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The Quest for a 100 percent DIY A-C Setup
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I have been working on a conversion of a R4 compressor to a Sanden compressor on my diesel SL and in that process have done a substantial amount of research on the various refrigerants that are available, with the goal of finding a setup that is capable of being 100% maintained by a DIYer. The information presented here is for informational and entertainment purposes only, and is designed to open up lines of thinking that might not otherwise be considered.
I would never advocate breaking the law, but obviously people do all manner of illegal things with their cars from speeding and running red lights, to removing EGR equipment to driving without a license or insurance, texting or calling while driving, driving under the influence, and so forth and so on. You break the law and get caught, be prepared to pay the consequences. Also I'm not intending this thread to be advocating for or against any strategy or system, and I would hope that any discussion that ensues would be focused on factual information and not opinion - and that any person making a decision outside the norm be respected and not attacked. At the end of the day, each person can and should make their own decision about what strategies they use and the risks they are willing to take to achieve their own personal DIY goals. Isn't that the goal of this forum? The Big Two If someone were to talk to an A/C shop, they would be led to believe that there are only two automotive refrigerants that are available - R12 and R134a. R12 was the original refrigerant (freon) that was deemed to be bad for the atmosphere largely through legislative fiat. R12 is generally not a DIY refrigerant for two reasons: First, it must be recovered and may not be vented into the atmosphere and second, cannot be bought without a license. Notwithstanding that reality, DIYers can spend $20 or so and take an open book test and get the technician license to be able to legally use R12, but most DIYers cannot afford the expensive equipment to be able to legally recover. The alternative to R12 is currently R134a, which is a suitable refrigerant for systems designed specifically for this refrigerant, but not generally a good replacement for an R12 system because of its higher head pressure and less efficient cooling properties. So a DIYer is generally faced with a choice of having someone else maintain their system or retrofit to a R134a system and live with the lower performance. Starting with an R12 system, a DIYer can make a conversion to 134a in a relatively straightforward manner. Provided that a system is either empty through leakage, catastrophic failure, illegally vented or recovered at an AC shop, a DIYer can do the retrofit to 134a as a DIY project. Ideally, the system should be flushed, the expansion valve replaced, a new receiver/dryer installed, hoses and o-rings replaced, oil replaced with a compatible oil, vacuumed and leak tested and then charged. The R12 fittings need to be replaced with 134a compatible fittings. (Details on this process can be found in threads across the net). The selection of an appropriate oil is a subject beyond the scope of this document. Starting with a 134a system, a DIYer can maintain the system without any real problems as 134a is available almost anywhere in convenient packaging designed to be handled by a DIYer. But we have a very interesting problem with 134a that prevents it being a true DIY system. The law requires that when working on a system, the refrigerant must be recovered and may not be vented to the atmosphere. All automotive A/C shops have equipment designed to recover both R12 and R134a and virtually none have any other capability. This brings us to a very interesting situation. A DIYer would like to be able to maintain the system without having to bring it to a shop to have the refrigerant recovered every time they need to work on it. R134a is a fascinating material that changes its characteristics depending on the vessel in which it resides! If it resides in an automotive AC system, it is a very dangerous and polluting material that must be handled by professionals with special equipment that prevent it from getting into the atmosphere. In fact if you look at a typical MSDS for 134a used in automotive AC systems you will see descriptions and warnings like First Aid MeasuresHowever 134a is one of two refrigerants that are used as the "air" in Dusters. In this environment, we see descriptions like "removes microscopic dust, lint and foreign particles. Cleans computers and keyboards, photographic and audio/video equipment - Ozone safe, non-voc, non-flammable, non-conductive..." Eco-friendly and safe - what could be better. So we have a fascinating conundrum where 134a in a duster can is designed and sold to be vented to the atmosphere in the context of keeping computers and other electronics clean, whereas 134a in an automotive system cannot be vented to the atmosphere under penalty of $25000 fine. In a process that can only be deemed alchemy, in one container (an AC system) the product is dangerous and regulated, yet the instant it comes in contact with a duster can, it is acceptable and encouraged to vent to the atmosphere, preferably dispatching some keyboard dust in the process. (I have attempted to determine exactly which component of an automotive AC system makes the 134a so dangerous, and I believe it is the desiccant in the dryer. Everything else is just metal and rubber, not unlike the components of the duster can.) This situation is kind of like the