I guess to the point here is cost and availabilty. Propane is surely cheaper and MUCH easier to obtain than anything else. Seems the "fill" instructions for propane are pretty much the same as other refrigerants. (other than amount and pressure)

BTW, Freeze 12 is non flammable and EPA accepted BUT it requires a certification to purchase and is relatively expensive.

I see I thought the freeze 12 was cheap and no license, I must be thinking of the Duracool.

Elombard, Freeze 12 is basically 80% R134 with 20%R142B mixed in. The additives are there to make it work on a R12 system I think. I am not crazy about it. It is nowhere near as light on the compressor as HC's are. There is someone on this board, named Fox I believe, who sells Duracool. Maybe he will step forward. Now Duracool, Enviro-Safe, or Hychill which is the leader in Australia, are all HC mixes. Basically Propane/Isobutane in varying percentages. Anywhere from 50%Isobutane/50%Propane to 40%Isobutane/60%Propane. Propane is what does the cooling. The Isobutane is there to help in oil movement and to lower head pressures. Besides, you would get maybe too much cooling with pure propane. The common practice is to put in one of the mixes and then boost it with extra propane for much better cooling. At least as good as R12 from what people say. Far better than R134. Probably the best percentage from the passenger standpoint is 20%Isobutane and 80%Propane. At least from what I have heard. There is also another product out there called Autofrost. That one is a little different. It has common R22 as the main gas, with something ese, I don't know what, to bring it down to acceptable head pressures for car compressors. I also heard that these propane/isobutane mixes tend to leak less. Who knows. Or who cares since it's so cheap.

Most coolants are flammable. I would go with Duracool. I will be converting my system to this, and I have heard that it is more efficient that R12 and cheaper too!

Good stuff - this is the way I am planning on going if I add the AC back on mine. Duracool advertises in some of the P car mags, they could probably help with your questions??

Ed,

I assume you'll be purging your system when/if you go to the Propane mix. If not the existing R12 will throw your calculations off. Also, which lubricant will you use? Synthetic?

Remember, Duracool (or whatever it's called now) is not EPA approved and is flammable. Mixing any other substance with R12 (or R134) is illegal.

End of Public Safety announcement.

If I am making a good point, it is so because I am not just spewing some opinion off the top of my head without any real resarch into the matter at hand. After all, an opinion should always be a reasoned judgement based on facts, not fiction. As to who is lobbying the hardest, or who is lobbying for that matter, it seems just about everybody. But never has it been more clearly evident as it is with the EPA's stance on refrigerants. The BS on this one reeks like it never has before. Again, all one has to do is to ask why the EPA does not allow the venting on what is supposedly a truly safe refrigerant. This question has many ramifications. And at the same time, why the EPA, an agency only in charge of POLLUTION issues, does not allow the use of a substance that is clean enough to cook with. Flamability? Since when has the EPA been in charge of making sure your car does not catch fire. That is the DOT's or the NHTSB's job. After all, was it the EPA that went after the Pinto? Strange protectionism, I mean, politics folks.:rolleyes: But on this matter, the BS is as clear as glass.

I just wish we could mature beyond this point and get to the issue at hand, which is how to use it. It's like trying to have a converasation about radar detectors, which gets sidetracked by someone arguing about the illegality of speeding. We should leave the political issues to the OT board, and get back to the technical over here.

Regarding the non-approved status of HC for R-12 retrofits, I believe it is legal to use HC IF you retrofit your R-12 to R-134a. Then, you can legally (according to EPA) convert to HC refrigerant. Of course, this is just lunacy.

Regarding using 100% propane, it will work as long as your evaporator doesn't freeze. I retrofitted a diesel Mercedes with straight propane, and vent temps get down to 20 degrees, while the evaporator freezes. In the early Mercedes design, the compressor is always on, and the fan speed is variably adjusted. If you have a temp switch on the evaporator (to turn off the compressor when vent temps reach 30 degrees), then you can run propane. However, I'm worried about this issue with oil transport via propane. Wouldn't you want the oil to be in the compressor all the time?

I recently read a ASE article that compared r134 to the substitutes. Propane was about 10% more efficient than R134a, with the primary/only drawback being the flammability of propane. To avert this issue, the article suggests a double loop system in which an external evaporator cools a liquid, like water. The water is then pumped into the passenger compartment where it passes a second heat exchanger, cooling the cabin air.

I do feel there is risk with running propane, but that risk is very small. What are the chances a crash creates a leak in the evaporator only (filling the cabin), while not breaking any windows or creating any air leaks that will vent the gas? I'm not saying it could never happen, but if we are looking for zero risk, we might need to consider never stepping in the car in the first place.

Lastly, and sorry for rambling, HC refrigerants are used in the petroleum industry (for chillers I believe), and in residential refrigerator compressors. If this stuff was so dangerous, I think we would hear about it.
jürgen

DITTO! :mad:

Australia spent millions upon millions testing it. Including crashes. The end result being no exposions. The reason being twofold. First the tiny ammounts in the system, which is less than a coffeee mugfull. And second how quickly it escapes from the system.

