Columbus AC Repair Question: What Are Thermostatic Expansion Valves?

Even if you know a lot about your home’s HVAC system, you might not know what thermostatic expansion valves do on your air conditioner. The thermostatic expansion valve, sometimes known as a TEX, TEV or TXV, is a critical piece that influences the efficiency of air conditioning and refrigeration units. A tiny sensor controlling the evaporating phase of the process, the valve can have a big effect.

Cool air is manufactured by the rapid movement of a refrigerant between liquid and gaseous states. Compound chemicals that are able to do this at a low temperature are compressed and expanded, absorbing and releasing heat at different points along the way. The TEV controls the flow of the refrigerant into the evaporator coils according to the temperatures of the various ingredients.

Cool Air 101

o condition air the refrigerant, (most often freon or another fast acting, low temp compound,) evaporates into a gas that runs through a coil and absorbs heat. Passing through a compressor, the freon condenses under pressure back into a liquid again and releases the heat, becoming cool enough to chill a party.

If too much freon is in the evaporator tube, and the pressure is not low enough to expand it into gas and absorb heat, it’ll work inefficiently for no gain. Too little freon and the conversion is also ineffective by not reaching the density needed to condense.

There are four types of valves with different benefits for different types of cooling environments. With its ability to minutely adjust to changing conditions, the thermal expansion valve creates the perfect mixture of pressure and freon for more complicated systems.

At the Starting Gate

An interactive device, the valve senses the evaporator pressure and temperature and adjusts the flow of the refrigerant so as to maintain a given “superheat”, (the differ­ence between the refrigerant vapor temperature and its sat­uration temperature). By controlling superheat, the TEV nearly keeps the entire evaporator surface active, while not permit­ting liquid refrigerant to return to the compressor.

Some valves operate on an electrical impulse from sensors that can measure the temperatures. Others are open all the time. The thermostatic expansion valve actually utilizes the pressure between the two sections to open or close itself, regulating flow based on the very same pressure it is designed to moderate.

Monthly Savings

Like the buildings they comfort, large air conditioning systems are varied and diverse. There are nearly as many thermostatic expansion valves as there are units to receive them. For more information about your home’s air conditioning systems or if you need any maintenance or repair in Columbus, give Quality Air Heating and Air Conditioning a call!