Why and How to Adjust a TXV / TEV
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- Опубликовано: 1 мар 2017
- Bryan explains why and how to adjust a TXV and what to consider before doing it.
A TXV maintains a constant superheat value at the evaporator outlet, and it needs proper refrigerant flow to do its job right. Some of them have screens in the inlet, and those screens may provide a restriction that prevents a TXV from doing its job.
TXVs also require sufficient liquid pressure to meter the refrigerant into the evaporator; the TXV drops the refrigerant pressure before it enters the evaporator. We have a target range of evaporator temperatures and pressures because we don't want the evaporator temperature to be too low in A/C and medium-temp refrigeration applications.
Before adjusting a TXV, consider checking for restrictions that resulted from contamination. Check to make sure the sensing bulb has been properly strapped to the suction line. The bulb should be fastened snugly to the line; if it's too loose, then it can't do its job properly. If the line is insulated, then the bulb may be insulated WITH the suction line.
Adjusting the TXV won't directly change the pressure; it will affect the superheat. So, adjusting the TXV is NOT the way to deal with low suction pressure. You only adjust a TXV to make it reach the target superheat. Also, see if you're measuring superheat inside or outside; the outside superheat may give you an inaccurate reading due to the likelihood of higher ambient temperatures.
Not all expansion valves are adjustable. You can tell if a TXV is adjustable by looking to see if they have a nut at the bottom. That nut covers an adjustable stem, which affects the position of the spring on the inside. (The spring pressure is a closing force that opposes the bulb's pressure, an opening force.) A non-adjustable TXV would have a flat bottom instead.
If you want to decrease the superheat and feed more refrigerant into the evaporator coil, you would turn the stem counterclockwise to loosen it. If you want to feed less refrigerant into the coil and increase the superheat, you'll tighten the stem and turn it clockwise. It's a good practice to adjust a valve in half-turn increments so that you don't overcorrect the problem. Once you make an adjustment, let the system run for a little while to make sure you're meeting your superheat target.
Allow the system to run for at least 15 minutes before adjusting the valve; there needs to be sufficient head pressure for you to get a good idea of the TXV's status. You'll also want to measure the superheat before you think about adjusting the TXV.
Check out an updated version of the video: • How to Adjust a TXV, T...
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Man, if I understand correctly, you are teaching HVAC students as a part of your activities. So, I wish I had a mentor like you years back when I was at the beginning of my way. You have a great talent to put the whole story short, clear and easy to follow. Your students are lucky to have such a great teacher.
Very informative. just saved my ass at a disaster of a job today. Got my superheat correct
I really enjoyed this detailed presentation on the Expansion Valve!
This Video will go into my most valued folder as an accurate reference point!
Thank you much.
This video Presentation is very informative to all people working on AC Units around the Country. Thank You.
Awesome video. Glad i watched. Found a 5 year old R22 4 ton split A/C system with a closed txv. Flat sensing bulb. I weighed the charge in and my suction and head were low. Ambient temp in the lower 70's. Need to go back when i have a good ambient to check the superheat and sub cooling. Parker said the valve comes set @ 10 degrees superheat.
Great video ,,for the technician out there ,,take a black marker and mark the bottom of the TXV before you start adjusting so you know where you started ,,make half turns ! Left or right so you can see where your sub cooling is going up or down..I wish On the videos you would show how it works
Thank u sir....
Dear sir. You explained in theory its 50% knowledge for us. Better if show me. Practically its 100% exalent for us sir.
Very good explanation on adjustment. Best check airflow and superheat at evaporator. Also ^ TD . I have only adjusted valves in refrigeration units, walk-ins and freezer. Ole style Q body valves were much easier to adjust and maintain S.H. For the smart super techs, if you listen to Bryan Orr might learn a wealth of knowledge.
Thank you. Very thorough. I appreciate all the "filler words"... they added the detail that I wanted to know.
Very accurate and thorough video.
Thanks so much for sharing your knowledge. 👍👍👍👍👍👍
Good stuff as always Brian!! 👍🏻👍🏻👍🏻
hey great video. what of expansion valve you using this video is it a gas charge sensing element or liquid cross charge.