old saying about a thermos bottle - how does it know to keep the hot things hot and the cold things cold? How does the 134a itself know where it resides so it can change its fundamental characteristics from dangerous to benign? So understanding this principle, a DIY person can easily create their very own simple and low-cost (and dare I say, magic) recovery system. By creating a recovery hose from a 134a fitting on the auto AC system and connecting it to an empty 134a duster can, through the magic of alchemy, the 134a refrigerant is transformed from an evil and dangerous gas, to a safe and environmentally friendly dusting agent for cleaning a computer. This transformation process happens in an instant, so there is no need to actually store the gas, it can be vented immediately as a dusting agent from the duster can. http://www.peachparts.com/shopforum/...1&d=1369464956 A person making decisions purely on logic, might feel entirely justified in venting 134a directly to the atmosphere without using the magic duster can, but would be well advised to do so outside the view of of any other human and certainly not disclose this action in any manner. What About Other Refrigerants? There are literally scores of refrigerants. An interested reader is directed to this page for a partial list - List of refrigerants - Wikipedia, the free encyclopedia In fact, the types of refrigerants is myriad - CFC, CFO, HCFC, HCFO, HFC, HFO, HCC, HCO, HC, HO, PFC, PFO, PFC, PFO, PCC, PCO and H among others. Not all, in fact most, refrigerants are not appropriate for automotive use - either because of physical attributes or because of undesirable characteristics or because of cost. But there are some fascinating alternatives to R12 and R134a that can be used with varying degrees of legality and desirability and effectiveness. Making no value judgements, recommendations or assertions, the reader is directed to the following options as interesting subjects for research and consideration. R-290 (Propane) - Propane is a refrigerant that is cheap, highly efficient and easily used within automotive system. Persons considering propane are cautioned against using propane fuel that is readily available in camping bottles or in heating cannisters or as vehicle fuel. This "propane" is quite impure with water and other hydrocarbons present in significant concentrations that can seriously degrade AC systems. Refrigerant grade propane should be used if this is considered. Propane can be vented so no recovery issues exist. EnviroSafe (propane/isobutane) - EnviroSafe is a proprietary mix of hydrocarbons that is optimized for automotive use. It is legal for conversion from 134a systems but not from R12 systems. This is a legal technicality not grounded in any practical or physical reality. Some say that an R12 system that has been converted to 134a can be legally converted. Envirosafe can be vented so no recovery issues exist. While not legal, EnvoroSafe is entirely compatible to be added to an existing R-12 or R-134a system (topping off). DuraCool (propane/isobutane??) - DuraCool is a proprietary refrigerant predomanintly or entirely hydrocarbon based. DuraCool can be vented so no recovery issues exist. R-152a (1,1-Difluroethane) - This is a fascinating material that is a potential replacement for 134a when that is ultimately phased out. Amazingly, this product is what is contained in dusters as well. In fact a quick YouTube search for "Duster as Refrigerant" will yield some fascinating videos about how to charge an A/C system with duster propellant. R-152 has one undesirable characteristic and that is if it does catch fire, the byproduct is HF a very poisionous acid gas that is quite nasty. Future systems will likely be double loop systems that can keep the R-152a outside the cabin. R-1234yf (2,3,3,3-Tetrafluoropropene) - Another potential replacement for R134a. There are some undesirable properties of this refrigerant that have caused MB to have come out against adopting this refrigerant. R-600a (butane) - Like propane, butane is a good refrigerant option. Can be vented so no recovery issues exist. Some modification to the system may be necessary because of pressure differences. R-414a (mixture of HCFCs) - Brands such as GHG-X4, Autofrost, Chill-It R-414b (mixture of HCFCs) - Brands inlcude HotShot, KarKool Freeze 12 (mixture of 134a and R-142) - Freeze 12 is one of many 134a blends Any discussion of HC based refrigerants inevitably comes around to flammability. While there have been no documented cases of HC refrigerants catching fire it is not a zero-risk proposition, though many (or even most) believe the risk to be so low as to be negligible... and others believe the risk is too much to bear. The bottom line is that there is no one ideal refrigerant. All refrigerants have undesirable characteristics. Highly efficient refrigerant gasses like CO2 and NH3 are undesirable because of either poisonous characteristics or extremely high head pressures. Regardless of the path a DIYer takes, ensure that the system is clearly labelled to prevent the inadvertent contamination of commercial recovery systems in the future that may not test for the refrigerant in the system. Be a good neighbor. Know the laws and regulations, and make your own determination of the suitability and level of risk that you take in any alternative system. Again, the purpose of this document is to explore options and alternatives for the DIY auto AC mechanic. Feel free to share your experiences or additional research, but please be respectful. |
This topic gets beaten to death every year when the weather gets warm. But that said, this is a great write up.
