Refrigerant Charging: What it looks like to have a Bad TXV Compared to just a Low Charge!
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- Опубликовано: 8 июн 2016
- Refrigerant Charging: What it looks like to have a Bad TXV Compared to just a Low Charge!
This is a system that is actually is charged properly but I am showing you what happens when you lose the pressure out of the TXV Bulb which is the opening Pressure that allows the Refrigerant to Flow through the TXV. I show you how we verified the correct Charge and how we are manipulating the TXV into a situation where it is only allowing a small amount of Refrigerant into the Evaporator Coil. I show you the Pressures, the Temperatures, and how much Superheat will be occurring in the Evaporator Coil! Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.
Tools Used In The Video
Yellow Jacket Refrigerant Gauge Set amzn.to/2aenwTq
Refrigerant hoses with valves amzn.to/2aBumVI
Digital Refrigerant Scale amzn.to/2b9oXYl
UEI DL389 Multimeter amzn.to/2xAdaJf
Magnet Jumpers- amzn.to/2PyKPQZ
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Information in this video is intended for educational purposes only. Any work related to the topics in this video should be performed by licensed technicians or by apprentices under the supervision of licensed technicians. AC Service Tech LLC is not responsible for any possible damages or injuries caused by the use or misuse of any information provided.
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Here is a link to the Imperial 535-C Kwik Charge Vaporizer for Charging Refrigerant- amzn.to/2wFHtBW
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Thoughtful video. I like that you had the system set up before starting the video, ie guages attached, refrigerant meter, line temperature display, pre-running the a.c. system ... all this so that the key points can be visually evident and your dialogue can address the point of the video. All in all, a very intelligent, informative video. Keep up the good work.
Thank you very much for your thoughtful perception and if you want to see anything else, I try to make each video different such as one will be to attach and how to disconnect the gauge set, one on charging a system with king valves, charging in superheat instead of subcooling and so on. Thanks!
Diagnosed a bad TVX today, high super heat, high sub cool. What you're showing is exactly what I was seeing on my gauges and temp probe.
Thanks for making this video, I was searching for something to help confirm what I was thinking/seeing, this was perfect.
Thanks DF!
Just graduated with an AAS Degree in Climate and Energy Control Technologies. Your videos have been very helpful to me during my studies. Thanks!
Thanks Game Wizard!
Glad you enjoyed it and these next couple of videos were somewhat in reply to some of the comments you made earlier about the TXV, so kudos! Keep those great questions coming! Thanks!
Are you talking degrees Fahrenheit or degrees Celsius??
Thank you very much for taking the time to make these videos. I have learned more from your videos in the past two weeks than i have in 2yrs. of tech. school. Please continue to produce these videos and share your knowledge to us newcomers in the industry.Thumbs way up!!!!!
I appreciate that very much and I am happy about hear about your enthusiasm for HVACR! Let me know of questions or videos that you would like to see in the future. Thanks again!
Thanks for your Thumbs Up and Comments! Glad you enjoyed the video!
You are awesome at explaining the refrigeratation cycle and what is happening thank you.
Thanks msmolik14!
this guy is wonderful, very clear and concise in his details
Thanks Wisemanmusic1!
Really great info! You have a lot of videos, gonna start watching as many as I can. Thanks for all the work that you put into these videos.
Thanks CheckmateGamer! Knowledge makes one very valuable, thanks!
i like how you explain everything, very informative.
Thank you very much! I am glad you enjoyed the video! Any questions, please ask on any of the videos! Thanks for the Comment!
Thanks for your videos. One of the best you tube sites. Been telling all our young guys to watch. Very educational.
I want the very best for those young techs, that they will be able to be the one everyone relies upon and be able to provide well for their families! Thanks William Gildea!
Very good explanation. There are so many things that can cause similar symptoms. Definitely takes a lot of experience to determine what is going on in a system. I'm still learning and your videos are a great help. Thanks for doing them.
Absolutely, after time you know where to start and what to rule out as the problem. When I started there wasn't videos like this on HVAC so for the one who is hungry, they will learn a lot!
Finally a video that makes sense!!
thank you for taking the time to make this vety helpful and educational video.
Im dealing with some problems right now and you are pointing me in the right direction.
please keep posting videos. i will subscribe!!!
Thank you very much, I am glad the videos help!
@acservicertech - I really enjoy your HVAC videos. Very well done, thanks for filming and posting!
Thanks Gerard!
Hey great video. I really appreciate how you go about teaching with the regular tools.
Thanks a lot Dwayne!
Best video on txv so far. Thanks!!!
Thanks miss tiendas!
Thank you for sharing . God bless your heart.
I am glad you enjoyed it, God Bless!
Extremely informative and very well put. Thank you
Thanks William!
