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#1 hazelm

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Posted 13 April 2018 - 10:06 AM

I have tried the internet but all I come up with just keeps talking about Freon and automobiles.    Freon is fading from the market. and my question concerns coolants in air conditioners, not cars.  Can any and all air conditioner coolants freeze? Thank you.



#2 exchemist

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Posted 13 April 2018 - 02:31 PM

I have tried the internet but all I come up with just keeps talking about Freon and automobiles.    Freon is fading from the market. and my question concerns coolants in air conditioners, not cars.  Can any and all air conditioner coolants freeze? Thank you.

All the refrigerants I know of will freeze at some temperature*.

 

However their freezing point is of necessity below the lowest temperature they can achieve in a refrigerator cycle, since the cycle relies on exploiting the Latent Heat of Vaporisation, i.e. the heat absorbed and released in the course of the phase change from liquid to gas and back again. 

 

* In fact, the only substance I can think that does not freeze at ANY temperature is helium, due to some rather neat  (or "cool", if you prefer, heh heh) quantum-mechanical effects. 


Edited by exchemist, 13 April 2018 - 02:33 PM.


#3 hazelm

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Posted 13 April 2018 - 02:49 PM

All the refrigerants I know of will freeze at some temperature*.

 

However their freezing point is of necessity below the lowest temperature they can achieve in a refrigerator cycle, since the cycle relies on exploiting the Latent Heat of Vaporisation, i.e. the heat absorbed and released in the course of the phase change from liquid to gas and back again. 

 

* In fact, the only substance I can think that does not freeze at ANY temperature is helium, due to some rather neat  (or "cool", if you prefer, heh heh) quantum-mechanical effects. 

Thank you.  That is what I wanted to know.  When a maintenance man told me my AC was "frozen",  I thought it the funniest thing ever.  Then I decided I was misinterpreting his meaning by "frozen".  But I found out today that the "freon" does indeed freeze into solid cakes of ice.  Since I know we are not using freon, I asked my question.   I'll tell you - maintenance men are walking encyclopedias. :-)



#4 JMJones0424

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Posted 18 April 2018 - 10:50 PM

It's possible that you are misinterpreting the meaning of "frozen" in this context.  For example, if the starting capacitor is blown, then you could describe your AC as frozen.  This has nothing to do with the triple point of the refrigeration material in your AC.  In this case, "frozen" is simply a descriptive term about your AC because it doesn't work.  Mechanical systems can be described as frozen regardless of their temperature if they fail to move.

 

It is highly unlikely that your coolant is freezing solid.  I don't know what your problem is, but in this case, your AC being "frozen" is not likely to be a statement about the condition of the coolant but instead, it is likely a statement about the functionality of the mechanism that moves the coolant.


Edited by JMJones0424, 18 April 2018 - 10:50 PM.


#5 hazelm

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Posted 19 April 2018 - 06:05 AM

It's possible that you are misinterpreting the meaning of "frozen" in this context.  For example, if the starting capacitor is blown, then you could describe your AC as frozen.  This has nothing to do with the triple point of the refrigeration material in your AC.  In this case, "frozen" is simply a descriptive term about your AC because it doesn't work.  Mechanical systems can be described as frozen regardless of their temperature if they fail to move.

 

It is highly unlikely that your coolant is freezing solid.  I don't know what your problem is, but in this case, your AC being "frozen" is not likely to be a statement about the condition of the coolant but instead, it is likely a statement about the functionality of the mechanism that moves the coolant.

Actually, it does.  I've had two maintenance men confirm it.  I forget "why" it freezes but it does  -  to a solid cake of ice.  When that happens the incoming air cannot get past it and then it's no AC.  You recognize when that is the problem if no air is coming out of your vents.  Remedy:  Turn off the AC.  Set the fan to blow constantly.  In about an hour or hour and half, the ice will be melted and air will start coming out of the vents.  Set everything back to normal  and - as a young friend likes to say "Bob's your uncle".

 

Confession:  I am not being intelligent there.  I just had an education from our very talented maintenance men while they were installing a new furnace and AC in my apartment.  One of them said he can hear the ice breaking up in his.  Guess he has better hearing than I.  I also found the same facts when I search "Can AC coolant freeze.

 

Fun learning new stuff?  :-)


Edited by hazelm, 19 April 2018 - 06:07 AM.


