(TXV) Thermostatic Expansion Valve Operation with Pressures! 3 HVAC Scenarios!

[@acservicetechchannel]

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[@StlPike2004]

Hello. Question for you please. I just had a new furnace and AC system installed. They installed a TXV-42 and the whole unit (the bulb and valve) is outside of the unit. The bulb is wrapped in insulation. Is that ok? I see a lot of videos showing the "bulb" hooked up inside of the unit on the A-coil.. I have an upflow furnace, so maybe the bulb is outside of the unit because the furnace blowing heat up across the coil (where the bulb could be) sn't good? Is there an issue with how they installed it?

[@jollyscaria1922]

Vrey vrey good welcomed thanyou gues

[@Adman0402]

So I just moved from installing to service, and I've been watching your videos since day 1 of hvac school. I just want to say that your videos have helped so much in the past, and I look forward to continue learning from you. You help so many people out, and you deserve major props man. Thanks for your time and your very informative videos. 👍

[@brianmcdermott1718]

Great video and tips . Thank you Craig.

[@acservicetechchannel]

Glad you enjoyed it

[@davepenprase]

Thank you great stuff well done

[@jasonjohnsonHVAC]

Outstanding explanation. You are definitely one of the best at explaining operation, diagnosis and repair.

[@biblebloopers946]

I am confused. How can the pressure on top of the diaphragm be different from the pressure underneath the diaphragm? If you're sensing bulb sits within inches from the external equalizer tube that feeds to the bottom of that diaphragm, then both pressures that are exerting force on the diaphragm should be equal. If I have 69 psi where are the external equalizer tube goes, then that converts to 40°. That's where the sensing bulb sits. So the sending bulb is also sensing 40°. That is filled with the same refrigerant that's in the system yet it's isolated from the system. So converting 40° over to psi you would get 69 PSI. So you're sensing bulb and external equalizer should be equal at the diaphragm. What am I missing? How is the pressures different?

[@bryanswanson5007]

The pressures are different because the bulb has saturated refrigerant inside which will raise and lower the pressure inside powerhead with changes in temperature on the suction line. Whereas the equalizer has 100% superheated vapor which the pressure does not change with temperature increase or decrease. That 40f temp is when the refrigerant is saturated as it is in the majority of evap, by the time the refrigerant all boils to 100% vapor and exits the evap, its 12 degrees warmer so 52f. So the bulb is sensing the 52f not 40f. Dont have pt chart on me but what it means is that the pressure in bulb,cappilary, and powerhead is higher pressure than 69 psi being taken at the equilizer. Hope that helps a bit.

[@soulme8186]

Hi Sir I have a question about capacitors can I send it to your email I will send you mine if that is ok appreciate it

[@k8aik8ai]

Where did this guy get his accent? He says "hode" instead of "hold" like there's no "L" and "oio" and "cio" instead of oil and coil

[@chrisdeanndavison3626]

What a great explanation and animations!

[@acservicetechchannel]

Glad you think so!

[@mehdibourha180]

I couldn't understand right now his got 423 views with only 48 likes it's not really fair

[@joeyf504327]

so why does super heat rise on a low charge if the txv is supposed to maintain super heat?

[@jeremymcguire7069]

After watching dozens of your videos over the last several months and learning something new from each of them, I just ordered a bundle of the paperback, workbook, and quick reference cards from your website. Thank you for your work making these educational videos, you have a gift as a teacher.

[@pingpong9656]

Hands down, the best explanation of a TXV...

[@jpp9876]

Ide like to better understand how low pressures can cause the refrigerant to not all evaporate in the a coil.

[@indoorcomfort6021]

As always, excellent content!!! Thanks from Indoor Comfort.

[@acservicetechchannel]

Much appreciated!

[@jimmysegovia2688]

good one Craig!!!! thank you for sharing!!!! man you really know your stuff.

[@acservicetechchannel]

Thanks for watching!

[@NMranchhand]

Gosh, you’re getting great at explaining complex HVAC concepts succinctly!

[@dc-wp8oc]

Is the TXV a generic device or product specific? Also, are the operating parameters (superheat for example) indicated on the TXV?

