TXV equalizer tube: does it feed liquid refrigerant
HTML-код
- Опубликовано: 12 сен 2024
- This one discusses the equalizer tube. Does it feed liquid refrigerant into the suction line. This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.
I really wish that these components that you open up to show what's going on inside were shown to me when I went to union school years ago, I'm a very visual person, when I can actually see what's happening it really sticks in my mind, thanks for doing what you do it's very helpful.
Welcome
GFM
Great video series. I recommend placing the bulb upstream of the ext. equalizer line in any classes I do on TXV's and usually get a few looks of disbelief and or eye rolls. I was taught this probably 25 years ago by a senior journey man and it stuck with me. Once I observed where the liquid was leaking past the push pins (I assume anyways) resulting in ~ 4 degrees of depression just down stream of the external equalizer line. I noticed sweat on the ext. line and put a thermistor about 2 inches down stream. Sure enough the temperature was lower there. TXV was not underfeeding, however the superheat was set a few degrees below factory setting so I suspect somebody must have adjusted it to make up for the temperature drop.You are correct that manufacturer's are placing the bulb down stream of the line. Can't really blame them as picking a spot for the bulb is getting harder it seems these days.Keep up the great work!!!Jamie
Thanks for the thoughts.
GFM
Jamie K has it right. Great videos!
@@michaellicitra7632 Best HVAC videos on RUclips.
all Rheem ruud air handlers and furnace coils show in the installation manual to mount the bulb downstream from the equalization tube I never even thought about it hurting anything good video!!!!
thanks for cutting one a part, never knew how equalizing tube was hooked up inside the txv.
+Dennis No-one Welcome
GFM
Equalization,weather internal or external, bulb goes upstream on factory systems. On built up systems, close to equalizer as possible. Equalizer is a closing force. Superheat spring is closing force. Powerhead is an opening force
This reminds me of a class I sat through for gas valves. The equalizer tube is much like the small channel feeding into the bottom of the diaphragm of the gas valve controlling manifold pressure. The spring tension on the manifold actually fights against the inlet pressure to control the manifold pressure. The instructor called it a controlled leak going on inside the gas valve which is kind of a good way to think of it. And, if any crud plugs up the inlet channel feeding into the bottom of the diaphragm chamber this stops the gas valve producing the correct manifold pressure. It's interesting how similar the principle is between a refrigerant txv and a combination gas valve is for a gas furnace.
They are quite similar.
GFM
Interesting.... great work. I agree. If any liquid woukd get by that need would evaporate immediately due to oressure drop
If anyone knows more please share. I think the Danfoss txv uses the equalization tube to divert excess refrigerant under low load. I have stores with all Danfoss valves that we've change to all sporlan and the floodback stopped, seemed to gain capacity due to less floodback. I might be wrong but when I see a sporlan txv with frost on eq tube, I fix it, Danfoss Valves typically frost the eq tube. Only observed from working on the crap
Good video. Never seen a Txv cut away like that. Very cool.
You can also get an automotive block-type TXV and easily disassemble and reassemble it, done it once to check if the valve seat was nicked or it was cross-charged (it was taken from a car with a variable compressor, and the valve isn't supposed to completely close with these compressors, just like it didn't when i tried to blow air through it right after freezing its power head).
A really good video. Better than in class teaching lol Thanks and keep it up!
perfect video, great cross-sectional view making understanding simple. Thank you GFM
Your cutaways are amazing :) Do you also have adjustable TXV cutaway?
+Guy Hakverdi You know I haven't done that. Good idea.
GFM
The equilasation line cant put liquid there because it is on the suction line going to the compressor, and it is not a flowing line. And the sensing bulb always needs to be behind the evaporator coil that you want to have metered for superheat. Sometimes you put the equalasation line right behind the evap coil if you need a perfect superheat management on the coil, some systems require this. ( sorry for me bad english im dutch ) like your video's a lot !!
+stefan hasenbroekv Thanks for the thoughts.
GFM
+grayfurnaceman no problem, do you do Large chillers as Well? Would like to see video's of that as well. Ill keep looking! Gj on the vids
Behind the evaporator? When it's still liquid???
Block type automotive TXVs are all externally equalized even though the evaporators are usually very small (supposedly to minimize hunting, since some compressors require a dampened TXV response to function properly). The refrigerant that flows out of the evaporator directly exerts a force on the diaphragm.
@@mbburry4759 Perhaps he just means "right after the evaporator's outlet".
Nice video and great job on the cutaway.
+Nicholas CeeA Thanks for the support.
GFM
Min 3:40 -- FINALLY figured out what that "equalizer tube" is for: high-pressure liquid-or-gas is going to sneak up the gap in those push rods into the valve area under the diaphragm and distort the valve action, so an "escape" has to be arranged for that pressure (hence the equalizer tube). Phew. (correct?)
Actually, no. The The equalizer places the evaporator in the same pressure area as the valve. This eliminates the pressure drop of the evaporator tubing.
GFM
@@grayfurnaceman
I'm referring myself to another GFM video, ruclips.net/video/iKdUCI2uBTg/видео.html : at Min 3:40 "... it's spring pressure + low-end evaporator (equalizer) pressure vs. bulb pressure.
Awesome video! I love the cut away! Quick question. I've been told that the sensing bulb has a "different kind of refrigerant" in the bulb and the tube, is that true?
