Thermostatic Expansion Valve | TXV
Thermostatic Expansion Valve, or as they are much more widely known, TXV's, are a metering system that is built into most of today air conditioning systems. In simple terms, a TXV monitors the temperature of the coolant flowing through the evaporator coil on your cooling system, and controls the flow based on that temperature, to allow the refrigerant to remain in or out of the coil for longer periods of time, which results in higher efficiency and SEER ratings!
The easiest way to envision the way it works… is to imagine the valve being the handle on your bathroom sink faucet, and you want the actual metal on the spout to stay between 110-120 degrees. If too much water is flowing, it will get hotter than 120, too little water flowing through and it will never reach the 110 degree mark. You would naturally adjust the flow to maintain the exact temp you want right? Well, that's what the TXV does as well, but it does it automatically.
Replacing the TXV is not usually something a homeowner should be doing, since you will also need refrigerant to complete the job. As we already know, without a license… not many homeowners can get refrigerant! If you do however have access to refrigerant or a technician who is going to do the work for you, you can get a TXV valve for less than $50 in most cases, and you only need to make sure its designed for the size and type or refrigerant of your system.