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They don’t make air conditioners like they used to, and the thermal expansion valve is proof of that. A wide range of technological perks are available on new A/C upgrades these days. Variable speed blowers and multistage compressors are just two of the energy-saving, comfort-boosting options that probably weren’t available when your existing unit was new. The thermal expansion valve, known in the industry as a TXV, is another.

If you’re upgrading, a TXV may come as an option on a brand new unit. It can also be installed by your contractor as a retrofit to your existing A/C. Here’s why and how a thermal expansion valve can help improve both the bottom line of your monthly cooling costs and the indoor comfort level in your home.  

How a TXV works

The expansion valve in a standard A/C unit meters the flow of refrigerant through the compressor and evaporator coil. Since refrigerant is the substance that conveys the heat out of your home, you’re probably thinking that more is always better. Actually, only when the cooling load is at it’s highest — such as during the worst heat wave of the summer — is full refrigerant output necessary or even desirable. The rest of the time, a reduced volume is adequate and more energy efficient.

Unfortunately, a standard expansion valve doesn’t know the difference between a record-breaking high temp and a more temperate day. The orifice in a standard valve is fixed and doesn’t adjust to changes in the household cooling load. What you get is a pre-set output of refrigerant which may or may not be a good match for the conditions of the moment. When it’s not a good match, the following consequences may ensue:

  • When the cooling load on the house declines but the refrigerant flow doesn’t, a phenomenon called “compressor slugging” may result as excess refrigerant floods the compressor. This can damage compressor components.
  • Too little flow may occur when a fixed output expansion valve meets acute temperatures outside the range of the average load it was designed to accommodate. When refrigerant’s insufficient, the compressor is starved and system performance and efficiency suffers. Because refrigerant also supplies lubricant to the compressor, expensive damage may also result. 

The TXV option

A TXV improves upon the old-school expansion valve by incorporating an adjustable orifice that continuously meters the refrigerant flow from zero to 100 percent output, according to the cooling load requirements of the moment. When TXV technology’s installed, the refrigerant flow adjusts to the interior temperature of your home, not the other way around.

Here’s how it works:

A temperature sensor mounts on the refrigerant line where it exits the evaporative coil. This sensor detects changes in the refrigerant temperature that sensitively reflect subtle temperature variations in your home. The sensor is linked to the adjustable orifice inside the TXV. When interior temperatures change, the TXV opens or closes to adjust the refrigerant flow proportionally. An increase in indoor temperature results in increased flow to the coil and compressor, while a temperature drop causes the valve to reduce flow.

Benefits of a thermal expansion valve 

  • When refrigerant flow is adjusted down to meet a decrease in the cooling load, the compressor draws less electrical current to do its job. Because the compressor is the biggest energy-consumer in the system, this reduction means greater efficiency. A TXV installed on an existing A/C will commonly boost the unit’s seasonal energy efficiency ratio (SEER) by up to two points. A compressor running at reduced output also generates less heat, which reduces wear and tear and increases average service life.
  • A TXV also provides insurance against low refrigerant levels — a common problem due to small leaks in existing A/C and improper installation procedures in new units. As many as three-quarters of air conditioners are undercharged and not meeting the manufacturer’s efficiency and performance specs. Because a TXV automatically compensates for changes in refrigerant flow to keep the level consistent, units equipped with this option are better able to maintain interior comfort and meet energy efficiency specifications. 

Northern Virginia’s established choice for HVAC excellence, Griffith Energy Services is looking out for your all-season comfort and efficiency. Ask us about equipping your new A/C upgrade — or retrofitting your existing unit — with the benefits of a thermal expansion valve option.

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