What a TXV Does (and why techs need to stop replacing them with a piston)
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- เผยแพร่เมื่อ 20 ก.ย. 2024
- Why techs need to stop replacing them with a piston? What a TXV Does? Craig from AC Service tech joins us and shares some of his knowledge on thermal expansion valves and shares his concern about techs replacing a TXV with a piston.
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It’s awesome to see the only two HVAC channels I watch collaborate and really helps to trust the information on either one
Exactly 👍
Lovebirds
What's the second one that you watch?
👍🏾🙏🏾
@@rmflores7096 AC Service Tech
I had a ton of fun teaching and joking with Bryan! Thanks for inviting me down for the collab!
Craig, it is so obvious that you totally enjoy what you are doing. Congrats!!!!
Great info for a newbie tech
Ac service tech is still my favourite channel out there ! 100%
Thank you for everything, we love your channel and Bryans.
Most knowledgeable HVAC guys on TH-cam!
Without a doubt these two guys are changing the course of modern HVACR technician quality learning & development and away from old school beer can troubleshooting and repair.
I see bad TXV's all the time here in Texas. I've yet to find a bad piston.
Say it louder for the people taking notes
How does the reliability of the electronic expansion valve compare to thermal bulb expansion valves? It seems to me that the mechanical advantage of a stepper motor screwing the expansion valve in and out would be a lot better and more reliable (less likely to jamb) than a thermal expansion valve using refrigerant bulb to push the valve.
@@gregorymalchuk272
EEVs break a lot. Better have a spare at the store. Also failed EEVs will burn up the control board and can send crazy voltage on your com.
you said it buddy ,,,,right on
You’re not lying bro, replaced my first clogged piston a couple days ago, I been doing hvac in Texas for a few years. I have replaced multiple TXV’s.
Top 2 guys in the HVAC industry i learned a lot from you thank you for everything
RESPECT
Go tell John Israel that he has a whole video on why he thinks pistons are better. You guys rock
this isn't the video about which is better? txv or piston?? this video is about why shouldn't change a TXV system to piston.
@@lordjaashin isn’t that the same thing? John Israel was converting failed txv evaporators to pistons. I’m not knocking on him either, I have mad respect for him too. Just saying.
@@timrob0420 if he's changing TXV based systems to piston based system then he shouldn't be doing it
@@lordjaashin I agree with that unless I’d customer is in a bind money wise.
@@timrob0420 the less moving parts the less the problems period i am 67 retired back in millwright aprentice school we where told that very early and now that i turned wrenches ,welded and did all the above i would agree with you for that reason ,,,,stay safe people
The reason I intend to replace my txt with a piston is the inherent low mtbf txvs have - pistons may be a little less efficient but they rarely if ever fail and that is far more comforting period
Love this! When I started in this trade I watched all of acservicethech’s videos and hvacr school’s videos. Really enjoyed this collaboration between you guys!
Currently in HVAC school right now and this channel has been an excellent resource for me. Thank you for making these videos.
Two of HVAC’s greatest educating mine combined to bring even more to our industry in higher education.
I’ve always wanted to be an HVAC instructor College trade schools when I retire.
By the time I get there you make my job easy I just have to refer to your videos and your books that you produce and just guide and instruct. Your content is so thorough and broad spectrum covering in detailed I cannot possibly do better. 👍👍👍
I had a customer that had a 16-seer 2-stage split system that I was called to for poor cooling. It was a 5-ton system and one of the past service company removed the TXV and put in a piston. And still without using the science of refrigeration the root problem had not been found. When this house was built, the system was somehow contaminated; likely no nitrogen used when braising. I determined the filter/dryer inside the condensing unit was plugged with an 8-degree temperature drop. I removed the filter in the condenser, and installed a new filter dryer at evaporator, installed a new TXV, recharged and tuned the system. The customer was extremely thankful since this was the first time since they owned the house to be able to keep it comfortably cool.
