Some guys are confused

[heatingman]

Riddle me This? Can different temperatures be present within a vesel that is in an active closed loop. I've read on other posts that when gas and liquid are present at the same time, they must be at the same temp. Someone said it's physics.

Well let us move beyond refrigeration. In the ocean is all the water at the same temp, its in a space that has water vapor present within the same chamber. How about a steam boiler, is there not superheated steam present in the boiler the same time subcooled water is present?

Here is physics. Both sides of the condenser are at the same pressure(excluding pressure loss to turbulation) yet incoming is gas and leaving is liquid, but dont they share the same space? It's called heat tranfer. So in order to loose all the subcooling from the condenser, to the reciever, there needs to be heat transfer.

[rich pickering]

Laminar flow in large diameter pipes can result in different water temps from the middle of the pipe to the outside of the pipe.

As long as there is constant change, there may be different temps, gas or liquid.

Stop the change and you may achieve equilibrium.

[snewman24]

[QUOTE=heatingman;1507426]Riddle me This? Can different temperatures be present within a vesel that is in an active closed loop. I've read on other posts that when gas and liquid are present at the same time, they must be at the same temp. Someone said it's physics.

Yes, different temperatures can be present in a vessel in a closed loop. Otherwise, you couldn't have superheat and subcooling. But where the liquid and vapor are in saturation and changing state, the temperature at the interface between them must remain constant until the change is 100% complete. Further up or down the loop, where you have 100% vapor or 100% liquid, you can have a change in temperature. The pressure-temperature tables are only valid at saturation.

So,for example, in a refrigeration loop, as the superheated discharge gas exits from the compressor it de-superheats until it reaches the temperature that corresponds to the pressure present in the highside. Then it enters saturation and starts to condense. Once this begins, its temperature must remain constant (at the vapor-liquid interface) until liquid is formed. Then as this liquid moves down thru the condenser, it can change its temperature and subcool because it's away from the saturation interface and no longer has to follow the pressure-temperature chart because it's now a 100% liquid.

[hvacbear]

Riddle me This? Can different temperatures be present within a vesel that is in an active closed loop. I've read on other posts that when gas and liquid are present at the same time, they must be at the same temp. Someone said it's physics.

Someone is right:)

Let’s review some definitions as a reminder:
Superheat is: heat added to a vapor beyond its point of vaporization.
Subcooling is: heat removed from a liquid after it has condensed.
Saturation: liquid and vapor present together at the boiling point (212 deg. for water at atmospheric pressure.)

In a sealed system the pressure differences influence the boiling point.
Throw some water in a sealed tank and 212 is no longer the boiling point it is higher.As the pressure increases the temperature increases ( review the gas laws Gay-Lussack, Boyles and Dalton’s laws for more.) The saturated pressure is the gage pressure you read.

In the evaporator the pressure is reduced mechanically (at the metering device) and the liquid boils. Once the liquid is gone then the vapor still absorbs heat (superheat) and increases in temperature.
Try this read gage pressure and put your thermometer on the suction line close to the compressor. Take the gage pressure and convert it to temperature on your P/T chart (or gages) then subtract from it the temperature reading. You will see a temperature difference (superheat).

You can measure sub cooling similarly take your discharge gage reading then take the temperature close to the metering device. Take the gage reading (converted to temperature as before) and subtract your temperature reading from it and you have Subcooling.




Well let us move beyond refrigeration. In the ocean is all the water at the same temp, its in a space that has water vapor present within the same chamber. How about a steam boiler, is there not superheated steam present in the boiler the same time subcooled water is present?

The ocean is not a sealed system or at the same temp.
Yes there is Superheated steam, sub cooled water present in a boiler there is also water at it's saturation point.


Here is physics. Both sides of the condenser are at the same pressure(excluding pressure loss to turbulation) yet incoming is gas and leaving is liquid, but dont they share the same space? It's called heat tranfer. So in order to loose all the subcooling from the condenser, to the reciever, there needs to be heat transfer.

You are correct there needs to be heat transfer (not temperature transfer). The heat transfer is a latent heat transfer measured in BTU's not with a thermometer (sensible heat) .

So what is the difference between the two "heats"?
Glad you asked.

