If the minimum temperature of the cold storage unit fails to meet the design requirements, it is necessary to investigate according to the logic of "simple first, then complex; low cost first, then high cost". The core handling steps are as follows:

1. Prioritize the investigation of basic operations and parameters

First, eliminate non-hardware faults: ① Check the designed minimum warehouse temperature against the set value of the temperature controller (for example, whether -18℃ in the freezer is mistakenly set to -10℃); ② Check the position of the temperature sensor. It should be fixed at a height of 1.5 meters in the middle of the warehouse, away from the evaporator outlet and heat sources (such as warehouse doors and lighting) to avoid signal misjudgment. ③ Confirm that the unit is operating at full load. For the variable frequency machine, check whether the compressor has reached the rated maximum speed. For the fixed-frequency machine, detect whether the working current is in line with the rated value. Eliminate mode limitations or unloading operation issues.

Second, focus on the cleaning and adjustment of core components

For key links in the refrigeration chain: ① Clean the condenser (for air-cooled types, use a high-pressure water gun to remove dust from the fins; for water-cooled types, clean the scale inside the tubes) and the return air filter screen of the evaporator, and check whether the fan is operating normally to solve the problem of insufficient heat dissipation and heat exchange efficiency; ② Fine-tune the expansion valve clockwise by 1/4 turn each time. Run it for 30 minutes and observe until the evaporator is evenly frosted to avoid insufficient liquid supply. ③ Manually start the defrosting function to remove frost layers exceeding 5mm from the evaporator, and simultaneously adjust the defrosting cycle (8-12 hours per time for the freezer).

Iii. Investigate hidden leaks and insulation issues

If the above steps are ineffective, the key inspection points are as follows: ① Use soapy water or a leak detector to check the welding points of the refrigerant pipeline and the valve interfaces. After finding the leakage points, re-weld them, maintain the pressure with nitrogen (≥2.0MPa/24 hours), evacuate the air, and then charge the refrigerant at the rated value. ② Check the insulation of the storage body, replace the aged door seals, fill the cracks in the walls, and reduce the leakage of cold. Through the above process, most problems can be solved by simple adjustments or maintenance. For complex faults, it is necessary to contact professionals to inspect core components such as compressors.