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Post by don on Apr 27, 2019 11:27:53 GMT
Here is a link to my post about evacuating the 1938 SO2 refrigerator. monitortop.freeforums.net/thread/1627/evacuating-so2-deja-vu?page=1&scrollTo=26667When I purchased the Envirotech hydrocarbon refrigerant years ago it was labeled as a drop in refrigerant for R-12 and R-134. Since then the government has become more anal. (If an r-12 system has been converted to r-134 then this can be used to replace it.) I have read that there are no conditions placed on the use of the hydrocarbon refrigerants to convert a system that did not originally use R-12 which is the case with converting SO2 systems to hydrocarbon. The 6 ounce container of Envirotech hydrocarbon refrigerant by weight actually occupies the equivalent of 18 ounces of R-12 by volume or 16 ounces of R-134 as indicated in a graduated charging cylinder. From my memory of years ago my research indicated it was colder and more efficient than the SO2 I wanted to replace. After purchasing it I called the manufacturer and asked my questions. They told me to bring an evacuated system up to 0# PSIG with atmospheric air and then charge the machine. I told him I would not do that and needed to charge from a 30 inch vacuum. He told me to go ahead and do that as it would work. The 1938 flat top refrigerator I converted had a 1/8 HP compressor and required 1 and 3/4 # of SO2 or 28 ounces. I transferred the ENVIROTECH to a Thermal (brand) charging cylinder as I wanted to put approximately 14 ounces equivalent by volume into the machine and add from there. I added a diaphragm refrigeration shut off valve before and after the capillary tube which I will remove after I have tested the machine in the heat of the summer. I fully expected to have to adjust the length of the capillary and the valves would have allowed me to do that without needing to remove the charge. Since the hydrocarbon refrigerant is entirely miscible with mineral oil and the refrigerator will be used in my garage which at times will be in the 40F range I added a strap on compressor crankase heater. This is a resource for capillary tube design. www.rses.org/assets/serviceapplicationmanual/620-98.pdf 1.The evaporator must hold all the system refrigerant on the off cycle. 2. The condenser must be able to hold the complete charge if the capillary were to plug. 3. The design temperature/pressure for the condenser is 35 degrees F above ambient. 4. The system pressures should equalize within a reasonable time I removed the float system completely as I wanted to minimize the charge and add a desicant filter drier with the capillary immediately after it for restriction protection. I transferred the HC to a charging cylinder and charged into a vacuum both of which are contrary to the given instructions. After charging the 14 ounces by approximate volume from the charging cylinder into the evacuated machine it had a head pressure approximately 35 degrees above ambient and the low side was 1-2# PSIG and the evaporator had a perfect frost pattern. It pulled down and cycled to my satisfaction. A capillary tube system high and low side pressures properly charged should equalize in a reasonable amount of time as explained in the above RSES manual link. The equalization time was over 8 minutes which should not be an issue as the GE compressor from that era uses an unloading mechanism to start unloaded. After it has been tested in the 95+ degrees ambient temperatures this summer I will drop the charge - remove the diaphragm valves and recharge . If it works satisfactorily after that I will probably do the same with my 1940 flattop with the same 1/8 HP compressor. I do not recommend anyone attempting this until I have ambient tested the machine this summer and removed the valves and recharged to prove it can be replicated. However in case I die before that happens I used 120 inches of .031 capillary from Supco (B-1). The refrigerator was the smaller B4-38-A with a CJ-1-B16 refrigerating machine. I believe that capillary tubing is sized to match the pumping capacity of the compressor so I plan to use the same capillary tubing on my larger Cu Ft flat top with the same 1/8 HP compressor. drive.google.com/drive/folders/0B8_jm7K-ahMaRDVxaEp2Slp5eW8 |
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Post by ckfan on Apr 27, 2019 15:15:30 GMT
Wow, sounds like you did some very involved work. Let us know how it turns out once it has some hours on it. It sounds promising.
