Case of air conditioner not cooling: from expansion valve to evaporator to compressor...maintenance is full of twists and turns

http://www.coolercondensingunit.com/supplier-310143-cold-storage-compressorThis article analyzes the maintenance case of an air conditioner in detail. The air conditioner was reported to be "not cooling", and the maintenance staff went through many twists and turns, such as replacing the expansion valve and evaporator, before finally finding out that the compressor was faulty.

Repair case details
Users reported that the air conditioner in their home had a "no cooling" failure, and maintenance personnel came to check. After starting the air conditioner, the machine stopped suddenly after running for about ten minutes. During this period, the F0 fluorine deficiency protection fault code was occasionally reported. The maintenance personnel used a professional detector to conduct a comprehensive inspection of the air conditioner and found that although the compressor could receive working signals, the maximum operating frequency was extremely low, only reaching 60Hz (it should be close to the rated high frequency under normal circumstances). At the same time, the exhaust temperature was abnormally low, about 35°C (normal exhaust temperature should be within a reasonable range), but other operating parameters were normal.

Based on these preliminary test results, the maintenance personnel relied on their experience to suspect that the air conditioning and refrigeration system might be clogged. After opening the outdoor machine panel and observing, it was found that there was severe frost in the section from the electronic expansion valve body to the four-way valve body. Maintenance personnel judge based on experience that severe frost here usually means that the refrigerant flow is blocked, which may be caused by a failure of the electronic expansion valve itself. Therefore, the maintenance personnel decided to replace the electronic expansion valve.

The maintenance personnel believed that there were still blockage points in the system, resulting in poor refrigerant circulation and abnormal throttling effect, which triggered the machine's fluorine deficiency protection. For this reason, the maintenance personnel disassembled the internal machine casing and removed the cross-flow fan blades. They found that the ice on the surface of the evaporator was extremely uneven. The lower part was severely iced, while the upper part was basically frost-free or very thin.

This uneven frosting phenomenon indicates that there is a serious blockage inside the evaporator (most likely the upper half of the pipeline), such as welding blockage, foreign object blockage, etc., which prevents the refrigerant from evenly distributing and evaporating throughout the evaporator, thus affecting the cooling effect. The maintenance staff applied to replace the internal unit evaporator.

When judging the quality of a compressor, you cannot just look at whether it can start up or run without load. You need to observe its frequency-increasing capability and long-term operating stability at the standard refrigerant charge and under load. "Can run without load, run for a period of time after loading to protect" is a typical manifestation of compressor performance failure, which may be caused by parts wear, etc. During maintenance, various testing methods should be used comprehensively to accurately determine its health status.

Shanghai KUB Refrigeration Equipment Co., Ltd.

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