Excellent video. Great explanation.
Thank you very much!
Your videos really helps me understand how air conditioning work.. i am an electrical technology studend and no knowledge in air conditioning , but im so much willing to practice air conditioning , so im learnibg by watching your videos and understandings what you are trying to explain, im also taking down notes." Subcooling and superheat should be understand to be a good ac service tech. Haha
Im filipino btw.
Thanks a lot for writing this note! I a glad that the videos are helping!
Thank you for posting this.
Glad to help!
excellent video thank's for sharing!!!
I can learn clearly from your videos
Thanks Luis! I appreciate it!
Great job again like always
Very good video on TXV valve .
Thank you very much!
Thank you brother is very helpful
Glad to help!
Great Great video! keep them coming.
This was very informative!
Thanks Blue Collar!
Like everybody below says, great video! I'm helping a friend with what I think is a bad TXV. Line is iced up behind the TXV. I had only a thermometer with me. In A/C mode, indoor Delta T was 10 Deg F . Good air flow. Supercool felt OK to the touch - that is it was definitely saturated liquid. ( a calibrated touch that is :-) . I'll go back and check it out better later. My question is, Shouldn't it be possible to be pretty sure without even installing gauges? Here is what I'm thinking, Rather than look at super heat and cool, look at "relaxation" that is what is the delta temp between the coil outlet line and the air temp passing through the coil. In watching your video, as you showed super heat and cool, I was wandering what the outdoor temp was - that is how "relaxed" the refrigerant was to the outdoor air temp. Also it seems that with a cheap IR thermometer you could measure the condenser face temp as you move up from the bottom. When you see the temp jump up you'll know how high up the liquid is. If the TVX line is icing and the liquid line is high you should be pretty sure the Charge is good and the TVX is bad ( assuming all the other issues you listed were not a problem) In the old days I would run my hand up to coil loops and find the temp jump to know that.
I'm new at this and I have learned a lot .. Thanks
Thanks a lot!
Nice Video, TXV is calculated Reg. no doubt I have some kinda restriction on the liquid line. My subcooling is 6 degs and superheat is extremely high. Does not sweat. This is a garage unit. Humidity can be high, garage isolated except ceiling. All duct work is metal. Blower is medium speed. I have not measure static pressure across the coil yet. no need system is screw right now. I have many as eight 90 deg turns in the lines, not sure if it flash at these points. Compressor was testing out to 350 psi at 20 amps. Coils were cleaned. Filter return is cleaned and calculated for this volume. 3.5 ton amana system. R22 system. Never worked in the garage after assembly. Worked in the house for 15 years. Its either TXV, or evaporator design hook up. Not sure if a site glass can cause restriction or not. Here is the kicker, I have a blend, not a true R22 refrigerate. I have tried MO99 and Nu-22. The companies swear they work. Much cheaper and safer for the environment. May change out TXV and throttle this valve like you did in the video. if this works, I could move to a piston, or adjustable type for the garage environment. I could move to a real R22 refrigerant, to see if the blends was the trouble. Compressor oil is OK. Filters are changed every time. I try a new blend. Most HVAC guys don't have experience, working with blends for R22 sub. They do work. Most avoid it. Can you shed some light on this with different blends with TXV that is designed for R22. About one year of experience. Engineer that has taken new direction.
This is truly amazing. I'm an apprentice, and your videos really help me understand more than just reading from a book. Can't wait to gain experience and move up.
Thanks a lot Running Coyote!
Good info had a system where I got stuck determining txv bad the low side will not come up 75 332 no matter what I did everything else was working but it was on a zone system
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good explanation
Thanks Chad Tinsley!
Thanks
Good video. Thanks
Thank you, glad you enjoyed it!
great video. thanks
Thank you for your Comment Jerry!
Thank you very much for the video. I enjoy watching your recordings because you go straight to the point with clear instructions unlike other techs uploading videos on RUclips.
-
I have a question to help me clarify your method of troubleshooting the TXV;
1. By adding the TXV bulb to the 33F iced water your low side gauge pressure immediately dropped. IF it DID NOT drop, would that mean your TXV bulb lost refrigerant meaning it was not functional?
2. And by having the temperature drop when adding to the water, does it mean the TXV if working properly?
Yes you got it and it is even more important for what happens when the bulb is in hot water as that is when the txv opens up the flow of refrigerant and decreases the superheat. Thanks
Airflow was set to the correct speed, the evaporator coil was very clean with no airflow restrictions. Took an amp draw of the blower motor and it was in Factory specifications. Verified proper air flow at each duct and that all returns were unblocked. Filter was new because of course they always change the filter before we get there before a service call. So I go out and hook my gauges up. R410a system. System had low suction pressure at about 20 degrees saturation and slightly low head pressure. I decided to add a little bit of charge and only the high side responded. Went inside opened up the evaporator again and noticed it all three capillaries were basically Frozen and that there were some coils that were developing Frost and some that were not. I diagnosed it as a restriction in the system. I even second-guess myself and was almost convinced it was a bad TXV. I did not use the ice water trick. I think I will use it from here on out. Thanks for the info.
