October 14, 2021
Thermostatic Expansion Valve in Foothill Ranch, CA

Air conditioning systems contain many components that must work together efficiently to cool your home. The condenser and compressor are the two parts that are familiar to many of our customers. Although it is not as well known, the thermostatic expansion valve is one of the four main parts of an air conditioning system. This guide will show how this critical component works within your air conditioning system to keep your home comfortable.

The General Purpose of a Thermostatic Expansion Valve

The thermostatic expansion valve, also called the TXV or TEV, controls the flow of the refrigerant into the evaporator. Since refrigerant is the liquid that helps cool the air in your home, the TXV is critical for the efficient operation of your air conditioning system and effective cooling of your home.

A properly functioning TXV will help your evaporator provide optimal cooling power by supplying it with the right amount of refrigerant at the right time. For this reason, the TXV is typically located as close as possible to the intake area of the evaporator. An optimized TXV will also keep too much liquid refrigerant from flowing backward into the compressor. This can help prevent compressor issues and potentially costly repairs.

Examining a Thermostatic Expansion Valve

To many people, a TXV looks a bit like an exterior home spigot used for a garden hose. It has a metal cap called a powerhead on top of a length of pipe. A TXV’s appearance is different from an exterior home spigot because it is typically larger and has two smaller pipes coming out from the sides of the vertical pipe. It also has a coiled capillary tube rising from the top of its powerhead. Thermostatic expansion valves are available in various sizes and can be used for industrial walk-in refrigerators and air conditioning systems.

An Inside View of a Thermostatic Expansion Valve

Before we explain how this important air conditioning component works, you’ll need to know more than its outward appearance or some appliances that use it. You’ll need a clear understanding of the TXV’s inner components.

The component that lets the TXV know how and when to perform is the sensing bulb. This bulb is filled with refrigerant. This refrigerant is different from the refrigerant inside the rest of the system and never mixes with the refrigerant inside the rest of the system. Although it is not a part of the valve itself, it is connected to it through the coiled capillary tube on the powerhead of the TXV and initiates the valve’s operation.

The diaphragm is located underneath the powerhead. It is made of thin metal sheeting and moves in response to pressure changes within the air conditioning system to help regulate refrigerant flow.

The pressure spring rests at the bottom of the diaphragm. This spring’s pressure can be increased by tightening the stem underneath it and decreased by loosening the same stem. Many TXV’s also contain a packing gland to prevent refrigerant from leaking near the stem.

Thermostatic Expansion Valve Components in Action

The sensing bulb contains a refrigerant that becomes more pressurized when the evaporator coil gets warmer. When the pressure increases enough, the sensing bulb sends pressurized refrigerant down the capillary tube, pushing the valve open. The amount the valve opens varies according to the pressure from the sensing bulb.

Pressure from the evaporator and the pressure spring both counteract the pressure from the sensing bulb. In other words, they work together to close the valve. Again, varying pressure levels result in various levels of valve closure.

If the combined pressures from the evaporator and pressure spring are greater than the pressure from the sensing bulb, the valve remains closed and the refrigerant does not flow. Therefore, the pressure from the sensing bulb must be the same or more than the combined pressures from the evaporator and pressure spring.

Refrigerant Regulation

Now that you know the main parts of a TXV and how they function independently, you’re ready to learn how they work together to provide cooling comfort.

The sensing bulb is located near the output end of the evaporator. Therefore, when the temperature of the evaporator increases, it increases the pressure inside the sensing bulb. Once the sensing bulb pressure rises, it sends its refrigerant through the capillary tube into the powerhead. A high level of pressure pushes the diaphragm down.

When the diaphragm is down, the valve is open, and refrigerant can flow through the valve. A very high-pressure powerhead opens the valve as much as possible. When the pressure in the powerhead is not as high, the valve only partially opens.

Regardless of how open the valve is, it allows the refrigerant to pass into the evaporator coil. Once the refrigerant is inside the coil, it removes heat from the system. When the fan blows across the evaporator coil, it pushes cool, refreshing air into your home.

As the refrigerant circulates and cools the evaporator coil, the temperature decreases near the end of the evaporator coil. As this temperature decreases, the pressure inside the sensing bulb also decreases. This, in turn, results in less pressure traveling through the capillary tube and into the powerhead.

As the pressure within the powerhead goes down, it exerts less pressure on the diaphragm. As a result, the valve moves towards the closed position. This restricts the flow of the refrigerant. When the temperature in the evaporator increases again, the pressure rises inside the sensing bulb, and the process repeats.

How a Thermostatic Expansion Valve Can Work for You

Since the TXV regulates refrigerant flow, it helps your air conditioning system work more efficiently. This is because a system with a TXV only uses the amount of refrigerant needed to cool your home. A TXV prevents excess cooling. Your system stops when room temperature reaches the temperature you program into it. This results in more reasonable energy costs.

A TXV-regulated system is also less costly to the environment. When your system is using the proper amount of refrigerant, it can last longer. The reduce, reuse, and recycle movement is about more than plastic soda bottles and unwanted junk mail. When you can get more use from your system, you delay disposing of it. This helps you generate less waste during your lifetime.

Although saving on energy and environmental costs are essential, there is a more immediate benefit of having this air conditioning system component. A TXV can help make your home feel more comfortable right away. This is because the TXV rapidly senses temperature changes and releases the right amount of refrigerant to cool your home to your specifications.

Keeping your home comfortable is our priority. Whether you’re searching for cooling or heating options, our team has solutions that will work for you. We offer installation, maintenance, and repair services designed to make your life easier and better. Whether you want an air conditioning system tune-up or a new heating system in Foothill Ranch or the surrounding areas, call or book an appointment online with White Mechanical, Inc. today for a home comfort upgrade.

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