Great video.Thanks for imparting and sharing your expertise with us. A request could U do a video on selecting a TXV for a particular evaporator coil what parameters would I need to consider.
so essentially when adjusting superheat setting your going CCW or CW facing the bottom of the valve at the stem not facing the power head?
Well explained thank you Sir
Thanks Brian, question please, I always have hard times brazing these short necked TXVs, I cannot easily roll them well with a wet rag, I use a strong neutral flame to make it fast but, the rag tip gets burned carbonizing the joint and the valve over heats rapidly, any suggestions? Thanks
It’s also important to note that superheat is pretty important to the compressor. It’s important to know what your superheat is before it reaches the condenser because if the superheat is perfect at the evaporator but too high at the condenser then that can create an issue.
Excellent video Brian. One of the few viewed that explains a TXV in simple English.
Enjoyed the Podcast ! Works good to pass the time while doing the
dishes, also picking up a thing or two here & there. been doing
refrig . since 1981, also information on whats going on in the trade
sometimes. Thanks for making them.
I'm at a lost of what copeland wants for their semi-hermetic compressors. I know they say generally a minimum of 20 degrees but does that 20 degree apply to all applications or just A/C ? What about low temp refrigeration? or chillers? There's not much info on this. I noticed some applications run high superheat such as low temp and it makes me ponder if these are typical running conditons or should i go after my TXV and adjust it to drop superheat temp. I guess overall having superheat is better than not having any.
I love all this fancy equipment now a days. I did refrigeration 40 years ago on 20 tonTurbo Ice Makers 12 plates 12 distributors on a txv and NEVER used a temp probe to do superheat.
Simple open txv till it just starts to flood suction, close it to bring frost line back to evaporator, DONE deal you are using all of the evap, and not flooding suction line.
And a txv with external equalizer tube that is attached to the suction line at the bulb
does just what I explained (it will kind of by pass the temp bulb) till the evap gets established.
Sounds similar to my first boss, he would go further by licking his finger and seeing if it would stick on the outlet of evap. He did this on freezer coils and ice machines.
Sounds interesting but how did you prevent slugging (liquid in suction line) when flooding?
Yup we use analog gauges n do what u said lol
this method I read many years ago in " Doolin's Bible". but that method was used for cap tubes with a critical charges not TXV's.
That's interesting then I work on turbos today I've got one that's running to 120 s and I got one that's running a hundred and fifty horse screw
for 404a if my suction is sweating like crazy can I choke the txv to raise the superheat to reduce the sweating?
You Stepped WAAAAY Outside of Explaining ANY TXV Action within the 3:00 minute mark for ANY HVAC TECH of 1-2 years ...........you are just speaking to Yourself at that point........KISS!
Thanks! Make sure to share your simplified video so I can watch and comment.
Thank you, very educative .
Very good advice to ADVICE guys
great video, thanks 👍
Great demo, thanks! 👍👍
Great video, thanks for teaching!!
Good explanation Bryan.
I'm really late watching this video but I just had a TXV unit installed that calls for 7-9 degrees of superheat. The subcool is dead on in the high 8s, but the superheat is at 24. I checked ductwork and there are no leaks that I could find other than a couple of tape joints that had a very minute amount of air coming out, I taped them up. But my delta T is still at 16, I feel like something is wrong with this install. Any ideas?
good information! Thank you for making videos!
Very good detail explanation thank u
Nice video thanks! But 5 min would be enough. first half is water of time. I also want to know, whether R22 TxV can be adjusted to fit R410a
If I reach the subcooling value to the exact number stated in the label of the condenser's unit charge value which is 10F but the superheat goes to 1 or zero.. should I adjust the TXV valve to increase the superheat value to normal levels??
Clockwise, increase superheat, Counter clockwise decrease superheat. Just like a clock, numbers increase going clockwise.
Took this guy an hour to not say that.. thank you.. jeez...
