1、 Refrigeration failure
Fault characterization: The temperature inside the box cannot drop to the set value, and the compressor continues to operate without any signs of cooling.
Diagnostic process:
Power troubleshooting: Check for poor contact or open circuit in the power supply line to ensure stable voltage (such as 220V/380V).
Refrigerant detection: Observe the pressure gauge at the low pressure end of the compressor. If the value is below 0.15MPa, refrigerant (such as R404A) should be replenished, and a leak detector should be used to check the leakage points in the refrigeration pipeline, with a focus on inspecting the welding joints and evaporator interface.
Compressor maintenance: If the operating noise of the compressor exceeds 65dB or there is severe vibration, the bearings or lubrication components need to be replaced; If the compressor motor is damaged (such as a broken winding), the compressor needs to be replaced.
2、 Abnormal temperature fluctuations
Fault characterization: The deviation between the displayed temperature and the measured value is greater than 2 ℃, and there is ice accumulation on the surface of the evaporator.
Diagnostic process:
Sensor calibration: Compare the difference between the return air temperature sensor and the independent thermometer. If the deviation is greater than 1 ℃, the sensor needs to be replaced and the probe should be cleaned of dust or condensed water.
Defrost function verification: Check if the defrost light is on normally and confirm that the defrost interval is ≤ 6 hours/time; Manually start the defrost program and observe whether the ice on the evaporator surface melts. If the resistance value of the defrost heating tube is abnormal (normal range 20-50 Ω), the heating module needs to be replaced.
3、 High/low voltage alarm
High voltage alarm:
Reason: Poor heat dissipation of the condenser (such as dust accumulation, fan failure), excessive refrigerant, and air in the system.
Solution: Clean the dust accumulation on the condenser fins and correct the direction of the cooling fan; Discharge excess refrigerant or evacuate and refill; Check for refrigerant leaks and replenish to normal pressure.
Low voltage alarm:
Reason: Insufficient refrigerant, frozen evaporator, clogged filter.
Solution: Use a leak detector to check for system leaks and replenish refrigerant; Defrost or replace the dry filter; Clean or replace the expansion valve.
4、 The door seal is leaking cold
Fault characterization: Cold air leakage at the door gap, condensation on the outside of the box, and energy consumption increased by more than 10% year-on-year.
Handling measures:
Sealing test: Insert A4 paper into the door gap. If the paper can be pulled, replace the door seal.
Emergency response: Temporarily use silicone to fill local damage and maintain short-term sealing effect.
5、 Abnormal condenser/evaporator
Condenser overheating: Clean the dust accumulation between the fins (if the dust thickness is greater than 2mm, it needs to be flushed with a high-pressure gun), and correct the direction of the cooling fan.
Evaporator frosting: Manually trigger the heating lamp to force defrosting. Check the resistance value of the defrosting heating tube (normal range 20-50 Ω). If there is an open circuit, replace the heating module.
6、 Frequent start stop of the system
Trigger condition: The compressor starts and stops more than 8 times per hour.
Solution:
Temperature controller adjustment: Increase the temperature control hysteresis (Δ T) to 1.5-2 ℃ to reduce the compressor load.
Voltage stability: Install a voltage regulator to control voltage fluctuations within a range of ≤± 5%.
7、 Maintenance suggestions
Daily cleaning: Clean the condenser fins and drainage holes monthly, calibrate sensors quarterly, and backup control system parameters.
Regular inspection: Check the refrigerant pressure value annually (R404A system low pressure end ≤ 0.3MPa) to ensure that the system is leak free.
Emergency response: When a fault code occurs, power off and restart first. If it recurs within 30 minutes, perform system diagnosis; The compressor should be stopped immediately if it continuously alarms for more than 2 hours to avoid burning out the motor.