[@imrankazi2759]

Gmg sir saw ur vidio very knowledgeable.thanx for ur help.from.imran kazi India bombay .2nd engineer on merchant ship.best regards😊

[@marklennon1580]

Thank you again for providing excellent information. Ps; your books are also an excellent source of information.

[@acservicetechchannel]

Glad you like them!

[@edlauren9434]

I am a licensed hvac/refrigeration contractor. I live your videos! Thank you! N

[@Jammalchristian99]

Thought the TXV maintains sub cooling that’s why you check the sub cooling when you have TXV & superheat when you have a piston. I’m so confused

[@claude77573]

Nice video. From what I see, the TXV only responds to dry bulb temperature / sensible heat. I don't know why it was necessary to say whether the indoor environment was humid or dry, as the TXV appears to be responding only to dry bulb. Wouldn't higher humidity increase the load (latent load) on the evaporator? Or does that just increase runtime, and the TXV is unable to measure the effect of humidity?

[@Aruiz665]

I'm curious how did you get your external equalization line pressure reading?

[@imrankazi2759]

Gmg sir saw ur vidio very interesting and simple to understand.best regards Imran kazi 2nd engineer Maersk tanker From India .bombay. Take care😅

[@theaustinite5320]

I always appreciate you, but my gages are fluctuate from 7 to 10 subcooling. Where’s the problem.

[@stefano8809]

Obviously when there is a superheat like that the system is exchanging properly. Even better until 5 k

[@waynechen6797]

the best explanation of TXV

[@mansourghadhban236]

Good job thanks for you from Iraq technician mansour

[@resurgensix]

Starting classes soon and your videos are really helping me get ahead of the curve. Much respect from Miami Beach.

[@acservicetechchannel]

Great to hear!

[@scottclute-e3g]

Do most community colleges teach HVACR technician classes??

[@scottclute-e3g]

Honestly, a friend of mine had to fly out to training in Arizona, from N.Carolina. A costly mistake,as he never applied that knowledge.

[@CubanMofo]

What happens if you permanently take off the sensoing bulb of the

[@Obelisk57]

Is the bulb supposed to sense the line temperature or the temperature of the air blowing over it?

[@JeffreyMorgan-t7g]

Robinson Jennifer Clark Ronald Perez Donna

[@wasimedoo7994]

One question sir how do you know the in and the out of the txv

[@danferpit]

Gilllllllllllllll

[@abudhaheerabu980]

Your videos are very very clear ,Sir

[@nareshsindhwal314]

I have bit of confusion with external equalized expansion valve. Can anyone help. TEV above diagphram gets superheated referigerant due to bulb. Where tapping for external equalizing line is taken after the sensing bulb, so below the diaphram should be superheated refrigerant as well. How come saturated vapour pressure is considered below the diaphragm.

[@bryanswanson5007]

No, the bulb/powerhead is seperate refrigerant than whats in the system and below the diaphragm , its not superheated vapor its saturated so will respond to changes in temperature on the vapor line. Below the diaphragm is superheated vapor. Correct. You take the pressure of the vapor line to convert into a sat temp, That sat temp is the temp where the refrigerant in the evap starts to boil off. That pressure is about the same at the equalizer as it is in the evaporator. Once all the sat refrigerant in evap boils off and is 100% vapor is when it starts to increase in temperature while remaining the same pressure as it absorbs heat from the air, this rise in temp is called superheat , so lets say your vapor pressure converts to 42f sat temp, you know that refr is boiling at 42f in the evap, but your vapor line temp rite at the bulb is 52f. This means youve superheated that vapor 10f. So if this was R410a your vapor line and equalizer would be at 123psig but since the bulb has a saturated refrigerant inside and will change in pressure with a rise in temp its sensing, if its sensing 52f then the bulb pressure would be 148psig and would force the diaphragm downwards to open the valve, as your heat load gets less and less, the vapor line temp lowers causing the bulb pressure to also lower and in turn starts throttling back towards closed. I could go deeper into this but i hope that helps you out.

