The Thermal Expansion Valve: An Advanced Feature You’ll Want in Your Next A/C

The thermal expansion valve exemplifies the continuing refinement of home cooling technology.

While it was installed in large, commercial air conditioners for many years, the TXV, as it’s known in the industry, is a relative newcomer in residential applications. It’s quickly become a standout efficiency and performance enhancement to both new high-efficiency A/C units, where it’s available as standard equipment from the manufacturer, or as a retrofit for installed air conditioners.

A thermal expansion valve makes your A/C smarter and able to automatically respond to changes in the home’s cooling load. The SEER (Seasonal Energy Efficiency Ratio) of a typical A/C can be increased as much as 11 percent simply by replacing the fixed standard expansion valve with a smart TXV.

What an expansion valve does
Refrigerant is the heat-absorbing substance that circulates though the evaporator coil to extract heat energy from your house. After the refrigerant absorbs the heat, it flows to the compressor, then to the outside condenser coil where the heat is dispersed into the air. On the way back to the evaporator to pick up another load of heat, the flow of liquid refrigerant passes through an expansion valve to convert it back to a vapor. This valve meters the amount of refrigerant reaching the evaporator and directly influences the energy-efficiency and cooling power of the air conditioner

Why a TXV is better

As the temperature in your home varies, the refrigerant flow requirements for optimum system performance change. Unfortunately, a standard expansion valve doesn’t. The static orifice incorporated in the valve delivers a fixed amount of refrigerant at all times, based on a calculation of an average range of temperatures and cooling load. In this day of high energy costs and increased demands for cooling performance, “average” simply isn’t good enough anymore.

How the TXV works
A thermal expansion valve improves upon average performance by continuously sensing the changes in the home’s cooling load and altering the refrigerant flow proportionately. The heart of the TXV system is a diaphragm-operated expansion valve that accommodates any cooling load by modifying the refrigerant flow across a range from zero percent to 100 percent. The valve is signaled by a bulb sensor attached to the output of the evaporator coil that monitors the temperature of refrigerant leaving the coil, a sensitive indicator of thermal changes inside your home. When refrigerant temps increase, the bulb sensor causes the diaphragm to open the needle valve and admit more flow to the evaporator. When the sensor registers a temperature decline, the valve is signaled to decrease refrigerant flow.

Delivering just the right amount of refrigerant to the evaporator is critical:

  • If the evaporator doesn’t get enough, cooling performance suffers. The system responds by running longer “on” cycles to meet thermostat settings. This impacts energy efficiency and increases cooling costs. The refrigerant formula also incorporates vital compressor oil. When the compressor is starved of refrigerant, the loss of lubricant can overheat the compressor and damage this expensive component.
  • But more is not always better, either. Circulating refrigerant at an output that exceeds the immediate requirements of the home draws unnecessary electrical consumption, increasing operating costs. Excessive refrigerant flow to the evaporator may also leave some refrigerant in the liquid state instead of vaporized, flooding the compressor. This can cause a damaging effect known as “slugging” and lead to premature compressor failure.

In addition, an A/C with a standard expansion valve has no mechanism to correct for refrigerant deviations caused by common leaks or an unprofessional installation job. A thermal expansion valve enables your air conditioner to automatically compensate for variations in refrigerant charge and still sustain normal efficiency and comfort.

And there’s more
Air conditioners that incorporate TXV technology typically include other user perks, as well. Look for these additional comfort and performance enhancements:

  • A two-stage compressor to match compressor output to the cooling load on the home.
  • An energy-efficient variable speed blower that maintains continuous air circulation and eliminates the temperature spikes and sags associated with conventional on/off blowers.
  • An intelligent programmable thermostat that displays reminders when routine maintenance is due as well as alerting you to any system problems that may require service.
  • A federal tax credit, extended until the end of 2013, of up to $300 on the installation of a high-efficiency A/C with a SEER rating of 16 or more.

In Mount Pleasant and greater Titus County, Wood Air Conditioning & Plumbing has been the choice for indoor comfort and efficiency for 56 years. Contact us today for more information on upgrading to the benefits of a thermal expansion valve for your A/C system.

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