Latent heat is hardest to understand so let's tackle it first.
In order for a substance to change state from a liquid to a vapor latent heat ( not temperature) must be added (latent heat of vaporization) for water this is 970 BTU’s per lb. ( One BTU = the amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit).

So if you take a one pound of water at 212 degrees in a pan you need to add 970 BTU’s before it will start to boil. Once it starts to boil still at 212 then you have saturation or liquid and vapor present at the same time at the same temperature. During this process you will see the thermometer remain at 212 the entire time even though you are adding heat. it will remain at 212 unless you increse the pressure.

Sensible heat is heat added to a substance that changes its temperature without changing its state. This is heat we can measure with a thermometer.

Let's look at one more thing what is in the suction line? Low pressure low temperature gas right! It enters the compressor that changes it to?? Yes, a high temperature high pressure gas no change of state but there is heat transfer (sensible). The gas continues to cool and reaches saturation (gas and liquid present) once the gas has given off the Latent heat of condensation in turns into a liquid and only then can subcool.

A lot of people do not understand this even though it is at the heart of everything we do. I hope my explanation helps you understand this better.

[heatingman]

Thank you for the responces, but I Know already what you are telling me. I posted this as a responce to another thread about subcooling w/ recievers that some people believe that 0 subcooling is normal at reciever outlet during operation. Trying to cause a dialogue.

[skpkey9]

Subcooling can be 0* depending on conditions and everything will be normal with unit. Granted yes, and on that same unit unit under a different situation there wll be subcooling.
Look at how some of your pumps are rated 65* return gas and 0* subcooling.
My whole point was if you are on a system with a reciever just because you don't readany subcooling does not mean grab the refrigerant or you'll be back ... it's our jobs to determine these situations

[ej45]

Riddle me This? Can different temperatures be present within a vesel that is in an active closed loop. I've read on other posts that when gas and liquid are present at the same time, they must be at the same temp. Someone said it's physics.

Well let us move beyond refrigeration. In the ocean is all the water at the same temp, its in a space that has water vapor present within the same chamber. How about a steam boiler, is there not superheated steam present in the boiler the same time subcooled water is present?

Here is physics. Both sides of the condenser are at the same pressure(excluding pressure loss to turbulation) yet incoming is gas and leaving is liquid, but dont they share the same space? It's called heat tranfer. So in order to loose all the subcooling from the condenser, to the reciever, there needs to be heat transfer.I like these type of topics, but I have to disagree. The receiver is at saturation. It has to be, you cant ague the laws of thermodynamics. If liquid and gas is in a vessel, its saturation. The liquid line leaving could cool to subcooling temps. As the subcooled lquid enters the receiver it experiences a pressure change not a temperature change. The liquid leaving the receiver and is compressed and could with pressure change again be subcooled with no temp change.

[ej45]

A condenser coil is a poor example of this because of the inherent pressure drop through the system. At the superheated discharge pressure of 250 psi the refrigerant passing through the coil experiences pressure drop and heat loss to 225 psi. That is why we dont calculate subcooling with compressor discharge pressure. Because of pressure drop through coil. Or we would have 40 and 50 degrees of subcooling. I sometimes think we forget a pressure change and only think in temperature.

[jayguy]

i think that some are arguing a technical point versus practical point.

from a technical standpoint, in a reciever where vapor and liquid are present, there isn't any subcooling...it is physics.

from a practical standpoint, imagine a large vertical receiver that is very low on liquid...no subcooling leaving the reciever.

now imagine that the vertical reciever is almost full of liquid...there is going to be some subcooling leaving the reciever. but from a real standpoint though, you really aren't going to have any real, useful subcooling. as the liquid line creates greater pressure drop than temperature drop, any useful subcooling that you had in the "full" receiver will be eaten up.

for you engineer/technical types (like me:) ), google "triple point"

[heatingman]

I like these type of topics, but I have to disagree. The receiver is at saturation. It has to be, you cant ague the laws of thermodynamics. If liquid and gas is in a vessel, its saturation. The liquid line leaving could cool to subcooling temps. As the subcooled lquid enters the receiver it experiences a pressure change not a temperature change. The liquid leaving the receiver and is compressed and could with pressure change again be subcooled with no temp change.

