Air Conditioning

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i wrote the following as part of a response to a A/C belt issue. Anybody thought about A/C refrigerants before?

I have a few ideas about using hydrocarbon (propane/isobutane/butane) mix for a/c, it is non-toxic, zero ozone effect, a 1 year atmosphere life. It's also dirt cheap and more efficient than both R12 (freon) and R134a. A true drop in replacement for those nasty chemicals. It is non-corrosive and perfectly miscible with both PAG and natural oils. As for the fire risk, there is about 300grams of it in the system (you use only a third compared to traditional refrigerants) meanwhile you got 60 litres of hydrocarbon in the boot.... All refrigerants are required to have oil finely misted within it, it's what lubricates the whole system especially the compressor. A rupture of the evaporator (inside the car) even with a non-flamable (but toxic) refrigerant still poses the risk of the fine oil spray igniting. Non-flamable oil, I don't think it exists.

Any thoughts/ideas appreciated.

I have made a vacum pump from a fridge compressor, pulls down to 28inches of mercury at 1000 feet above sea level. It already had a r12 compatible schraeder valve, too easy.

Dom
 
evaporator leak, 300 grams of gasoline dump into a closed chamber
under pressure. the oil is not blended with your refrigerant only suspended
when it hits the lower pressure atmosphere it turns to gas.
at about 14:1 air to fuel ratio and a spark, which happens several times
every minute,
BIG K- F######-BOOM
sorry for the expletive

yes you have much more in the boot
it never enters the passenger compartment[/b]
 
Remind me what the flash point of propane and butane is between 250-300 PSI. This is nothing new. Down in mexico it is common to run straight propane for refrigerant. There are several cases of explosions every year, either due to accidents or the use of spark type leak detectors. Around here, they stopped selling the spark type detectors because of this. It works, but its not a good idea.
 
It seems to me there are 2 scenarios where a combustible quantity of hydrocarbon could exist in the passenger compartment. First, a punctured evaporator/hose whilst the unit is functioning. Second, a leak whereby the 300grams leaks slowly without ignition into the compartment. Waiting to blow up.

The first would be a like propane torch for a few seconds. There is no oxygen inside the evaporator so no exposion could occur. The blowtorch effect could be disasterous. it may result in severe isolated burns and a collision.

The second is a significant danger. A spark from dodgy wiring or a cigarette could cause explosion if the doors were shut and opening and closing the door didn't reduce the vapour below the ignition point. Does anyone know the vapour/air ratio it requires to ignite?

That said, I don't think the first is very likely. Evaporators are not as hard as a petrol tank but how many times have you had a petrol tank puncture? Most tanks hang exposed underneath the car, and still puncture is very rare. Internal rust causing a hole is much more common.

The second is more likely. But, In OZ propane has a pungent, distinctive smell. If you smell the gas on opening the door, leave the door open. Propane is heavier than air and in the case of a slow leak would settle in the footwell, well away from the interior light.

I still think the oil in a system poses a risk of the blowtorch effect, even if the propellant is non-flamable.

I think the risks are very low. In most OZ sedans the only thing between you and the petrol tank is the upholstery of the back seat. Any petrol vapour leak in the boot (trunk) poses serious risk. There is no firewall from the passenger compartment to the boot. Smokers don't think twice about smoking in a sedan.

Is my DIY, do it cheap mentality clouding my judgement?
 
"The second is more likely. But, In OZ has a pungent, distinctive smell. If you smell the gas on opening the door, leave the door open. is heavier than air and in the case of a slow leak would settle in the footwell, well away from the interior light."

But robaby prety close to the jamb switch whicj turns it on


How id the oil carried in the refrigerant? Is the desiccant compatible with hydrocarbons?

And if it ever gets sold (at least in the US), if they find out who stuffed a refrigerant not on the SNAP, you go to jail
 
Apologies for the spelling in the last message. I'm using a computer at the hotel I'm staying at and it's keyboard doesn't touch like mine.