[@norinretrescu2474]

Hello, I watch your technical videos on KZbin and I think you can help me. I have a misunderstanding and maybe you can help me solve it. With the AC installation, the main purpose is to cool the room, with the "heat pump" installation, the main purpose is to heat the room. We know that both installations are based on the thermodynamic properties of the refrigerant. My question is: When the goal is to maximize the cooling of the room, the settings of the installation on the refrigerant side (expansion valve and others), is it different from the settings when we want to maximize the heating of the room? As an example: If the priority is to cool down, we adjust the expansion valve in one way, but when we want to maximize the heating of the room, we adjust the expansion valve slightly differently. Or what other adjustment differences are there (if any) on the same refrigerant installation if we want to speed up cooling or heating. Thank you very much

[@bryanswanson5007]

no, thats not what the txv is for. It only maintains superheat. Never adjust it. Theres no speeding up heating or cooling a space. The unit needs to be sized correctly for the given space to heat or cool properly. There are no adjustments to the txv to boost performance.

[@studyallthetimeallthetime8473]

ok I dont know why I keep getting lost with that, why was 36 degree F used? that couldn't have been the outside ambient.

[@studyallthetimeallthetime8473]

smh its the saturated temp, smh I must be tired.

[@tractor629]

What would cause the pressures in a residential split AC system to NOT equalize or take a long time to equalize after the compressor shuts off? It has a factory installed TXV in the evaporator coil. The problem I’m having is the compressor is not able to restart “even after like 30 minutes” due to the unequalized pressures. When I allow the pressures to equalize through my gauges it starts just fine... Any suggestions would be appreciated..

[@zanzibarjones896]

my ac unit whether on or off, has a metallic whistle faintly coming from the 2 exposed copper pipes outside. to me it sounds like a metallic version of when you just barely leave water trickle through your plumbing. i suspect that is refrigerant flowing through the system..even when the ac unit is off. weird. could this be the txv getting 'stuck' and allowing refrigerant to flow back into the condensor/compressor(?) that is outside? sometimes it makes the noise all day and night. sometimes only before and after running, and eventually stops til the next on/off cycle. it seems like lately it is mostly all the time. help?

[@luiselizalde6757]

Waooo, as always something new to learn, teacher you really know what we still need to learn, thanks for such as excellent videos, thanks teacher we really appreciate your videos, keep going with more videos.

[@acservicetechchannel]

Glad you enjoyed it

[@captainmigs1655]

So is subcool temperature decreased vapor refrigerant?

[@mannys9130]

Subcooling is the degrees of temperature that the high pressure liquid refrigerant is below its saturation temperature. Below saturation temperature, the refrigerant exists as a liquid. Above that temperature, it exists as a gas. For example, if you have R410a at 297psi which is 85*F, it has been subcooled by 10*F. It is 10*F below its normal saturation temperature of 95*F because it has traveled through a condensing coil which cooled it off a lot. That is subcooling, and it's what you talk about when you're talking about the liquid or high pressure line of the system. When you deal with the vapor/gas phase of refrigerant in the low pressure line, that is when you talk about superheat. Superheat is how many degrees of temperature the gaseous refrigerant is above its saturation temperature at its present pressure. A low pressure line pressure of 112psi which is 49*F would have 12*F of superheat because R410a's saturation temperature at 112psi is 37*F.

[@NMranchhand]

That was really one of your best lessons (among many) vis-a-vis the integrated use of graphics and spoken explanation. One suggestion though: you didn’t direct student attention to the changes in your brilliant graphic of the mix of dark blue/light blue. I only noticed late that they were changing to reflect the position of the liquid up and down the evaporator. I think many students might not have gotten the implication of controlling how much of the evaporator is exposed to the saturated state and thus the latent heat of evaporation, which, of course, is the only heat-absorbing state since the temperature cannot rise. I think this terrific aspect of your video deserves spoken attention with the latent heat eye-opener.

[@bryanswanson5007]

The saturated state is not the only state where heat exchange takes place. otherwise superheat and subcooling would not exist. Think about it. It is however where the most btus are exchanged when compared to sensible.