What continues pressure drop once the chamber is at the incomming pressure? It's not like a expansion tank, because the top of the chamber is refrigerant, not air. Heres another one for ya, and I have no clue what the answer is, What keeps the liquid refrigerant from expanding to fill the entire space, like co2 does into soda, or is that what accounts for the pressure change? A fluid expansion w/o flashing? Just a very abstract thought once I started on a boiler wavelength.

[hvacbear]

What continues pressure drop once the chamber is at the incomming pressure? It's not like a expansion tank, because the top of the chamber is refrigerant, not air. Heres another one for ya, and I have no clue what the answer is, What keeps the liquid refrigerant from expanding to fill the entire space, like co2 does into soda, or is that what accounts for the pressure change? A fluid expansion w/o flashing? Just a very abstract thought once I started on a boiler wavelength.

Why does it have to be at saturation? If the pressure increses (like when liquid fills the reciever compressing the vapor) and raises the boiling point of the liquid you will have some vapor that was previously evaported and liquid not boiling and definately not at saturation.

[bertoh]

Why does it have to be at saturation? If the pressure increses (like when liquid fills the reciever compressing the vapor) and raises the boiling point of the liquid you will have some vapor that was previously evaported and liquid not boiling and definately not at saturation.

when the liq enters the reciever it will not compress the vapor on top of the receiver , freon will condense to a vapor. i think the expansion tank scenario threw you, air is non condensable and will compress ( except at super hi press and super low temp). that freon will condense to a liquid.
no point having a receiver if it is going to rob that subcooling made in the cond to bring it back to 0 SC, then pump it thru a liq line, drop in press, to reach a TXV as a saturated mixture , just to throw a curve to the TXV.
if their wasnt a sight glass on receivers no one would beconfused about this SATURATION condition of gas/ liquid mixture.

[heatingman]

when the liq enters the reciever it will not compress the vapor on top of the receiver , freon will condense to a vapor. i think the expansion tank scenario threw you, air is non condensable and will compress ( except at super hi press and super low temp). that freon will condense to a liquid.
no point having a receiver if it is going to rob that subcooling made in the cond to bring it back to 0 SC, then pump it thru a liq line, drop in press, to reach a TXV as a saturated mixture , just to throw a curve to the TXV.
if their wasnt a sight glass on receivers no one would beconfused about this SATURATION condition of gas/ liquid mixture.

Im noy thinking compress so much as absorb, if yo heat water that is under pressure and there is air in the circuit, the air can be absorbed into solution not alot of air, but some, like co2 into soda, and in a boiler it is true and that is proven.

[hvacbear]

when the liq enters the reciever it will not compress the vapor on top of the receiver , freon will condense to a vapor. i think the expansion tank scenario threw you, air is non condensable and will compress ( except at super hi press and super low temp). that freon will condense to a liquid.
no point having a receiver if it is going to rob that subcooling made in the cond to bring it back to 0 SC, then pump it thru a liq line, drop in press, to reach a TXV as a saturated mixture , just to throw a curve to the TXV.
if their wasnt a sight glass on receivers no one would beconfused about this SATURATION condition of gas/ liquid mixture.


So let me get this straight:
You are saying that when the liquid refrigerant goes into the reciever which has its outlet on the bottom that as it fills the vapor will condense and not compress? Also that the liquid in the liquid line would saturate before the TXV for what reason?

[bertoh]

what i am saying is first the vapor on the top of the receiver is at or near its point of condensation. picture the PH diagram, an upside down U leaning to the right, and picture your theoretical compression diagram in that.its a rectangular box except for the angular right side that is the compression.the condenser is the top line from right to left. where it crosses the U to the left of U is subcooling.between the two sides of upside down U is saturation(both liquid and vapor present, with a varying amount of enthalpy.low enthalpy to the left and higher enthalpy to the right.what i am saying is the (vapor) on top of RC is just at the left edge of inside the U.it takes nothing to change it from (vapor) to liquid.as SC liquid comes down from cond that alone will absorb some amount of low enthalpy vapor as it fills RC. it will not compress that (vapor).
secondly,i am not saying the liquid in the liq line will saturate.
i am saying the opinion of alot in this post is (liq and vapor present in RC means we are at saturation ie no SC exists in liq leaving RC)
i am saying opposite.i said who in their right mind would put in a RC if all it did was bring that nice SC liq leaving cond back to saturation ie no subcooling.
then by the time it makes it to TXV it has dropped in press, but remained at same temp giving you flash gas entering TXV.