#6 exchemist

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Posted 19 April 2018 - 06:35 AM

Actually, it does.  I've had two maintenance men confirm it.  I forget "why" it freezes but it does  -  to a solid cake of ice.  When that happens the incoming air cannot get past it and then it's no AC.  You recognize when that is the problem if no air is coming out of your vents.  Remedy:  Turn off the AC.  Set the fan to blow constantly.  In about an hour or hour and half, the ice will be melted and air will start coming out of the vents.  Set everything back to normal  and - as a young friend likes to say "Bob's your uncle".

 

Confession:  I am not being intelligent there.  I just had an education from our very talented maintenance men while they were installing a new furnace and AC in my apartment.  One of them said he can hear the ice breaking up in his.  Guess he has better hearing than I.  I also found the same facts when I search "Can AC coolant freeze.

 

Fun learning new stuff?  :-)

Aha, now we get the picture. What has happened is not that the refrigerant has frozen in the circuit, but that water ice has formed on the cooler, due to the combination of the heat exchanger in the cooler being <0C and the humidity of the air that is drawn through it.

 

I should have thought that in a well-designed and well-operating AC unit, a cooler temperature <0C would be avoided. Normally, liquid water condenses out of the air on the cooler, and this is drained off. (We are all familiar with the drips from a window-mounted unit overhead!) If it freezes, then it can't drain away and it will build up and eventually prevent the cooler from working properly.  


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#7 hazelm

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Posted 19 April 2018 - 06:52 AM

Aha, now we get the picture. What has happened is not that the refrigerant has frozen in the circuit, but that water ice has formed on the cooler, due to the combination of the heat exchanger in the cooler being <0C and the humidity of the air that is drawn through it.

 

I should have thought that in a well-designed and well-operating AC unit, a cooler temperature <0C would be avoided. Normally, liquid water condenses out of the air on the cooler, and this is drained off. (We are all familiar with the drips from a window-mounted unit overhead!) If it freezes, then it can't drain away and it will build up and eventually prevent the cooler from working properly.  

Makes sense to me.  They did say, though, that the freezing was in the circulation pipe. That looks difficult to me because that pipe wasn't very large around.  (The new one is larger around.)  Plus, it is - or was - just passing in front of the furnace.  I'm not sure I'm making sense there.  Think hanging your arm out a window.  The pipe comes from the box with the coils (atop the furnace) and down past the furnace and hot water heater. 

 

All right. Please tell me where what you are calling the "cooler" is.  It is no doubt one of the sections that has another name on what I copied.  Could it be the coils that sit atop the furnace?  And would that be part of that circulation pipe?

 

I shall return.  Thanks. 



#8 exchemist

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Posted 19 April 2018 - 07:43 AM

Makes sense to me.  They did say, though, that the freezing was in the circulation pipe. That looks difficult to me because that pipe wasn't very large around.  (The new one is larger around.)  Plus, it is - or was - just passing in front of the furnace.  I'm not sure I'm making sense there.  Think hanging your arm out a window.  The pipe comes from the box with the coils (atop the furnace) and down past the furnace and hot water heater. 

 

All right. Please tell me where what you are calling the "cooler" is.  It is no doubt one of the sections that has another name on what I copied.  Could it be the coils that sit atop the furnace?  And would that be part of that circulation pipe?

 

I shall return.  Thanks. 

In a refrigeration circuit there is a high pressure section, extending from the discharge side of the pump to the expansion valve, and a low pressure section from the expansion valve to the intake of the pump. The refrigerant is liquid in the high pressure section but turns to vapour as it expands through the valve nozzle, which causes it to cool, due to absorbing Latent Heat of Vaporisation. The cooling heat exchanger is positioned just after the expansion valve, so the cold vapour passing through it it can absorb heat from whatever it is that is to be cooled. This is the bit that can get ice on it if it gets too cold.

 

After this the vapour, which is by now less cool, due to having absorbed heat, goes into the pump which compressed it, thereby liquifying it again, whereupon the latent heat of vaporisation is released, making the liquid discharged from the pump quite hot. This flows into a radiator which rejects the heat into some suitable heat sink.  The liquid refrigerant is now back to close to ambient temperature and ready to go once more through the expansion valve, repeating the cycle.

 

I can't work out from your description which bit is where, but in an AC system the radiator will be outside the building so that it can eject waste heat into the external air, and the cooler will be close to where the air is drawn in from the house to be cooled. 

