What Is a Thermostatic Expansion Valve?

October 20, 2021
Thermostatic Expansion Valve in Fieldale, VA

One little-known but extremely important component in home cooling systems is the thermostatic expansive valve. Found just at the evaporator inlet, this valve regulates the flow of refrigerant through the system. When too much refrigerant is allowed to move through the evaporator, its coils will freeze over. Conversely, when there’s too little refrigerant, the evaporator can overheat and cause accelerated air conditioner wear. If your AC system is having a hard time keeping your Martinsville, Virginia, home cool, a damaged thermostatic expansion valve (TEV) could be the reason why.

When the AC System Blows Warm Air, the TEV May be Damaged

One common sign of a damaged TEV is having the AC system blow out warm air rather than cold air. There are many possible causes for an under-performing air conditioner. Thus, if your cooling system has been on for a while and indoor temperatures haven’t dropped, you should troubleshoot the issue by first checking your air filter and the temperature setting at the thermostat.

A dirty, clogged air filter can diminish AC performance by decreasing airflow and making the system work harder. If someone has changed the setting on the thermostat without your knowledge, this can leave you with an uncomfortably warm living environment as well. However, if neither of these things appears to be the source of the problem, you should schedule a professional HVAC inspection to have the TEV checked.

A Damaged TEV Can Cause the Evaporator Coils to Freeze

Freezing evaporator coils is another common sign of TEV problems. This issue often means that too much refrigerant is passing through the system via the liquid line. TEVs moderate the flow of refrigerant based upon pressure and temperature. Problems that cause either of these two things to fluctuate dramatically can throw the TEV off. When freezing or frosting occurs, cooling system performance will decline and far more serious mechanical issues can arise.

TEV Troubles Can Cause the Compressor to Run All of the Time

Blockages along the liquid line through which refrigerant flows, a partially closed TEV, or one that’s stuck in an open position can all cause the AC compressor to run nonstop. Moreover, even as the compressor works overtime, the indoor environment won’t become noticeably cooler. This is a problem that can also expedite wear on the compressor and set the stage for early system failure.

If your home cooling system is under-performing, constantly running, or experiencing freezing at its evaporator coils, we can identify and solve the underlying problem. At McKinney Heating & Air Conditioning, we’ve been helping homeowners all throughout the greater Martinsville and Fieldale areas keep their HVAC systems in top condition since 1972. We also provide generators, tankless water heaters, and indoor air quality services. Call us today to request a quote or to schedule an appointment for repairs.

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