[ej45]

I dont see very many receiver systems, but the systems I have been around that were for refrigerant storage never had subcooling. Just for kicks I dug out an old refrigeration piping book and read about sizing receivers.

This information stated that when installing a zero subcooling refrigeration system to size the receiver for 80% full. If subcooling is needed to size system and charge to fill receiver, ie..all liquid

This is an interesting topic and have been thinking about jobs in the past.. I worked on a Burley ice rink chiller that used large receivers with sight glasses and piped in LPA pumps between the receivers and txv valves to gain subcooling.

I still think any subcooling achieved at the condenser is lost at the receiver due to pressure loss. (not temp) That compressed liquid hitting a tank is going to loss pressure.

We dont see recievers on typical modern air conditioning systems for two reasons, refrigerant charge and efficiency. lack of subcooling??

[ej45]

This is a quote from a highly respected forum member that is retired from York. (dont hold that against him) RichardL quotes....Here we go again.....
A Receiver installed on ANY system that has built into it's design, ANY degree of subcooling is absolutely and totally USELESS!!!
It matters not that you have 5°f subcooling or 25°f subcooling, "there ain't gonna' be NO vapor" (Non-Liquid) Anywhere in said Liquid line. Unless of course we change elevation, or Add heat to the liquid line somehow to eliminate the sub-cooling...
There is NO logical reason today to EVER have a receiver installed on a unit that has designed into it a subcooler!!
Store Extra Refrigerant for pumpdown???
What a load of horse crap.....
The Damn receiver was FULL of refrigerant the moment sub-cooling occurred...
Some of the finer computer room units that use the "Headmaster Control Valve" uses a receiver but it holds a refrigerant charge large enough to totally flood the condenser to maintain head pressure..This unit cares not about subcooling at all..
Just stop and think for a minute....
You have a P/T chart..
Pick any pressure-any refrigerant..
Now sub-cool it 20°f...and tell us all how in the hell you can have a Partially filled receiver...
The receiver on such a system is nothing more than a large fitting stuck between the Condenser and Evaporator...
Any such reciever on a well designed condenser today does NOTHING but add to the required refrigerant charge...
If that is the purpose, then just install a larger liquid line...
The results will be the same in the end...

[heatingman]

Thank you ej45, thats pretty much what i thought, but in better words.

[skpkey9]

You guys are so confused.....
This discussion has been around for a very long time ....
air conditioning and refrigeration are totally two different animals try using those theories in refrigeation and guess what , you'll be back
Try this discussion in refrigeration forum you know what you will hear
NOT this again Just like what was said by RichardL.
Now I truly understand the frustration of this topic.
So, you guys do it your way and go back as many times as it takes to get the job right ....And we will move on to our next jobs...

And example for ya real job. Commercial Tech went out to Walk in Cooler then I hear is him talking about where the subcooling level was I tried to explain to him unless he s diagnosing a TEV on a reciever system subcooling is irrelavent . Next thing I know I'm going back out there to correct what he did . ie.. adjusted TEV and charge
box now operating properly ...
So forgive me if my views differ from yours

[skpkey9]

On example that was a commercial ac tech..

[heatingman]

On example that was a commercial ac tech..

I understand that the subcooling is moot point, since almost all systems w/ recievers have subcoolers also, but what I want to know is that if what you are telling me is true about subcooling becoming zero once a receiver is used, then what happens in the receiver to cause this. Ie heat gain, or pressure drop, or what is it? I've looked in every book I've got from Trane manuals to ARI books to RSES sam manual, and nobody realy gets into it. I do refrigeration too, just not as much as I used to. I extemely rarely got call backs. I've allways been a stickler for the basics, and the theory behind the basics. Because no mater how complicated the system is, if you have a solid foundation of the basics, you can work through anything. So please don't take offence when I don't take what you're telling me at face value, and move on. I need a concrete reason, that can be verified in a book. So if you have such a book, tell me what it is and I'll buy it.

