Common Faults and Troubleshooting Methods for Air-Cooled Modular Chillers

Air-cooled modular chiller units are widely used in refrigeration scenarios such as commercial buildings and industrial workshops. They consist of multiple modular units operating together, offering convenient operation and maintenance and strong adaptability. During operation, these units are susceptible to malfunctions due to factors related to heat dissipation, water circuits, refrigerant, electrical systems, and compressors. Most malfunctions can be quickly identified and handled according to standardized procedures based on observed symptoms. The following sections detail common malfunction phenomena, causes, and standardized handling methods, categorized into six main types: pressure protection malfunctions, heat exchange and temperature malfunctions, water system malfunctions, compressor malfunctions, electrical and control malfunctions, and abnormal operating condition malfunctions, balancing practicality and professional expertise.

I. Pressure protection faults (high pressure/low pressure protection shutdown)

1. Compressor high-pressure protection

Fault symptoms : The unit alarms and shuts down, the compressor cannot start, the high pressure gauge reading is far beyond the standard operating value, and the high pressure protection interlock is repeatedly triggered.

Key causes : poor condenser heat dissipation, excessive refrigerant charge, poor ventilation in the unit's operating environment, blockage in system pipelines, and malfunction of the high-pressure switch.

Troubleshooting methods : ① After shutting down and disconnecting the power, clean the condenser fins of dust, oil, and debris, unclog any blocked heat dissipation gaps, and restore heat dissipation efficiency; ② Check the refrigerant pressure, recover excess refrigerant as needed, and strictly follow the charging amount specified on the unit's nameplate; ③ Improve the equipment installation environment, remove obstructions around the unit, ensure sufficient ventilation space, and avoid operation in a high-temperature, confined environment; ④ Check the system piping and valves to ensure that the piping is unobstructed and the valves are fully open; ⑤ Verify the high-pressure switch, replace it directly if it is malfunctioning or damaged, reset the protection system, and restart the unit for trial operation.

2. Compressor low-pressure protection

Fault symptoms : Low pressure alarm of the unit, frequent start-stop or direct shutdown of the compressor, sharp decline in cooling effect, and easy frosting and icing of the evaporator.

Key causes : refrigerant leakage, insufficient refrigerant, clogged dryer/expansion valve, blocked or bent pipes, or malfunctioning low-pressure switch.

Troubleshooting methods : ① Conduct a comprehensive inspection of pipe joints, welds, and valves to identify refrigerant leaks. After repairing leaks, evacuate the system and add the same type of refrigerant. ② Disassemble and clean the dryer filter. Replace it if it is severely clogged. Unclog or replace any blocked expansion valves. Simultaneously clean any debris from the system pipes. ③ Inspect the refrigerant lines, straighten any bends, and straighten the lines to ensure smooth refrigerant circulation. ④ Verify the low-pressure switch and sensor circuitry. Replace any faulty or damaged parts promptly. Restart the unit and observe the pressure and operating status.

II. Temperature and Heat Exchange Faults

1. Exhaust temperature overheat protection

Fault symptoms : The unit's exhaust temperature alarms, the compressor shuts down due to high temperature, and after running for a period of time, it repeatedly trips, resulting in weak cooling capacity of the unit.

The root causes are : insufficient refrigerant leading to inadequate compressor cooling, poor condenser heat dissipation, compressor overload operation, blocked exhaust pipe, and malfunction of the exhaust temperature sensor.

Troubleshooting methods : ① Check refrigerant levels; add refrigerant promptly if low; investigate for hidden leaks. ② Thoroughly clean the condenser fins; check for abnormal fan speeds to ensure effective heat dissipation. ③ Check the unit's load conditions; avoid prolonged full-load or overload operation; investigate for compressor jamming or wear. ④ Unblock the exhaust pipes; remove accumulated scale and debris to ensure unobstructed exhaust. ⑤ Calibrate the exhaust temperature sensor; reposition or replace it if it is misaligned, malfunctioning, or damaged; calibrate the temperature parameters.

2. Abnormal inlet and outlet water temperatures, poor cooling effect

Fault phenomenon : The unit is operating normally, but the chilled water temperature cannot be lowered, the outlet water temperature is too high, the cooling rate is slow, and it cannot reach the set cooling temperature.

Key causes : insufficient or excessive refrigerant, abnormal opening of electronic expansion valve, poor condenser heat dissipation, insufficient water flow, unreasonable unit temperature setting, and excessively high ambient temperature.