I think the Isobutane has a dual purpose. To help carry the oil and to reduce the head pressures. I read somewhere that full propane fill is somewhat close to a full r22 fill. With the isobutane, it becomes more like r12. But with lower head pressures on the compressors. All still very compressor friendly. Turbo, how did the compressor hold on full propane. I ask because with full propane, it should cool like crazy.

I am leaving right now to get a tapping kit for the nozzle. Along with a r12 hose. Hopefully I can find one. I'll be back in a couple of hours and see what I can come up with.

Me being the guy that doesn't like to make waves, always thinks of the repercussions of travelling a lot (which I do) and having some work done (even a 'simple' recharge, which these days is a evac and recharge) and the mech doing the work having his equiptment contaminated by whatever mix of gases is in my system. If I tell him ahead of time, he (rightfully) is not going to touch my system. How about when you sell the car? Are you going to disclose it? Me neither, I guess.

I'll stick with the OTC stuff. My stock system works fine across the Mojave Desert for the last 4 years.

OK, so I probably need to get some of this Isobutane/Propane camp fuel. With propane, charged by weight, the pressures are mighty high. However, once you get some airflow across the condenser, the pressures come down pretty good.

The compressor is a brand new unit. I can't even remember the brand. It's a popular Japanese unit. Nippondenso, maybe. With propane, I think one could honestly get the cabin air temps down in the 50s, if desired. If cools like mad, AS long as you get airflow across the condenser. When in the driveway, I recall vent temps in the mid 40s. Once you got on the road, the temps steadily dropped, and with the auto evap fan control, the slower fan speeds = even colder evaporator temps. That's why you'd get low 20 temps when the car was cooled.

BTW, if you charge propane only, you can charge vapor or liquid (just don't slug the compressor), but if you charge a isobutane/propane blend, you need to charge by liquid due to differing vapor partial pressures. However, if you charge an entire can of the blend, you're gonna get all the mix out regardless.

good luck. I just need to do some refining to get perfection. I'm sold on the HC products.
Jurgen

What do the planes use on the ground in their A/C?

(I know they use ground units in some instances... but what does their APU turn for A/C?)

The reason R134a is the standard is not because of its cooling properties. It is because the A/C manufacturers and automakers are "in bed" with the company that makes R134a. Funny, if Duracool is not EPA approved, why are there so many distributors in the US? And how come the military uses it? I'm not trying to sell everyone on Duracool, but I have read some pretty impressive statistics on this compound. I know, I know, don't believe everything you read... I am only giving them credit for half of what I've read! From the test results and pelican feedback that I've read, it is twice as efficient as R12, with R134a not even in the same room. The nice thing about this compound is that you do not need to switch compressor oil. You do, however, need to completely evacuate your system. You are not allowed to mix R134a or R12 with this compound. Also, you will need to put on the correct fittings on the discharge and suction connections.

Good luck!

BTW, the Duracool conversion kit is $59, and that includes the coolant.

Actually, some folks have just thrown duracool over whatever remnants of freon were in the system and did all right.

Just picked up an R12 manifold gauge set with all the hoses and connectors. Now I have to figure out how to rig the hose on to the Benzomatic propane nozzle. Worse comes to worse, I'll just marine-tex the thing together. Or chop the end of the hose and slip and clamp it over the nozzle. Easy enough.

Lucky for me, my compressor is damn old. If it craps out, oh well. I could probably use a fresh one anyway.

Ed:

Mixing the two is not adviseable, since Duracool contains some lubricating properties that are not compatible with other coolants.

BTW, be sure to take note of the difference in pressures of the two substances. The Duracool pressures will be lower than that of R12 or R134a; you certainly do not want to overfill the system (which will cause your system to not blow cold) and damage your compressor.

Why did this turn into "which refrigerant should we use to replace R12?" That was not the question.

I did my research and I came to the same conclusion as Ed. This is my own choice. I am also interested in fill procedures and not "hey look what the EPA says about that not being legal"

ACTUAL QUESTION:

If I have my local shop suck out my R12, can I charge with HC in the next few days without re-vacuuming, without losing effectiveness? I ask because I would rather not buy a vacuum pump.

TIA for Technical Answers, but not Dogma.

Most planes use air cycle machine for A/C. Somewhat inefficient unless you have lots of airflow. Which is something we have a lot of.

Some of the ground units do use a conventional freon-based system. The coolant used depends on it's age.

Very rare that an airplane uses a freon cooled system. Once airborne, the problem becomes keeping the incoming air warm enough.

Last week, I saw -77 degrees Centigrade at altitude. Minus 97F or so.

Sorry, didn't mean to become part of the 'dogma' crowd, but seems it went that way again.