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New Information Regarding Wide Spread TXV Failures

Posted by AC Contractor on August 25, 2014 at 9:15 PM
A TXV is a metering device for the refrigerant. It controls how much is fed through the system at a time. Although they are far from uncommon, they are a relatively new technology in air conditioning. Many air conditioning and heating systems today continue to use a fixed orifice or piston as a metering device. Thermal expansion valves can improve a system's efficiency and we rarely don't see them on equipment that is 14 SEER and higher. With the new federal minimum efficiency standards set to take place next year the percentage of HVAC systems that utilize a TXV will increase substantially. One negative of TXV's is they will break more often than a fixed orifice. Recently, there have been widespread failures of expansion valves that have impacted many manufacturers. After a thorough investigation it appears that replacing the TXV will solve the issue. Below is an official statement from Danfoss.

For the past several months, there has been a significant increase in the number of “no cooling” complaints coming from new residential air conditioning and heat pump installations. A system inspection typically shows the unit running with a very high superheat and low suction pressure, leading to the conclusion that the thermal expansion valve (TXV) wasn’t functioning properly. Once the TXV was replaced, the system operated fine which seemingly confirmed the TXV was the cause of the problem.

Danfoss has been working with our partners to resolve this issue. After weeks of collaboration and significant hours of lab time, it has become apparent the TXV is not the root cause of this problem. Our chemical and metallurgical experts have determined that a chemical reaction (hydrolysis or polymerization) with organic compounds from the system is the root cause. These newly formed chemicals result in a dark sticky substance adhering to the orifice cone. Once this happens, the orifice gets blocked and system failure occurs. This conclusion is shared by all our OEM partners as well. In these cases, Danfoss recommends replacing the TXV (like for like) per the system manufacturers instructions.

We do not recommend trying to clean the TXV in the field. Field experience shows that after the initial valve is replaced in the system this failure mode rarely re-occurs. Danfoss, together with our OEM partners, has done a thorough review of our factory and manufacturing processes. We can confirm the organic compounds found blocking the valves are not used anywhere in our processes. For this reason we can be certain when we say the Danfoss TR6 valve is not the root cause of the problem. However, it is important that, as an industry, we get this issue behind us. Therefore, Danfoss continues to cooperate with our partners to assist in finding the origin of the root cause that will eliminate the issue going forward and minimize issues in the field.

We will continue to update the industry via our website (www.northamerica.danfoss.com) and direct communications such as this. For more information, please contact your local Danfoss account manager or field system engineer.

Many manufacturers use Danfoss expansion valves, however, we have only seen this issue affecting Frigidaire, Lennox, Maytag and Rheem systems. We can not guarantee your system is not affected if you do not have one of these brands. For more information on air conditioning and heating equipment, contact Tampa area air conditioning experts Melo Air today.

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1 Comment

Reply John busick
10:58 PM on May 31, 2017 
My Trane, 4 ton. Was diagnosed with bad TXV valve. Unit only 4 yrs old and still under warrentee. Now they want to charge me 350.00 due no falt of my own. Valve is free.