@@Z-Ack spw turns 1/4 turn at a time then wait 20 or 30 minutes to stabalize. But you should not have to adjust TXV unless system is mixed matched in tonnage or some long line set. I am not an expert on this but I did stay at a Holiday Express last night.
whats the reason why having lot of refrigerantion oil at the filter drier.ty
just a little about dirt ,,,i ran into so many contractors about brazing with nitro ,,,,they say oh i never had problems or call back because i did not use nitro ,,,,,then it becomes an arguement ,,,,and i am talking about guys with years of experience ! ,,,its all about the money first , get my house cool for as low as you can ,,,lol i am old school i was a certified welder with over 30years experience when i decided to go to school for HVAC . every tech tries to impress the other LOL ,,,,,just saying this school is good stuff for all of us ,,,,i am retired but love to learn more
Mine maintains superheat of 21 degrees with a sub cool of 12.8 degrees with manufactor specs call for 13 degrees for a temperature of 90 ambient, it's a 12 year old icp r22. :)
Great Video. Thanks
I go off manufactures specs txv’s coming preset from Factory. I think adjusting can make things worse, replace with new one better safe then sorry instead of tinkering with it and trying to get it dialed in. Week later your back on the roof and the comp is flooded.
thanx for the awesome vid
a question sir, the ac in my car, it is cold at idle but blows warm air when moving/revved. all the necessary things have been replaced with new ones ie cooling coil, condenser, expansion valve, filters. the only thing i havent done is adjusting the expansion valve
plus, the low side pressure increases when the engine is revved, can this be the source of my problem? tqvm
So how do you determine what your superheat should be? With ac I understand it’s five or take 1 or 3 but on critical charge systems how do you know?
Great video 🤙🏽
great video thank you
What i am always wondering: Is such a TXV fast enough? How many seconds does it take between change of temperature of the refrigeration fluid behind the evaporator and change of temperature and pressure in the sensing-bulb? I guess, that can take half a minute or more.
thank you for sharing!!!!!!
Great video ty
Hey guys what s the best way to adjust 3 x TEV danfos valves
So it's fitted with manuprop MT 160 compressor and 3 evaporators
Thks Tony
My trane unit 410 subcool is 10 and the saturated evap coil temp is 50f is that normal? My old trane r22 evap sat is around 38 to 40
Thanks for your superb explanation. Very helpful and I'll probably refer to it again. :-)
I am an ectrician by trade but the ac at my house quit cooling. Its not cooling at all. The condensor I think came with the house and it was built in 1987. The inside unit was installed around 2000. Its a 3 ton ac unit 120 volts. It stopped cooling about a year ago and it quit working all at once. The compressor is running and I had a friend check the freon and he said it is low but not so low it should have quit working. I'm thinking it might be the TXV. I have airflow going thru the unit, its just not cold at all. Any idea's
Will this work for a heat pump
Whats super heat? Is it the unit heat has to 20 degrees above outside temp.
Yes a CSV makes complete sense and not those other misleading confusing names
i think that must make schedule and record 1st revolution per 15 minutes or each half revolution per 10 minutes and type of revolution left or right and see the results if good or not to make it easy in case return it back.
Thank you for your videos they are very instructive
Hi Ben Brian Great tutorial, I really like watching your studies and I wish I had the opportunity to study with you. Who knows, maybe one day it will come true. I have a professional question. I am a technician of industrial cooling systems. How do I know how to correctly measure subcool and superheat according to the seasons? Is it summer? Does it change? Because it's colder or hotter outside? And what is recommended to be in cold rooms at low temperatures? 4 degrees Celsius and minus 18 degrees Celsius Thank you very much appreciate it..
On the 3 x evopators the orifice is no 3 thks Tony
What if my evaporator suction line is frozen.... on r410 ac heat pump split system, does it mean that superheat most likely too high?
No it means either your filter is dirty, indoor motor is bad, airflow restriction, or a freon leak. What's the pressures?
Great videos!