Troubleshooting methods : ① Calibrate the refrigerant charge amount and fine-tune it according to the operating pressure to ensure refrigerant circulation matches the operating conditions; ② Inspect the electronic expansion valve to check for problems such as sticking, excessive/inappropriate opening, and slow response. If faulty, repair or replace the valve body; ③ Thoroughly clean the condenser, check for malfunctions in the cooling fan, and improve heat exchange efficiency; ④ Inspect the water system to resolve insufficient water flow issues; ⑤ Adjust the unit's temperature control parameters appropriately to avoid setting the temperature too high, and appropriately reduce the unit load in high-temperature environments.

3. Defrosting abnormality, defrosting protection alarm

Fault phenomenon : The unit cannot defrost normally under heating conditions, the fins are severely frosted and icy, triggering the defrost protection to shut down, and the heating effect is greatly reduced.

The root causes are : abnormal defrost temperature sensor, unreasonable defrost cycle parameter settings, failure to activate antifreeze mode in low-temperature environments, and poor heat exchange of the fins.

Troubleshooting methods : ① Check the installation location and wiring of the defrost temperature sensor. Replace it immediately if it is malfunctioning or damaged to ensure accurate temperature detection; ② Readjust the unit control system and set the defrost start and end cycles appropriately to adapt to low-temperature conditions; ③ In autumn and winter low-temperature environments, turn on the unit's anti-freeze mode in advance to prevent the fins from freezing; ④ Clean the surface of the fins of debris and scale to ensure unobstructed heat exchange.

III. Water Flow System Failure

1. Insufficient water flow, water flow protection shutdown.

Fault symptoms : The unit alarms for water flow, automatically shuts down and locks, and the fault persists after restarting; cold water circulation is poor.

The root causes are : circulating water pump failure, pipe blockage, dirty or clogged water filter, valve not fully open, air accumulation in the pipe, and malfunctioning water flow switch.

Troubleshooting methods : ① Check the operating status of the circulating water pump, troubleshoot impeller wear, motor failure, and pump blockage. Repair or replace any faulty pumps. ② After shutting down the unit, disassemble and clean the water filter to remove scale and impurities from the filter screen, and perform regular sewage discharge. ③ Thoroughly check all water valves to ensure that all valves are fully open and free from throttling or locking. ④ Open the air vent valves in the water system to completely remove any accumulated air and prevent insufficient flow due to air blockage. ⑤ Verify the flow switch and wiring. Replace any abnormal signals or damaged switches promptly, reset the protection settings, and then test run the system.

2. Freeze protection against low water temperature

Fault phenomenon : When the temperature drops in winter, the unit triggers the antifreeze protection and shuts down. The water temperature remains low, which may lead to the risk of pipe freezing.

Key causes : Low ambient temperature, unit not using antifreeze function, stagnant water circulation, malfunctioning antifreeze switch, and abnormal water temperature sensor.

Troubleshooting methods : ① Keep the unit powered on and in standby mode in low-temperature environments, activate the automatic antifreeze mode, and turn on the auxiliary heating device if necessary; ② Ensure the water pump continuously circulates at a low speed to prevent the water in the circuit from freezing; ③ Check the antifreeze switch and temperature sensor, and replace faulty parts in a timely manner; ④ In extremely cold weather, add compliant antifreeze to the water circuit and ensure proper insulation of the pipelines.

IV. Compressor Core Fault

1. Compressor overload protection

Fault symptoms : The compressor operates at excessive current, the thermal protector trips and the compressor stops, the compressor body gets hot, and the overload alarm is frequently triggered.

Core causes : unstable power supply voltage, excessive load, poor heat dissipation, abnormal refrigerant, compressor mechanical wear, and short circuit in the windings.

Troubleshooting methods : ① Check the power supply voltage and three-phase current to identify and resolve issues such as phase loss, excessively high/low voltage, and stabilize the power supply; ② Reduce the instantaneous load of the unit to avoid multiple modules operating at full load simultaneously; ③ Clean the cooling system to ensure normal heat dissipation from the compressor body and condenser; ④ Calibrate the refrigerant quantity to identify and resolve issues such as excessive or insufficient refrigerant or pipe blockage; ⑤ Check the compressor winding insulation value to identify and resolve wear and jamming faults, and replace the compressor if mechanical damage is severe.

2. The compressor cannot start.

Fault phenomenon : The unit is powered on normally, the fan and water pump are running normally, but the compressor does not respond, does not start, and makes no running sound.

The root causes are : compressor contactor damage, control circuit open circuit, overload protection not reset, compressor winding burnout, and main control board signal failure.

Troubleshooting methods : ① Reset all protection switches of the unit and clear fault codes; ② Check the compressor control circuit and wiring terminals, tighten loose circuits, and repair open circuits and loose connections; ③ Test AC contactors and relays, replace them directly if contacts are burnt or components are damaged; ④ Use a multimeter to test the continuity and insulation performance of the compressor windings, replace the compressor if the windings are burnt out; ⑤ Check for faults in the main control board output signals, and repair or replace the control board.