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Post by turbokinetic on Apr 27, 2019 22:49:41 GMT
Here is a link to my post about evacuating the 1938 SO2 refrigerator. monitortop.freeforums.net/thread/1627/evacuating-so2-deja-vu?page=1&scrollTo=26667When I purchased the Envirotech hydrocarbon refrigerant years ago it was labeled as a drop in refrigerant for R-12 and R-134. Since then the government has become more anal. (If an r-12 system has been converted to r-134 then this can be used to replace it.) I have read that there are no conditions placed on the use of the hydrocarbon refrigerants to convert a system that did not originally use R-12 which is the case with converting SO2 systems to hydrocarbon. The 6 ounce container of Envirotech hydrocarbon refrigerant by weight actually occupies the equivalent of 18 ounces of R-12 by volume or 16 ounces of R-134 as indicated in a graduated charging cylinder. From my memory of years ago my research indicated it was colder and more efficient than the SO2 I wanted to replace. After purchasing it I called the manufacturer and asked my questions. They told me to bring an evacuated system up to 0# PSIG with atmospheric air and then charge the machine. I told him I would not do that and needed to charge from a 30 inch vacuum. He told me to go ahead and do that as it would work. The 1938 flat top refrigerator I converted had a 1/8 HP compressor and required 1 and 3/4 # of SO2 or 28 ounces. I transferred the ENVIROTECH to a Thermal (brand) charging cylinder as I wanted to put approximately 14 ounces equivalent by volume into the machine and add from there. I added a diaphragm refrigeration shut off valve before and after the capillary tube which I will remove after I have tested the machine in the heat of the summer. I fully expected to have to adjust the length of the capillary and the valves would have allowed me to do that without needing to remove the charge. Since the hydrocarbon refrigerant is entirely miscible with mineral oil and the refrigerator will be used in my garage which at times will be in the 40F range I added a strap on compressor crankase heater. This is a resource for capillary tube design. www.rses.org/assets/serviceapplicationmanual/620-98.pdf 1.The evaporator must hold all the system refrigerant on the off cycle. 2. The condenser must be able to hold the complete charge if the capillary were to plug. 3. The design temperature/pressure for the condenser is 35 degrees F above ambient. 4. The system pressures should equalize within a reasonable time I removed the float system completely as I wanted to minimize the charge and add a desicant filter drier with the capillary immediately after it for restriction protection. I transferred the HC to a charging cylinder and charged into a vacuum both of which are contrary to the given instructions. After charging the 14 ounces by approximate volume from the charging cylinder into the evacuated machine it had a head pressure approximately 35 degrees above ambient and the low side was 1-2# PSIG and the evaporator had a perfect frost pattern. It pulled down and cycled to my satisfaction. A capillary tube system high and low side pressures properly charged should equalize in a reasonable amount of time as explained in the above RSES manual link. The equalization time was over 8 minutes which should not be an issue as the GE compressor from that era uses an unloading mechanism to start unloaded. After it has been tested in the 95+ degrees ambient temperatures this summer I will drop the charge - remove the diaphragm valves and recharge . If it works satisfactorily after that I will probably do the same with my 1940 flattop with the same 1/8 HP compressor. I do not recommend anyone attempting this until I have ambient tested the machine this summer and removed the valves and recharged to prove it can be replicated. However in case I die before that happens I used 120 inches of .031 capillary from Supco (B-1). The refrigerator was the smaller B4-38-A with a CJ-1-B16 refrigerating machine. I believe that capillary tubing is sized to match the pumping capacity of the compressor so I plan to use the same capillary tubing on my larger Cu Ft flat top with the same 1/8 HP compressor. drive.google.com/drive/folders/0B8_jm7K-ahMaRDVxaEp2Slp5eW8
Hi Don. Thank you so much for the article on cap tube theory. That is a great read. I am sure that Aaron (Birkie) will really enjoy that as well. Looks like your conversion is nicely hidden under the top of the Flat Top cabinet. I love those "stealth" conversions like that.
One thing I'm missing is how long ago you've done this conversion and how long it's run? It sounds like it's been in operation for quite a while?
It's great to see others who are passionate about keeping these old machines running and overcoming the difficulties we tend to face as hobbyists in this field.
Sincerely, David
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Post by don on Apr 28, 2019 16:55:51 GMT
I waited for a day in the mid 70's here in Minnesota to do the final evacuation and test charge. It ran for two days in the low 70's and since then four days in the 40's and 50's.
A friend of mine has a father who is a retired refrigeration engineer. I had him ask his father if he had any pointers on cap tube design on a changeover from a SO2 high side float system. He told his son I was getting in over my head. He probably knew that the compressor evaporator condenser refrigerant and capillary have to be designed around each other. I worked with a person who was at one time a technician for an ice machine company. He said once they had the capillary tube close in size and length they would add and remove to it inch by inch with performance measurements at each adjustment.
If this size and length works in a 95 degree F ambient I will remove the valves and recharge with a lesser amount of refrigerant straight from the dispensing can and not a charging cylinder. I would like to see the pressures equalization time in the 5-7 minute range.