It sounds like a liquid line restriction. Liquid line restriction such as bad txv, clogged strainer, clogged filter drier would be high subcooling high superheat vs a low charge would be low subcooling high superheat. Thanks
thanks you every much you are good teacher i have promble like that low suc pressure
Thank you for your Comments! They are appreciated!
always interesting to review things ,,,,,,thanks we get old ,,,,, we forget LOL
Excellent!!
Thanks JJY!
Nice video
Thanks Aswad!
Good one.
Thanks Juan, Merry Christmas!
@@acservicetechchannel Merry Christmas, Master ;)
Okay thanks was wondering
Thanks Eric!
Can you do a video on a TXV hunting. Went on a call with the bulb mounted downstream of equalizer tube, Watched ice have to form outside the unit valve would open and thaw ice just on the downstream side of tube, then close again. Keeping coil frozen inside unit. This was also on a high velocity system. I am not a fan of the high V systems anyway. Thanks
Can you do a video about miss matching ac and coil sizes and wrong piston device size the problem they will cause by not having the correct match or correct piston device size on coil!
Thank you for the great videos. I have a 4 ton
System 410A . Customer had called me telling the outside unit sounded like something was stuck in the fan .
When I got there put my gauges on .
And low side was 158 high side 278
SH 15 SC 1.3 .. at first I was thing txv . But now second guessing my self maybe compressor valve . Would you have a idea
Thank you
I ran into a bad txv today. Had 30 degrees or more of superheat even with fan on the lowest fan speed. Only way to bring down the super heat was basically to take the fan out of the equation. Brand new system. Set up for downflow. Adjusted txv to allow more rrfrigerent to flow. That did raise the low side pressure didn't help with the problem of high superheat. Going to try and open it a bit more before I put on a new one and see if I can get it to act like a fixed orfice device just for the hell of it.
There could be a blockage at the screen from braze or junk in the lines or a clogged filter drier. It won't work like a piston but try to get around 10-14 degrees of superheat by adjusting. You could try the bulb in hot water then cold then hot again to try to get it to move but basically if it won't hold 10-14 degrees of superheat then change it out,, check the screen and replace the filter drier, thanks
Awesome
What about if the TXV bulb just comes loose?
I think I have that issue at my house
My sub cooling is high, unit calls for 10-12 but it’s 18 (it’s a TXV system)
super heat is like 1..
Temp split is 20
Suction line temp is 42
Liquid line temp is 75
Outdoor temp is 75
I just don’t have access to my basement tenant is on vacation..
I have a 40 year old Friedrich AC system that has worked very well for me. Years ago it developed a leak in the evap coil which I replaced. It has worked OK since then except that now the evap coil froze up. A service tech said he thinks it's low on R22. I also noticed the drain channels have a lot of rust flakes in them. (they are not plastic like newer ones.) Could those flakes be blocking the evap drain? Should I replace it with a newer coil?
Just worked on one and I put the tvx bulb in warm water cause the suction line would look right when I turn on the system but after few minutes the pressure would go down, so after putting the bulb in warm water the suction pressure didn't go up. Bad txv?
so there's more refrigerant now in the the condenser coil (when txv is in ice water)l.But why does temp and pressure drop on the high gauge? shouldn't the pressure and temp on high side go up since there's a back up of more refrigerant in the condenser ? thanks.
very good explanation! thank you sir
i have one question that bugs me out: why at the moment you dipped in the bulb into the water ice the pressure reading changed quickly. but when messing with the adjustment screw on the TXV in order to bring the superheat higher or lower we have to wait for minutes to see the changes??
the adjustment screw adjusts the pressure on the spring. tinkering with the bulb on the txv is more immediate because it reacts immediately to the heat applied to the bulb and closes/opens the suction line quickly. the adjustment is just a spring and therefore you need to wait a couple minutes to see if things are getting better and so you don't overshoot the mark.
@@tylerfabish5578 aah i got it! thanks !
One day I hope I'm as savy as you are
good nfo, so how does the bulb lose refrigerant, also when the txv is bad will it cause suction line to also freeze up at condenser unit,
If it leaks out of the bulb or the tube rubs and creates a hole or at the top of the txv head possibly, it will lessen the amount of refrigerant going into the evap and over time it could freeze up out to the condensor but right after turning it on and waiting 5-10 minutes there would be high superheat due to low refrigerant, thanks
Do you have any videos on mini split systems (ductless)? Specifically, what do you look for on a seasonal checkup? I understand that you really can't check superheat on those and that if you think your charge is off you have to recover and recharge by weight. Is delta T the only thing you can really check on a seasonal service checkup for a mini split? (aside from filter cleaning, coil cleaning, etc..)
