A/C Help & Knowledge Please
#11
07-12-2018, 08:19 AM
Pro Wrench
"The United States does not require automobile owners to retrofit their systems; however, taxes on ozone-depleting chemicals coupled with the relative scarcity of the original refrigerants on the open market make retrofitting the only economical option."
Manufacture and distribution of dichlorodifluoromethane without a license is what's prohibited in this country and despite Wikipedia's claim that retrofitting is the "only" economical option, there are various ways to legally and legitimately maintain OE equipment in classic cars. The only efficient way to convert an R12 based system to R134a is to replace the compressor and the condenser with up-rated units however R134a is also now being banned in many countries. The absolute best way to convert an R12 system is to make the aforementioned hardware changes and use R152a, aka keyboard cleaner, whose ozone depleting properties are completely insignificant yet whose cooling properties are far superior. Plus at $3 a can it's extremely economical.
Deputy, thanks for the explanation. I'm wholly versed in the function and properties of the refrigeration process and it's components. At the risk of sounding pedantic, the refrigerant doesn't absorb any heat and humidity. It's the change in state of the refrigerant from liquid to gas which when dispersed onto a evaporator that produces the cooling effect, and the air blown over this evaporator is thereby chilled through coming into contact with the exterior of it. The removal of moisture from the air is exactly the same thing that happens when you place a glass of ice water on the table. The ambient air contacts the colder surface of the glass, the moisture condenses out of the air and runs down the glass. Or into the floormats of your Disco if you have plugged drains, as the case may be.
Whenever I drive my cars, the air coming out of the vent IS what's important to me. OffRoadFrance's remark that he was seeing temps of 10°C with the disclaimer "considering the ambient today", and knowing that France is in the middle of their summer as well, I figured I would pose the question "Is 10°C acceptable for Discos?", hoping for some relevant contributions from what other board members may experience in their vehicles to guide me in the rehab of my own. In any event, I drew a vacuum last night and after 72 hours I'll see if it's held before attempting to introduce some over the counter R134a into the system. I don't want to rush it and take a chance on even a tiny leak in the system which would let the gas escape due to it's ecological impact.
Thanks again guys.
#12
07-12-2018, 05:11 PM
Camel Trophy
Join Date: Oct 2016
Location: St. Clair County, Michigan
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I'm just going to politely disagree.
Every A/C course l've ever taken (Thermo King, Carrier, etc) have never explained its process in those terms.
Did a quick search...
Scroll down to the explaination on how the evaporator works. They use the word "absorb".
How Car Air Conditioning Works
Second paragraph from the end, they describe "drawing" heat from the ambient air.
https://www.wisegeek.com/how-does-ai...oning-work.htm
Cooling the air would mean you are cooling the air, like taking a large cube of ice and setting it in a room, where it changes the air temperature by transfer.
A/C removes the heat from the ambient air inside the cabin, giving the sensation that it is cooler then the air existing in the cabin and your body temperature.
I'll never forget the first course l ever took on A/C (Thermo King, and l think they know their stuff)...the first thing they asked was..."What does the A/C system do?" Someone said, "It cools the air." The instructor said, "If you believe that...raise your hand." Pretty much...everyone raised their hand. The instructor worked around the room hitting everyone in the head with his hat...that had their hand up...saying..."A/C systems don't cool the air...they remove heat from the air."
Anyhow, this has always been my understanding of A/C systems and theory.
Brian.
Every A/C course l've ever taken (Thermo King, Carrier, etc) have never explained its process in those terms.
Did a quick search...
Scroll down to the explaination on how the evaporator works. They use the word "absorb".
How Car Air Conditioning Works
Second paragraph from the end, they describe "drawing" heat from the ambient air.
https://www.wisegeek.com/how-does-ai...oning-work.htm
Cooling the air would mean you are cooling the air, like taking a large cube of ice and setting it in a room, where it changes the air temperature by transfer.
