Thermostatic Expansion Valve Defined

Thermostatic Expansion Valve in Rosenberg, TX

The air conditioning system in your home is very useful in regulating the temperature and airflow for comfortable living. Unknown to many homeowners, such systems have particular components that work together to give desired results. From the surface, it may not be easy to spot all the parts which perform various functions to make our homes comfortable. Even as you install your HVAC system, it is important to ensure that it is designed to contribute to energy efficiency.

Understanding the Thermostatic Expansion Valve (TXV)

In line with the minimum efficiency regulation, home equipment such as refrigerators must be designed to ensure energy efficiency and improve their performance. One device that forms part of the refrigerator and air conditioning systems is the thermostatic expansion valve (TXV). Its function is to control the flow of the refrigerant into the evaporator. It is crucial for air conditioning systems specialists to understand the design of the TXV and how it works. Custom Comfort Air has qualified professionals ready to install and service Air Conditioning systems, including thermostatic expansion valves.

As a precision device, the TXV is designed to boost the performance of the evaporator and prevent the escape of excess refrigerant into the compressor. In an air conditioning system, the TXV plays a vital role in separating different sides of low and high pressure. The pressure of the liquid refrigerant entering the valve is reduced when the valve limits the amount that enters the evaporator.

Contrary to what many people believe, the thermostatic expansion valve does not regulate air temperature, humidity, suction pressure, or head pressure. It only controls the flow of liquid refrigerant into the evaporator depending on the amount of load in the evaporator. A bigger load in the evaporator will trigger the TXV to allow more liquid refrigerant. In comparison, a smaller load will attract a small quantity of liquid refrigerant passing through the valve. This leads to the efficient performance of a compressor and an air conditioning system. Any attempts to control any of these variables using the TXV may lead to system damage or failure.

Functions of the Thermostat Expansion Valve

Some of the essential functions of the thermostatic expansion valve include the following:

  • Reducing the liquid refrigerant pressure: This is the most critical function of the TXV. The refrigerant inside the condenser exists under high pressure and comes out with the same level of pressure. However, it cannot pass through the evaporator with the same pressure level and hence has to be lowered. The TXV allows the pressure to drop to levels consistent with the pressure inside the evaporator through throttling. When the pressure drops in the evaporator, there is a cooling effect achieved. In air conditioning systems, the cooling effect is essential in regulating temperature in homes.
  • Keeping the evaporator active: Activity in the evaporator is critical for the functioning of the whole system. The thermostatic expansion valve keeps the evaporator active by allowing the flow of liquid refrigerant through it. The TXV allows more refrigerant flow when the evaporator has a higher load and reduced flow when the load is smaller. This balance is necessary as the evaporator will only achieve optimal functioning when there is a match between the load level and pressure.
  • Enabling the required level of flow of the refrigerant: There is the necessary amount of refrigerant that can flow through the evaporator at any given time to enable optimum performance. Depending on the load inside the evaporator, the TXV allows a certain level of flow and pressure to ensure that the liquid refrigerant does not overflow into the compressor. That way, both the evaporator and the compressor perform efficiently.
  • Contributing to evaporator efficiency: For the evaporator to function efficiently, it must receive enough refrigerant. When the temperatures are high indoors, the evaporator will need more liquid refrigerant to allow heat absorption to generate a cooling effect. When indoor temperatures are high, the evaporator requires more refrigerant to absorb that heat. Under low indoor temperatures, less refrigerant is needed by the evaporator. It is impossible to achieve energy efficiency in your whole refrigerating plant or A/C system when the evaporator fails to get the exact amount of refrigerant it needs.

The thermostatic expansion is an advanced metering device that has the ability to detect how much refrigerant is required at any given time by the evaporator depending on the cooling load. It is able to adjust the flow and supply to the necessary amount within the acceptable pressure levels.

Components of a Thermostatic Expansion Valve

One of the most critical parts of a TXV is the valve needle which allows the valve to open and allow varying amounts of liquid refrigerant into the system. There is also a sensing bulb whose function is to detect the temperature of refrigerant coming off the evaporator. The sensing bulb is attached at the end of the evaporator outlet. The sensing bulb is helpful as it allows the valve to know the temperature levels, determining how much refrigerant is released.

A flexible diaphragm at the top of the TXV is responsible for moving the valve needle when a high cooling load is detected. When the temperature at the evaporator outlet increase, signifying a higher cooling load, pressure in the bulb also increases, pressing down and opening the valve needle to let in more refrigerant. On the other hand, increased pressure in the evaporator indicates a lower cooling load, which pushes the diaphragm up and closes the valve to limit the amount of refrigerant flowing into the evaporator.

For the valve needle to function correctly, there must be a balance between the evaporator/spring pressure and the bulb pressure. For that reason, the valve is never fully closed or opened except in extreme situations. In most cases, it opens just enough to let in the required amount of flow to address the cooling load at any given moment.

Diagnosing a Faulty Thermostatic Evaporation Valve

Here are some things that may be a sign that your TXV is having problems:

  • Low pressure in the evaporator
  • High superheats in the compressor and evaporator
  • Abnormally high discharge temperatures
  • Low condensing pressure
  • High sub-cooling in the condenser
  • Low condenser split

Maintenance and Servicing of Thermostatic Expansion Valve

If you have the thermostatic expansion valve installed correctly within your air conditioning system, you may not need any form of maintenance. However, if you notice anything unusual in its operations, it may need to be serviced. Your TXV system needs to be installed and serviced by professionals who understand how it works and the crucial components in the system.

Call Us for Your Air Conditioning Needs

Custom Comfort Air provides heating & air conditioning services in Sugar Land, TX, and the surrounding areas. We offer a range of services, including AC and heating repair, installations, and maintenance. Our family-owned local business has been serving residents for many years. We have fast and reliable certified technicians and promise a 100% satisfaction guarantee. As Lennox Premier Dealer, our reputation is unquestionable. We are the best of the best and have highly trained HVAC professionals capable of handling any comfort issues within your home. Contact us today for more information.