[@leiladaquil6587]

Sir,I would like to ask,when compressor is off,does the txv is closed or a little open?If it is closed due to spring action on superheat adjusting screw then when compressor is on the pressure will push the needle valve so the refrigerant can flow.the diapraghm automatically control the volume and pressure depending on pressure the sensing bulb transmitted or communicated to it.

[@ronilogarcia5610]

how to determine orifice size of expansion valve with respect to cooling capacity in tons of refrigeration using R-22?

[@leiladaquil6587]

it looks that the evaporsppptor fan is transferring heat into evaporator coil and it controls along with evaporator coil.That is why when cabin temperature changes,the heat transfer of blower into bulb is so changing.This differential exhibit changes in txv orifice valve gas inlet area.The changes in area of valve opening also changes the flow volume,

[@eddiemontelongo6665]

Do you remove the black plastic on the bulb y/n?

[@acservicetechchannel]

On the pinched off small tube used to fill the bulb? You can just leave that on. We are insulating around the whole bulb anyway, thanks.

[@joelrueda6548]

Thank you Craig I have learned a lot from your excellent videos!

[@acservicetechchannel]

Glad you like them!

[@jkbrown5496]

I was watching an Emerson TXV training video on the Jackson Systems channel. Someone asked the instructor about testing a TXV part. Apparently, you can cool them with ice water on the bulb/powerhead to close and use your body heat to warm them up to open. Don't apply a flame or anything. You have blow through the valve while cooling/warming to feel the valve close and reopen. I tried this with an automotive TXV and it works. If anyone wants to get a "feel" for the valve operation.

[@davem388]

@AC Service Tech LLC great videos. Do you work on commercial refrigeration systems as well?

[@deathntaxeset]

How do you take an external equalization tube pressure? Temp probe?

[@zainaabdin]

Science+ technology+ experience = success....salutes from an amateur.

[@AAminy]

thanks

[@seank1847]

G'Damn. I am nowhere near certified or have ever worked on AC, but considering I potentially have a tXV issue with my system this did an AMAZING job explaining it! Thank you!

[@manueldejesushuezofuentes6275]

Buenos días Su cátedras son magistrales y me gustaría que fueran en español para Saludos desde Guatemala...el país de la eterna primavera...

[@l.crossjr]

Awsome animations. Can you explain controlling Hotgas bypass and fan cycling.

[@argenismoreno7253]

This is a great video. Thanks a lot from Venezuela 🇻🇪

[@TurboDieselFury]

That was the best explanation of super-heat that I have ever heard. Thanks.

[@lugongguo8125]

I totally understood TXV after watching this video. Thanks a lot!

[@sharky5570]

Absolutely perfect explanation!!!!

[@acservicetechchannel]

Glad you think so!

[@SubramaniamLakshminarayanan]

Thank you for explaining superheat so nicely. Being new to HVAC, I was always in confusion over sc and sh. Now to look for and learn on subcooling.

[@mehdibourha180]

Thank you for the explanation 🙏👍

[@acservicetechchannel]

Glad it was helpful!

[@saintsgun588]

Why does superheat sometimes fluctuate if the txv is set to maintain a specific superheat?

[@wasimedoo1506]

Very nice information thanks

[@acservicetechchannel]

So nice of you

[@anthonyrodriguez243]

Best videos around thank you

[@acservicetechchannel]

Glad you like them!

[@kennethlobo4420]

Thanks great explanation.

[@acservicetechchannel]

Glad it was helpful!

[@annatrutv]

This Video So good thanks a lot ..

[@acservicetechchannel]

Glad you liked it!

[@jerryhobson2730]

Thanks for another great video.

[@acservicetechchannel]

Thanks for watching!

[@salemalmatouq2171]

How can i order the books?

[@acservicetechchannel]

www.acservicetech.com/store or amazon.com/shop/acservicetech and we also have our ebook at our website and on google play and the apple book store, thanks!

[@Pennconst101]

I understand this is a very loaded question. Are TXVs universal as far as sizing? Can a 3 ton r410a txv (of course connectors permitting )be installed on any 3 ton 410a system?