A/C removes the heat from the ambient air inside the cabin, giving the sensation that it is cooler then the air existing in the cabin and your body temperature.
I'll never forget the first course l ever took on A/C (Thermo King, and l think they know their stuff)...the first thing they asked was..."What does the A/C system do?" Someone said, "It cools the air." The instructor said, "If you believe that...raise your hand." Pretty much...everyone raised their hand. The instructor worked around the room hitting everyone in the head with his hat...that had their hand up...saying..."A/C systems don't cool the air...they remove heat from the air."
Anyhow, this has always been my understanding of A/C systems and theory.
Brian.
Deputy, thanks for the explanation. I'm wholly versed in the function and properties of the refrigeration process and it's components. At the risk of sounding pedantic, the refrigerant doesn't absorb any heat and humidity. It's the change in state of the refrigerant from liquid to gas which when dispersed onto a evaporator that produces the cooling effect, and the air blown over this evaporator is thereby chilled through coming into contact with the exterior of it. The removal of moisture from the air is exactly the same thing that happens when you place a glass of ice water on the table. The ambient air contacts the colder surface of the glass, the moisture condenses out of the air and runs down the glass. Or into the floormats of your Disco if you have plugged drains, as the case may be.
Last edited by The Deputy; 07-12-2018 at 05:14 PM.
#13
07-12-2018, 06:00 PM
Pro Wrench
You’ll get no disagreement from me whatsoever. The clarification is was providing was for your statement “the Freon can only absorb so much heat and humidity”. This would insinuate that the refrigerant itself is doing some kind of absorption and this is incorrect. The rest of your disagreement seems to be semantics so we’re on the same page.
#14
07-12-2018, 06:11 PM
I'm just going to politely disagree.
Every A/C course l've ever taken (Thermo King, Carrier, etc) have never explained its process in those terms.
Did a quick search...
Scroll down to the explaination on how the evaporator works. They use the word "absorb".
How Car Air Conditioning Works
Second paragraph from the end, they describe "drawing" heat from the ambient air.
https://www.wisegeek.com/how-does-ai...oning-work.htm
Cooling the air would mean you are cooling the air, like taking a large cube of ice and setting it in a room, where it changes the air temperature by transfer.
A/C removes the heat from the ambient air inside the cabin, giving the sensation that it is cooler then the air existing in the cabin and your body temperature.
I'll never forget the first course l ever took on A/C (Thermo King, and l think they know their stuff)...the first thing they asked was..."What does the A/C system do?" Someone said, "It cools the air." The instructor said, "If you believe that...raise your hand." Pretty much...everyone raised their hand. The instructor worked around the room hitting everyone in the head with his hat...that had their hand up...saying..."A/C systems don't cool the air...they remove heat from the air."
Anyhow, this has always been my understanding of A/C systems and theory.
Brian.
Every A/C course l've ever taken (Thermo King, Carrier, etc) have never explained its process in those terms.
Did a quick search...
Scroll down to the explaination on how the evaporator works. They use the word "absorb".
How Car Air Conditioning Works
Second paragraph from the end, they describe "drawing" heat from the ambient air.
https://www.wisegeek.com/how-does-ai...oning-work.htm
Cooling the air would mean you are cooling the air, like taking a large cube of ice and setting it in a room, where it changes the air temperature by transfer.
A/C removes the heat from the ambient air inside the cabin, giving the sensation that it is cooler then the air existing in the cabin and your body temperature.
I'll never forget the first course l ever took on A/C (Thermo King, and l think they know their stuff)...the first thing they asked was..."What does the A/C system do?" Someone said, "It cools the air." The instructor said, "If you believe that...raise your hand." Pretty much...everyone raised their hand. The instructor worked around the room hitting everyone in the head with his hat...that had their hand up...saying..."A/C systems don't cool the air...they remove heat from the air."
Anyhow, this has always been my understanding of A/C systems and theory.
Brian.
X1 .................. too true Brian. In simplistic terms, yes, it cools the air but in truth AC reduces the heat in the ambient air.