Is this novel all about how you are such a super-duper AC tech?
Working together is fantastic; two heads are better than one. Among the finest
First Bosnian Bill with The Lock Picking Lawyer. Now this. Awesome!
Encouraging to see that 2 AC masters instead of competing to see who is better than the other. They are pooling their knowledge to help others.
Never had a piston fail
Refrigeration guys know TXV is way better than a piston or cap tube.
Great video, Craig dose an awesome job.
For refrigeration yes, for residential AC it’s not necessary. I’ve done both for 15 years
@@newkidontheblockism agree as far as ease of use and less breakdown. But the TXV is there for efficiency ratings. Going green and no longer making enough electricity ⚡️ has utilities scrambling to get the overall load on the grid lower. We are devolving as a nation on stuff that used to be basically available to everyone.
@@NorCal-refrigeration funny, I was reading your comment thinking this guy must be from California then I read you name 😁
@@newkidontheblockism yep
I personally present it to my customers like this, “are you concerned with efficiency because you want a greener earth or do you want to save money?” If money is there concern, which it almost always is, then I let them know it’s more economical to purchase a base line model which will cool your house the same and have fewer repairs because the little bit of money you may save over the lifetime of your AC will be whipped out and then some by the cost of repairs.
Great, great collaboration. Properly!
I've done it multiple ways. Replaced TXVs with pistons and vsversa. All comes down to the situation. I've also cleaned clogged strianers when other techs condemned the valve.
Installed a new "Premium" packaged unit one year ago. Replaced the indoor txv today due to it failing. They're junk. I'd take a piston any day of the week.
Hi, I maintain over 100 Rheem package units at our resort. The other day, I responded to a call where water was leaking into the ceiling. When I arrived, the evaporator coil and compressor were covered in ice.
There is a lot of debate around the shop as to why this happened. Airflow was okay. The coil was clean and after thawing everything out, the blower motor didn’t have any problems pulling the filter panel closed on it’s own.
Some of the technicians believe that the doors to the room below were the cause because they were open to the4 hallway, even though the hallway was being cooled by another package unit.
The high side gauge was only about 10 degrees above ambient (104 / 115), and the low side gauge was around 42 degrees. I’m accustom to seeing the high side gauge around 30 degrees above ambient. The compressor was pulling 15amps on all three legs and the condenser coil was clean.
I moved the TXV bulb outside the unit, and nothing changed with the low side press/temp which made me pause. Adding refrigerant didn't change anything either. There was 6 degrees superheat and almost 0 degrees of sub cooling, but package units are difficult to make accurate measurements because all the components are tucked away in the cabinet.
I think something is wrong with the TXV, but I don't know how to make a positive diagnosis with a package unit. The other technicians believe, that the coil can still freeze even with 75 degree air is flowing through it. Any thoughts?
Two masters together :D best video ever, please make more like this.
I normally do not replace a TXV with a piston. One of the few time was when I had 3 brand new TXV fail after replacing a evap coil. It was late and the supply house was closes.
Three brand new that failed TXVs or improper brazing methods.
Good explanation. One thing not mentioned, almost all systems are rated with a txv. If someone tries to cover poor install practices by installing a piston then the system isn't even rated and won't perform as intended. I've never had an issue with a txv on a system I installed. I have seen a 5 ton unit only provide 4 tons of cooling with a piston instead of a txv. Installers swapped it out instead of the factory installed txv. They are there on purpose. Thanks for the content.
Good man.
I'm guessing they used the wrong size. That's a very big difference.
@@consaka1 A piston is no better than a capillary tube. It’s OK for systems that run at a fixed heat load. They can’t maintain superheat, or meter the proper amount of refrigerant according to the heat load. That’s the reason they are called a fixed restriction refrigerant control.
Great video! The other thing that makes Txv superior to a piston is that it can open more during hot conditions to let in more refrigerant than a fixed orifice could.