+Kevin R It depends on the valve. Most A/C valves have the same refrigerant as the system.
GFM
+grayfurnaceman excellent, thank you!
+Kevin R Welcome
GFM
Most automotive TXVs have a mix of refrigerants and an absorbent charge inside the power head (no "bulb" on these). This is called "cross charged" and allows one to set the superheat vs suction pressure curve as needed by the application. Such a charge allows steady operation of the TXV and prevents it from closing completely so that variable displacement compressors can both adjust the displacement steadily (some of them rely on the suction pressure to adjust the displacement and the suction pressure, to keep the evaporator from freezing, and go haywire when the TXV hunts superheat) and so that the compressor can always be supplied with oil even when the evaporator is very cold. On my channel i test such a cross-charged TXV myself and show how the metering pin slowly returns open after partly closing due to a cold power head. On the other hand a valve that contains the same refrigerant found inside the system is called "parallel charged" and may "hunt" superheat more than the first.
thank you for sharing. It is a very useful knowledge.
Welcome
GFM
thanks for sharing your expertise ...
I think its a hang up from when txv's/tev's were made with poorer manufacturing tolerances, I've seen them installed both ways and not noticed any difference in operation.
Having said that, I have also seen valves fail and dump enough liquid down the equalizing line to cause the valve to close in refrigeration applications due to old age etc.
+heavydiesel I have to agree on that. I have also seen them done both ways.
GFM
+grayfurnaceman
I believe that when this happens then the equalizer line is frosted over, but maybe this only happens in lower temps such as refrigeration??😎
+HVAC/R Junky
Nice cutaway on the valve!😎
thank's gray excellent video thank' s for sharing!!!
+jimbola77 Welcome
GFM
Good video and explanation GFM
Great video! What did you use to cut the TXV?
Just a sawsall.
GFM
If a guy or a girl, can't learn from this man, they just can't learn.
Sir if sensing bulb below is broken, does Equalizer work same like Sensing bulb?
Or both have different fuction.
Can u pls explaing both function clearly.
Waiting for reply
The equalizing tube is there to account for any pressure drop between the TXV end of the coil and the outlet of the coil where the bulb is mounted.
The sensing bulb controls how much the valve opens.
GFM
Down stream means the direction of refrigerant flow? Away from evaporator ? Thank you
Yes.
GFM
Hey GFM. Where is the bleed port on these TXV's? Is it just a small hole between the suction and the liquid line?
I don't have any cutaways of a bleed TXV. It is just a small hole between liquid and suction.
GFM
You can also set the bulb charge so that the pin never closes the valve completely and effectively acts as a bleed port, no need for one... employed in automotive TXVs, i've disassembled one of them and there's no bleed/bypass whatsoever, the pin perfectly closes the valve seat if i grab it with my fingers and try to close the seat with it, but when i reassemble the valve and freeze the power head with canned air, the valve still stays open a little... so complete valve closure can also be prevented by the bulb charge...
How do you determine TXV Spring psi?
Is it possible to trick valves to open if the bulb blows its charge?
+Frank Machine Nothing that I would recommend.
GFM
Yea, i heard a guy put a coin under the powerhead once till he could get back with a txv on monday.
If you do this, you are taking the risk of flooding your evaporator and damaging your compressor. If it were my own AC and I understood the risk, then maybe I would do this but I wouldn't do this to a customer's AC. You are on the hook for damaged components and your boss isn't going to be happy if anything happens.
hi -I don't understand 1-for the model T2/Te2 without third pipe from thermal expansion valve-when the valve are close the orifice -the presure wrere are going ?
2 the model with three pipe -third are conected at exhaust of evaporator -when the termic valve are close the pressure are going in bypass from third pipe ?
And also who close the selunoid valve and the pressure of the compressor where are going ? the baypass are after this valve
many thanks
where I can find a animation of this ?
1. When the valve closes there is no gas passing from high side to low side.
2. When the valve has the equalizer tap, and the valve closes, there is no bypass from High side to low side.
When the solenoid valve closes, the compressor continues to run until the low pressure switch opens the compressor circuit. The pressure made by the compressor continues to condense gas to liquid in the condenser.
I have no idea on the animation.
GFM
I don't understand, the pressure are go higher, no?
The pressure in the evaporator, in the off cycle, will raise to its saturated pressure/temp.
GFM
I will ask again -pressure to out of compressor 14 bar - go to condenser after to filter and now passing through solenoid valve to expansion valve -----when close the selunoid the pressure 14 bar where go ?normaly are rise --the line have a expansion valve TE2 external egualizator -this egualizator when working if the selunoid are closed ?
meny thanks
I bet if you installed a sight glass on the equalization tube, you wouldn't see any liquid refrigerant whatsoever. Any miniscule amount that gets through those clearances is going to flash instantly once it hits the low pressure.
I thin you are right.
GFM
What happens if you have a blocked equalization tube?
Superheat will be off by the pressure drop of the evap.
GFM
@@grayfurnaceman Does this answer mean an increase in superheat and starving the feed?
What is the use of equalizing line ??
The diaphragm that opens the valve is subject to bulb pressure sensed at the suction line. In addition, the evap pressure pushes on the diaphragm. There is a pressure drop between the entrance and exit of the evap coil. The equalizing tube compensates for that drop.
GFM