[jayguy]

i have never seen a receiver system where the receiver was AFTER the condensor...well, i saw one. it shelled compressors every single year. i installed bypass valves around it so that it could be used as a true refrigerant storage tank during service work.

the only receiver systems that i have seen (without head pressure controls added to the system) is where the condensed refrigerant enters the receiver at the top, then the liquid is pulled out of the bottom and then re-enters the condensor subcooling loop. the receiver just acts as a liquid/gas separator.

i do not understand the reasoning behind adding a receiver AFTER the condensor. if you did add a receiver after the condensor and you did not have any head pressure controls, as you charge from an empty system, the liquid could not start to back up until it hit the TXV, then it would back up to the receiver. as you continued to charge the system (trying to get subcooling) the receiver would fill up to the top and then start to subcool INSIDE the condensor. you are not going to get any real subcooling outside of the condensor in a practical sense. (sure, there are liquid pump systems, running through colder environments, etc. but if we were to properly engineer a system anyway, we would not be putting the receiver after the condensor). so there isn't any pressure drop or temperature increase or subcooling "lost" at all. there just isn't any to begin with in a system as described above.

[jayguy]

air conditioning and refrigeration are totally two different animals try using those theories in refrigeation and guess what , you'll be back


CO2 and ammonia refrigeration systems not withstanding...

i disagree. i have heard this arguement many times before as well. refrigerant is refrigerant...it doesn't act any differently at 0F evap temps or 40F evap temps. it still has the 3 "S's" superheat, saturation and subcooling. sure, refrigeration is way more complicated, lots of different controls, different oils due to lower temps, different refrigerants which show greater energy effeciency, etc. but proper design and maintainance to ensure oil return, subcooling (and quantity, if designed) at the TXV, superheat at the compressor, etc. are required by all refrigeration systems (low temp and ac).

you can apply ALL of the refrigeration controls and ideas to commercial air conditioning with great success...albeit overkill. you can also apply all of the refrigerant ideas in commercial air conditioning to refrigeration and get ok results...not great results. refrigeration requires a greater, in depth, knowledge of how refrigerant works in order to deal with special circumstances such as defrosting, winter time operation, very long compressor run times, large rack systems and effeciency. but the principals are the same.

most customers that use refrigeration are by nature in a low profit industry (ie, food) and pratcially live on the energy effeciency savings that a good, properly running refrigeration system deliver.

but to say that they are 2 different beasts (like working on a VCR and mowing grass are 2 different beasts) is a bit overstated. the principals are the same. a properly trained service technician should be able to service either refrigeration or ac system without much trouble. the difference is in experience, not learning an entirely different industry.

[skpkey9]

Jay guy first how did those transformers work out for ya. Did you ever figure out the problem?
ok now on to this ....
You don't work on refrigeration or you would have said "Yes, the reciever does come after the condenser coil " If it did not . How could you store liquid in it ... Compressor -> condenser coil -> reciever -> out ... to be simple.. and if you wanted headmaster valve go ahead and throw it in between compressor and condenser coil. All a reciever is... A storage vessel to ensure that you have a full column of liquid available to the TEV and for pump down if system needs it and yes, the two fields are different or you would have a lot more combo techs out there.

Not trying to stir the pot , just help alittle:D

[heatingman]

Hey Jay, I've never engeneered a system that involved the use of a reciever, but I've worked on alot of systems that do, primarily Liebert computer cooling equiptment. All of those have factory installed receivers, and there piped between the condensor and the txv, but they also use head pressure controls. All the books that I've got have the receiver between the condensor and the txv, or 3/4 of the way through the condensor, and then piped back to the rest of the condensor to complete the job. I've never seen one before the condensor, but it would make sence to put it there if the only purpose was pumpdown capacity.

[skpkey9]

To store hot gas... how obsurd! I'm done with this thread . But jay let me know how it turned out (transformers)

[heatingman]

Think about it skpkey, close of the LL what happens? It backs up into the condensor and builds pressure, that pressure would need somewhere to go, why not to a receiver before the condensor, like I said, I've never seen this done.

