PLEASE NOTE: I AM NOT AN EXPERT ON AUTOMOTIVE REFRIGERANTS. THIS SUBJECT MATTER HAS NOT BEEN REVIEWED BY ANY EXPERTS AND IS PROVIDED FOR EDUCATIONAL PURPOSES ONLY AND MAY CONTAIN ERRORS. USE AT YOUR OWN RISK !
WARNING: HYDROCARBON BASED REFRIGERANTS SUCH AS: Duracool®-12A (TM) , RED-TEK 12A (TM) , Enviro-Safe (TM) , Frosty Kool (TM) AND OTHERS ARE FLAMMABLE AND MAY BE ILLEGAL FOR YOU TO USE FOR YOUR INTENDED USE.
THE PURPOSE OF THIS WRITE UP IS TO CONTRAST DIFFERENT REFRIGERANT OPTIONS AND THE CONTROLLED RISKS ASSOCIATED WITH THEM IN ORDER FOR THE READER TO DECIDE IF THEY ARE ACCEPTABLE FOR THEIR APPLICATION
Hello Mudders. It's been a while since I wrote anything up. Recently I decided to do some AC work on my 85 FJ60 and wanted to get it done before it starts getting too warm here in Las Vegas.
UPDATE: I wrote the post in March of 2018. It is now October 2020 and my AC system has not needed a top - off and it is still working BEYOND my expectations.
The purpose of this write up is not so much about the AC repairs but the choice of refrigerant I chose and why. You Have been warned.. This is a Nerd Alert..... there is talk of flammable and toxic gases, of testicular cancer, and frostbitten skin.. along with a bit of science ahead in this post. So if you are easily bored.. move on to the Rig Pics and Eye Candy.
Hydrocarbon Refrigerants have many performance and environmental advantages over synthetic, especially in R12 applications. They are gaining in popularity even among Domestic USA appliances where up to 150g charges are now allowed in the USA.
If you stick around It is my hope that this post can serve as a summary of the many sources and peer reviewed publications I have found so that the reader may make their own conclusions as to whether or the safety and efficacy of a hydrocarbon refrigerant is right for you to use in your vehicle application and even your home refrigerator or wine cooler.
This is a long post. If you want to get to the good parts, read the Review of MVAC Refrigerants And Their Characteristics, Flammability and Explosion Risk, and DURACOOL CHARGING INSTRUCTIONS FOR MVAC APPLICATIONS
I try to acclimate myself to the 110F plus heat we get in the summer here in Southern Nevada but at times you need more than just the windows down to cool off. Having a working AC system can be critically important for safety here. Since converting my AC system to R134 I was really not pleased with the cooling performance. I could tell the compressor was working harder due to higher head pressure required to get R134 to cool. In the thin summer air my poor 2F motor has to work really hard to get my heavy Expo-build up the hills and passes here and running the AC at the same time was out of the question.
Recently, I had a rock strike my front condenser and a slow leak developed. By the time I noticed it all the refrigerant had leaked out. I ordered a new Denso condenser and drier and a Sanden gasket kit. While I was waiting for parts to arrive I started researching which refrigerant to use. I was not keen on going back to R134 and some shops can still charge up R12 if you want to pay the price. However it is performance I am after and I really did not want to flush out all compressor oil from the system again in order to go back to R12 and Mineral Oil. I decided on DURACOOL® 12a which is a hydrocarbon based class of refrigerant.
We have all heard about “Drop In Replacements” for R134A and R12 retrofitted systems. Most of them are hydrocarbon blends of purified propane ( R290 ) and isobutane ( R600A ) which can be used in refrigeration and AC systems designed for R-12 and R134a. Commonly referred to as 12a hydrocarbon refrigerant it provides better cooling than an R-12 system retrofitted to R-134a, with much greater energy efficiency as well. Unlike R-134a, 12a hydrocarbon refrigerant is completely compatible with the gaskets, hoses and oils used in most R-12 systems which use barrier hoses. Head pressure ( the high side of the compressor ) is typically lower that R12 and R134a and typically only 35% of the original refrigerant charge is required to charge they system. The blend is also classified by the EPA as an A3 / H220 flammable refrigerant. However with the necessary treatment I believe ( and studies have shown ) that risks can be mitigated to a very acceptable level in their use. This category of hydrocarbon refrigerants are generally referred to “Natural Refrigerants” becoming more commonplace. At the time of this writing the EPA is allowing refrigerant charges of up to 150g in domestic refrigerators in the USA. Hydrocarbon refrigerants are here to stay so if you are worried about flammability please read on. ( FYI: That can of Glade air Freshener in your bathroom has 113g of R290 propane as a propellant)
This current push is largely due to the fact that natural refrigerants have a zero impact on the Ozone Layer, minimal impact with respect to global warming and are now permitted by the EPA to be vented into the atmosphere instead of recovered during service. In the 1990’s the EPA issued rulings on the use of 12a hydrocarbon refrigerant in MVAC applications that were not favorable which were largely due to flammability concerns. Those rules still stand today despite the EPA approval of a new refrigerant called R1234-YF and R-1234ze which are classified as mildly flammable. The 12a hydrocarbon refrigerant cannot be patented as it is a natural product and the other refrigerants such as R1234-YF has backing of the large chemical companies. If you ask me.. something does not pass the smell test on this.