From my experience 1) R12 is cheap, a can costs about $10 more then a can of R134 these days which is cheaper then any conversion 2) Shops won't touch a car with anything other then R12 or R134 because they do not want to contaminate their supplies or equipment. 3) It's illegal to charge your A/C system with propane, this is clearly written on the EPA website and anyone telling you otherwise is either an idiot, or thinks that you are one. Installing R134 fittings so that one can say that it's not an R12 system won't get you far if a freak accident happens, caused by propane in your A/C system. With that said, it can work pretty well as a refrigerant and as long as you understand the above, it's your risk. 4) All the other refrigerants seem to be blends. These are usually a blend of refrigerant and a lubricant to help carry the stuff through the system. They can work well, but as they are a blend, they cannot be used for topping up as the blend will leak at different rates. In order to maintain the balance, a vac and complete charge is required. Blends can be identified as the jug will state that you should charge the system as a gas (with the jug being the right way up). If you know that your system is leak free and in good shape, stick with R12, nothing works better and it's not expensive anymore. |
LOL @ the air duster vent system. I had always found the air duster vs. ac venting rules truly asinine.
Note that most air duster cans now are R152. You can use this to cool your vehicle as well, but it is somewhat flammable (not as much has Propane though). http://www.sae.org/events/aars/presentations/2008/manhoekim.pdf AUTO A/C FORUM - AUTO AIR CONDITIONING TROUBLESHOOTING HELP AT THE COOL ZONE! :: View topic - Experimental 1974 Chevrolet rustbucket goes in to full force http://web.archive.org/web/20060716152810/http://home.earthlink.net/~bob1.gardner/id21.html -J |
Another note about R152:
http://www.sae.org/altrefrigerant/presentations/presw-hill.pdf Note that venting the entire ac charge into the cabin didn't get anywhere close to the flammability threshold... Also note that R12 gives the best cooling... |
When I replaced my R4 last time I used the EnviroSafe hydrocarbon refrigerant because everything I had read about it sounded good. It is a larger molecule so it is less likely to leak, and you use quite a bit less of it to begin with, about 1/3. It supposedly takes less power to turn the compressor as well. That was before last summer and so far so good. Blows cold and hasn't leaked out.
R12, R134a, and even antifreeze are flammable when earosolized so I'm not too warried about the propane and isobutane in the refrigerant. |
Take a few steps back and look at it this way: a/c service is a once every 10-20 year proposition. The original system definitely lasted at least 10 years. (Most cases). Repairing it in its original fashion ( in our case r12) will yield consistent results.
Doing the best possible repair the first time around ensures that it won't have to be a yearly "DIY". It should not be that to begin with. |
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I'm not advocating any particular approach or system, only teeing up some ideas and options for those inclined to go a different route to have as a starting point for research and ultimately making an informed decision... whatever that may be. |
Be aware that R134 is being replaced and will soon be like R12 as far as availability. My opinion is there is nothing wrong with R12. It was a theory that it caused a problem in the ozone layer. Not a proven fact. DuPont had the rights on R12 and it had run out. R134 was the replacement made by Guess Who, DuPont. R134 is far more dangerous to humans than R12 every was.
They have the R134 replacement ready (HFO 1234yf) which is very similar to R134 but it will be illegal to convert a 134 system to the HFO 1234yf or HFO 1234yf to R134. Also HFO 1234yf is flammable. Maybe the propane and butane replacements are not so bad. They don't harm the environment. Paul |
I have used Duracool in all my classic cars since discovering it ~2001. EnvirOSafe & Freeze12 are similar hydrocarbons. I had converted my 65 Newport to R-134A, but felt the York compressor was working too hard. The rules that shops must follow is to first convert to R-134A, then to HC's. If you want to know why, read on the EPA website, but makes no sense. Most shops won't use HC's, I expect for the same reason CA plumbers keep copper pipe in the rulebook. Many reasons not to use R134A - much worse greenhouse gas than R-12, poisonous when burns, corrosive, PAG oils absorb water vapor, poorer refrigerant, now costs $15/can. HC's work slightly better than Freon. You could just put R-134A fittings on, pull a vacuum, and fill with HC's since it is compatible with PAG oils, but the EPA might have a spy camera in your garage. Who knows now that the federal phone and web hacking has come to light. BTW, R-134A is being phased out so that is a dead end. Re the ozone hole that got R-12 eliminated, the defective frogs in Costa Rica was not due to uV but rather to a pathogen that was always there. You don't hear about the ozone hole anymore, even though other countries are still using Freon.