[skpkey9]

Think about this ... how hot a recovery tank gets, thats just in a recovery situation with liquid entering. now think about capacity of that reciever with hot gas entering. The reciever might as well not exist at this point.

[heatingman]

Think about this ... how hot a recovery tank gets, thats just in a recovery situation with liquid entering. now think about capacity of that reciever with hot gas entering. The reciever might as well not exist at this point.

Your right holding tank setup like that would probably cause violent expansion of liquid when it tried to backfill, and therefore would be no good.

But I still want an answer for what happens internally to cause a net loss of subcooling. Pressure drop, or heat gain?

[skpkey9]

Subcooling is telling you how much refrigerant is stacking in the condenser coil and the change of state of the refrigerant. the same way superheat tells you whats happening in the evap coil. Once you introduce a receiver to the circuit you no longer stack refrigerant in the condenser you are now storing it in the receiver waiting for its trip to the TEV. That's why on some systems you will get 0* subcooling.

[skpkey9]

Also think about once liquid leaves that condenser coil there is no air drawn across it like in the condenser coil it is now liquid stored in a tank for lack of a better term.

That is why in colder climates they will install heaters on the receivers on certain applications to keep the pressure up.

[heatingman]

So, there will be no subcooling on the way to the reciever?

I swear I've had subcooling in the teens on Lieberts, but it's been a while.

Your point about no liquid stacking makes a good deal of sense.

[skpkey9]

Depending on application and condition it is possible to get subcooling
Just keep in mind on a system that has a receiver you DO NOT charge by subcooling.
It then only becomes a diagnostic tool as I stated in the previous thread.

[hvacbear]

what i am saying is first the vapor on the top of the receiver is at or near its point of condensation. picture the PH diagram, an upside down U leaning to the right, and picture your theoretical compression diagram in that.its a rectangular box except for the angular right side that is the compression.the condenser is the top line from right to left. where it crosses the U to the left of U is subcooling.between the two sides of upside down U is saturation(both liquid and vapor present, with a varying amount of enthalpy.low enthalpy to the left and higher enthalpy to the right.what i am saying is the (vapor) on top of RC is just at the left edge of inside the U.it takes nothing to change it from (vapor) to liquid.as SC liquid comes down from cond that alone will absorb some amount of low enthalpy vapor as it fills RC. it will not compress that (vapor).
secondly,i am not saying the liquid in the liq line will saturate.
i am saying the opinion of alot in this post is (liq and vapor present in RC means we are at saturation ie no SC exists in liq leaving RC)
i am saying opposite.i said who in their right mind would put in a RC if all it did was bring that nice SC liq leaving cond back to saturation ie no subcooling.
then by the time it makes it to TXV it has dropped in press, but remained at same temp giving you flash gas entering TXV.

Take a look at this: http://hvacreducation.net/ExampleLessons/repository/handouts/mod1-141_handout6.pdf

If you have saturation in your reciever then the line on the right would go in and out of the saturation curve.

[skpkey9]

Will talk more tomorrow, getting late
You guys are so frustrating:D

[jayguy]

To store hot gas... how obsurd! I'm done with this thread . But jay let me know how it turned out (transformers)

blew a couple more fuses...i still do not know why! everything checks out. it is real simple wiring. installed 2 more fuses...still running today. they have been doing the electrical system upgrade for about a year. upgrading from 200 VAC to 460 in a hospital, so everything has to go real slow. still trying to find out how to do a better job of field troubleshooting "weak" transformers other than megging them. all of the links that were sent had good info on them...just not much for field work that "proves" without a shadow of a doubt. thanks for asking!

