Thermostatic Expansion Valve Fundamentals
Your air conditioning system transforms your home into a comfortable, blissful haven. Knowing some critical facts about this system can help you get the most from it. The following information about the thermostatic expansion valve can give you insight into the inner workings of this important air conditioning system component.
Some Other Names
The thermostatic expansion valve is known by a few different names. Many technicians will use the term TXV when referring to this component. Other individuals call it the TEV. We prefer TXV and will use it during this brief overview.
Regulating Refrigerant Flow
The purpose of the TXV is the regulate the flow of refrigerant in your air conditioning system using the right dissolved oxygen measurement tools . Refrigerant is critical for cooling your home because it is the fluid that removes heat from air so that the fan behind the evaporator can blow refreshingly cool air throughout your home. If you notice your ac unit isn’t as efficient as it was before, have it inspected by a professional ac repair technician to determine the problem and have it fixed. If the ac unit is beyond serviceable, then consider getting Professional AC Installation services.
Thermostatic Expansion Valve Appearance
A TXV looks like a giant capped pipe with a second pipe running perpendicularly through it. The cap-like portion is called the powerhead. A coil on top of the powerhead runs to a sensing bulb located in a different part of the air conditioning system.
Where to Find This Component
The TXV is in the refrigerant delivery line that carries refrigerant from the condenser to the evaporator. The sensing bulb, a separate but critically connected part, is in a different location.
Deconstructing the TXV
Before we consider how the TXV works, we will explain its parts. The sensing bulb senses the temperature changes needed to start the cooling process. The capillary tube connects the sensing bulb to the TXV and carries its supply of refrigerant. This refrigerant is separate from the refrigerant in the rest of the air conditioning system. As you travel down from the top of the powerhead, the first internal part is a diaphragm. This diaphragm is a thin piece of metal that responds to pressure changes. A pressure spring is at a level below the horizontally intersecting pipe.
The Ideal Gas Law Drives TXV Performance
Pressure changes play a significant role in TXV operations. As you’ll soon learn, pressure changes open and close the TXV to release or stop the flow of refrigerant within your air conditioning system. The Ideal Gas Law states that pressure increases when temperature increases. When the temperature decreases, pressure decreases with it. This law in action is what drives TXV performance.
A TXV can fail if it’s too open and overfeeding or too closed (underfeeding). Contaminants from a dirty evaporator coil, oil, or moisture can cause the valve to get “sticky”. In addition, a blocked return air vent can cause a TXV to go bad. Trying to diagnose or troubleshoot a faulty TXV can be difficult and time-consuming. Working with refrigerants requires an EPA 608 license, so a trained ac repair specialist is a must. Improper installation or replacement could cause damage to your air conditioning system.
Cooling From the TXV’s Vantage Point
Since the sensing bulb is near the evaporator, it warms and cools with the evaporator. As the evaporator becomes warmer, the sensing bulb heats with it. As the sensing bulb heats, the pressure of its dedicated refrigerant supply increases and moves down the capillary tube to the powerhead.
Once the refrigerant is inside the powerhead, pressure begins to build there. Since the diaphragm is located immediately below the powerhead, it quickly lowers as the pressurized refrigerant arrives. Since the force that drives the diaphragm depends on the temperature increase in and around the evaporator, the diaphragm moves according to this pressure change. As a result, the diaphragm partially or fully opens. When the diaphragm is open, refrigerant can flow from the condenser to the evaporator.
As the refrigerant moves into the evaporator, it removes heat. When the system falls to the programmed temperature, the pressure forcing the diaphragm down drops. As this happens, the force from the evaporator and the pressure spring work together to shut the TXV. Without fresh refrigerant flowing into it, the evaporator gets warmer, and the cooling cycle of your air conditioning system repeats.
Enjoy Multiple Benefits
The TXV provides multiple benefits for you, your air conditioning system, and the environment. Since your system only cools when you need it, you save on energy bills. The system benefits since this valve will reduce the time your system is cooling. A TXV also prevents other problems that occur when refrigerant backs up into the condenser. This helps your system make a positive environmental impact.