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tried this stuff on a 98 ford truck last year, so far so good
Air Conditioning Refrigerant | Canadian Tire http://www.redtek.com/win_12a_chargeinstall.html |
As R12 is not, under any circumstances, legal this side of the border, and there are no on-line, open book exams that will get you a license here, that leaves, A) a pro AC shop that will tell you a proper R134a conversion involves a new condenser, dryer etc, so the budget is blown ( NOT myth, was told this by a shop when I wanted to get the air working on a 92 Dodge), or B) one of the HC systems (Duracool, Redtech).
As these are sold openly and over-the-counter, I am surprised that they are illegal to use! I have used both (Canadian Tire is closer than the outfit that deals Duracool by about an hours drive), and I have had good luck with both. (Atmospheric venting was performed by another car in one case, and believe it or not, by a large bird that did not yeild right of way on the highway in the other. Aluminum condensers do not like impacts, one of the tubes cracked.) If you haven't had an accident, I would suggest going to a shop and having the system evacuated. This will give you a piece of paper that you can use to prove you have not mixed refrigerants which IS illegal. The following can apply no matter what you use for a refrigerant. A vacuum pump can be made from the compressor unit from a junked dehumidifier and some fittings. CAUTION: if you are going to solder an adapter to the compressor line, DON'T. ANY RESIDUAL COOLANT IN THE UNIT THAT IS TREATED TO A FLAME CAN KILL YOU. THE BREAKDOWN BYPRODUCT WILL POISON YOU. Make your manifold for a check valve, vacuum gauge and refrigeration hose and either get a swage lock compression fitting, or double flare fitting. Pulling a vacuum on the system you are working on will check for leaks and dry it out (most of the water/moisture will boil off and be drawn out). Then, you can add oil (the same compaies that sell the refrigerant sells cans of recharge oil), and the add the refrigerant as per instructions. My nickels worth (pennies have been discontinued in Canada). |
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on automotive systems NEVER LEAK CHECK WITH A VACUUM!!!!! always use dry gas to pressurize the system and check for leaks. PERIOD!!! if you check for leaks with vacuum, YOU WILL DESTROY YOUR DRYER! |
If you've had a significant leak isn't the dryer toast anyway?
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As long as you've got positive pressure in the system there's no way for air/moisture to get in. In a completely empty system over a period of time you'd get moisture from the expansion/contraction due to temperature differences...same as a diesel storage tank.
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(The chart isn't mine, but it was copied from a open source page, and therefore is not stolen, either. It is here to indicate that people who have a lot more expertise than I use vacuum on AC systems and presumably, don't destroy them.)
"At sea level, water begins to boil and change into a vapor state at 212 degrees Fahrenheit. If we increases the pressure we can raise the boiling point of water. If we wish to lower the boiling point of liquid, we simply remove the pressure that's on top of that liquid. That's how we boil water out of an air conditioning system. We use a vacuum pump to bring the system to a level of near perfect vacuum so the water will boil off and be carried away as a vapor. It's important to note that ambient temperature has much to do with the point at which liquids will boil under vacuum. The greater the temperature, the fewer microns of vacuum will be required to start the boiling process. The chart below shows how temperature plays a role in the level of vacuum needed to boil water. boiling point (F) Inches Hg 120 26.45 110 27.32 100 27.99 90 28.50 80 28.89 70 29.18 60 29.40 50 29.66 40 29.71 30 29.76 20 29.82 10 29.86 All values are at sea level. Subtract 1 inch for each 1000 ft. above sea level" (I couldn't keep the formatting, but the figures are correct,) My comment about checking for a leak was prompted by the fact that if you can't maintain a set vacuum, you have a leak, not that leak testing was the primary purpose of putting the system under vacuum. I was making a reply to the 100% DIY idea, as it is far more likely that a DIY person would have access to air as a test medium than, say, a tank of dry nitrogen and the appropriate regulators. I also made the assumption that if the original setup was working, there would be no need to work on it, and if one was to be working on it, then the system has been opened to replace something, and as a result, have been exposed to ambient air and moisture, after which, the reciever / dryer should be replaced. As has been noted, moisture in an AC system is a very bad thing, and air would occupy space that should be the refrigerant. And, yes, I am aware that the setup I mentioned will not achieve a perfect vacuum, but it can generate a useful amount. |
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