If you have an air conditioning unit that is malfunctioning, your technician may have found that it’s your thermostatic expansion valve (TXV). But what is this valve, what function does it perform in your equipment, and why can it be the problem?
How TXVs work
To explain how expansion valves keep you cool, you have to understand how refrigerant works in your air conditioning unit. Refrigerant is a fluid that goes through different phases throughout your system. In the AC unit, there are four distinct components-- a compressor, a condenser coil, an evaporator coil, and a metering device (the TXV) -- all of which have an effect on the refrigerant.
The compressor compacts the vapor molecules, which raises its energy and temperature. That hot, high-pressure gas moves on to the condenser. The condenser cools things down a bit, turning the high-pressure gas into a high-pressure liquid. The evaporator coil is attached to a fan which pulls air in from the home environment. In this section of the process, the hot air and cooled refrigerant experience a thermal exchange caused by a pressure drop from the TXV resulting in cooled air and warm, low-pressure gas. This gas then moves on to the compressor to begin the cycle again until the air in the environment reaches the temperature set on your thermostat.
TXVs control the flow of refrigerant to the evaporator coil. That's it. There are many misconceptions about how they work and what the symptoms are of a failing TXV. The only function of an expansion valve is to control refrigerant to the evaporator coil. However, there are other factors involved that determine how well the valve operates.
Is the TXV really the problem?
It is important for service technicians to look into a few other possible causes before simply diagnosing a broken-down AC unit with a failed TXV. Checking for appropriate refrigerant level, clean filters, proper air flow and clean evaporator coils should be high on the list.
Ask your technician what procedures they used to diagnose your system. Find out what other possibilities were eliminated and why. If the technician cannot answer these simple questions you might want to get a second opinion.
Do you have other questions about problems with your air conditioning unit or any other component of your HVAC system? Please do not hesitate to call the professionals at Burgeson’s. We are always available for educational opportunities in answering questions like these.