Common faults and solutions for screw chillers

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Low pressure over-limit protection: Solution: Replace or clean the filter element； Clean the intake filter. Dirty or frozen blockage at the inlet of the expansion valve: Solution: For dirty blockage, disassemble the expansion valve and clean it. Ice blockage: Replace the dry filter and then restart operation. Insufficient refrigerant: Solution: Check for leaks and add refrigerant. Low water flow: Solution: Rule out issues with the pump and clean the water filter. Water temperature too low: Solution: Increase the setting value of the sensor. Motor overheating: Solution: Faulty cooling solenoid valve ； The cooling circuit is closed or the flow rate is too low ； The motor is damaged. Exhaust temperature too high: Solution: Too low suction pressure, insufficient liquid in the evaporator, and excessive overheating, all of which lead to high motor temperature and exhaust temperature ； The condensation pressure is too high and the compression ratio is too large, resulting in excessively high motor temperature and exhaust temperature. High-pressure protection, air in the refrigeration system: Solution: Release air after shutting down the machine. High voltage protection, poor cooling: Solution: Lower the water temperature ； Clean the condenser. High-pressure protection, excessive refrigerant charge in the system: Solution: Remove some of the refrigerant. Oil protection pressure: Check solution: Replace or clean the filter element ； Check the oil pressure differential switch. Too low high pressure, too low cooling water temperature: Solution: Increase the cooling water temperature ； Reduce the cooling water flow rate. The cooling water flow switch activates as a protection measure in case of water shortage or too low water flow rate; solution: clean the water filter and check the water pump. The compressor will not start: reverse phase, missing phase, or excessive/insufficient voltage; solution: repair the circuit or adjust the phase sequence. The motor windings are burned out or the shaft is stuck: Solution: Repair or replace the compressor. Incorrect parameter setting: Solution: Reset it. The water temperature sensor is faulty: Solution: Replace it. Insufficient cooling capacity: Insufficient refrigerant; solution: Add more refrigerant. The expansion valve is not open enough or is blocked; solution: Increase the opening degree of the expansion valve and clean any blockages. Excessive load; solution: Reduce the production volume or add more equipment. Temperature protection for the compressor motor coil: The motor is under excessive load, or the cooling system is not functioning properly or is turned off. Coil protection switch failure. The electrical system is faulty, resulting in excessive temperature rise. The motor coil is defective, resulting in excessive temperature rise. Cooling failure is caused by an incorrect motor temperature setpoint or a malfunction in the motor temperature display. High-voltage cabinet failure. The compressor cannot start; solutions: the ambient temperature is too low, or the viscosity of the lubricating oil is too high. Capillary obstruction. Foreign objects are stuck in the relief hole of the pressure regulating solenoid valve, preventing it from closing. The volume control piston is stuck. The pressure regulation oil circuit is blocked. The crude oil filter or essential oil filter is clogged. There is a fault in the fuel supply pipeline; the fuel pressure is insufficient or no fuel can be supplied. It is not possible to establish pressure differential oil supply. The compressor cannot be unloaded. Solution: The solenoid coil of the capacity control valve is faulty; the piston rings of the capacity control valve are worn and cannot provide a complete airtight seal, allowing large amounts of refrigerant to enter the capacity control oil cylinder. Insufficient amount of lubricating oil. (Low oil level or insufficient oil supply) The gasket on the exhaust end cover is damaged, allowing gaseous refrigerant to enter the oil pressure cylinder. The control voltage for the solenoid coil of the volume control valve is incorrect. The volume control piston is stuck. The unit control system is defective. The fuel supply pressure is too high. The motor temperature is too high. Solutions: Faulty cooling solenoid valve; the cooling pipeline is closed or the flow rate is too low. The motor is damaged. The motor temperature setting is too high. The motor has poor insulation. Solution: The wire connections of the compressor motor are damp or exposed; the compressor motor is defective. The compressor motor terminals are faulty, clogged with dust, or have foreign objects in them. The insulation of the electromagnetic contactor and vacuum circuit breaker is poor. Internal acidification of the system damages the insulation. When the coil operates at high temperatures for a long time, its insulation deteriorates. Frequent startups cause coil degradation. The refrigerant has too high a water content. The motor fails to start under full load, and the voltage regulator valve does not return to its initial position. Solution: The voltage is too low or incorrect ； The starting voltage drop is too large ； Motor failure ； Under-phase, reverse-phase operation ； Motor protection switch activated ； Incorrect wiring of the motor coil ； The exhaust shut-off valve is not open ； Restart once a sufficient amount of time has passed since the last shutdown ； The connection isn’t secured properly. Abnormal vibration or noise; solution: Bearing damage. Compressor liquid compression. The rotor overheats due to mutual friction or friction with the casing. Loss of oil leads to poor lubrication of the components. Pulse resonance of the pressure regulating valve, resonance of the unit caused by poor piping with no flexible expansion, excessively high exhaust temperature. Solutions: Excessively high superheat of the refrigerant entering (insufficient refrigerant, abnormal expansion valve). Excessively high pressure (clogged liquid lines, poor cooling, excess refrigerant, air in the system). Oil loss or low oil level. The bearing is damaged, causing friction in the rotor. The operating conditions deviate significantly from the design conditions. The inhalation pressure is too low; solution: The filter or liquid tube is blocked. The compressor intake filter is clogged. Refrigerant leak. The flow rate or concentration of the ethylene glycol aqueous solution is too low; there is a fault with the electronic expansion valve (including issues related to suction temperature and suction pressure). It is recommended to conduct an inspection of the cooling station once a month, which includes checking whether the pressure in the cooling system is normal ； Are there any issues such as poor contact, overheating, or aging in the electrical wiring? ； Are the three-phase voltages and three-phase currents of the compressor, water pump, and oil pump motors balanced? ； Are all the fastening screws loose? ； Is there any abnormal noise? ； Should the water filter be cleaned or replaced? ； Check whether the circulating water quality meets the requirements.