Accumulator with piston :) keep it simple
Very seldom do I get an opportunity to listen to Two of the most knowledgeable HVAC instructor. Thank you
I’ve put in hundreds of pistons. One TXV system. ZERO failed pistons. 1 failed TXV. I avoid issues.
Hahaha
I agree! A TXV is slightly more efficient, but when it fails, and the homeowner is hot and miserable, you don’t have cooling or efficiency as far as I’m concerned.
TXV restrictions are synonymous with taking out compressors, I think I will pass when possible.
@@pyacobel I'd bet replacing compressors is also synonymous w/ TXV restrictions due to techs not using N2.
Have you tried pulling a good vacuum?
Great video! The explanation couldn’t be better 💯👏. Since the contact area between the TXV sensing bulb & coil outlet line is not optimal (because both are round-shaped), I think adding thermal paste could improve heat transfer for better temperature sensing. Kind of what happens with temp sensor probes & thermowells.
Craig is awesome 👏! Thank you so much for sharing him on your channel.
Wow, you guys make a great teaching team. Great training video. Thank you , looking forward to seeing more in the future.
Awesome video guys, thank you very much!
Hello Your videos are very nicely structured tutorial A Plus rating. Im new at HVAC. Even though I diagnose home issues Im looking into installing a TXV into vehicles. Im experimenting right now It’s more a hobby.
You also have a pressure drop in that line set, which is different than the pressure at the TXV bulb. To measure superheat accurately, there should be a tap at the bulb location, and the pressure and temperature should be taken there. That is what the valve is seeing. Bulb should never be mounted at the bottom of the pipe. Temperature will be affected by oil. Great video.
Add in allowance for depending where your checking superheat on system
Do you think it might be a good idea to use thermal paste on bulb. To make sure it transfers heat.
Yeah. Did you check out all the light coming through that interface?
That's what I was thinking. Honestly surprised that's not a standard practice.
These are the two best hvac channels together in one. Love to know what these two do.
TXVs help prevent refrigerant migration and flooding of the compressor when the system is off because of hard shut off and pressures not equalizing. This is why a hard start is recommended with TXVs especially in long line applications.
Exactly. Three phase systems do not require the hard start kit though. Proper refrigerant control on the off cycle has saved many a compressor from flooded starts.
Very true, but does not explain how many non TXV systems are still operating that have surpassed 40 years of doing already and are still going strong even through 100 degree days
Thank you so much 2 Masters HV-AC SOLUTIONS 🙏
God bless you all Thank you again and for your Video
Re: the sensing bulb & proper heat transfer - in electronic applications they had & may still use a white paste to ensure good heat transfer between a metal enclosed semi conductor device like a power transistor and a heat sink device.
That type of paste could help transfer heat from the copper tubing to the txv’s sensing bulb body.
You could see a bunch of light between the bulb and the line in this video. I wondered if that was considered acceptable.
both of you guys are amazing, learned alot from you both. KNOWLEDGE IS POWER
Had 1 txv fail that I put in, in 40 years but have seen installers from different companies purge lines with freon and not use vac pump when installing new equipment.
They need to get in a different line of work where there sloppiness and lack of detail doesn't end up screwing over the customer.
@@consaka1 you know when you find a 8 year old compressor with a hole rotted through the can. It was never pumped down. Builder model in new construction at time of manufacture had 5 year parts warranty. Instslled by one of the largest company's in area.
Most guys i know swap to piston cuz its "easier", and charge the same price as a txv repair. But ive seen undersized pistons get installed and single sided pistons get put on heat pumps. Just replace the TXV. Its super easy, less trouble, and if the system is 10yrs or older you'll know it wasn't debris clogging it. So the new one should last.
pistons save service calls he just said it when a txv fails when did you see the last piston fail?
agrees love pistons. Never had one fail, had new TXVs be bad out of the box or system oils react with seals in a txv killing them.
Love to learn from SoCool Wizards. You guys are a great team. Thanks for all your mentoring.
