressor is too low, causing the low pressure protection relay to act. The suction pressure of the compressor reflects the evaporation pressure, the normal value should be 0.40~0.60MPa, and the protection value is set to 0.20MPa. If the suction pressure is low, the amount of return air will be small, and the cooling capacity will be insufficient, resulting in a waste of electric energy. For the compressor motor with return air cooling, the heat dissipation is poor, and the motor is easily damaged! The solution is the same as the high pressure fault, try to keep the compressor in the normal pressure range.
03. Low valve temperature failure
The outlet temperature of the expansion valve reflects the evaporation temperature, which is a factor affecting the heat exchange. Generally, the difference between it and the outlet temperature of the refrigerant water is 5.0~6.0°C. When a low valve temperature fault occurs, the compressor will shut down. When the valve temperature rises, it will automatically resume operation with a protection value of -2.0°C.
04. Compressor overheating failure
The thermistor is embedded in the compressor motor winding, and the resistance is generally 1kΩ. When the winding is overheated, the resistance value will increase rapidly. When it exceeds 141kΩ, the thermal protection module SSM will act to cut off the operation of the unit. At the same time, the overheating fault will be displayed, and the TH fault indicator will be on.
05. Communication failure
The control of each module by the computer controller is realized through the communication line and the main interface board. The main reason for the communication failure is the poor contact or open circuit of the communication line, especially the interface is damaged by moisture and oxidation. Board failure, improper selection of the address dip switch, and power failure can all cause communication failures.
The above five fault phenomena are common, and understanding these fault phenomena, judgment ability, and solutions have an irreplaceable role in extending the service life of the screw chiller!
PREV：Analysis of common faults and maintenance of chillers NEXT：What should I do if the compressor load of the screw chiller is burned out?