In truth, one only needs the AC at set at 4-5C below the ambient air to experience the 'cooling effects' of AC which is more economical than introducing 'chilled air at say 10C' into the already overheated cabin area.
#15
07-12-2018, 06:32 PM
Thanks for your concern. I am quite sensitive to the sustainability of our planet, so much so that I have dedicated my life's work to it. To your point ,
"The United States does not require automobile owners to retrofit their systems; however, taxes on ozone-depleting chemicals coupled with the relative scarcity of the original refrigerants on the open market make retrofitting the only economical option."
Manufacture and distribution of dichlorodifluoromethane without a license is what's prohibited in this country and despite Wikipedia's claim that retrofitting is the "only" economical option, there are various ways to legally and legitimately maintain OE equipment in classic cars. The only efficient way to convert an R12 based system to R134a is to replace the compressor and the condenser with up-rated units however R134a is also now being banned in many countries. The absolute best way to convert an R12 system is to make the aforementioned hardware changes and use R152a, aka keyboard cleaner, whose ozone depleting properties are completely insignificant yet whose cooling properties are far superior. Plus at $3 a can it's extremely economical.
Deputy, thanks for the explanation. I'm wholly versed in the function and properties of the refrigeration process and it's components. At the risk of sounding pedantic, the refrigerant doesn't absorb any heat and humidity. It's the change in state of the refrigerant from liquid to gas which when dispersed onto a evaporator that produces the cooling effect, and the air blown over this evaporator is thereby chilled through coming into contact with the exterior of it. The removal of moisture from the air is exactly the same thing that happens when you place a glass of ice water on the table. The ambient air contacts the colder surface of the glass, the moisture condenses out of the air and runs down the glass. Or into the floormats of your Disco if you have plugged drains, as the case may be.
Whenever I drive my cars, the air coming out of the vent IS what's important to me. OffRoadFrance's remark that he was seeing temps of 10°C with the disclaimer "considering the ambient today", and knowing that France is in the middle of their summer as well, I figured I would pose the question "Is 10°C acceptable for Discos?", hoping for some relevant contributions from what other board members may experience in their vehicles to guide me in the rehab of my own. In any event, I drew a vacuum last night and after 72 hours I'll see if it's held before attempting to introduce some over the counter R134a into the system. I don't want to rush it and take a chance on even a tiny leak in the system which would let the gas escape due to it's ecological impact.
Thanks again guys.
"The United States does not require automobile owners to retrofit their systems; however, taxes on ozone-depleting chemicals coupled with the relative scarcity of the original refrigerants on the open market make retrofitting the only economical option."
Manufacture and distribution of dichlorodifluoromethane without a license is what's prohibited in this country and despite Wikipedia's claim that retrofitting is the "only" economical option, there are various ways to legally and legitimately maintain OE equipment in classic cars. The only efficient way to convert an R12 based system to R134a is to replace the compressor and the condenser with up-rated units however R134a is also now being banned in many countries. The absolute best way to convert an R12 system is to make the aforementioned hardware changes and use R152a, aka keyboard cleaner, whose ozone depleting properties are completely insignificant yet whose cooling properties are far superior. Plus at $3 a can it's extremely economical.
Deputy, thanks for the explanation. I'm wholly versed in the function and properties of the refrigeration process and it's components. At the risk of sounding pedantic, the refrigerant doesn't absorb any heat and humidity. It's the change in state of the refrigerant from liquid to gas which when dispersed onto a evaporator that produces the cooling effect, and the air blown over this evaporator is thereby chilled through coming into contact with the exterior of it. The removal of moisture from the air is exactly the same thing that happens when you place a glass of ice water on the table. The ambient air contacts the colder surface of the glass, the moisture condenses out of the air and runs down the glass. Or into the floormats of your Disco if you have plugged drains, as the case may be.