 

Maybe someone more familiar with these installations can comment further. (I had one when I lived in Houston but that was nearly 20 years ago. Here in London we only bother with AC in the car. Houses don't need it.) 


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#9 hazelm

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Posted 19 April 2018 - 11:39 AM

In a refrigeration circuit there is a high pressure section, extending from the discharge side of the pump to the expansion valve, and a low pressure section from the expansion valve to the intake of the pump. The refrigerant is liquid in the high pressure section but turns to vapour as it expands through the valve nozzle, which causes it to cool, due to absorbing Latent Heat of Vaporisation. The cooling heat exchanger is positioned just after the expansion valve, so the cold vapour passing through it it can absorb heat from whatever it is that is to be cooled. This is the bit that can get ice on it if it gets too cold.

 

After this the vapour, which is by now less cool, due to having absorbed heat, goes into the pump which compressed it, thereby liquifying it again, whereupon the latent heat of vaporisation is released, making the liquid discharged from the pump quite hot. This flows into a radiator which rejects the heat into some suitable heat sink.  The liquid refrigerant is now back to close to ambient temperature and ready to go once more through the expansion valve, repeating the cycle.

 

I can't work out from your description which bit is where, but in an AC system the radiator will be outside the building so that it can eject waste heat into the external air, and the cooler will be close to where the air is drawn in from the house to be cooled. 

 

Maybe someone more familiar with these installations can comment further. (I had one when I lived in Houston but that was nearly 20 years ago. Here in London we only bother with AC in the car. Houses don't need it.) 

Does this help?  I copied it from the article that I read.  It is a perfect picture of what we have in this building.

 

To get a better sense of how your air is cooled, it helps to know a little bit about the parts that make up the air conditioning system. A typical central air conditioning system is a two-part or split system that includes:
 

  • The outdoor unit contains the condenser coil, compressor, electrical components and a fan.
  • The evaporator coil, which is usually installed on top of the gas furnace inside the home.
  • A series of pipes, or refrigeration lines, connecting the inside and outside equipment.
  • Refrigerant, the substance in the refrigeration lines that circulates through the indoor and outdoor unit.
  • Ducts that serve as air tunnels to the various spaces inside your home.

 

One thing it does not say but the maintenance man said is the fan inside the furnace blows the air to our vents to  cool in summer or to warm in winter.



#10 hazelm

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Posted 19 April 2018 - 11:46 AM

In a refrigeration circuit there is a high pressure section, extending from the discharge side of the pump to the expansion valve, and a low pressure section from the expansion valve to the intake of the pump. The refrigerant is liquid in the high pressure section but turns to vapour as it expands through the valve nozzle, which causes it to cool, due to absorbing Latent Heat of Vaporisation. The cooling heat exchanger is positioned just after the expansion valve, so the cold vapour passing through it it can absorb heat from whatever it is that is to be cooled. This is the bit that can get ice on it if it gets too cold.

 

After this the vapour, which is by now less cool, due to having absorbed heat, goes into the pump which compressed it, thereby liquifying it again, whereupon the latent heat of vaporisation is released, making the liquid discharged from the pump quite hot. This flows into a radiator which rejects the heat into some suitable heat sink.  The liquid refrigerant is now back to close to ambient temperature and ready to go once more through the expansion valve, repeating the cycle.

 

I can't work out from your description which bit is where, but in an AC system the radiator will be outside the building so that it can eject waste heat into the external air, and the cooler will be close to where the air is drawn in from the house to be cooled. 

 

Maybe someone more familiar with these installations can comment further. (I had one when I lived in Houston but that was nearly 20 years ago. Here in London we only bother with AC in the car. Houses don't need it.) 

I wonder if you are talking about a heat pump.  It sounds like a heat pump and you could have had that in Houston.  They do not work well farther north.  Maybe someone here lives further south and will recognize if what you describe is a heat pump.  They are good in Texas and east and west from there.  In Kansas, where the apartment complex owner had put them in, we had a hard time keeping warm.



#11 exchemist

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Posted 19 April 2018 - 01:24 PM

I wonder if you are talking about a heat pump.  It sounds like a heat pump and you could have had that in Houston.  They do not work well farther north.  Maybe someone here lives further south and will recognize if what you describe is a heat pump.  They are good in Texas and east and west from there.  In Kansas, where the apartment complex owner had put them in, we had a hard time keeping warm.

