#TXV

The piston (fixed orifice) and TXV (thermostatic expansion valve) are the two most common metering devices in use today, though some modern systems utilize an electronically-controlled metering device called an EEV (electronic expansion valve). It should be noted that there are other types of fixed-orifice metering devices, like capillary tubes; however, their use is not […]

As we discussed in an earlier podcast, a TXV maintains a specified and constant superheat at the evaporator coil outlet. It does this through a balance of forces between the bulb pressure (opening force), equalizer pressure (closing force), and spring pressure (closing force). We can actually adjust the spring pressure on some valves. But why […]

Photo by Ulises Palacios Refrigerant circuit restrictions can be common things like a plugged filter drier or a restricted metering device. They can also be more difficult to diagnose and stem from exotic issues like a kinked liquid line, blocked evaporator feeder tube, or a compressor connected improperly with a discharge line full of solder […]

When mounting a TXV bulb or checking bulb placement, there are a few important considerations (listed in order of importance): Mount the bulb on the suction line. Flapping in the breeze is no good. Mount it TIGHTLY with a proper metallic strap (usually copper, brass, or stainless steel)—not with zip ties or tape. Position it on […]

We’ll never run out of content to discuss as long as thermostatic expansion valves exist. Deal with it. Today, we’re going to focus on the powerheads of TXVs. This article will focus on what the powerheads do, how they work, and some basic troubleshooting procedures involving TXV powerheads.   What is a powerhead, and where […]

I just noticed this portion of the Carrier air handler sticker for the first time the other day. I'm like most techs; it's easy for us to ignore the great info posted right in front of us on the data tag. That's because so many of the notices contain info we are used to seeing. […]

This is the tale of how I found myself stuck on a service call for over 12 hours on a weekend due to my failure to re-diagnose an issue. I was working for a service company that had many accounts with local gas stations. These were large customers, and we did everything we could to […]

  I walked into a supply house the other day and looked at a “universal” expansion valve on the shelf. The friendly guy behind the counter saw me and walked over. After saying hello, he said: “That's a great valve; it's even balanced port.” Now, I am a bit of a troublemaker. I should have […]

There is a lot of misunderstanding about the HSO (hard shut-off) or “non-bleed” TXV (thermostat expansion valve) and what makes it shut off, why it exists, and how it “magically” opens. Once you understand the forces inside the valve, it is quite simple, obvious, and sadly devoid of any magic. The Three Forces  The TXV […]

In this episode, Bryan talks with Jamie Kitchen from Danfoss about why and how thermostatic expansion valves (TXVs) fail and how they function in the first place. As fixed orifices become a dying breed with the development of higher-efficiency systems, TXVs take over the mantle as the primary method of expansion. Expansion valves meter the […]

In this episode of HVAC School, Bryan covers the basics of heat pumps. Heat pumps are common technologies in Florida. They reverse the sequence of the typical refrigerant circuit: the indoor coil can become the condenser, and the outdoor coil can become the evaporator. Heat pumps can achieve that transition via a reversing valve, which […]

In this episode of HVAC School, Bryan talks to Leslie about the deceptive TXV. Thermostatic expansion valves, also known as TXVs or TEVs, are metering devices that maintain superheat. They contain an external equalizer. External equalizers give the pressure reading that you would normally take with a suction gauge at the end of the evaporator […]

In this episode of HVAC School, Bryan covers the “5 pillars of refrigerant circuit diagnosis” and why they matter. They are: Superheat Subcool Suction pressure Head pressure Air temp split (delta T)   These 5 readings give you a holistic idea of the A/C system. Instead of getting hooked on checking only superheat and subcool […]

In this episode of the HVAC School Podcast, Bryan talks with Jeremy Smith about refrigeration tips, terms and processes. They also cover the similarities and differences between A/C and refrigeration. Being on-call as an A/C tech is not all that different from being on-call as a refrigeration tech. Similarly, the principles of heat transfer don't […]