TXV Troubleshooting - Short #245

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 17 June 2025

⏱️ 12 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

In this short podcast episode, Bryan walks through some common thermostatic expansion valve (TXV) troubleshooting scenarios. Many of the same principles apply to troubleshooting electronic expansion valves (EEVs). These dynamic metering devices maintain a constant superheat.

Troubleshooting does NOT start and end with the TXV. First, you need to inspect components (especially filters, ductwork, and filter-driers) and confirm the airflow and charge. You can use measureQuick to monitor superheat, subcooling, static pressure, and other key measurements, and the TrueFlow grid can give you a true idea of the CFM your system is moving. Keep in mind that superheat and subcooling values can vary by system.

Airflow problems and filter-drier restrictions may mimic failed TXV conditions. Ideally, the liquid line filter-drier will be located indoors, and you can check for a pressure drop across it by looking for temperature differentials. You need a full column of liquid going into the filter-drier, and you can use a thermal imaging camera to see the desuperheating, condensing, and subcooling phases inside the condenser coil.

The TXV has a bulb that can be loose, improperly mounted, or improperly insulated; when there is an issue with the bulb, there will likely be low superheat. The bulb should be on a clean and [ideally] horizontal portion of the suction line, and it should be strapped with copper or stainless steel straps. Insulating the bulb is especially important when it's externally located and when low superheat or flood back is a concern.

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Transcript

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0:00.0	Yippity Kai-I-A. This is the HVACC school podcast. This is a short episode that hopefully
0:09.7	helps you remember some things you might have forgotten along the way as well as helps
0:12.9	you remember some things you forgot to know in the first place. And we're talking about the
0:16.5	TXV again. TXV troubleshooting. And we talk about this a lot. We've talked about this a lot over the years. A lot of this does also apply to the electronic expansion valves. If people are like, wow, why aren't you talking about that? A lot of the same principles work here. Before we get to that, let's thank our great sponsors.
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1:39.6	To learn more, visit HVACR school.com slash Santa Fe.
1:44.1	That's HVACR school.com slash Santa Fe. That's HVACR school.com slash Santa Fe.
1:49.3	All right.
1:49.9	So first things first, I'm not going to do the whole full, long version of this.
1:54.5	This is a truncated or a shortened version of this podcast for those of you who just want
1:59.2	to know where to start and what to do.
	...

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