Any refrigeration circuit is a heat pump. 

 

What people usually call "heat pumps" are ones that are run to get the benefit of the heat rejected at the hot end. But the radiator on the back of your fridge is expelling heat from the inside of the fridge out into the room. That's a heat pump too. And that is what your AC system does as well. 


Edited by exchemist, 19 April 2018 - 01:25 PM.

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#12 hazelm

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Posted 19 April 2018 - 01:35 PM

Any refrigeration circuit is a heat pump. 

 

What people usually call "heat pumps" are ones that are run to get the benefit of the heat rejected at the hot end. But the radiator on the back of your fridge is expelling heat from the inside of the fridge out into the room. That's a heat pump too. And that is what your AC system does as well. 

All very true but they don't work well in winter time because - I'm told - the ground has frozen too far down.  I spent two years with one a while back.  Poor maintenance man spent his days trying to keep apartments warm.   They seemed to do better with AC but not with heat.


Edited by hazelm, 19 April 2018 - 01:35 PM.


#13 exchemist

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Posted 19 April 2018 - 01:52 PM

All very true but they don't work well in winter time because - I'm told - the ground has frozen too far down.  I spent two years with one a while back.  Poor maintenance man spent his days trying to keep apartments warm.   They seemed to do better with AC but not with heat.

Yes that will be a problem I'm sure, if the area from which the heat is extracted is not sufficiently spread out and deep enough to avoid the chilling effect of winter. 



#14 hazelm

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Posted 19 April 2018 - 03:06 PM

Yes that will be a problem I'm sure, if the area from which the heat is extracted is not sufficiently spread out and deep enough to avoid the chilling effect of winter. 

I am glad I got my head around that now.  I'm still not 100% sure how what I have works but think I have a pretty good idea.  Now if I could get my head around how these computers work but that isn't going to happen.   Maybe I'll just stick to relativity.  :-)



#15 JMJones0424

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Posted 20 April 2018 - 10:41 PM

Actually, it doesn't.  Your refrigerant is not freezing.  I highly doubt that any of your maintenance men have confirmed such a thing, as had they encountered such a problem they would have been absolutely confounded.  Instead, I think that what you are experiencing is a failure to communicate.

 

This is all really quite simple.  

 

An AC system works by first compressing a gaseous refrigerant.  This increases its temperature according to Boyle's Law.  Then, this compressed refrigerant is cooled down, usually by passing ambient air over a heat exchanger that is placed outside the residence.  This is the big box that contains a fan and blows hot air outside your house.  The now compressed and cooled refrigerant is then pumped into the home where the pressure is reduced at the evaporator, thus dramatically dropping the temperature of the refrigerant.  This is pumped through a heat exchanger that absorbs the heat of the ambient air in the home into the refrigerant.  This is the part of the system that is inside your home and includes the blower that annoys you as it is running and the air filter that prevents crap from clogging the coils.  The refrigerant is then pumped back out to the compressor outside where the cycle repeats.  The only difference between this and a heat pump is in the efficiency of the shedding of the heat on the compressor side.  A geothermal heat pump uses a fluid cycled through pipes in the earth to transfer heat to the ground rather than the ambient air.  I don't think there's any reason to believe your problem has anything to do with whether your system is a conventional AC or a heat pump or a geothermal heat pump.  I think you are simply failing to understand what your problem is.

 

Now that we have a better understanding of what was said to you by your techs and what your observations are, I think we can come up with a realistic explanation of your problem.

 

1) Your refrigerant is not freezing.  Such a claim is almost ludicrous on Earth and would require your system performing in ways that it was not designed to perform.  There's a reason why you've failed to google instances of refrigerants freezing.  This is not your problem.

2) Your AC system is not frozen in the sense that it can still pump refrigerant from the compressor to the evaporator.  I'm guessing here, but I am convinced by your description that this isn't the problem.

