What Is a Thermostatic Expansion Valve? | HB Home Service Team
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Thermostatic Expansion Valves (TXV) are found on large central air conditioning systems. They measure refrigerant flow, pressure, or temperature within the system to operate efficiently.

TXVs can be fixed or floating type with internal capillary tubes that connect the evaporator and condenser. Some TXVs use a capillary tube with a piston to control their position. Others have a separate spring-loaded plunger.

How Does the TXV Transfer Energy?

The TXV’s thermal expansion process provides a cooling effect when needed and releases the pressure when it isn’t. This helps regulate superheat, which converts liquid refrigerant into vapor in an air conditioning and refrigeration system.

The transfer of energy occurs through pressure. Ambient heat or on-cycle heat increases the pressure inside the refrigeration system. As a result, the liquid turns into vapor in the evaporator. Then, it is sent it back through the TXV where its caps release the pressure to transition to its off cycle.

When cooling occurs, a continuous supply of liquid is pumped back through the TXV, releasing this extra pressure. As its caps contract, they cool down and release superheat to keep the temperature optimal for cooling throughout the system.

When the pressure inside a refrigeration system decreases, subcooling happens. This is when the liquid becomes vapor and is rereleased through the TXV’s caps. This ensures there is enough lubricant within the system to prevent wear and tear.

Why Is the TXV Important in a System?

The role of the TXV is to provide superheat, subcooling, and cooling through its thermal expansion process. Also, it keeps these temperatures at an optimal level so that equipment reliability is enhanced throughout its life cycle.

The amount of liquid pumped back through the system is directly related to its net suction pressure. If there isn’t enough liquid in the system, it will malfunction, leading to equipment damage or failure. The liquid refrigerant must pass through the TXV’s caps in their contracted state. This is to ensure temperatures are at optimal levels.

The caps expand when the pressure inside of the system increases and contract when it decreases. Another factor that determines how much liquid will be pumped back into a system is its suction pressure. There won’t be much pushing through the TXV caps if there is more refrigerant in the evaporator, which regulates superheat and subcooling. A lack of lubrication within the system can be another reason it malfunctions, eliminating its life cycle.

What Will Happen When a TXV Fails?

If there is too much liquid in the evaporator, it will get pushed through the TXV caps if they are open, resulting in inefficient operation. A closed cap will result in a lack of fluid within the system, which causes it to malfunction.

A TXV might not regulate superheat and subcooling when they are in their off-cycle, leading to high pressures. This will damage equipment and ruin its life cycle.

Also, a cap might fail because of wear and tear or parts breaking down after many years of use. If the internal seal between the caps is broken, it will allow too much liquid to pass through, which causes the same problems mentioned above.

Other issues can arise when one section malfunctions. Routine maintenance and repairs can make a significant impact on the reliability of your equipment.

What Can You Do When a TXV Fails?

If you suspect that a TXV is malfunctioning, get it repaired by a professional technician. Depending on the extent of damage, it may be necessary to replace some parts.

A packing gasket attaches the caps to the body of the TXV. It is made of rubber which can get worn out over time and may need replacement. Diaphragms change liquid into vapor when it expands during its on-cycle or turns it back into liquid when it cools. It can break down after time, causing a lack of liquid or fluid to enter the evaporator or release too much liquid.

At this point, you have an idea of how a TXV operates and its significance. Always contact a qualified technician to maintain your system. For professional assistance, you can reach out to the HB Home Service Team (PA).

We handle heating and cooling, plumbing and other related services for your home or business. We will be happy to hear from your and assist you in the best way possible. So, wait no more! Contact HB Home Service Team (PA) serving Central Pennsylvania today for more information.

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