The rest of this write up will consist of studies and citations on hydrocarbon refrigerants as it applies to Motor Vehicle Air Conditioning (MVAC) applications. Where possible I will provide url links but also citations, as links tend to move around or get broken over time.
Review of MVAC Refrigerants And Their Characteristics:
R12 or Dichlorodifluoromethane is a colorless gas usually sold under the brand name Freon®. (Freon® which is a common catchall phase for refrigerant which is actually trademarked by DuPont) and a chlorofluorocarbon halomethane (CFC) used as a refrigerant and aerosol spray propellant. It is largely non-toxic to humans and is non-flammable but very harmful to the Ozone Layer. Typically when used in MVAC applications R12 is combined with Mineral Oil to lubricate the compressor. If an MVAC system is catastrophically decompressed in an accident or component failure the atomized mineral oil becomes very flammable. The MSDS from National Refrigerants lists the Auto Ignition Temperature “ Not Known”. Note: When exposed to sunlight or heat R-12 decomposes. One of the by products of this is highly toxic Phosgene Gas ( Mustard Gas ) R-12 is still available for purchase with a 609 EPA certification but no longer produced in the United States due to EPA regulations as it was banned by the Montreal Protocol in late 1993
R134 or 1,1,1,2-Tetrafluoroethane also known as norflurane, R-134a, 134a, Forane 134a, Genetron 134a, Florasol 134a, Suva 134a, or HFC-134a is haloalkane refrigerant a with thermodynamic properties similar to R-12 (dichlorodifluoromethane) but with insignificant ozone depletion potential and medium global warming potential. It is generally considered to be non flammable but shares the same flammability issues with the PAG Oil or Ester Oil lubricant used for the compressor during a catastrophic decompression. Auto Ignition Temp is 1328°F. It is also considered a testicular carcinogen. It is rumored that EPA plans a phase out to R1234-YF by encouraging the manufacturers to increase the price. As of January 2018 the EPA is requiring a 609 certification to purchase large cylinders of product. The availability of small cans for the general public remains the same at this time however the cans must have self sealing valves.
ELF ATOCHEM NORTH AMERICA INC ( One of the larger producers of R-134a ) states in their MSDS the following "Respiratory Protection (for discharge of R-134a) IN INADEQUATELY VENTILATED AREAS, A NIOSH/MSHA APPROVED (TC-18C) SUPPLIED AIR RESPIRATOR/SCBA IS REQUIRED. Ventilation:CHECK AIR FOR CONTAMINANT & FOR OXYGEN DEFICIENCY. USE LOCAL EXHAUST SYSTEM IF VENTILATION IS INADEQUATE. Protective Gloves:SYNTHETIC RUBBER/NEOPRENE Eye Protection:GOGGLES Other Protective Equipment:LIQUID GLOVES ARE RECOMMENDED FOR PROTECTION FROM COLD. Work Hygienic Practices: REMOVE/LAUNDER CONTAMINATED CLOTHING BEFORE REUSE. DESTROY CONTAMINATED SHOES." A later safety bulletin revises this for well ventilated areas as well !
R1234-YF or 2,3,3,3-Tetrafluoropropene, is a hydrofluoroolefin (HFO) with the formula CH2=CFCF3. This colorless gas has been approved as a replacement for R-134a as a refrigerant in MVAC applications. Most all automotive manufacturers are switching to R1234YF as of the 2017/2018 Model year. R1234-YF has been classified as H220: Extremely Flammable in the MSDS from National Refrigerants. However ASHARE ( American Society of Heating and Air-Conditioning Engineers ) states it is mildly flammable with an A2 designation. When combined with compressor oil under pressure it becomes extremely flammable during a catastrophic decompression.
In the atmosphere, HFO-1234yf degrades to trifluoroacetic acid, which is a mildly phytotoxic strong organic acid with no known biodegradation mechanism in water. In case of fire it releases highly corrosive and toxic hydrogen fluoride and the highly toxic gas carbonyl fluoride. As of 12/15/19 there are grave environmental concerns about trifluoroacetic acid permanently contaminating ground water aquifers now.