Just these two art this point but they include the weigh in process. Temp differential on VRF systems as long as there's not high humidity in the building. Thanks - ruclips.net/video/QpzOSQt2fpI/видео.html - ruclips.net/video/gRNhSWNkIWY/видео.html
Do I need to invest in psychrometer if I have TXV systems? I do property management
I've always wondered the correct way to TEST if the bulb is bad. I've read and heard to place the bulb in warm/hot water. I've read to place the bulb in your hand for 10 min and then check. I've also read that you can use a hair drier on the bulb to test it. It would be great to know the correct way to test/troubleshoot the bulb.
You can do these tests but also high superheat and high subcooling is an indication of a liquid line restriction which we replace the txv, strainer or check the strainer, and replace the filter drier, thanks Blue Collar!
what about a clogged dyer, checking temp on either side of the dyer
This is a brilliant way to failsafe against flood back.
Thanks kdmq!
Is there any further test you would take to reach the conclusion of poor system airflow or fail tev? I will take a quick cfm measurement on the return with a vane anemometer and sometimes even cut open ductwork to provide more airflow. Still sometimes end up scratching my head.
If you use a vane anemometer make sure to use a transition box with a completely unrestricted opening to do away with the fins of the grill or register. Low airflow would read low pressure, low superheat with correct or high subcooling. Liquid line restriction would be low pressure high superheat, at least until the beginning of the evap freezes and then continues through the coil, thaks Kevin!
Would you ever use ultrasonic leak detector to check txv, and me not knowing what a good txv should sound like, what would a bad or malfunctioning one sound like?
You would really be looking for high superheat and normal to high subcooling. That would be your indication of a bad txv, or other liquid line restriction such as filter drier or screen, thanks
Informative video, well done. Your audio is hi and low.
Thank you, glad you enjoyed it and thanks for letting me know!
awsome video. how common do you find that the txv is your problem and how common do you find you just have to replace the top body of the txv (bulb)
The txv is all one unit on the non electronic ones which are most common. Thanks for your Comment!
+acservicetech cool i also watched your videoes on superheat and subcooling just trying to figure out with out using any of those charts how to get target superheat and target subcooling with the calculation and how to crunch all the numbers
Exactly that's a beautiful thing. Once you get that down, it becomes a diagnosis procedure in your head! Great, keep at it!
I replace a TXVon a Rheem outdoor heat pump last week because it was completely shutting down refrigering flow. After further inspection I saw that the cap Tube connecting the sensing bulb to the TXV powerhead had a crack in it. I’m wondering if the sensing bulb losing its refrigerant charge was the cause of the TXV completely shutting down refrigerant flow or if that was just a coincidence. Because I could have just replaced the powerhead and not gone through the refrigerant removal process and pulling a vacuum etc.
I tested my TXV by placing the bulb in ice water and warm water to see how it regulates the evaporator. It makes a difference so I believe it is working properly. Not sure how to diagnose just a bad bulb. If the ice water/warm water test does not have any impact then it could be bad bulb, stuck valve, clogged TXV. I suppose you could replace the powerhead first to see if it fixes the problem (easy job), if not then plan to replace the entire TXV. My bulb was mounted inside the air handler (Trane Heat Pump), so I relocated it to the outside for easy access to test.
Only getting about 7F across the evaporator, 79F at return and 72F at register. Ambient temp is 89F. R-22 Refrigerant. Evaporator changed 3 years ago. Condenser has been thoroughly washed. Discharge 270 psig with 105F liquid line temp. Suction 78 psig with 78F suction line temp. The Hi side swings from 270 to 250 every few minutes. Decided to change out the TXV. After replacing TXV the system performed the same with only 6-8F across the evaporator. I have tried soaking the condenser with water for 30 mins which brings down liquid line temp but still only get 6-8F across evaporator. When changing out TXV the refrigerant was blocked at compressor and reused. System vacuumed for 10 minutes. Does the TXV need to be adjusted? Do I need to fully recover the freon and put a fresh charge?
The system would need to be vacuumed to 500 microns before refrigerant is introduced. Each time you open the system up, the filter dryer should be cut out and replaced. Did you try putting the txv bulb in hot water to see if your 31 degree superheat would decrease? It sounds possible that the charge should be fresh from a new bottle. Why was the evap changed three years ago?I would test txv first to see if superheat decreases but I would likely be recovering, replacing the filter drier and putting fresh r-22 in. I am assuming that the txv bulb is in the proper place. I have videos on bulb placement, vacuum pumping, and bulb in hot water. Just search through the search box on the top right of the channel page. Thanks and I hope that helps you!
can you make a video just for target superheat and subcooling on the whole calculation?