[@bryanswanson5007]

yes

[@balasubramaniyan1516]

Good explanation

[@acservicetechchannel]

Keep watching

[@biblebloopers946]

I'm confused If the sensing bulb is sitting on the suction line measuring a temperature of 52 degrees and the external equalizer line is just downstream of that taking the pressure, wouldn't the pressure inside the suction line be equivalent to the temperature of the sensing bulb?

[@mannys9130]

I believe it's because the refrigerant in the sensing bulb is saturated whereas the refrigerant in the suction line is not. 🤔 Not sure though.

[@acrepairnearme]

Great video!!!!! But why some TXV doesn't have external equilizer?

[@jkbrown5496]

Internal equalization is permissible when the design of the evaporator is such that there is no a significant pressure drop across the evaporator so the pressure coming out of the TXV is essentially the same as that after the evaporator. Seen more with, say ice cream machines, and not likely with AC evap coils which have a lot of small tubes.

[@biblebloopers946]

If the bulb is sensing the temperature of the evaporator outlet, and that is the temperature inside the suction line, then how is the pressure lower downstream from that bulb that's being taken from the external equalizer?

[@mannys9130]

The compressor is decreasing the pressure of the suction line and increasing the pressure of the liquid line.

[@scha0786]

Awesome stuff, love it

[@acservicetechchannel]

Much appreciated!

[@vshahid1001]

Is it ok to move the sensing bulb further, or insulate it so it only senses the suction line temp and is not affected by the rest of the air in the evap box? I find that it reduces the superheat while controlling it well and improves efficiency. By doing that, I effectively control the superheat in a TXV system when it is not set sufficiently low by the installer.

[@acservicetechchannel]

you could but just make sure that you have at least 8 degrees of superheat after moving and checking, thanks!

[@kennethlobo4420]

Great video.As the job of the TXV is to maintain constant superheat in the evaporator,why is it recommended that when U charge refrigerant on a system that has a TXV u use sub cooling method?

[@acservicetechchannel]

As you add refrigerant to the system, you won't see a change on the vapor side because the txv is controlling that. You will just see a change on the vapor side, thanks!

[@davildavil5183]

Greatrst explaination ever

[@shine-cg9uf]

Great 📹.!

[@BF1940]

GREAT!!!

[@mrgreen9086]

What do you call the line after the txv or metering device? I want to say suction line, but that's closer to the inlet of the compressor.

[@chrisdeanndavison3626]

I don't know that the line has a specific name, distributor maybe? Most of the time it goes into the distributor which divides the low-pressure liquid into different paths to travel through different sections on the evaporator.

[@mrgreen9086]

@@chrisdeanndavison3626 that sounds about right I've seen that more on the commercial side

[@mrgreen9086]

@Cee Bee I've heard them being called that as well lol

[@Dyllanes_Ingeniero]

Hi ... I am in México 🇲🇽. Do you have in *C ?. Farenheit no. Thanks

[@etlawson6939]

Have you tried Spaniard sites?

[@Dyllanes_Ingeniero]

@@etlawson6939 yes 👌👍

[@mannys9130]

Just use Google to convert the temps give in the video to *C.

[@Trust_Jesus]

Thanks!! I now know everything there is to know yo fix an ac!! Because of this video I can now go get my contractor license and start me an AC business this week!! Wish me luck...

[@MaMa-qh4dy]

Maybe you should watch a few more of Craig’s A/C videos? Hmmmm

[@Trust_Jesus]

@@MaMa-qh4dy naw! I been studying HVAC for 2 whole months so I'm more than ready!! I just bought me a company van and I got my first job tomorrow!! Its just an install so its gonna be a breeze....

[@MaMa-qh4dy]

@@Trust_Jesus Great! There ya go! We’re all praying for you AND your customer. Haha

[@Trust_Jesus]

@@MaMa-qh4dy ahhhh I'll be fine!! I've watch all of Craig's videos so that makes me an expert 😉

[@wasimedoo7994]

How do you know the in and the out of the TXV thanks