12a HYDROCARBON REFRIGERANT (12a) is a mixture of hydrocarbons specifically purified propane (R-290) and isobutane (R-600a), and is therefore considered nearly non-ozone-depleting when compared to R-12 or R-134a. The mixture can be used in refrigeration systems designed for R-12 and R-123a. 12a provides better cooling than an R-12 system retrofitted to R-134a, with much greater energy efficiency as well. Unlike R-134a, 12a is completely compatible with the hoses ( NOT TO BE USED WITH RUBBER HOSES FOUND IN THE 1960 MODEL YEARS ) and oils used in R-12 systems and seals, making the conversion much easier to accomplish. 12a is also patent-free due to its non-synthetic nature. Common trade names include: Duracool®-12A, RED-TEK 12A, Enviro-Safe, Frosty Kool and others. The difference between the products is mostly the R-290 to R-600 ratio, the addition of a Mercaptan ( sulphur or pine ) smell for leak detection and the use of lubricant some also have UV dye added. 12A has an auto-ignition temperature of 1635°F and is categorized as an A3 and H220 Extremely Flammable rating which is the same category for R1234-YF according to the MSDS from National Refrigerants. In practice, the required weight of 12a needed to give the same refrigeration capacity and performance as R12 or R134a, is between 35% and 40% of the original system charge by weight. Significantly less product use by weight than either traditional products alone lessens the flammability risk in MVAC applications. The 12A Molecule approaches three times the size of R-134a which makes it less prone to leak as does the fact that 12a operates at lower pressures. Also both propane (R-290) and isobutane (R-600a) are used as aerosol propellants in many products.
The EPA considers the 12A category of refrigerants as a second generation, non-ozone depleting replacement for R-134a and all other non-ozone depleting R-12 substitutes. The EPA's Final Rule, issued April 1, 1994, states: "In this final rule, the agency has determined that second generation replacements, if they are non-ozone depleting and are replacing non-ozone depleting first generation alternatives, are exempt from reporting requirements under Section 612”. They are not a direct replacement for R-12 and can only be legally used in systems that already use or have been converted to R-134a. Also several states have prohibited the use of flammable 12a refrigerants Including Arizona, Florida, Idaho, Louisiana, North Dakota, Oklahoma. But they allow the new flammable R1234YF refrigerants However I have found no mention of those states prohibiting them in domestic and commercial refrigeration applications. The EPA ruling on prohibiting 12A in applications that used R-12 (Prior to conversion to R-134a) makes no sense to me other than a bureaucratic play to quell the public's impulse to use them in the early 1990’s when R12 was being phased out. The regulations to me, make no sense at all technically but that is my view not the EPA's
In summary all refrigerants are flammable to some degree especially when mixed with their respective compressor oil and released as a mist under a catastrophic decompression. Also know that when handling ALL these refrigerants there is a risk of frostbite if it should get on your skin in the liquid state. So yeah… all this stuff is nasty to some degree in a MVAC application. Your skin can get frozen, you nuts can get cancer and fall off ( Joking of course.. about the falling off ), you can get burned by flames or hydrogen fluoride and inhale lovely phosgene or carbonyl fluoride gas. One must use the proper personal protect gear like gloves and safety glasses when handling, and use safety precautions like no smoking or open flames when working on MVAC systems. Lest we forget.. There are other flammable liquids under your hood as well like gasoline, brake fluid, power steering, ATF fluid, gear oil, and even the antifreeze.
Practical Safety Studies
There are roughly 10 - 20 million vehicles that are using 12a worldwide. Mostly in Asia, Europe, the US and Australia. If there was a serious problem with hydrocarbon refrigerants you would know about it by now. There a few notable papers written about them in the 1990’s demonstrate that under the normal circumstances found in an MVAC application the margin of safety was good. Most of the mishaps occurred when untrained MVAC technicians were servicing the system or the vehicle lacked the proper labeling to notify the technical that a hydrocarbon refrigerant had been charged in to the AC system.
The first study I wish to point out is Usage and Risk of Hydrocarbon Refrigerants in Motor Cars for Australia and the United States by I. L. Maclaine-cross , School of Mechanical and Manufacturing Engineering, The University of New South Wales, UNSW Sydney 2052, Australia
The author of the study calculated that there is the possibility of a hydrocarbon refrigerant fire in one out thirty million vehicular (30,000,000) use hours.
The second study is a flammability / ignition source study by Razmovski, V., 1994, , Safety of Hydrocarbon Refrigerants for Car Air Conditioning Systems, B.E. thesis, School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, 97 p.
"Razmovski searched for ignition sources using a propane welding torch attached to a cylinder of hydrocarbon refrigerant. The car was parked in a sheltered outdoor position with fine weather. She started the engine and allowed idling until it reached normal operating temperature i.e., typically for ten minutes. She ignited the welding torch then adjusted it to give a stable yellow flame about 70 mm long. She extinguished the flame with an air blast and tested for easy re-ignition with lighted matches and cigarette lighter.