I have, check out the superheat as well as the subcooling playlist. Please let me know if you have any questions after watching them. Check the ones that say Step by Step as they will likely be even more broken down into steps. thanks
+acservicetech I understand how to get target super heat and sub cooling, but instead of checking a chart I want to know how the actual calculation is done. I understand your videos. Thanks
Are you talking (IDWB x 3) - ODT- 80 divide by 2? That works for superheat if you dont have your slide ruler
saturation point @ evaporator minus temp. @ suction service port is = superheat.
superheat is temp increase from middle evaporator to suction service port or comp. inlet.
from center of condensor or saturation point to outlet of condensor at discharge port is temp. decrease or subcooling.
discharge pressure converted to saturated temp. minus discharge temp @ discharge port or compressor outlet is = subcooling...
Hey man great video, quick question for you, I have a Lennox R22 residential AC system with TXV on the indoor unit. indoor split is 10 degrees, Suction line: 26.5, Liquid line:184, Superheat: 64 and Subcooling: 29.6 if there is a restriction how do I locate it? Filter dryer has a 1.5 degree difference across both ends.
Sounds like it as long as you double checked with another temp sensor just to make sure. If you added more refrigerant, the subcooling would just go up so it is not refrigerant, it is not low airflow because of the high superheat. I will say this though. How are you getting a 64 degree superheat when the suction temp is 26.5? That would mean your conditioned air within the building was higher than 90.5 degrees. Is that right. It would likely need to be closer to 95-100 in the building to get that superheat. It is usually the filter drier, strainer, txv and rarely it will be a distributor tube. You may want to plan to change the txv, strainer, and filter drier if i am understanding what you are saying. The temp across the filter drier may be close to normal depending on the location of where it is installed and the surround air temp. Thanks
acservicetech Thank you for quick response, im in NY, today it was around 70° ambient inside the house temp was 77°, supply was reading 55 and return was 65. TXV replacement requires system recovery and vacuum, right?
Subcooling is essential for determining a charge. But what if there is a receiver separately under the condenser. How then is SC applicable?
In refrigeration, we verify the charge level differently in that we try to increase the load and drain the receiver but still attain 1-2 degrees of subcooling in a clear sight glass. If the product can't come out then we monitor superheat and still a clear sight glass, thanks. Maybe check these videos out on the receiver. They are mainly about the function in the refrigeration cycle- ruclips.net/video/BllcbdD_tJQ/видео.html -- ruclips.net/video/RofUUMl5x84/видео.html
What do frozen capillary tubes indicate? All three Capillary tubes on the low side of the txv were frosted
Low refrigerant charge, liquid line restriction, or low airflow. You would need to check vapor sat temp along with superheat and subcooling to determine which one, thanks
Excellent video!! One question. Why doesn’t head pressure rise when the TXV shuts down. Seems to me like it would.... Also, is there any way to rule out a bad compressor in situations like this. I guess what I’m asking is of the compressor wasn’t pumping right what might the symptoms be?
When the txv shuts down supply of refrigerant into the evap coil, the subcooling increases. Look up "acservicetech bad compressor valves" thanks
@@acservicetechchannel
Since superheat is not valid for TXV systems to adjust charge, can subcooling be used for determining the correct level of charge regardless of whether it's TXV or capillary tube/piston setup? Or is superheat measurement always called for with the orifice tube systems?
Subcooling can only be used with txv systems since the txv controls the subcooling. The most important issue is superheat determines how much heat is absorbed to begin with and keeps the compressor safe from saturated state entering into the vapor compressor, thanks and good question DTR RTD!
On the superheat measurement of an R22 orifice system, it showed the expected value of 21.3 called for on the sticker on the condensor housing, but the subcooling came in at 5.2 degrees. Is there a recommended subcooling value for orifice tube systems or is that only applicable for txv systems as you mentioned?
Wondering if the 5.2 subcooling would indicate a low charge, since a higher level of charge should increase that figure.
Is the charge level only determined by the superheat measurement with non-txv systems?
Hi one question is a txv problem when pressures and subcooling keep moving subcooling goes from 2 to 10
What refrigerant vapor and liquid pressures, seer unit roughly, and superheat? thanks
I got a service call once where this 1 1/2 ton Rheem heat pump would work fine on A/C mode but on heat mode the high side (or low side i don't remember) would rise more 500psg and the high pressure switch would turn it off. I changed the TXV and filter dryer and that fixed it. Can some explain to me how this can happen?