[jayguy]

i do not remember saying anything about discharge gas going into the receiver and then into the condensor. i can't see that anywhere in this thread...maybe i can't see.

like i said before, i have seen many installations where the receiver is after the condensor...but they have always had head pressure controls of some kind piped to them. i have engineered many refrigeration systems...i do not get to do that much anymore, regrettably. i really like refrigeration work. it gets to be a lot more exciting at times and really stretches your mind...makes ya think hard!

like i also said before, i do not think that the fields are different. refrigeration is more complex for more complex reasons.

stir, stir, stir:D

[heatingman]

Jay look at post 22

[bertoh]

http://hvac-talk.com/vbb/showthread.php?t=75685&highlight=refrigerant+receiver
did a search on this subject, check out the link, it should put this to bed for a while. hats off to andy and john for explaining this in way more convincing terms .but i have to disagree with skpkey SC is the only way to charge this type of system, interpeting what that number SC should be based on ambient and load on evap is the tricky bit
superheat on TXV system is primarily a test of TXV, but also load on evap, airflow etc.you could have a proper sized TXV on normal operation but hunting wildly on system with poor airflow. but all things being right SH is just diagnosis of the valve and diaphragm

[skpkey9]

You CAN disagree thats the wonderful thing about this.
But, keep in mind for everything you find to support your thoughts there will always be something else to support the opposite.
My thoughts are based only on real world experiences and what I've come across over the years, although you don't know me or what I've done, the last company I was at in one year worked on roughly 1500 pieces of equipment with only 4 call backs ( commercial ac , refrigeration and some residential ac ). So keep doing what works for you and I'll keep doing what works for me.:p :D

[ej45]

1500 units in a year at 2080 hours of regular hours, your fast too...lol

I still argue that people are saying that in a dynamic system that the laws of thermodynamics do not apply is pure BS. If this is true then all the superheat and subcooling measurements are incorrect? right? Because its a dynamic system so a suction line that appears to have 10* superheat could have liquid in the gas called FLOOD BACK?. An a system that has 20* subcooling could not be a solid column of refrigerant then because of this new principle of Dynamic Thermodynamics?

If I have a pot of water boiling on the stove a 212* saturation and dump a cup of 192* (20* subcool) water in the pot. Does this pot stop boiling and subcool or the two temps stratify because of moving dynamic motion and have boiling water on top and subcooled water on the bottom? ( does heat raising to the top still apply to a dynamic system?)

stir...stir...stirring

[skpkey9]

Subcooling is showing you how much liquid is stacking in the condenser
If you have a receiver in line now liquid will stack in the receiver.
Receiver serves two purposes refrigerant storage during pumpdown, and to maintain solid column of liquid to TEV...
EJ45~ sorry But, I won't give in.:p :D

[heatingman]

Skpkey, I have to admit I'm a convert, as it applies to refrigerant, what you say now makes perfect sense.

In a closed loop system, w/o a reciever, the refrigerant is pushed through the condenser until it reaches the metering devise. The metering device causes the pressure difference between the high side and the low side, but it also causes the refigerant to slow down, which inturn alows more heat to be removed in the condenser which allows the refrigerant to lose more heat, thus causing subcooling.

In a system w/a reciever,the refrigerant is brought to saturation in the condenser, but the refrigerant does not slow down in the condenser, it slows down in the receiver. During low load or low ambient conditions, there will be more liquid in the receiver, and if it fills to the top, this is how the subcooling will occur.

In either setup you will need subcooling at the evaporator, and in a receiver system, this is accomplished w/ subcoolers.

[bertoh]

skpkey, i will keep doing it my way. just finished checks on commercial cold storage systems and was measuring from 2 - 8 deg subcooling leaving receivers, with anywhere from 10- 75 % full receivers.
4 callbacks in a year?very good!! is every call a new problem (not warranty),thats good management

[skpkey9]

Bertoh~ Well keep in mind a resturant has many pieces of equipment, and a lot of buildings over here have multiple ac units. And we covered the state of Florida. My duties also included going back and repairing what other techs were unable to repair. The problem solver if you will.
Managment was good but owner is an idiot. So Ihad to move on to bigger and better things.
Keep in mind depending on conditions you will have subcooling as I stated earlier. It is up to us the service techs to interpret the readings and make these systems operate properly. There will be variables

[bertoh]

well if i knew you were tech support of some sort or top tech, i would have kept my opinions to myself.those restaraunt systems are complex, havent seen any in 15 years.as for the multiple a/c units, as you stated in post 19 they are two different animals , how do you switch hats so well?keep up the good work, and i am sure all those techs that you are bailing out are glad you are there to carry them

[skpkey9]

No choice but to become a combo tech.
Grew up doing this.