3. Abnormal noise or excessive vibration from the compressor.

Fault symptoms : The compressor makes a metallic knocking sound and a buzzing noise when it is running. The whole unit vibrates violently and the operation is unstable.

Core causes : loose compressor mounting bolts, worn internal parts, refrigerant slugging, pipe resonance, and aging gaskets.

Troubleshooting methods : ① Stop the machine and tighten the compressor mounting bolts, replace the aging vibration damping pads, and eliminate machine vibration; ② Adjust the refrigerant circulation parameters, check for liquid slugging caused by excessive expansion valve opening, and prevent liquid refrigerant from entering the compressor; ③ Inspect the unit's piping, add vibration damping brackets, and eliminate pipe resonance noise; ④ If the abnormal noise is persistent and accompanied by abnormal pressure and current, disassemble and repair the internal parts of the compressor, and replace severely damaged parts directly.

V. Electrical and Control Faults

1. The entire generator unit cannot be powered on.

Fault phenomenon : After the power is turned on, the unit does not respond at all, the control panel is not lit and there is no display.

The root cause is : main power failure, circuit breaker tripping, fuse blown, power line broken, or main control power module damaged.

Troubleshooting methods : ① Check the external power supply line to confirm that the mains power is normal, and reset the tripped circuit breaker; ② Check the fuses and circuit breakers inside the unit, and replace them with the same specifications if they blow; ③ Check the power lines and terminals, and repair any open circuits or burnt-out issues; ④ Inspect the main control power module and transformer, and replace any faulty or damaged parts in a timely manner to restore power supply to the unit.

2. Control panel errors and parameter inconsistencies.

Fault symptoms : The panel displays garbled characters, parameters jump automatically, errors occur frequently, and the unit starts and stops uncontrollably.

The root causes are : control program malfunction, sensor signal interference, poor circuit shielding, and motherboard failure.

Troubleshooting methods : ① Power off and restart the unit, reset the control system parameters, and restore the factory default settings; ② Check the wiring of each temperature and pressure sensor, ensure proper shielding and grounding, and eliminate signal interference; ③ Troubleshoot sensor faults and accurately replace damaged components; ④ If the program or mainboard faults cannot be repaired, refresh the program or replace the main control board.

VI. Failure of Fan and Auxiliary Systems

1. Cooling fan not rotating or rotating at an abnormal speed

Fault symptoms : The condenser fan does not start or runs too slowly, resulting in extremely poor heat dissipation and the unit is prone to triggering high-pressure protection.

Core causes : fan motor burnout, bearing jamming, fan capacitor damage, control circuit failure, blade jamming.

Troubleshooting methods : ① Manually inspect the fan blades, remove any tangled debris or obstructing foreign objects, and correct any deformed blades; ② Inspect the fan capacitor and motor, and replace any faulty capacitors or burnt-out motors directly; ③ Troubleshoot the fan control circuit and relays, repair any circuit faults, and replace any damaged electrical components; ④ Test run the fan to ensure uniform speed and no jamming or abnormal noise.

2. Auxiliary heater malfunction

Fault phenomenon : The auxiliary heater does not work under low temperature conditions, triggering the heating protection alarm, and the heating capacity is insufficient.

The root causes are : water shortage in the heater, temperature switch disconnection, heating element burnout, and control circuit failure.

Troubleshooting methods : ① Check the water circulation to ensure the heater is full of water and there is no water shortage or dry running; ② Reset the heater temperature protection switch and calibrate the temperature control sensor; ③ Check the continuity of the heating element and replace any burnt or damaged parts promptly; ④ Inspect the heating control circuit and contactor, and repair any faulty points.

VII. Key Points for Routine Maintenance and Fault Prevention

1. Clean the condenser fins and water filter regularly, and drain the water once a month to prevent dust and impurities from causing poor heat exchange and pipe blockage.

2. Check refrigerant pressure and level every quarter, investigate pipeline leaks, and strictly prohibit operation with excessive or insufficient refrigerant;

3. Regularly calibrate protective components such as pressure switches, temperature sensors, and flow switches to ensure that the protection functions are sensitive and effective;

4. Check the power supply voltage and wiring to avoid electrical faults caused by phase loss, unstable voltage, or loose connections;

5. In cold seasons, turn on the antifreeze mode in advance, and do a good job of insulating the pipeline to prevent freezing and cracking.

6. Avoid prolonged operation of the unit under overload and in high-temperature, enclosed environments. Reasonably adjust the operating load to extend the service life of the equipment.