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Training Event Tech Session Wrap up (Part 1)

By Richard Hawkins

There were some great classes presented at the 2023 MACS Training Event and trade show held in Nashville, TN on February 2nd through February 4th.  Starting with today and continuing over the next 4 weeks, I will be covering four of those classes.

TXVs, Superheat, MOP, and More w / Gene Dianetti

 We will begin with the class titled TXVs, Superheat, MOP, and More w / Gene Dianetti.  This was a 1.5-hour class which contained a tremendous amount of information about expansion valve design and their operation and troubleshooting.   In an interview that I had with Mr. Dianetti, he indicated the following:

1.  Technicians don’t always seem to understand what things like subcooling, superheat and other terminology associated with A/C system operation mean.  As a result, there was a slide titled “Definitions” which contained these things and then there was a lot of detailed discussion about them in the class.  Please refer to figure #1.

The need for understanding these terms as they relate to A/C system operation was stressed in the class.

2.  An expansion valve must have a constant flow of liquid refrigerant to it in order to function properly. This is accomplished by proper condenser function.  Please refer to figure #2.  

Proper condenser function is key to a constant flow of liquid refrigerant to the expansion valve.

3. Expansion valves control superheat. They do not control the temperature or pressure in the evaporator.  Please refer to figure #3.

This slide describes expansion valve function.  Note there is nothing in the slide that indicates they control temperature or pressure.

4. It is important to understand the role that superheat plays in A/C system function.  Please refer to figure #4.

This slide illustrates the need for superheat.  It also illustrates the effects of excessive superheat and no superheat.

5. In addition to these four items, the class stressed the importance  that proper expansion valve operation has on compressor reliability.  Please see figure #5.

Potential problems that can occur if an expansion valve is not functioning properly.

6. The presentation closed with 10 slides dedicated to trouble shooting expansion valves.  Please refer to figure #6.

This troubleshooting chart is in one of the 10 troubleshooting slides.

The entire presentation can be viewed in the “members only” section on the MACS website. In addition, there were two MACS Service Reports published on the operation and function of expansion valves which are referenced in the presentation.  They were published in September and October of 2020 and can also be found in the MACS “Member’s only” Archives.

Visit the MACS website for more information about membership and the 2024 Training Event in Orlando, FL!

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