My heat pump is the opposite, works fine in heating but not in cooling. So I might have to replace the filter drier and the TXV?
Today i can across a system ( with txv) where the sub-cooling was fine @11 degrees...of 10 degrees posted..
the super heat was @40.9 degrees...Suction sat @ 36.7 ...line @ 77.6.....inside temp was 75 and the outside was 84 ( high side 308 psig=98 and line temp 87......checked txv looked good.....why the high super-heat....Checked filter looked good....return size looked good
....I didn't check coil size ---could that be a factor.....any suggestions ..I am still learning
Thank you
What was the temp diff between return and supply? Was the TXV bulb mounted properly and securely? What is the txv size? If the txv is undersized that could happen, or if the coil was oversized by 1.5 ton or larger, or the blower motor was way oversized then the txv could possibly not keep up. More likely though, the txv bulb might not be mounter tight or the txv bulb could have lost some charge and not applying opening force on the txv head.Check out the txv videos playlist. I hope that helps, thanks for the Comment!
i had a new install call back because the evap was freezing up, n coil and txv 410a. new outdoor unit as well.
my high side 286pisg and my low 92psig. subcool rated 10 and my subcool was correct. added refrigerant and ounce at a time but after a while my high side was at 390ish and my low side was at 107. sc and sh were high but my evap was no longer below freezing.
im thinking new txv bad
Yes or a restriction. Very likely a txv. Did you see what happens when you put the bulb in hot water? Does it open up and reduce superheat while increasing vapor pressure?Here is the TXV troubleshooting playlist ruclips.net/p/PLxnHR5_D2ojy2EYzy0YIJkce9sFIQj4-j
+acservicetech thanks, my Saturday on call turned into 4 recalls for new evap installs. all the same issue. I trust our installers so I didnt check to see if air was bypassing the n coil. different installer each time, either a recall on parts or they used too much solder without running nitro through .
Shouldn't you be at 120 psi on your compound side and 325 or so on discharge side..? Sounds to me that for 410a you may be undercharged..?
Where do you teach at?
I wish i would have seen this video sooner i had a job that the evap coil was freezing up i eliminated the air filter, the under charge, cleaned both coils, txv was changed and checked the ducting and it still froze i eventually checked blower speed it was on high i lowered it and it froze faster so im thinking it was the motor to late now they are having a new system put in
Thanks for the Comment! On a system with a slightly undersized blower, the charge will look good for maybe the first 20 minutes and then you notice the vapor pressure dropping below freezing. The vapor pressure normally will drop as the temp is lowered in the building but an undersized motor will have a more dramatic affect that will continue below freezing.
HI A.C Sean here . So today I changed out two 5 ton R22 compressors on a Lennox L series RTU . After I weighed back in the refrigerant according to factory charge for each compressor and the unit was running for some time while I was checking the pressures I got stumped as to why the low side pressure was only just above 50 psi and the high side was 188 psi . It was at txv metering device and so my subcooling was 70 degrees but and super heat 14 . I tried to add more refrigerant to each compressor to try and bring up the low side psi but I could only get head up to 220 and the low side stayed around 56 before I stopped adding r 22 . Any thoughts ?
Do you mean you had 70 degree actual temp on the liquid line? Not 70 degree of subcooling correct? So three things make a low sat state/low side pressure on a system. One is low refrigerant charge. We know thats not it. Low airflow which would be indicated by normal superheat and normal to high subcooling, Liquid line restriction which would be high superheat and high subcooling. For your reference, low charge would be high superheat, low subcooling. So normally, determine if it is either low charge or liquid line restriction and if it is neither than it is low airflow. Is it possible to take a door off to allow more airflow across the coil for testing sake to see if the pressure rises. It may rise anyway some due to the heat absorption even if it is liquid line restriction. I hope this helps!
I get how the superheat would be higher with less refrigerant in the evap, but if there is more refrigerant in the condenser why would subcooling also be high? Wouldnt the temperature drop less if there was more refrigerant to cool down on the condenser side? im stuck here, thanks
ok i think i get it, since now it has more passes in the condenser (its basically has more time spent in the condenser) and so more heat is rejected?
Hi there, i watch your videos regularly, and also im reading the book but one topic still remain unclear to me. Thats line restriction. Im trying to figure out what is the whole procedure from diagnosing, symptoms and over solving it. Please refer me to sole of your videos if there is one like that.
Thanks,
Zoran
You would want to read the troubleshooting part of the book where I have a liquid line restriction with a correct charge and another with a overcharge. A liquid line restriction is usually the metering device, or screen in front of the metering device or the filter drier. Any time you find one with high superheat and normal to high subcooling on a TXV system replace all three components after a pump down, thanks!