Very useful
Thank you very much for explain in theoretical way. I used to think it would be better for the video to be 50% long, after I complete it I think 25% would be more clear. I did gained from this video, yet just as other comments 100% practical video might be better. For example, how to adjust a R22 TxV for R410a or vice versa. And, TxV is used as reference measurement, what we can based on to do the adjustment? Like you want to calibrate a 2.5% pressure gauge clock you need a 1% gauge right?
I have r507 chiller operating at 1 to 4degC . What is reco. Superheat..I test it once, measure it in the evaporator, suct.temp is -1C then suction pressure is 50psi..according to chart 50psi is -10C . So my SH is 9deg.C..is this right?
I work for a Fluid Chillers inc. We shoot for 15 degrees Fahrenheit superheat, but mainly we don't want the compressor to ice up. Low-temperature evaporators are very susceptible the heat load supplied to them. And even though he calls it a constant superheat valve, they're anything but. As the load begins to drop so will the superheat unless you have an electronic expansion valve. In a low load situation a superheat of 10 degrees Fahrenheit is fine but then as the load increases you could have a super heat as high as 40 or even 100 degrees Fahrenheit depending on how hot your load is. We're on chillers from 68 degrees Fahrenheit setpoint all the way down to -80 degrees Fahrenheit setpoint. I'm a huge fan of electronic expansion valves the stepper motor on the valve is so much more Superior than your silly diaphragm valve
Will vacuum to 500 micron damage the pressure head of the TXV?
No. It's not part of the system. I assume you are talking about the power head.
Excellent video, You will find most expansion valves are set real close for the proper super heat out of the evaporator. Many factors like laid over coil fins, wrong RPM motor or fan blade pitch can cause fake readings. My question is How much coffee did you drink before filming this:)
We have a freezer at my job place R404a and it start to freeze the suction line all the way too the compressor,could it be the txt?
No think air flow or your refrigerant is low.
If you have freezer temps it is normal to have a freezing suction line. The evap will have a temp of approximately -15 degrees. If your superheat is 10 degrees then the line temp will be -5 which will freeze the condensation. Check your superheat, if it is in the normal range then it is ok.
Good video thx
This is great stuff. But I'm confused. I'm relatively new to the trade. How come when your dealing with a split system they tell you if you have a piston you charge for superheat but txv/tev it's subcooling you go off of? But the valve actually keeps a constant superheat? Sorry for my ignorance just want to better my understanding!
The superheat is controlled by the TXV, the subcooling is determined by your charge
Thank you
No, thank you.
Will adjusting txv let me lower the temp? Coldest I can get so far on my car is 45F. And would like to drop it more. My txv has a spring adjustment. I also tried switching from r134a to r152a
Love your classes. Outside is subcool. Isn't it?
You say adjusts a TXV to get correct super heat what about adjusting it for Sub cooling? I installed a Danfoss tr6 into a system that had a piston orifice and now I'm having trouble charging to 10 deg Sub Cool. I'm at 7-8 degs and cant get it any better. Oh and it not responding to charge because I've gone for low to over and still cant make the ideal S/C
Can you not put a stainless steel pipe clamp around that bulb to mate it to a copper line? Or will the SS react with the copper?
I have used stainless worm clamps forever. Rule of thumb - clean and tight, never use cork tape or foam tape.
Problem with that is that metal is conductive and what you're trying to avoid is changing the temperature based on conditions other than the temperature of that copper. This is the reason we use cork tape, as it is a insulating material. Remember that the bulb reads temperature, and that the TXV converts that temperature into pressure and back. For proper operation and easier troubleshooting, avoid using a conductive material around the bulb.
One thing you forgot to mention: column pressure. A system, where the evaporator unit is in the attic, or in the basement, creates a different pressure at the valve, than at the ground level condenser unit, the result of liquid in the high pressure line. Old units, with R-22 refrigerant will show bigger differences, then newer units, with R-410, or R-134.