3) Your AC system is incapable of transferring heat from the evaporator side to the compressor side.  The most likely cause for this is that you are low on refrigerant and because of this it is not able to carry enough heat away from the evaporator in your home in order to prevent the air exchange coils from freezing over due to ambient moisture in the air inside of your home.  If you had sufficient refrigerant, then enough heat would be transferred to the refrigerant to prevent the formation of ice on the coils.  This is why your techs described your AC system as being frozen.  It is important to note that the problem isn't that the refrigerant is frozen, as such a thing is ludicrous, but instead that you do not have enough refrigerant to prevent the air exchange coils from freezing over from the condensation of the ambient moisture from the air inside your home.  Ice is a very good insulator.  Insulation is not what you want in a heat exchanger.  Insufficient refrigerant leads to the formation of ice on the outside of the evaporation coils because you are failing to remove the heat and the temperature drop is too great on the decompressed side due to insufficient pressure of refrigerant.  This ice formation then insulates the coils which prevents what little refrigerant you have from transferring heat further exasperating the problem.

 

You likely have a small refrigerant leak somewhere in your system.  Depending on the size of the leak and how often you need to recharge the refrigerant, it may be more economical to periodically recharge the system rather than fixing the problem.  The only other possible situation is that your coils are very dirty and this dirt and mold and mildew are acting like a insulation that is preventing your AC from working.  I don't think this is likely to be the problem, though, unless the air filter hasn't been changed for years and you live in a very humid environment.  I have frozen over the coils in a house when I was doing drywall work and the sanding dust clogged up the coils.  Unless something similar has taken place, it is more likely that you simply need more refrigerant.  Your techs should easily be able to determine that this is the case, as they can measure the pressure before and after the compressor.

 

I have one rental property that requires twice annual recharge of freon.  It costs me less money to do this than it would to fix the problem because the rent and value of the property is so low compared to the cost of replacing the system.  There will be a time that this is no longer the case.  Fixing a small leak is not a cheap job, and it is often cheaper to just replace the entire system.  You have to determine if fixing the problem is worth the cost.  If you are only replacing a few pounds of refrigerant per year, then it may make more sense for you to ride it out until the situation worsens.  This is a decision that only you can make.

 

Regardless, the takeaway here is that while your AC is freezing over, your refrigerant is most certainly not freezing.  Talk to your technicians, they might actually know more about the situation than you and your googling ability do.

 

As a side note, I have had a problem in the past which caused a slow leak that you should check for.  On the outside of your home, you should see two lines running to the condenser unit.  One of them will likely be insulated, that's the low pressure line coming back from your evaporator. (Remember how the AC works.  It doesn't make any sense for the refrigerant to absorb heat after the evaporator, but you want it to shed heat before the evaporator, so the cold line flows outside the house, not inside).  Both lines will have ports that the techs will use to attach their gauges.  Check the caps on those ports.  I had one house where one of those caps was dirty, and when it was screwed down, it very slightly opened up the valve.  This almost certainly isn't your problem, but it doesn't hurt to check.


Edited by JMJones0424, 21 April 2018 - 03:38 AM.


#16 hazelm

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Posted 21 April 2018 - 04:26 AM

Whew!  I'll forget half of that but no matter because:

 

1.  I do not have a problem now.  I have a brand new furnace and AC - the indoor part of the AC. The outdoor part was replaced a few years  ago, they say.  So, all is well now.

2.  No, not my decision.  Property owners' decision which is why I had this battle every summer for four years before they decided to fix it for good.

2a.  Well, let's reword that to be fair.  New owners came in and bought the place a few months ago.  Their decision was "this ancient piece has to go".  And out it went.

3.  We get new filters every year.

4.  Yes, there was a small leak.  They'd fixed that leak before but it evidently didn't hold.  As a result:

5.  It was constantly needing more refrigerant - at the rate of once a month all summer every summer. 

6.  Humidity?  This isn't the most humid place in the world but, believe me, in summer time it runs a close second. 

7.  And, yes, I did find a web site that said the "coolant" freezes.  I tried to find that again yesterday but could not.  Blame that on Google which/who keeps changing what it shows.

 

Now, my apologies for sounding a bit flip.  I don't really mean it that way.  I do appreciate your explanation.   It's just that I feel good having the system purring like a contented cat and leaving me free to worry about something else. 

 

Have a good day and keep cool - or warm, as the case may be.



#17 JMJones0424

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Posted 21 April 2018 - 04:33 AM

Meh.

 

I don't care about what site you can link to that explains why a refrigerant freezes in a home AC system.  What I care about is that you understand why such a thing isn't possible and why this isn't the problem you were facing.

 

I am glad your situation is fixed.  Too often landlords are negligent in their responsibilities.