What is a txv on an air conditioner

Air conditioning systems are a must-have in residential homes. Your AC unit has numerous components such as the condenser, evaporator, compressor, and the TXV or thermostatic/thermal expansion valve. What is a TXV on an air conditioner?

The thermostatic/thermal expansion valve or TXV is what makes it possible for your air conditioning unit to operate and function more efficiently. Your AC will work harder if there is a faulty valve and this can result in potential damages to the rest of the components. In order to troubleshoot or replace a thermostatic/thermal expansion valve, the first and most important step is to know what it is and where it is located.

TXV on air conditioners – What is it?

The TXV or thermostatic/ thermal expansion valve is the device used in certain air conditioning systems to ensure that the unit operates in a more efficient manner. The TXV does it by making sure that the AC evaporator has the right amount of refrigerant liquid. The air conditioner will need to work harder when cooling the air if there is too little refrigerant. On the other hand, the presence of too much refrigerant in the unit may accumulate in the lower part of the evaporator’s input line. 

The basics of refrigerant flow

The TXV plays an important role in the HVAC industry. This valve controls the amount of refrigerant that gets released to the evaporator section. Through this, it controls the difference between the current refrigerant temperature and superheats at the evaporator outlet. As a result, it maintains the stability of the saturation temperature at current evaporating pressure. 

The function of the TXV is to control the refrigerant flow to the evaporator as a response to the cooling load.  In addition, the TXV measures the outlet superheat and reacts to it by decreasing or increasing the amount of refrigerant that flows to the evaporator to help retain a constant superheat.  

The TXV in an air conditioner can be found between the condenser and evaporator in the refrigeration cycle. Its main body is brass-made and it includes both outlet and inlet valve. The inlet can be found at the lower part while the refrigerator outlet can be found on the side. A removable cap is found on the adjacent side where the superheat can be adjusted. Some other components are capillary tube, powerhead, and sensing bulb is often stainless steel-made.

The coil can sense once the superheat has been stretched out with the bulb sitting at the evaporator’s exit. Its purpose is to make sure the refrigerant boils off and leaves the evaporator slightly superheated vapor and stops the liquid refrigerant from getting into the compressor. To ensure that the device doesn’t get destroyed or prevent damages to it, the liquids shouldn’t be compressed. There is a separate refrigerant in the bulb to ensure the refrigerant doesn’t mix with the other parts of the AC system. 

Pressure and superheat

The superheat is responsible for boiling the refrigerant within the bulb that creates pressure as this boils. The pressure will then travel through a hollow capillary tube towards the powerhead, with this powerhead controlling the refrigerant flow.

The TXV has a detachable cartridge found within the inlet. It features an orifice working with this valve for controlling the refrigerant. Cartridges have different sizes depending on the required cooling capacity as well as the specific type of refrigerant used. 

The condenser is where the refrigerant comes from and it goes through the inlet to enter the valve body. This enters as medium temperature and high pressure saturated liquid. This will then pass through the body of the valve then upon leaving, this will exit the valve all the way through the outlet in which there is a conversion to low-temperature, low-pressure liquid mixture or vapor. It influences the phase of pressure temperature and controls the refrigerant flow as the pin connects to the control head’s diaphragm. 

How does the diaphragm function?

The diaphragm refers to that thin metal sheet moving down and up with the pin. Found under the diaphragm, there is an adjustable spring for controlling the superheat. There is a sensing bulb sitting at the evaporator’s outlet. The result is that the evaporator’s cooling load boosts the evaporator outlets’ superheat. Since its sensing bulb contacts directly with the evaporator outlet’s pipe, thermal energy gets transferred that makes the refrigerant within this sensing bulb boil and expand.

Once the refrigerant boils and expands, it can increase the pressure within. This pressure will increase and make its way to the capillary tube then travels towards the chamber on top of the diaphragm. Once there is an increase in pressure, this will travel down the diaphragm then down the pin. This pin controls the amount of refrigerant flowing through the orifice assembly within the valve. This pin that gets pushed down towards the stop will open the valve. The refrigerant flow will increase when the stopper is pushed down. Once the evaporator’s cooling load goes higher, the outlet’s superheat also increases.

The outlet’s sensing bulb will detect this with the refrigerant within boiling to cause an increased pressure along the capillary tube. The pressure will then push down the diaphragm then will push down the pin opening the valve then letting in more flow of refrigerant. When there is more refrigerant flowing,   the superheat will also decrease to decrease the pressure within the capillary tube and sensing bulb. It means that there will be less pressure to push down the diaphragm. The spring will push back up the diaphragm that can make the pin move up. Once the pin goes up, the stopper loaded with spring will start closing the orifice that will reduce the quantity of flowing refrigerant.

The Bottom Line

The TXV in an air conditioner repeats constantly then stabilizes the valve to make sure that the right amount of refrigerant will be flowing. The technician will adjust the superheat’s amount by turning the adjuster right or left. It will change the device’s sensitivity to let you tune the TXV and regulate the superheat.

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