Good information, good refresher. Boring from a video presentation viewpoint, watching a TXV be turned over and over for 19 minutes. I would expect that from an average Joe, not from a "School". But, still very good information. I got the "How" from this but still a little fuzzy on the "Why and When". Did you mention that adjusting the TXV is the LAST thing to do? And that the charge, clean condenser coil and evap coil, correct airflow through each should all be nailed down first? You may have, I just may have missed it. A have seen dudes just reef on that stem, many turns in one shot. You correctly advised against that. Good jjob overall, thanks.
Failure rate of tevs is fairly low. They can fail. But modern tev's are fairly reliable. They are more like to be destroyed by someone who doesn't know how to keep them cool while brazing.
my succion is going into a vacuum opening my low pressure switch in about 30 secs.. I only have a txv and filter drier in my system.. can I say it's either or that's bad?
LEAK !
Leak?????lol
Xnlt explanation of a tev thank u..
Happy to help
How can we make it with EXV ?
Without charging the gas, the pressure in the suction increases and the cooling decreases, why is this problem happening?
So if TXV is icing up and the house temp doesn't go below 78 --- is that a clogged TXV? Thx in advance!
Not necessarily... the TEV causes a restriction, so condensation is normal. Frost is probably an indicator of high superheat. I.e. not enough refrigerant. Just my guess.
@@LemonDuc figuring out why it's low on refrigerant is the fun part! 😁
can a txv hunt with a slight undercharge? considering load, airflow and valve are sized properly.
The basic rule is:
Not enough superheat = not enough refrigerant.
Too much Superheat = too much refrigerant.
If a TXV hunts a lot check the bulb placement and how well it is attached to the suction line, mount your bulbs at 10 oclock or 2 oclock, never at 6 oclock.
Make sure bulb has full contact with the line, you may need to sand off any oxidation or grime that has built up on the copper before mounting a bulb.
Insulate the bulb with Cork Tape or Permatape after mounting.
exactly the opposite. Low on refrigerant = high superheat, High on refrigerant = low superheat
Not so fast ! I agree that low on refrigerant = high superheat The other part can vary. Why ? Mainly because we could run into restrictions for any number of reasons: bad or stuck TXV, clogged or partially clogged strainer, partially stuck pump down valve, restricted drier, etc. There is only one variable that I can promise. IF there is a bad restriction, and if the system is tight AND correctly charged, the liquid (refrigerant charge) will back up into the condensor because it can't get to the evaporator. When you take the pressure readings and temperature readings on suction and particularly liquid lines, the evidence will be far too much sub cooling on the condensed side (because the liquid is back up into the condenser side.) Try this one out: I once had a system that was only two years old but wasn't cooling correctly in 90's. I was told to change it out and replace it. As I recovered the refrigerant, I discovered that the unit had never had the accurator (for metering refrigerant) installed. It was running "hollow pipe". This was the fault of the installer.
@@repetemyname842 You would be exactly right, if you measure temperature right at the expansion valve. In this video, he's measuring temperature at the OUTLET of the evaporator, after the warm air has heated the volume of refrigerant injected into the evaporator coil. That's why it seems opposite from intuition. I had to re-watch that part of the video, until I realized that the bulb, and the temperature are both at the outlet of the evaporator, then it actually made sense to me.
@@aaronmouzin7258 You're right, if you measure right at the expansion valve. The bulb of the TEV and the measurement are taken at the OUTLET of the evaporator coil, AFTER the warm air has heated the volume of refrigerant. That's why, counter intuitively, less refrigerant results in more superheat. There just isn't the volume of refrigerant necessary to absorb the heat from all the warm air passing through the evaporator coil. If what you say is right, it's time to replace that air filter!
It a dryer was installed. Would help in keep the txv free debris so it wouldnt get stuck.
Brilliant
That's cool, I like it (Y)
Can somebody tell what kind of tool set he is working the name brand?
