The Importance Of Servicing A Faulty Thermostatic Expansion Valve

Air-conditioning problems are not always accompanied by any unusual mechanical sound. The only apparent symptom of a malfunctioning AC system may be its inability to maintain a comfortable temperature. Homeowners who suspect that their AC system is simply low on refrigerant may have a different problem and need to have the thermostatic expansion valve serviced.

Air-conditioning systems typically contain some type of orifice that forces pressurized liquid refrigerant into a gaseous state. The orifice usually leads directly into a coil of metal tubing referred to as an evaporator. As the refrigerant evaporates into a gas, it undergoes a drastic drop in temperature. A blower fan is then able to move the cooled air from your AC evaporator to the living spaces of your home.

Dynamic valve operation

Newer AC systems with a higher level of efficiency are more likely to contain a thermostatic expansion valve (TXV) instead of a fixed orifice. A TXV provides a more precise measuring of refrigerant under a wide range of operating conditions. Because a TXV is more complex than a fixed orifice, the valve is somewhat more likely to require attention.

The symptoms of a failing TXV may be very similar to the symptoms of a low refrigerant charge. For that reason, the professional diagnosis of a problem entails attaching pressure gauges to your AC system in order to evaluate the flow of refrigerant. If your system is found to have the correct level of refrigerant, the TXV may need to be repaired or replaced.

Optimal refrigerant flow

In contrast to a fixed orifice, a TXV is capable of increasing or decreasing the flow of refrigerant.The TXV is attached to a thermal bulb that acts as a sensor, providing temperature information to the valve. The sensing bulb is installed near the evaporator, but the sensor is also useful in protecting other AC system components.

Additional benefits of a thermostatic expansion valve

After interior heat is absorbed into the cool evaporator coils, the refrigerant gas is forced onward to the compressor. A properly functioning TXV helps ensure that the temperature of the evaporator is such that the coils never contain liquid refrigerant. The compressor is designed to compress gas only, so the compressor could be damaged by liquid refrigerant.

Even if your AC system is making no unusual noises, a decline in its cooling capacity is reason enough to contact a service specialist, such as fromAirwaves Heating & Air Inc. The thermostatic expansion valve and the fixed orifice are both relatively small parts, but they play a major role as refrigerant is continuously recycled.through your AC system.


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