I will not be testing this machine by adding and removing to the length inch by inch.
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Post by turbokinetic on Apr 28, 2019 23:45:33 GMT
I waited for a day in the mid 70's here in Minnesota to do the final evacuation and test charge. It ran for two days in the low 70's and since then four days in the 40's and 50's. A friend of mine has a father who is a retired refrigeration engineer. I had him ask his father if he had any pointers on cap tube design on a changeover from a SO2 high side float system. He told his son I was getting in over my head. He probably knew that the compressor evaporator condenser refrigerant and capillary have to be designed around each other. I worked with a person who was at one time a technician for an ice machine company. He said once they had the capillary tube close in size and length they would add and remove to it inch by inch with performance measurements at each adjustment. If this size and length works in a 95 degree F ambient I will remove the valves and recharge with a lesser amount of refrigerant straight from the dispensing can and not a charging cylinder. I would like to see the pressures equalization time in the 5-7 minute range. I will not be testing this machine by adding and removing to the length inch by inch. It sounds like you have a great path forward with your retrofit! It seems that these units are more forgiving than the modern higher power-density systems around which the article was written. Therefore, I bet you'll have no problems with it after a few adjustments. Thankfully the equalization time won't matter since the compressor has a mechanical unloader in it. These can re-start immediately even with a fully unbalanced and hot system.
Sincerely, David
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Post by don on May 1, 2019 12:16:51 GMT
I had a surprise
My high side hose blew the end gasket and dumped the charge. After this happened again later I researched the issue and found that butyl refrigerant hoses cannot be used with hydrocarbon refrigerants. The gasket at the swivel must have had butyl in it.
When it warms up into the +70F degree temperature here in Minnesota I am going to remove the shut off valves evacuate and recharge with a lesser amount of refrigerant and continue evaluating the performance with this size and length of capillary tubing.
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Post by birkie on May 1, 2019 13:35:38 GMT
That cap tube article is neat - by far one of the most accessible and thorough descriptions I've read. It still is challenging mental model compared to high-side floats, but I think I understand them better after having read that article.
As far as the ruptured high-side hose - wow! Was the evaporator at a higher temperature than the ambient temps outside?
Using the float chamber as a receiver would probably be wise. I know that the condenser and float have enough volume to allow the entire charge to exist "happily" on the high-side. (Interestingly, the DRs use so much refrigerant that it actually can fill the entire float chamber and condenser.. but they have a high-side dome, so the excess refrigerant that doesn't fit in the condenser will just collect in the sump under the oil).
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Post by don on May 1, 2019 18:25:34 GMT
It appeared that the seals were blown out of the end of the refrigerant hose that has the check valve to prevent refrigerant release. I replaced that hose and the leak quit. The check valve end leaked with and without a blank off flare fitting in the end. After removing the clip and the outer part I hack sawed it in half and found no obvious reason for it to fail.
My high side hose blew the end gasket and dumped the charge. After this happened again later I researched the issue and found that butyl refrigerant hoses cannot be used with hydrocarbon refrigerants. The gasket at the swivel must have had butyl in it.
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Post by don on May 20, 2019 12:19:52 GMT
When I removed the diaphragm valves on my hydrocarbon changeover experiment I found that the tubing to the entrance of the evaporator was filled to the brim with clear mineral oil. I had to tip the refrigerator on its side to drain out enuf oil so I could braze the capillary tube to it. Instead of charging 14 ounces by equivalent volume I charged approx 9 ounces (3 oz x 3 factor = 9 by volume) straight from the container. It was not enuf and adding more slowly over a period of several days I am now at about 14 oz equiv. There is a large amount of gurgling and the evaporator appears to be plugged with oil which is insulating the evaporator from a proper heat transfer. The low side line is very cold leaving the evaporator back to the compressor which makes it look like the oil is preventing a heat transfer.
As a comparison I turned on my larger flatop which is in the same garage/ambient and watched the frost pattern/noise. The larger machine had a perfect frost pattern with a barely discernable gurgling and the low side line was not cold all the way back to the compressor.
Refrigerant 12 is famous for oil return in refrigeration. Refrigerant 22 is not so famous, Maybe the hydrocarbon refrigerant does not cause a chemical reaction with the oil but is not miscible enuf for the proper oil return with this evaporator design?
The refrigerator cycles on and off with the abient temp in the seventies. The frost pattern is not perfect like the larger SO2 refrigerator in the same garage. My plan is to continue running the changeover machine this summer with the hope that the oil in the evaporator eventually returns to the compressor. On the off cycle the refrigerant will have all migrated to the cold evaporator and if the hydrocarbon refrigerant is truly miscible in mineral oil it should happen.
