While it’s not the best-known component in your central air conditioner, the expansion valve is vital to the comfort you expect when you set the thermostat. It’s better known by its abbreviation: TXV, which stands for thermal expansion valve.
The TXV incorporates a valve that precisely restricts the flow of refrigerant as it enters the AC evaporator coil inside the indoor air handler. Here’s how it works to convert warm refrigerant back to a state that helps create comfort.
- In normal operation, the valve opens very slightly, allowing warm, high-pressure liquid refrigerant to spray through the valve and instantly depressurize.
- Rapid depressurization causes the refrigerant to instantly convert into a frigid mixture of liquid and vapor as it flows through the evaporator coil.
- The cold, low-pressure refrigerant efficiently absorbs heat from indoor air flowing through the evaporator coil.
- As the heat is extracted from the warm indoor airflow at the coil, air flows into ductwork and circulates throughout the house.
What Can Go Wrong?
The TXV is generally a reliable and proven component. However, malfunctions may occur after years of operation. Some of the symptoms of a faulty TXV include:
- Frost or ice continuously appearing on the indoor evaporator coil.
- Instead of cycling on and off during AC cycles as normal, the system compressor runs all the time.
What Now?
A qualified HVAC technician will first eliminate a few other potential causes of these symptoms in order to reach a diagnosis that the TXV is defective. While it might be technically possible to remove and attempt to repair the defective valve, the cost of doing so is often not practical. In most cases, simply installing a new TXV valve is usually the best course of action.
For more information about the AC thermal expansion valve and what to expect if it malfunctions, contact the pros at Ace Hardware Home Services.
