The thermostatic expansion valve — also known as a TXV — is a precision air-conditioner component critical to efficient cooling. While refrigerant is the lifeblood of an air conditioner, the TXV is the device that ensures the system circulates the correct amount of refrigerant at all times to accommodate changing cooling demands in your house.
Here’s a basic description of the refrigerant flow:
- The cooling cycle in a typical air conditioner is a circle. Frigid refrigerant vapor flowing through the indoor evaporator coil extracts heat from the house, then flows to the outside condenser coil, where that heat is dispersed into outdoor air. The low-pressure flow of now warm, liquefied refrigerant circles back toward the evaporator coil and enters the thermostatic expansion valve.
- Refrigerant’s unique chemical properties allow it to convert from a warm liquid back to a cool vapor that absorbs heat effectively. As the thermostatic expansion valve constricts refrigerant flow and increases pressure, a needle valve inside the unit meters the precise amount of refrigerant entering the evaporator coil based on a temperature-sensing bulb that measures immediate cooling-load requirements.
- As refrigerant is released through a tiny nozzle, the rapid pressure drop converts the warm liquid back to a cold, vaporous substance, absorbing heat efficiently as it circulates through the evaporator coil again.
What Might Go Wrong?
While a thermostatic expansion valve is a reliable component, like any mechanical part, it may be affected by wear and tear and other issues. Typical problems include:
- The TXV needle valve is stuck open or closed.
- The valve is clogged by debris.
- The sensing-bulb unit is defective.
Symptoms of Possible Thermostatic Expansion Valve Failure
- Your AC blows warm air constantly.
- Temperature control is inconsistent.
- Ice forms on the evaporator coil.
- There is expensive compressor damage due to liquid refrigerant.
- High monthly cooling costs.
What Should Be Done?
A TXV is not serviceable or replaceable by the homeowner. A qualified HVAC technician is required to pinpoint the problem and open the refrigerant system for cleaning, repairs, or replacement of this component.
For professional diagnosis of potential issues with the thermostatic expansion valve, contact the cooling experts at Detmer and Sons.