Don't get me wrong. I understand that a correctly working TXV is better than a piston. My problem is I see a lot of TXV's that are poorly performing but not bad enough to justify the cost of replacing. A few years ago I went to a rent house with a 4 year old Payne unit with electric heat. It was a insufficient cooling call. Had high subcooling and superheat. I replaced the TXV after driving across town and waiting in line at the Carrier dealer. About 6 months later I get a insufficient cooling call from the property owner. Same condition as before. Replaced TXV under warranty this time I eat the labor, etc. Less than a year later, same damn thing. This time it got a piston conversion and I haven't been back since. Now when I replace a TXV I make it abundantly clear that the labor warranty last until my tire makes the first revolution. I always flow nitrogen when brazing and use good a evacuation process.
I would not blame that on TXVs in general. Must have been a design problem with the valves, or you just had plain bad luck. It wasn’t your fault. I always used Sporlan or Alco valves, and never had a repeat problem in 45 years. Maybe you were using valves that were sold domestically, but were made in China.
Greatest crossover so far this year!!
Very nice. Learned a few key things. Thank you guys.
The problem I have with them is that their theoretical effeciency improvements don't line up with reality. I replaced the TXV in my own system with a piston, and comparing before and after runtime data on days of the same temperature I'm seeing a 2-5 percent loss in efficiency. Considering what I spend on cooling here in southern Michigan that's $15 a year. One service call on a TXV and any cost savings it gives the customer over the life of the equipment is gone. Not worth it. Now if I was in Florida or Arizona and I'm running my ac all day, all year I could see the advantage, but for people in the Northeast, Midwest... doesn't make sense.
I didn't see them give any efficiency specs comparing the two. I'll have to go back and watch again.
@@consaka1 That's the main point of them. Old systems from like the 90's had pistons. TXVs provide greater efficiency by controlling the flow of refrigerant. No doubt replacing a TXV with a piston uses more power, but in a low cooling area, the difference is minimal. For older clients on a fixed budget who normally get cold anyway, I recommend throwing in a piston instead of a txv replacement. It's cheaper to replace with a piston and more reliable. Sure it will use more power, but they don't use the AC much anyway - some keep the AC on 78 degrees.
The only two channels I trust. Awesome !!!
Never heard of this problem. Only complaint i have is difficulty finding amount of superheat required. 10° when in doubt has served well.
Patching a small tube we used to put a piece of 1/4" OD over the tubing your patching male the 1/4" tubing long enough to staw away from the open ends. Heat the 1/4" on both ends and pinch it down and braze the ends
Great svc to our industry....well explain by both of you....tnk u 👦
Pistons never fail but TXV‘s or more soothing to the system
I use to replace TXV...with pistons all the time.....realiabity more important that effciency.....and you will probably have to replace a TXV...in 10 years....and just one change...will pay what little bit of energy saving you get with a TXV...salute to Goodman...for trying to keep Pistons in majority of there units...
Government is making TXVs mandatory on all new AC systems :(
@@georgekolos5255 Show me where its required to have a TXV...
It's great lesson. Very informative. Thank you sir
Regarding TXV bulb mountings. Put the little tailpiece so that any liquid refrigerant that may be in the buld doesn't settle in the little tailpiece section/ bend it upwards/ don't mount bulb vertically with that little tailpiece on the bottom??
At least I always am mindful about such
Awesome video thanks again. Will share with the new guys at the shop
Good info from 2 knowledge techs.
WOW 2 Juggernauts of the Rap, i mean Hvac game! Love to see this collab. Very nice. I follow 2 of u guys.
Nice man!
Many helpful techniques and explanations. Thank you.
Got a 4 ton system installed in my home this year in the Dallas, Tx area. Told the tech, don't even think about installing an evap coil with txv. When it's 106 degrees outside like it is today, I don't give a rats ass about efficiency.
Im in california and in 17 years i only replaced a handful of txv's. Most times it wasnt installed properly and i just had to strap them in the proper position.
