**Midea Air Conditioner, Repair Case: System air leakage causing indoor unit water leakage**
**Cause Analysis:** During the trial operation of a newly installed unit, water droplets were found on the indoor unit fan wheel, accompanied by a spraying water phenomenon. After inspection, the air conditioner was properly installed, with unobstructed waterways and normal drainage from the drain pipe. Upon opening the indoor unit panel, it was found that the assembly between the evaporator and the base was in good condition. However, a gap was discovered between the left support of the evaporator and the left side fin of the evaporator, leading to air leakage. Sealing the gap with sponge reduced the spraying water phenomenon after running for some time, but the fault was not completely resolved.
After re-opening the indoor unit panel, the surface temperature of each flow path of the evaporator and the temperature of each U-tube were checked. It was found that there were differences in the temperatures of the surfaces of each flow path of the evaporator and each U-tube, preliminarily indicating uneven refrigerant flow (refrigerant bias). Using a pressure gauge to measure the return gas pressure of the low-pressure valve, it was found that the system pressure was lower than the required pressure for the ambient temperature, approximately 3kg.
**Repair Measures:** After adding refrigerant until the pressure slightly exceeded the specified pressure for the ambient temperature, the unit was run for 20 minutes. Observations showed no water droplets on the fan wheel, and the fault was eliminated.
**Experience Summary:** When the ambient temperature is high and the temperature difference between the outlet temperature and the ambient temperature is large (commonly known as a large difference between return air temperature and outlet temperature), if the gap for return air at the evaporator is too large, hot air forms inside the chamber. The condensation water produced by the mixing of cold and hot air adheres to the fan wheel as water droplets, causing the spraying water phenomenon. Additionally, if the surface temperature of the evaporator is uneven, this kind of fault can also occur. For faults caused by uneven surface temperature of the evaporator resulting in water droplets on the fan wheel, they can be resolved by adjusting the amount of refrigerant (adding or reducing). Whether to add or reduce refrigerant should be determined based on the return gas pressure of the low-pressure valve and the ambient temperature. If the temperature difference on the surface of the evaporator exceeds 9 degrees, it can be considered that there is a partial blockage in some flow paths of the evaporator, and this fault can only be resolved by replacing the evaporator.
**Source of Article:** http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3760772