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Post by turbokinetic on May 20, 2019 12:39:19 GMT
When I removed the diaphragm valves on my hydrocarbon changeover experiment I found that the tubing to the entrance of the evaporator was filled to the brim with clear mineral oil. I had to tip the refrigerator on its side to drain out enuf oil so I could braze the capillary tube to it. Instead of charging 14 ounces by equivalent volume I charged approx 9 ounces (3 oz x 3 factor = 9 by volume) straight from the container. It was not enuf and adding more slowly over a period of several days I am now at about 14 oz equiv. There is a large amount of gurgling and the evaporator appears to be plugged with oil which is insulating the evaporator from a proper heat transfer. The low side line is very cold leaving the evaporator back to the compressor which makes it look like the oil is preventing a heat transfer. As a comparison I turned on my larger flatop which is in the same garage/ambient and watched the frost pattern/noise. The larger machine had a perfect frost pattern with a barely discernable gurgling and the low side line was not cold all the way back to the compressor. Refrigerant 12 is famous for oil return in refrigeration. Refrigerant 22 is not so famous, Maybe the hydrocarbon refrigerant does not cause a chemical reaction with the oil but is not miscible enuf for the proper oil return with this evaporator design? The refrigerator cycles on and off with the abient temp in the seventies. The frost pattern is not perfect like the larger SO2 refrigerator in the same garage. My plan is to continue running the changeover machine this summer with the hope that the oil in the evaporator eventually returns to the compressor. On the off cycle the refrigerant will have all migrated to the cold evaporator and if the hydrocarbon refrigerant is truly miscible in mineral oil it should happen.
Hi Don; thanks for the update on your HC refrigerant conversion. I would think that the oil should be well miscible with HC refrigerants. Afterall they are both petroleum and came out of the ground as a mixture which was separated at a refinery.
Interestingly, these fridges were designed so that miscibility wasn't necessary. The evaporator header provides a place for the oil to separate and rise to the surface of the SO2. The return line to the compressor is from the top of the header, so that it skims off the oil.
When you have a miscible refrigerant and oil, there is a "distilling" action in the evaporator, where the mixture gets more and more concentrated (more oil) until the level rises to the return line area. There will always be some mixed refrigerant and oil going back through the return since the two never completely separate in the evaporator. It will reach an equilibrium state and should stabilize, but you may not see a well-defined frost line as with the SO2.
I've replaced (miscible) R12 with (non miscible) R152A in several capillary-tube Frigidaire refrigerators with similar evaporator designs. These units don't pump oil out of the compressor, in the same way as the GE Scotch-Yoke machines do, so it may not be a good comparison. But it is interesting. There didn't seem to be any difference in the performance of the two.
Also replaced (non miscible) SO2 with (also non-miscible) R152A in multiple CK Monitor Tops (same compressor as your Flat Top) and not had any unusual frost lines. The frost line rises and falls based on system load on these machines. Heavy loading creates a higher frost line. The variance was less with SO2 than it is with R152A; but not by an alarming amount. These retained the high-side float.
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Post by don on May 20, 2019 21:16:59 GMT
TEMPERATURE GLIDE
I believe and see in hindsight that a refrigerant that must be charged as a liquid is a mixture of refrigerants. From what I understand Envirocare is a combination of propane with a boiling point of -43F and butane with a boiling point of 30F. The propane would boil at the start of the evaporator and the butane would continue on to the end of the evaporator. That is the frost pattern I see on the evaporator.
I visually saw the oil filled tube at the entrance to the evaporator. I can hear the loud gurgling that confirms the oil is there and need to wait to see if it returns to the compressor. I will observe the machine this summer to see if this compromise works. Maybe the capillary tube would work best with r-152 which is not a mixture of gases.
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Post by turbokinetic on May 20, 2019 22:08:09 GMT
It will be interesting to see!
Back when the first BS with refrigerant bans was a new thing; I tried several of the blends for auto A/C. They worked, but those systems have a very high velocity flow and extremely high BTU capacity. I think that any effect from separation was negligible on those systems because of the extreme turbulence keeping everything mixed. Having said that; I stopped using them because of another issue with auto A/C.... leaks. All of the systems leak and over time the blend would change because certain parts would escape before others. The performance changed over time, ultimately leading to a compressor failure. In a fridge, I doubt that the system would suffer much in this regard because they are pretty well leak-free.