Jermaine Sims Testo wireless probes. adjustable (crescent) wrench is a kobolt it looks like
clean the coils that fixes most super heat problems!
ok i just learned this the hard way, 9:00 min in, i was working on a walk in and reading the temp/ psi at the condensing unit, so i think i bungled the super heat. i had i lot of bubbles inside the sight glass a more experienced technician said just add more 404a till the bibles stop and than just a bit more. i did. bit, but now i don't real know if its a leak or broken txv? i should have done a leak check but hind sight is 20/20 i guess.
ho to adjust at bat 12:00
Will adjusting the TXV also also the ac to dehumidify the air? If so how?
no
@@mikemc8495 So I thought that a AC can dehumidify as well? Is so how?
@@mikemc8495 So what does the TXV do?
It meters the flow of refrigerant
@@JPEBeard hey, when you lower the temperature of air the moisture is condensed into water leaving the air dryer
is this a video about how the valve works or a troubleshooting video????
If you know one you can do the other, if not don’t feel bad, if it was easy anybody could do it !
My company keeps trying to use these thermal expansion valves on low temperature Chillers that we manufacture. They are anything but an constant superheat valve. The electronic expansion valve it's so much more Superior especially with variable heat loads. The problem I have is the electronic expansion valve controller wants to fault out if I run the suction pressure into a vacuum period or if I run my suction line temperature below - 59 degrees Fahrenheit. Then the controller wants to fault out and close the expansion valve completely. When I talk to an engineer at Sporlan he asked me how low do you want to go. I'm like negative 100 degrees Fahrenheit. He just laughed at me.
good
I just had my AC unit serviced and the guy refilled the refrigerant since it was completely empty. Now my AC unit is really struggling to pump cold air - i was thinking of giving this valve a half turn to allow more refrigerant through - is it possible it was reinstalled "too closed"?
If your system was empty it has a refrigerant leak. DONT touch the valve. If it's not keeping up it's probably losing refrigerant at a high rate.
Lennox warranty is givin back out adjustable indoor txv when it comes to stock txvs ..and guess what they are coming out closed.so you might as well start the system with it wide open and close it til your gauges look good..now at wide open within the first 20 mins the compressor will start making out chattering noise
How about testing the bulb with ice and warming the bulb
Yea, good idea.
I've heard of guys warming the bulb to see if the valve opens up I've done it myself especially if you're expecting possible moisture in the system but I've never heard of anybody icing a valve I suppose you could if you were just looking for action in the valve cuz I know the expansion valves can go full open but there really isn't a closed state the only ones that actually go closed are the EV valves
Why do people say reducing superheat (smaller safety factor against liquid) uses more of the evaporator / is more energy efficient?
Well you dont want your evap coil being filled with liquid 80%-100% of the capacity. You want it to the point where in the middle of the coil its vapor (thats what you wanna feel to feel cool)..some people over charge a unit to the point where that vapor point happens at the suction line which at that point its past the blower motor cool air going back to the compressor and not your house instead of cooling you its cooling the copper lines itself ..its just like car you want your combustion to happen inside the engine not at the exhaust thats why you hear and see dumb high school kids now adays doing dumb mods to the cars that make it sound like gun shots thats combustion happening at the exhaust and not at the engine
Every expension valve is set to 50 %?
Automatic expansion valves are AUTOMATIC. What you want is for them to meter an OPTIMUM amount of refrigerant into the evaporator coil for maximum efficiency. At start up or when hot, they should go wide open. As the heat load is "worked off" the outlet of the evaporator gets cooler and cooler or drops in temperature. The sensor bulb senses that and throttles back refrigerant for a now smaller or lighter load. So one, many can be adjusted for greater or lesser flow, BUT ONLY within say a 20% range. More realistic is 40% - 100% open Depends on actual temperature and load. It takes a supermarket two days to level out a load on the refrigerator cases ! Adjustments are made by professionals with top notch meters and gauges.
What is the issue if low superheat at the outlet of evaporator coil and also low suction pressure for R22 system?
Confirmed Evaporator coil is clean and supply fan at high speed. Suction pressure at 50 psi only with return of 80 F.
Discharge 215 psi.
a tricky question for insiders. I think there is a restriction in suction line---kink somewhere, just a thought,an outsider
its a lack of airflow across the coil. ductwork is likely junk, undersized return.....
Follow instructions on location of sensing bulb, very important!