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1. High pressure failure: 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 pressure is too high for a long time, it will cause the compressor to run too much current, easily burn the motor, and easily cause damage to the compressor exhaust valve. Naturally, what should be done is to control the compressor exhaust pressure within a safe range. Inside!
The reasons for high voltage failure are as follows:
The cooling water temperature is too high and the condensation effect is poor;
The cooling water flow is insufficient, and the rated water flow is not reached;
The condenser is scaled or blocked;
Overcharged refrigerant;
The refrigerant is mixed with non-condensable gases such as air and nitrogen;
False alarms caused by electrical faults.
2. Low pressure failure: 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 return air volume will be small, and the refrigeration capacity will be 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 solution is the same as the high-pressure failure, try to keep the compressor in the normal pressure range.
The causes of low voltage failure are as follows:
Insufficient refrigerant or leakage;
The flow of refrigerant water is insufficient and the heat absorbed is small;
false alarm caused by electrical failure;
The outside temperature is low.
3. Low valve temperature failure: 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 5.0~6.0℃. 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 -2.0°C.
Low valve temperature failure causes are as follows:
A small amount of refrigerant leaks, which is generally manifested as a low valve temperature failure rather than a low pressure failure;
The expansion valve is blocked or the opening is too small, and the system is not clean;
The refrigerant water flow is insufficient or the evaporator is blocked;
False alarms caused by electrical faults, such as poor contact of valve temperature wires.
4. 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, and the overheating fault will be displayed at the same time, and the fault indicator will be on.
Compressor overheating failure causes are as follows:
The compressor load is too heavy and the overcurrent is running;
Compressor overcurrent operation caused by electrical failure;
The overheating protection module M is damp or damaged, the intermediate relay is damaged, and the contacts are bad.
5. Communication failure: The computer controller controls each module 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 poor contact caused by the interface damp and oxidation. Electronic board or general interface board failure, improper selection of address dial switch, power supply failure can cause communication failure.
The above five failure phenomena are the most common, and understanding these failure phenomena, judgment capabilities, and solutions has an irreplaceable effect on prolonging the service life of the screw chiller!