Butane its self is similar in boiling point to SO2; so a pure butane charge could be an option. I tried this in a Frigidaire, which was originally an R12 system. The problem was the butane pressure was too low and the system capacity was greatly reduced. That one ended up with R152A and is still operating flawlessly.
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Post by birkie on May 21, 2019 2:35:31 GMT
ooh, diabolical! A zeotropic mixture like that would have problems in a flat top, good catch. R152a would likely be more successful, though unfortunately you're likely back to square one as far as finding the right length.
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Post by don on May 23, 2019 12:47:20 GMT
I had another high side hose gasket failure which resulted in a loss of charge. This is the second one. Nearly all sources for hydrocarbon refrigerant information state generally that hydrocarbon refrigerants are compatible with the materials generally used in refrigeration systems. However I found one site that had the warning " Hoses are critical - Cheap, hydrocarbon-rich refrigerants can quickly degrade hoses and gaskets on the high-pressure side (in red) of an air-conditioning system. When these poor substitutes for HFC-134a leak, they pose a serious fire risk " At the Redtek hydrocarbon website they have a compatibility chart www.redtek.com/win_12a_elascompat.html Maybe the hose gaskets will work temporarily for evacuating and charging and then must be removed. I had the left the gauge set on continously so I could easily monitor the pressures in this experiment. The hydrocarbon experiment is now over because of the temperature glide and the two high side hose failures . The temperature glide of this hydrocarbon blend left me with an evaporator that formed ice on the first third of the evaporator and the remaining two thirds just very cold . If this hydrocarbon blend worked I had plans to relocate my system access valves underneath and closer to the compressor and out of the refrigerator interior. I would have used and would recommend an electronic temperature control with a remote sensor attached to the evaporator to remove the the temp control switch electric switch out of the cabinet interior. Refrigeration systems in industrial explosion proof rooms must have all the wiring enclosed in sealed metal conduit connected to an inert gas supply that keeps a positive pressure inside the conduit keeping flammable gases out. I bought this 1938 flattop for $7.50 and had decided to use it for experiments as it showed hard use and had no resale value. Is there a brand of r152 duster refrigerant that does not have the added irritant smell in it? |
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Post by turbokinetic on May 23, 2019 16:24:36 GMT
I had another high side hose gasket failure which resulted in a loss of charge. This is the second one. Nearly all sources for hydrocarbon refrigerant information state generally that hydrocarbon refrigerants are compatible with the materials generally used in refrigeration systems. However I found one site that had the warning " Hoses are critical - Cheap, hydrocarbon-rich refrigerants can quickly degrade hoses and gaskets on the high-pressure side (in red) of an air-conditioning system. When these poor substitutes for HFC-134a leak, they pose a serious fire risk " At the Redtek hydrocarbon website they have a compatibility chart www.redtek.com/win_12a_elascompat.html Maybe the hose gaskets will work temporarily for evacuating and charging and then must be removed. I had the left the gauge set on continously so I could easily monitor the pressures in this experiment. The hydrocarbon experiment is now over because of the temperature glide and the two high side hose failures . The temperature glide of this hydrocarbon blend left me with an evaporator that formed ice on the first third of the evaporator and the remaining two thirds just very cold . If this hydrocarbon blend worked I had plans to relocate my system access valves underneath and closer to the compressor and out of the refrigerator interior. I would have used and would recommend an electronic temperature control with a remote sensor attached to the evaporator to remove the the temp control switch electric switch out of the cabinet interior. Refrigeration systems in industrial explosion proof rooms must have all the wiring enclosed in sealed metal conduit connected to an inert gas supply that keeps a positive pressure inside the conduit keeping flammable gases out. I bought this 1938 flattop for $7.50 and had decided to use it for experiments as it showed hard use and had no resale value. Is there a brand of r152 duster refrigerant that does not have the added irritant smell in it?
Hi Don. Again, thanks for the great follow-up on the experiment you have done. As for the R152A, I have been using Office Depot brand duster cans. They often come on sale on Amazon very cheaply. If not on sale there, you can get them for about $16 for 3 cans at the Office Depot store. The bitter agent is in extremely low concentrations and it will generally stay in the can as an oil film; when charging in vapor form.
It is not "on sale" at the time I'm posting this link, but in the past, the 3-packs have been about $8 www.amazon.com/gp/product/B00DB8NSG6
I've been using this brand for auto A/C and fridges for about 6 years now and not had any issues. The cans work with a standard R12 side-puncture can tapper.
You did really well for $7.50 on that fridge! 
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