You can test the temp across the filter drier to see if you have a temp drop across it. If it is less than a degree, it is good, thanks
What should the temperature be of the air coming out of the condenser?
That would depend on the seer rating of the condenser. The sat temp that we are normally running at is 90 to 105 unless the seer rating is low or the fins are dirty, thanks
Carrier system, 3ton, 410a:
50° saturation lowside with a 10° SH. 108° highside with a 10° SC. 9° temp split with high electric bill. Bad txv? Compressor? (8.2amps) Both? Air flow was fine.
this reads more like an overcharge. is it a txv or a piston? what is the outdoor and indoor temp at these conditions?
a bad compressor will usually just be not compressing as efficiently. You're pressures will be closer together than usual. in other words, the low side will be reading higher than normal, and the high side will be reading lower than normal. One house i went to the compressor was fucked from being overworked, and when i put the hardstart on it it was running 50psi suction side and 100 psi liquid side.
Goodman heat pump charge unit for cooling cools perfect. customer complained heat pump shutting off for high head pressure. I believe the other txv is bad and not over charge. couldn't verify, customer wants to leave the unit as is. question should a heat pump be a weighed in charge or can you trust a sub cooling method?
You can trust the subcooling method if you charge in cooling mode but if charge in winter then you must use the weighing process. That is an intermittent problem then I am assuming as it was working fine when you left but now there is a problem? It would be nice to see when this is going off on high pressure and what the pressure is. Thanks!
Great video.... But riddle me this. Assuming all else has checked out and the Puron System has a high side of 350PSI and a low side of only 88PSI.....how can you differentiate between a bad TXV and a partially plugged liguid line dryer? THere is very little cooling, say a differential of 7 degrees. There is no frost on the TXV or evap coils and there good air flow. Subcooling is 10 degrees. It seems in either case, the system is undercharged,....but how can you for sure know its the TXV or the dryer? Its a carrier
FYI, I took the TXV bulb off and dunked it in boiling water, then into ice water, then into boiling water, repeat. Finally left it in the boiling water. Turned on the system. Pressures were exactly the same in the boiling water as they were with the bulb attached to the evap
Great Question! The pressures should not be the same. Did you check the superheat? The way that you tell a plugged filter drier or restriction from a bad txv is that if you have low temp diff across the coil, in this case only 7, when you put the bulb in boiling water the superheat is supposed to decrease. When you put the bulb in ice water, the superheat should goe up. The txv is supposed to be controlling the superheat so if it is not and you have the correct subcooling then the txv is at fault. Thanks!
If there is no restriction on refrigerant flow entering evaporator and you have low evap pressure due to dirty filter, slipping belt etc then i assume this would not affect the subcooling as is the case with a restriction on refrigerant flow
Actually subcooling would be low due to excess sat state in the evap coil. I have all this spelled out in the book I am putting together and excited to be getting it out soon, thanks
Thank you. That makes sense. Less refrigerant in high side so less liquid for subcooling to take place. Looking forward to the book.
Yes that's right, thanks Michael.
What if the saturation temp of the evaporator coil is high, around 67 deg. Subcooling is around 8 deg. Temp in house is 84 deg, supply air is 72 deg. Refrigerate 410 , 2 ton unit expansion valve, discharge line temp is 132 deg, superheat around 7 deg, more refrigerant added only raises head pressure and no change in evaporator coil temp, refrigerant removed and temperature decreases but so does cooling? Compressor sounds funny as if internal relief valve is open ever so slightly, and unit will not pump down below 45 , charge was weighed in to factor specs, new refrigerant added, blower speed checked and confirmed with static pressure, no heaters stuck on, and no air bypassing evaporator coil? High suction pressure around 189 if I remember correctly. I'm ready to replace compressor.? Any tips?
Well, disregard this post, fixed the problem by changing out the compressor which was defective, had bad valves which was causing the issue, just as I suspected was wrong. Thanks anyways.
That was a good diagnosis, yes you were doing all the right troubleshooting!
Great video.
I have a unit that was low on refrigerant (r22). I searched for leak and found it on the evaporator coil and it was in a place I could not repair. We replaced the coil that came with a 410a txv, put a r22 txv on coil. The unit runs with high subcooling and high superheat suction saturation temperature is low about 29 degrees sometimes lower. Unit froze up the other day. Checked filter etc. all looks ok. I pulled the txv bulb off and put it in my hand. Suction saturation went to about 34 degrees and superheat decreased. I think the txv may be bad possible loss of charge in the bulb. What are your thoughts? Thanks
Sounds like too small of a txv size, or bad txv, or clogged filter drier if it was not changed. Thanks
acservicetech filter drier was replaced when new Evap was installed. Thanks for your input.
acservicetech just an FYI I replaced the txv. Problem still remained. Due to possible efficiency issues (new coil on old condenser) I adjusted the txv, opened one full turn. As of now the problem has gone away. Superheat and subcooling look great. I just wanted to share the experience to possibly help others avoid the same problem I had.
