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    What is air conditioner expansion valve?

    2017/10/30      view:

    The expansion device is the fourth major component in air conditioner units. It’s also known as meter devices.

    Air conditioner expansion valve is the divided point between the low side and the high side of the air conditioner units. Another dividing point is air conditioner compressors.

    The meter device is located indoor (air handler) units with the evaporator coils. It’s small and hard to see, unless you open the evaporator compartment.

    Types of air conditioner expansion valve

    Have a few types of ac expansion valve in air conditioner units:

    1. Thermostatic expansion valve

    2. Capillary tubes

    3. Automatic expansion valve

    I’ll discuss the operating principles of two types of air conditioner expansion devices, the thermal expansion valve and the capillary tube.Thermal Expansion Valve

    The thermostatic expansion valve (TEV or TXV) is used for refrigerant flow control and operates at varying pressures resulting from varying temperatures. This valve maintains constant superheat in the evaporator.

    Thermal expansion valve has a sensing bulb, which is connected to TXV by a length of capillary tubing. The capillary tube transmits sensing bulb pressures to the top of the TXV valve’s diaphragm.

    Capillary tube metering device

    A capillary tube is a refrigerant control; its common types of air conditioner expansion valve. The capillary is simply a length of tubing with a small inside diameter which acts as a constant throttle on the refrigerant entering the evaporator.

    A fine filter or filter drier installed at the inlet of the capillary prevents dirt from blocking the tube.

    A recent development in the design of capillary tubes for air conditioning system uses capillary tubes with a larger insider diameter and a longer tube length. A larger diameter tubes are less likely to become plugged with dirt and other impurities than a smaller diameter tube.

    The long length provides the necessary resistance to create the desired pressure difference across the metering device.

    The capillary tube equalizes the pressure in the system when the unit stops. This pressure equalizing characteristic of the capillary allows a low starting torque motor to be used with the compressor.

    Typically, a capillary does not operate as efficiently over a wide range of conditions as does the thermostatic expansion valve. However, because of its counterbalance factors in most applications, its performance is generally very good.

    Refrigeration systems using a capillary tube doesn’t require the use of a liquid receiver since all the liquid is stored in the evaporator during the off cycle. However, a suction accumulator is often found in the suction line to prevent any non vaporized refrigerant from reaching the compressor.

    This will prevents damage to the compressor when excessive liquid refrigerant enters the evaporator on a low evaporator load condition.

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