The extinguished torch was played over the hot engine, electrical, ignition and exhaust. Then the door, light and brake switches, fan motor, relays and cigarette lighter were tested in the passenger compartment. Each test took over fifteen minutes and 50 to 100 g of flammable refrigerant were used for each test depending on the model. Razmovski found no ignition sources either inside or outside the passenger compartment in the five cars tested."
The extinguished torch was played over the hot engine, electrical, ignition and exhaust. Then the door, light and brake switches, fan motor, relays and cigarette lighter were tested in the passenger compartment. Each test took over fifteen minutes and 50 to 100 g of flammable refrigerant were used for each test depending on the model. Razmovski found no ignition sources either inside or outside the passenger compartment in the five cars tested."
The third study is a good overall review on the use of Hydrocarbon Refrigerants. Performance and Safety of LPG Refrigerants I. L. Maclaine-cross E. Leonardi School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney NSW, Australia 2052
The Abstract of the paper is as follows: "Ozone depletion and global warming require replacement of chlorofluorocarbon refrigerants-like R12. The hydrofluorocarbon R134a is non flammable, difficult to synthesize, has zero ozone depletion and high global warming. LPG refrigerants are highly flammable, occur naturally, have zero ozone depletion and negligible global warming. In Germany, most new refrigerators use R600a and many heat pumps and air conditioners now use R290 with measured energy consumption 10 to 20% lower than R12, R134a or R22. LPG mixtures have successfully replaced R12 and R134a in over 100,000 US car air-conditioners. Abboud (1994) measured the air-conditioner performance of five popular Australian cars with R12 and then LPG mixtures in our laboratory. He recommended 60% by mass commercial propane from Bass Strait and 40% commercial butane. This gave typically 10% more cooling than R12 with satisfactory superheat and typically 8% higher condenser pressure. Refrigerant property parameters show that R600a has half the leakage, pressure loss and condenser pressure and double the heat transfer properties of R12 and R134a. This explains the energy consumption savings of R600a refrigerators. Redesign of heat pumps and car air-conditioners for R600a could yield greater benefits. The insurance risk increment from LPG flammability for domestic refrigerators is zero. The increment for car air-conditioner is negative because of the high cost of R12 and R134a repairs. For large systems, ventilation of plant rooms and other LPG safety precautions can make insurance risk increment zero or negative if required."
Flammability and Explosion Risk
Hydrocarbon based refrigerants are flammable. As stated before care must be taken when handling them especially when replacing a non-flammable fluorocarbon with a hydrocarbon Refrigerant. When charged into a normally functioning MVAC system it is my opinion that they are safe and the risk of a catastrophic discharge and subsequent ignition are very remote.
Hydrocarbon Refrigerants do not spontaneously combust on contact with air.
Three elements need to be present.
- There needs to be a release of hydrocarbons.
- The Hydrocarbon Refrigerant needs to mix with the correct proportion of air, the range of flammability being between 2 and 10%. Outside of these limits combustion cannot occur.
- An ignition source exceeding 440 degrees C must be present.
The handling and use of hydrocarbons requires adequate safety measures. This is especially true if a system is being considered for retrofitting and replacing a non-flammable fluorocarbon with a hydrocarbon refrigerant.
That being said there are a few videos available where a controlled release of 12a was conducted in a vehicle and ignited with a spark plug with news cameras rolling and fire crews standing by. The videos did demonstrate the flammability of the product but how often are spark plugs found in the passenger compartment that happen to be wired to proper power source of ignition and have access to free air (IE: They are not screwed into the head of the motor like they should be) . That is not realistic in my opinion.
The last video is the explosion at UNSW with Dr Ian MACLAINE CROSS intentionally placing himself in the passenger compartment of a passenger car and discharging two 170g cans of 12a and lighting a match. I will not spoil the video but he he does not die and is seen at the end of the video in the hospital with his burns bandaged up and displaying somewhat of a smile. Please do not attempt to replicate this experiment. It had been repeated twice before without harm to anyone. But in this filming it went bad and researchers received mild injures and it ultimately ended up in the equivalent of an OSHA court where guilty verdicts were entered. The experimenters should have worn more PPE gear like face shields and nomex yet, it clearly demonstrates the survivability of a very unlikely worst case scenario. Now after seeing it ask yourself, after you notice a catastrophic discharge of your MVAC unit..... You smell it and see a white mist. And then you light a match or flick a lighter ? Slim chance. More likely you would roll down your window and the ignition problem goes away as you dilute the concentration of gas in the process. If an MVAC system did catastrophically fail not all the refrigerant will escape. The remainder will stay in the system in equilibrium with the atmosphere.
UNSW Explosion Dr Ian MACLAINE CROSS
... CONTINUED ON THE NEXT POST
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