Steps to determine the cause of the failure of the thermal expansion valve

Steps to determine the cause of the failure of the thermal expansion valve

1. When the refrigerant of the refrigeration system leaks completely, or there is no refrigerant flowing through the thermal expansion valve due to other reasons, the valve body of the thermal expansion valve will not be frosted. So first of all, it should be determined whether it is a malfunction of the thermal expansion valve. Use a wrench to loosen the inlet nut of the thermal expansion valve, and observe whether there is refrigerant liquid spraying out. If no liquid is ejected, it is not a malfunction of the thermal expansion valve. If liquid is sprayed out, it is basically a blockage of the thermal expansion valve, and then immediately tighten the buckle for the next inspection. When determining or troubleshooting the fault of the thermal expansion valve, the thermal expansion valve may be removed. Note that before removing the valve, the outlet valve of the liquid receiver should be closed, so that the compressor runs to a low pressure (when it is in a vacuum) and stops before removing the expansion valve.

　　2. Tap the side of the inlet of the thermal expansion valve with the handle of the wrench lightly. If you can hear a little sound of liquid flow and the valve body starts to frost, it is confirmed that there is a dirty blockage and the filter is blocked. The troubleshooting method is to remove the valve, clean it with absolute ethanol, dry it, and reinstall it to restore normal use. If the tap is invalid, it is difficult to draw conclusions and continue to check.

　　3. Rinse with boiling water or heat the valve body with an alcohol lamp for several minutes. If you hear the sound of liquid flow and the valve body begins to frost, and the suction pressure rises, it can be confirmed that there is an oil blockage or an ice blockage. If the intermittent blockage occurs during the operation of the refrigeration system, it can be concluded that the ice blockage has occurred , Because the typical feature of ice blocking is periodic blocking. At this time, the water in the system should be completely removed. The method is to remove the desiccant filter, replace the desiccant, let the refrigeration system run for 10-20 minutes, then replace the desiccant, and absorb the moisture contained in the refrigerant until there is no ice blocking.

4. If you hear the sound of liquid flow when heating the valve body, but there is no periodic plugging during operation, it can generally be judged that the oil blockage has occurred. In order to confirm the oil blockage, you can disassemble the thermal expansion valve to see the blockage Whether there are mushy oil stains. The cause of the oil blockage is too much wax in the refrigerating oil, the wrong oil brand is selected, or the effect of the oil separator is not good. These factors should be checked one by one, troubleshooting, and replacement of suitable refrigerating oil.

5. If the heating of the valve body is not effective, it can be denied that the ice block and oil block have occurred. It may be that the thermal expansion valve itself has failed. Remove the thermal expansion valve and blow or suck into the outlet joint of the thermal expansion valve with your mouth. If the blowing or inhalation fails, it means that the valve needle is closed, and the refrigerant leakage of the temperature sensor has occurred, and the thermal expansion valve should be replaced.