How to Adjust a TXV, TEV or TX Valve

Bryan does an in-depth review of how to adjust a thermostatic expansion valve, also known as a TXV, TEV, or TX Valve. He explains why one would adjust a TXV and how to tell if a TXV is working.

You almost never need to adjust a TXV unless you're trying to prevent floodback or fixing a TXV that was adjusted by someone else. Adjustments should be very slow, and it's unwise to do an adjustment without a valid reason to do so.

The TXV has a few different sources of force. The bulb exerts an opening force according to the temperature of the suction line, as the TXV tries to maintain a constant superheat. So, the bulb needs to be mounted to the suction line sufficiently, and the powerhead needs to maintain enough refrigerant charge. (Some powerheads are replaceable, and others are not.) The internal or external equalizer also applies a closing force to counter the opening force. Spring force also exerts a closing force to assist the equalizer's closing force.

For a TXV to work properly, it needs to have a full line of liquid going into it. Therefore, you need to make sure that you have sufficient subcooling or a full sight glass. Before condemning or adjusting a "bad TXV," be sure to check your superheat with probes or clamps to ensure that you don't have a different problem. (It's also worth mentioning that evaporator and compressor superheat can vary quite wildly, especially if the suction line is very long.) TXVs also don't set superheat at a fixed temperature; there is a range based on load conditions. You also don't want to adjust the valve so that it's too far open, as that can cause floodback.

We have to adjust TXVs based on evaporator superheat, and the bulb should be insulated and well strapped to the top or side of the suction line. When you're ready to adjust the TXV, remove the stem cap on the bottom to expose the spindle.

It's easy to make the adjustment if you make a mark at the edge of the spindle. That way, you can keep track of how many turns you make. Many manufacturers recommend turning the spindle only a quarter-turn at a time. Turning the spindle clockwise compresses the spring, which allows less refrigerant to enter the evaporator coil and increases the superheat. Turning the spindle counterclockwise has the opposite effect (less closing force).

Balanced port TXVs help balance the inlet pressure; refrigerant flowing in through the inlet of the valve also affects the valve, and the balanced port tries to prevent it from having as much of an impact. Balanced port TXVs make the operation more stable over a wide range of load conditions.

Hard shutoff or non-bleed TXVs shut when the system turns off. These TXVs are a bit more likely to require a hard start kit in single-phase residential applications.

[benh]

How many cranks to get to the center of a TXV-pop Brian? Ohoone, t-whoooo, thr-heee, *owl crunches the powerhead*


Edit: Had to, also great video.

[eatcommies]

Just a quick heads up on using a marker to mark txv position, if there is moisture on the valve, ink might rub off during adjustments, I try to scribe on it instead, (learned this the hard way) also leave the brass cap in the visible area so you don’t forget to put it back on:).Another Good Video! Thank You!

[Val-xiwe]

Thank you for updating this!! The video in your previous one was giving me a headache!!

[happyhappysheep]

Thank you very much for this video. This is very educational, very detailed useful information.

[kyleinthought]

Great video, nice graphics and pace. Thank you!

[Kevin-ibgv]

Think of the handle on your water faucet at home. Turning on the water (counter clockwise), allows more water (refrigerant) to flow. More refrigerant flow equals more evaporator cooling and less superheat (cooler). Too little superheat? Turn the "handle" clockwise just like at the faucet, making less refrigerant flow, warming up the coil, and increasing the superheat (warmer).
Half a turn at a time and wait 15 to 20 minutes between turns to stabilize.

[mithileshramteke]

Thank you for very very nice explanation HVAC school

[janibashamolla]

Thanks a lot sir....for good information about TXV...

[drair-kpcx]

Excellent video. Question: Why do some manufacturers (eg. Goodman) recommend adjusting SH in Stage 1 (not 2) to 6 degrees on the compressor side? After watching your video, this seems wrong (or are they using their own parameters?).

[t]

Awesome video it helps a lot …. Thanks a lot

[emsathebest]

Hi. Great video and explanation but can you make a video or quick explanation how the txv works in heating mode. Does it allows revers flow and if it does not how the refregirent flows in the other way? Thank you!

[mohammadabdulfattah]

Thank you bro , really very good explanation 🌹👍

[robert]

Thanks for the video. Hope you're still reading the comments. So a question, when you use a larger inside coil (say 3 ton compressor single speed and 4 ton inside coil) do you move the txv bulb down on the coil to lower position where it should be flooded properly? Seems like the compressor would not be able to provide enough liquid for the larger coil, at least for the txv to work properly and not hunt. I see the use of larger coils is common now. Of course, the remaining, say 1/4 of the evaporator above that point would still continue to make heat transfer and of course that would affect the superheat right? How are they making it all work. Any thoughts? Cheers.

[DJV]

Adjustable txv is equivalent to an adjustable fuel pressure regulator in the car world
Too much psi means high fuel pressure meaning too much gas being dumped cleaning out your gas tank too fast or blowing fuel line seals/gaskets

Too less of fuel pressure can damage your engine due to fuel starvation and spark only being present in the chamber causing damage melting piston

[jimmitchell]

can you talk sometime about water source heat pumps

[prk]

hi, could you please make a video on loading and unloading mechanism and its troubleshooting? And how external equalizer work fitted in TEV

[x]

What about TXV valves that have a circlip on the spindle so the actual spindle is not screwing in or out, it would apparently be threaded onto something inside in which case screwing it in May lift the spring retainer up and reduce tension on it. I can't see the brand because it's burned off from somebody who replaced it before, but it's not opening enough want to make sure I'm going the right direction. But definitely the stem does not move in or out as you turn it, so it's obviously only moving something inside of the body, but you cannot tell which direction

[grashoprsmith]

Great video! If the spindle cap was left off, would that affect operation in any way?

[DJV]

Yeah but lennox factory workers will have you dumping 4-5lb of r410a thinking .
1.the factory workers only added 1lb of r410a to the heat pump
2.youd think when you ask for a warranty indoor txv they send you the same one but they send you a shut screw adj txv ..
But we all good now the 3lbs was needed anyways to raise the subcool to spec

[janeilquino]

Sir.good day.what is the correct adjustment txv low superheat or high superheat.thanks and god bless