Suction saturation has gone up. All looks good. Thanks again
👍
How can you tell if the evaporator coil itself is blocked with dirt?
Hey Steve, you can drill a small hole in the triangle tin plate if you can't see behind. Some have a plastic knockout. You could also take a pressure reading across it with a manometer. The target would be in the evap coil manufacturer install booklet, thanks
I'm doing a couple of units at a apartment, the indoor units are old and txv. tried to charge and low side doesn't change, high side subcooling goes up and suction line is freezing up. saturation temp in evaporator reads below freezing with leads me to think txv is bad
That could be liquid line restriction or low airflow, depending on the initial superheat within ten minutes with a non frozen evap coil. Low superheat is airflow, high superheat is liquid line restriction. Check out the videos on that subject- ruclips.net/p/PLxnHR5_D2ojxZI3-xx03Bttxe3xCqUD87
acservicetech in this situation, txv is okay, airflow is low, will the txv be successful in maintaining superheat? or in other words, will checking superheat while having a working txv show low superheat with low airflow?
What if there is a restriction on a cap tube? What are the tell signs
Here is a video on that- ruclips.net/video/L7VkLsXGaQ8/видео.html -- normal to high subcooling with high superheat. If the unit was low on charge then you would see high superheat with low subcooling., thanks
Residential split sytem R 22 scroll compressor. After a minute or two the pressure slowly keeps going down. High was 275 low was 40 psig. Added charge after checking filter, and fan motor. High side went to 300 low side continued to fall. Compressor finally went off. System has a filter drier sight glass and txv. i think it's restricted but i havent tested the txv.
If it is restricted then you will have a freezing evap and high superheat with normal to high subcooling. If it is airflow then you will have normal to high subcooling with little to no superheat, thanks
Thank you. The suction line is warm outside and inside. 84F in 81F out. Air temps Didn't even have time to check if the filter drier was clogged. Compressor went off. Prbably high head. 300 106.4 near condenser ambient temp. system is 5 years old. Motor fan and wheel look clean so i ruled out clogged evap.
I found the T.X.V. was completly shut. Replaced it with new one. Weighed the charge in. Suction was 55 liquid 285. Weather is cold so i need to go back when its warm to test system. May need to adjust superheat subcooling. will adjusting the superheat raise the suction pressure or should i add more gas?
If this is a comfort cooling system with a txv, you would monitor superheat to be around 10-16 degrees, the evaporator coil sat temp above freezing and a subcooling as listed on the rating plate on a 70 degree or higher day, thanks!
I guess where i was confused was both charging and adjusting the TXV will change the superheat. Thats why im going by subcooling.
Hi Craig, question, is it true that when we are replacing an old r22 outdoor condenser with a new r410a condenser, we really do not have to change the txv in the indoor r22 air handler. I have always done it but some of the people here in town don't do that. is it true ? if not changed, what would happen ?
Ha ha that is not good! You definitely change the txv to r410a otherwise you will have an inefficient system with higher superheat. Wow that is really pretty bad!
@@acservicetechchannel I completely agree with you. But I stopped arguing that it is wrong what they do. I guess at the end of the day is what you do what really matters. Thank you buddy.
@@budgetcoolingandheating4059 this is true. They must not be looking at their low side gauge or delta t after the changeouts, man that's awful!
I reaaly appreciate your videos. I am currently working on a new split system. Ran for two weeks before it was shot with a nail in the liquid line. I replaced the bad section. After weighing in the 410a gas and test ran the system the pressures are very low on both sides. I confirmed the the txv is 410a. Both a coil and condenser are Airtemp and the furnace is carrier. Only thing i can figure is wrong is airflow too low or bad txv. Any thoughts?
So I would need superheat, subcooling, indoor wb and outdoor db in order to tell if it is liquid line restriction, low airflow, or low charge, thanks Shawn!
Show where you put the temp probe
Hey Alex, RUclips does not allow me to change these videos. The temp probe for reading superheat and subcooling are within 6 inches of the service valves and taped to the tubes, thanks
Instead of a cup of ice in the attic and then running out side to see the gages can you just unhook the condensers fan? Then watch the gages from a chair?
What if a r22 unit has a txv and capalary tube In the same system(york)
That is actually a txv with normal distributor tubes attached from the txv to the coil. Distributor tubes are normal on txv and piston systems and a larger in internal diameter than capillary tubes, thanks Gary!
Thank you sir ..