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HVAC School - For Techs, By Techs

Jun 10, 2021

In today’s podcast, Trevor and Bryan discuss how to troubleshoot thermostatic expansion valves (TXVs/TEVs). They also dive into the various types, applications, and components of TXVs.

TXVs are metering devices that control evaporator superheat to protect compressors from harm. Controlling heat also regulates pressure, which improves efficiency and prevents issues like floodback and overheating. TXVs contain several components that manage the forces that open and close the valve. These components include powerheads, diaphragms, springs, and more. The components all contribute to a delicate balance that can be broken when they fail or are installed improperly. TXV failures lead to high or low superheat and eventually compressor failure. 

When you diagnose a TXV, you may encounter hunting, broken powerheads, filthy screens, and improperly sized valves. Once you verify the cause of the issue, you’ll likely have to adjust the TXV, replace a component, or replace the whole TXV. That can be a tricky decision that will largely depend on the type of failure, the type of TXV (conventional vs. balanced port), and the TXV’s application (residential HVAC, refrigeration, etc.).

Join Bryan and Trevor as they cover:

  • Opening and closing forces
  • Internal and external equalization
  • Non-bleed/hard shutoff TXVs and design limitations
  • Conventional valves vs. balanced port valves
  • Brazing in TXVs
  • Strapping the TXV bulb to the suction line
  • TXVs in refrigeration vs. HVAC
  • Liquid quality, sight glasses, and subcooling
  • TXV sizing
  • Suction pressure/superheat hunting
  • High and low superheat causes
  • Adjusting vs. replacing valves

And much more...


Check out Emerson’s HVACR training HERE. Then, navigate to “Contractor Tool Box Talks with Emerson.”

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