Whenever I drive my cars, the air coming out of the vent IS what's important to me. OffRoadFrance's remark that he was seeing temps of 10°C with the disclaimer "considering the ambient today", and knowing that France is in the middle of their summer as well, I figured I would pose the question "Is 10°C acceptable for Discos?", hoping for some relevant contributions from what other board members may experience in their vehicles to guide me in the rehab of my own. In any event, I drew a vacuum last night and after 72 hours I'll see if it's held before attempting to introduce some over the counter R134a into the system. I don't want to rush it and take a chance on even a tiny leak in the system which would let the gas escape due to it's ecological impact.
Thanks again guys.
I'm by no means a 'tree hugger' but I'll never knowingly or intentionally cause damage to the environment, but, equally I agree that R134 isn't by any means an adequate replacement for R12 (freon) but the cost penalty to replace R134 with the next generation of refrigerants is to me so penalising I'll stick with the status quo.
It's like electric cars or motorbikes, I have an issue with them, the cost to replace the batteries, the environmental damage caused in the manufacture of batteries and then the ridiculous power costs for recharging batteries and the abysmal distance achieved after fully charging them. To me the internal combustion engine has a long road to travel as yet until they economise a viable alternative, as for NOx, all engines emit NOx be they petrol or diesel.
#16
07-12-2018, 06:42 PM
You can't just go by what coming out of the vent, it all depends on the outside temperature, humidity level and condition of the A/C unit. Most units are designed to pull about 30/40 degrees of heat/humidity out of the cabin area. So, if it is 95°F...you'probably see about 54°F out of the vent. However, if it is 95°F and the humidity level is 70%...then you will see less cooling. The freon can only absorb so much heat and humidity. It is all based of the amount of freon in the system and the size of the cabin area being cooled. The more people you have inside the vehicle will affect cooling performance, too.
If l remember correctly...R134a in its natural state is about -15°F and R12 was -30° and that's why it cooled so much better...it was a colder gas (and the properties of the gas were better at what they do too)...so it could absorb more heat and humidity.
One thing to remember about filling R123a systems...they do not like being over filled. A few oz. to much and they start going the other direction in cooling.
Brian.
If l remember correctly...R134a in its natural state is about -15°F and R12 was -30° and that's why it cooled so much better...it was a colder gas (and the properties of the gas were better at what they do too)...so it could absorb more heat and humidity.
One thing to remember about filling R123a systems...they do not like being over filled. A few oz. to much and they start going the other direction in cooling.
Brian.
X1 ........... you are perfectly correct. The effects of R12 are far greater than R134a due to the boiling points being totally different. R12 (freon) is far superior as a refrigerant to R134a but the former has a markedly deleterious environmental effect.
#17
07-13-2018, 02:33 AM
Camel Trophy
Join Date: Oct 2016
Location: St. Clair County, Michigan
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You’ll get no disagreement from me whatsoever. The clarification is was providing was for your statement “the Freon can only absorb so much heat and humidity”. This would insinuate that the refrigerant itself is doing some kind of absorption and this is incorrect. The rest of your disagreement seems to be semantics so we’re on the same page.
#18
07-13-2018, 07:44 AM
Pro Wrench
Really now... Would the dumbest person you know also need to be told that the size of the cabin, the number of people in it, or the outside temperature all affect the temperature or the air coming out of the vents? Or were you just contributing that assuming that I might be that person?
Politeness aside, assuming that I am the dumbest person you know it's comforting to think that you hang out with some very smart people.
Thanks again for your explanation of what affects the air coming out of the vents, should you ever stumble across an actual observed number, which was my request, I would be interested to hear it. Don't forget to include outside temp. I think it's safe to assume that the size of the cabin of your Discovery is roughly the same size as my Discovery, and that the number of people will be the same, give or take one or two. However, feel free to include that as well. I asked the question because I'm interested in real world observations as I rehab my Disco to help me determine the health of the entire system, flaps, ducts, compressor, etc. So far I have 10°C on a summer's day in France as my benchmark. If anyone else has any info, I'm still interested.
