1. Common causes of temperature sensor failure
When the expansion valve supplies liquid frequently and sometimes less or the expansion valve is not closed in the system, the degree of overheating, and the degree of subcooling are not correct. The reason may be that the temperature sensor is out of order.
1) The capillary tube of the temperature sensing bag is broken, causing the filling material in the temperature sensing bag to leak out, resulting in the inability to transmit the correct signal to the actuator of the thermal expansion valve.
2) The wrapping position of the temperature sensing bag is incorrect.
2. How to deal with the fault of the temperature sensor？
Under normal circumstances, the temperature sensing package should be installed as far as possible on the return pipe of the horizontal section of the evaporator outlet, which should be far away from the compressor suction port and close to the evaporator, and it is not suitable to be installed vertically. When the diameter of the horizontal return pipe is less than 7/8 (22mm), the temperature sensing bulb should be installed on the top end of the return pipe, that is, "one o'clock" of the suction pipe. When the diameter of the horizontal return pipe is greater than 7/8, the temperature sensing bulb should be installed below the axis of the return pipe at about 45 degrees to the horizontal axis, that is, at the "3 o'clock" position of the suction pipe. Because installing the temperature sensor bulb on the upper part of the suction pipe will reduce the sensitivity of the reaction, it may cause too much refrigerant in the evaporator. Installing the temperature sensor bulb on the bottom of the suction pipe will cause turbulence in the liquid supply, because there is always a small amount of refrigerant. The liquid refrigerant flows to the location where the bulb is installed, causing a rapid change in the temperature of the bulb.
When installing, the temperature sensing bulb needs to be wrapped with a copper sheet, and the surface of the return air pipe should be derusted. If it is a steel pipe, the surface should be painted with silver paint after rust removal to ensure good contact between the temperature sensing bag and the return air pipe. The temperature sensing bulb must be lower than the upper cavity of the valve top diaphragm, and the head of the temperature sensing bulb must be placed horizontally or downwards. When the relative position is higher than the upper cavity of the diaphragm, the capillary tube should be bent upward into a U shape to prevent liquid from entering the membrane. On-chip cavity. In order to avoid that when the system suddenly shuts down, the refrigerant liquid or oil accumulates in the horizontal pipe section where the temperature sensor bulb is located and affects the performance of the temperature sensor bulb, the pipe section behind the temperature sensor bulb should be made.
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