Air conditioning helps you stay comfortable in our humid climate. Our team at Northwest HVAC Heating & Cooling wants you to get the most from this crucial home system, so we’ve assembled the following guide to help you understand the thermostatic expansion valve. It is often referred to as a TXV. Together with the evaporator, condenser and compressor, the TXV is a significant component that supports the efficient functioning of your air conditioning system.

How to Spot the TXV

The TXV looks like two pipes that cross one another at a 90-degree angle. The pipe in the horizontal position has a cap called a powerhead. The powerhead has a metallic coil emerging from it. This coil later straightens into a pipe that leads to a metallic oval called the sensing bulb.

The TXV is located on the refrigerant line. The sensing bulb is beside the output end of the evaporator.

A Closer Look at the TXV

Since it is the part that spurs the rest of the system into action, we’ll begin with the sensing bulb. The sensing bulb is filled with an independent refrigerant supply that responds to temperature changes.

If you trace the path from the sensory bulb to the TXV, you are tracing the path of the capillary tube. This thin metallic pipe brings refrigerant to the TXV from the sensing bulb. It begins as a straight tube and becomes coiled as it nears the TXV.

Once you reach the TXV, there is a diaphragm that lies directly below the powerhead. The diaphragm is a thin, moveable piece of sheet metal. There is also a coiled piece of metal that acts as a pressure spring.

The TXV’s Purpose

The TXV opens so that refrigerant is released into the evaporator when it is needed for cooling. When the room has reached the programmed temperature, the TXV shuts to stop any excess refrigerant from flowing through the system.

A Fundamental Law

To understand TXV operation, we must first briefly explain the ideal gas law. This law states that temperature and pressure increase together. Therefore, as the temperature of an air conditioning system increases, the pressure of its fluids also increases.

TXV Operation

As the evaporator heats, the sensing bulb gets warm. Following the ideal gas law, the sensing bulb’s refrigerant pressure increases and eventually travels through the capillary tube to the TXV.

Once the pressurized refrigerant reaches the powerhead, it pushes the diaphragm down. As the diaphragm moves down, the valve opens so that the refrigerant can flow from the condenser to the evaporator.

Since refrigerant removes heat, the temperature at the end of the evaporator and inside your home drops. When the temperature has decreased to the level you have programmed into your thermostat, the evaporator and sensing bulb temperatures fall. This causes the pressure to drop and the diaphragm to rise to its starting position.

The pressure spring and pressure from the evaporator work together to shut the valve. When your home gets warmer than your selected temperature, this cooling cycle repeats.

Valuable Benefits of a Thermostatic Expansion Valve

The thermostatic expansion valve provides customizable cooling when you want it. As a result, your system isn’t cooling your home when it’s not needed, so air conditioning components don’t wear down prematurely. This helps you get the most use from your system.

An air conditioning unit that runs only when you need cooling also helps you keep your energy bills more manageable. Since the system is running efficiently, it does not waste energy. You can also more easily budget your energy use because your air conditioning system is using energy at a consistent rate.

Using less energy is only one way the thermostatic expansion valve helps conserve natural resources. Getting the most use from air conditioning systems throughout your life means you will dispose of fewer systems. As members of the Energy Trust of Oregon, preserving our beautiful Pacific Northwest environment is a part of our mission at Northwest HVAC Heating & Cooling.

Technical Expertise at Your Disposal

As a proud homeowner, you want the best for your residence, and that requires maintaining its primary systems. Our team specializes in listening to their concerns as we provide residents throughout the Vancouver region with a full range of high-quality heating and cooling services to support their indoor comfort. That includes installation, maintenance and repair. Contact us at Northwest HVAC Heating & Cooling today to obtain more information or to schedule an appointment.

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