Well done !!
Good video, Brian you have a great voice for this stuff. I am a little confused, your title say "and why techs need to stop replacing them with a piston" but at 15-18 sec you said "and why you may not want to replace a piston with a TXV" did I miss something in the video or was that a mistake?
Another fine / informative joint video. 👍. Thanks guys .
Great video and very informative 👍. Thankyou n keep sharing knowledge much appreciated 👍
LL driers should be installed just in front of the metering device anyway, per manufacturers instructions. Part of the job of the dryer is filtration to protect the TXV and is you install it out at the condenser you have all that line before the metering device.
You got to love these 2 guys.Great videos 😜
Commercial Tech's do on occasion need to adjust an expansion Valve things like a substantial altitude difference or Line Length's in a system. Low Temp Application's or some other Tech was visited by the Good Idea Fairy.... Residential systems almost always have "Bleed Thru" TXV's That allow a system Pressure to equalize on the off Cycle and compressor's (Single Phase) to start easier... On a System that uses a 3 phase compressor the starting Torque is a lot higher and you can use "Non Bleed Thru" TXV's This acts like a Pump Down System. Good Idea when you are concerned about "Liquid Slugging" of a Compressor.... An Expansion Valve Bulb mounted in the airstream after the Evaporator will compensate for "Latent" Load and should not be insulated (Per Lennox Factory Engineer Columbus Ohio Circa 1980). If mounted anywhere else "Especially External" it needs to be well insulated.... Talking Production Had an Install Crew at a new building 20 some apartments Mount the Equipment Braze in the Lines Pull Power and Control wires out to the condensers and the inside units. All I needed to do was Hook up Line and Control Wires Hook Up Gauges and Check (Bless) the Charges. OMG Every one was a Piston. Every one had the Piston that shipped with the Evaporator in place. Every one had the Piston that matched the Condenser in a plastic bag in the controls of the Condenser. Every one started freezing up (Slowly) on Start up.... That was not my Week...
The liquid line filter drier is supposed to be installed at the inlet of the evaporator anyway. That's the only place I've ever installed them. If you read the installation instructions , that's where the manufacturer wants them
Right before the TXV?
@@tmst2199 yes
@@HVACRTECH-83 filter dryer, then sight glass, then TXV. The sight glass helps to insure the TXV has a solid column of liquid, which is required for its proper operation.
@@rodgraff1782 site glass isn't a required device. It's optional but not needed. Either way filter dryer belongs inside at the inlet to evaporator unless it's a heat pump system that has one in the outdoor section
@@rodgraff1782 a site glass doesn't help ensure a solid column of liquid at the txv inlet. It only allows for observation of the state of the refrigerant flowing through it. Don't want anyone to be confused by your comment
This is awesome. I have been watching you 2 for some years keep it up. 💯
Nice video
Question
About to make a hole on a refrigerant line.
If I put nitrogen 50 psi and then drill a hole
Will push out all the copper debris?
Wearing PPE.
Put a little less, 50 psi will shoot those copper peels out. However 5-10 psi would probably be best
If possible I will always go with a piston type metering device for residential AC. They fail after x amount of years always/ guaranteed to eventually fail. Same reason of why if we ever find a failed one that we do our best to replace with a fixed orifice. The 1/2 supposed SEER efficiency simply is not worth it for anyone if/ when thier TXV fails
How about so many places that your stuck with an old 1/4" / 5/8" lines set that you can't change/ no one upgrades to correct size and also no one talks about how such affects a new systems performance/ efficiency and maybe also life span of new system?
Thanks!
Great video!!! Thanks for teaching
Thank you so much for these great videos. Would love to see a video on how to install a un light hardwire. It correctly , thank you in advance
Could some sort of heat sink grease be use at the sensing bulb interface to promote better heat sensing?
At 11:50, he says to run a rubbed thru EQ tube back into the suction line if there is room. He didn’t say what to do if it’s one of the distributor tubes has rubbed thru.