ORF, I would encourage you to look into the R152a, perhaps even before you're in a position to need to. Its saturation temperature is well below that of 134a which makes it even more efficient, some reports indicate up to 20%, requiring lower system pressures and less energy consumption (better gas mileage) to remove the same amount of heat. Better still is that it's <$5 for 325g, so you can fill your vehicle for under $15. I'm not sure what it costs in France but I would be surprised if it's wildly different. You can buy it at any office supply store. And finally, read the Wiki page on its properties with regard to the environment. Here's an except.
"As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years)" - Wiki R152a
There are many reports on the internet demonstrating that it's a drop in replacement for R134a, the only downside being that due to higher output temperatures it can be taxing on the compressor. I hadn't considered using it this go round but this discussion has me asking myself why I wouldn't. If my system holds vacuum I may just put it in this weekend and will report back.
Edit: I have no idea if PAG46 is compatible with R152a and since I just filled my system with that I may be restricted to R134a. Hopefully that info exists somewhere.
Politeness aside, assuming that I am the dumbest person you know it's comforting to think that you hang out with some very smart people.
Thanks again for your explanation of what affects the air coming out of the vents, should you ever stumble across an actual observed number, which was my request, I would be interested to hear it. Don't forget to include outside temp. I think it's safe to assume that the size of the cabin of your Discovery is roughly the same size as my Discovery, and that the number of people will be the same, give or take one or two. However, feel free to include that as well. I asked the question because I'm interested in real world observations as I rehab my Disco to help me determine the health of the entire system, flaps, ducts, compressor, etc. So far I have 10°C on a summer's day in France as my benchmark. If anyone else has any info, I'm still interested.ORF, I would encourage you to look into the R152a, perhaps even before you're in a position to need to. Its saturation temperature is well below that of 134a which makes it even more efficient, some reports indicate up to 20%, requiring lower system pressures and less energy consumption (better gas mileage) to remove the same amount of heat. Better still is that it's <$5 for 325g, so you can fill your vehicle for under $15. I'm not sure what it costs in France but I would be surprised if it's wildly different. You can buy it at any office supply store. And finally, read the Wiki page on its properties with regard to the environment. Here's an except.
"As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years)" - Wiki R152a
There are many reports on the internet demonstrating that it's a drop in replacement for R134a, the only downside being that due to higher output temperatures it can be taxing on the compressor. I hadn't considered using it this go round but this discussion has me asking myself why I wouldn't. If my system holds vacuum I may just put it in this weekend and will report back.
Edit: I have no idea if PAG46 is compatible with R152a and since I just filled my system with that I may be restricted to R134a. Hopefully that info exists somewhere.
Last edited by ahab; 07-13-2018 at 08:18 AM.
#19
07-13-2018, 10:53 AM
Camel Trophy
Join Date: Oct 2016
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[LEFT]Really now... Would the dumbest person you know also need to be told that the size of the cabin, the number of people in it, or the outside temperature all affect the temperature or the air coming out of the vents? Or were you just contributing that assuming that I might be that person?
Politeness aside, assuming that I am the dumbest person you know it's comforting to think that you hang out with some very smart people.
Politeness aside, assuming that I am the dumbest person you know it's comforting to think that you hang out with some very smart people.
Brian.
#20
07-13-2018, 11:23 AM
Pro Wrench
No need to let it rest so long as we're all learning something, the bulk of your input was solid information. And I'm not so hung up on myself that I can't admit that your language of removing heat is in fact the appropriate way to refer to the process, whereas my explanation was a bit hokey despite the fact that the end result is still the lowering of the temp inside the cabin. I hope we're not arguing as well, life it too short. 
Debating is fine and I have thick skin so no need for anyone to worry about insulting me however sometimes that plays to my disadvantage when I assume everyone else feels the same.
Debating is fine and I have thick skin so no need for anyone to worry about insulting me however sometimes that plays to my disadvantage when I assume everyone else feels the same.