Also, where the heck are you getting couplings that small? Never seen them before and have had many older guys tell me they don’t exist. It’s a very common problem to see and I’d love to have some input on how to handle that. I was so upset when you didn’t cover that lol.
I have to tell these guys I get what they are saying, but I’ve been know to use a piston in place of a junk txv. As long as you use the rite piston and the system is working within peramiters it’s fine to do that. I don’t do this on newer systems, in a pinch I’ve done it on old systems that it really didn’t matter especially when you have a customer who is cheap. I carry all sizes of pistons,
I’ve heard so many guys argue about the part at 10:00 where you say the tail needs to be mounted up in a vertical position. Why is that? What does it do?
Thanks for the knowledge
Another argument against zip tie is that they won't conduct. Although minuscule a metal/copper clamp will help conduct temp into the txv bulb
Great team up!
I think a lot of older techs, or really, techs who don't like TXVs are just writing themselves out of a job. TXVs are basically the new normal, even for standard efficiencies. They typically work much better than pistons, all these failures? Lack of vacuums, to be quite frank. I've seen it happen, where guys pull a 10-20 min vac or do the purge. Of course pistons will survive, but not TXVs, nor the longevity of the unit. I used to be afraid of replacing TXVs, then I discovered the hot block or viper wetrag, made easy, done easy, pull a good vac, and I ain't ever back to replace it.
Great lesson.
The industry doesn't braze with N2, a reality many places. I saw it. Pistons are less sensitive so... Now I use N2 but I am sent to do electrical, too slow in others opinion.
TXV is simply superheat controller device + expansion metering device at the same time
Great job and video like always
the dream team on deck
Thank you. Question? What is the allowable temperature drop across the inlet of txv and the outlet of it
Why does daikan/Goodman/Amana recommend adjusting the superheat? I think it’s odd I only see that you should adjust them for those units. But I’ve never adjusted one to see what would happen. And I’d that can fix a problem with the txv
Do either of you (Bryan, Craig) see a non-brazing technology coming down the pike anytime soon?? From what I’ve seen , the most difficult part of AC service is dealing with the system charge. It seems that every time you want to change a part (filter/dryer, TXV), you have to recover the charge. If our line sets were installed with threaded connections and “ isolation “ valves, you could possibly change parts with the system charged . Is this a pipe dream or do you see this as feasible ?? Comments welcome , thanks 👍.
I'm not a tech, but it doesn't seem like it would be possible to insert something back into the refrigerant line that doesn't contain any air.
Hey brother!
Thank you!
Awesome job guys ..
2 Great Havac Techs
Thanks Guys
I still don't get the equalization line job, if the bulb got warmer it will push the needle down to get more refrigerant, but now the equalizer tube will get more prussure and it will be pushing the needle back up !!
The guy with sunglasses looks like he needs a beer!
R-410a TXV's fail WAY more that R-22 TXV's used to, that being said, I've changed out quite a few in the last 10 years, and always replace the head and the guts as well, the body is just a body, no need for brazing in a new body. (Commercial application units obviously).
How does the reliability of the electronic expansion valve compare to thermal bulb expansion valves?
@@hvac-r977 Halleluja, brother. I see ads actually promoting these great, higher-pressure systems. What a joke.
@@gregorymalchuk272Good question. I'd guess it's better, as the bulb sometimes loses its refrigerant charge.
@@hvac-r977 well if they go with R-458A, then yeah. Fits the whole dumb “lower gwp” crap, works low pressures, and honestly is one of the best retrofits for 22 used. I say it should replace 410 period
@@gregorymalchuk272 don't really like them seems to take more time diagnosing gotta check air flow ohms from the sensors and see if the mechanical part of it works also voltage to the board
Excellent video
I’ve read in some manuals that is says 8 inches from any bend does that make a difference?
The only reason a tech replaces a txvs with a piston is there customers get tired of paying service calls to replace them . They loose multiples of what they save with them.