And I can't type or spell worth crap
 
I think the biggest problem is in collisions where the reciver-drier bursts. You have a relatively large quantity of liquified flamable gas suddenly exposed to oxygen and more sources of ignition than you can count. Almost all the explosion problems I've heard of were on systems that leaked out the pressure, and allowed oxygen to leak in. If the ratio is correct, the entire system goes out in a big way. Anyway, with some of the substitute florocarbons availiable, like freeze12, there isn't really a need to use anything that has the slight chance of beeing dangeous.
 
Propane is very tolerant to poor fuel mixtures (read that as " it likes to 'splode")
oh, and if it ever hits something in the 210*f range, it turns to a gas and stays there. warehouses that were merely on fire before have been leveled by this phenomonon. Yes, i do know about the blow-out valves on forklift tanks, and the stories i've heard, they worked just fine throwing flames close to 100 feet. but that sudden phase change is a real nasty thing.

there's enough potential for fire in an accident as it is, no reason to add another, easier, one.

If it wasn't for having to think about everything going all wrong all at once, i'd say go for it. but that's not the real world.
Ern
 
8) if you take R-12 and expose it to high temps, like on an exhaust manifold, you get phosgene gas which is toxic, but does not explode. R-134a might become flammable IF you get the temps high enough, and the freeze 12 is also flammable, but with propane/isobutane/butane you have a serious enough hazard that the EPA has it on the not approved list for refrigerants as you have a potential bomb in the car. yes it will work, and work well as a refrigerant, but then so does ammonia(one of the first refrigerants, and was used by the british navy untill well into the 50's).
 
Minor correction: EPA doesn't approve of hydrocarbon refrigerants for mobile refrigeration systems. However, for commercial refrigeration systems, that might even cover acres of "factory" or cold warehouse operations, EPA has given HCs its full blessing.

Mysterious, isn't it, how not 'everybody' had to convert over to Dupy's R134a?

Other notes[or nasty argument triggers!]:
*R134a has a relatively low ignition point.
*Many 'ozone-killers' are reportedly blown right out the vents in the production of R134a; no EPA problem here!
*A typical space shuttle launch puts more 'ozone-killing' agent(s) into the atmosphere than a full year of leaky R-12 A/C systems at its 1980's worst!

Potentially, many dangers of fire & explosion exist in moving HC-fueled vehicles. Even diesel fuel injectors(Mine "break" into a mist-like cloud @ 2500psi. Newer units are much higher!) could cause fires, if safeguards, seals and controls weren't in/on the vehicle. Ill-conceived and poorly implemented systems (any type of sytem)will always exist, and carry with them a greater threat to safe operation. There are just too many good HC A/C systems running in Europe and other places not to believe that HC refrigerant can be relatively safe, non-polluting, long-lived, and inexpensive.

Okay, throw them rocks!

J.R.
 
You can solve ALL your problems with a product called Johnsen's Freeze 12. I converted mine over to it and it works great, no A/C hoses to replace, no sky high compreesor head pressure, and it mixes with any A/C oil you may have in your system. No I am in no way affiliated with this company, just sharing some money saving info. I was going to convert to 134a and replaced my lines and bought a new dryer, but I got to reading in some A/C forums where these people with old type compressors had converted to 134a and blew their compressors up because of the head pressure, (134a runs at twice the head pressure R12 does) and only mixes with certain oils. A friend in my car club told me about Freeze 12 so I tryed it. It cost me 40.00 to pull a vacuum, put in 8oz of esther oil and 2 cans of Freeze 12 in my 1970 Maverick with its original compressor, and it will FREEZE you out. Try it you'll love it.
www.freeze12.com Most shops are carrying it now, check around.
 
Whoever said R134a runs at twice the head pressure was either embelishing to make thier point, or filled the system by the sight glass, which is wrong. To run the system at twice the head pressure could put it at over 500 psig. Most 134a systems will not (and should not) see over 320-350 psig (this is according to arizona temps, which can get high). This is higher than r12, to be sure. Thats why installing a binary switch is so important (and often overlooked) in a typical conversion. I have seen people do a lot of things they aren't supposed to do with A/c systems, like mixing refrigerants. The thing I look at as far as the HC refrigerants is that these systems were not made to run HC, and it may be safe, it may not, but I have no experience running HC, and so, as I don't know what is safe and what isn't, I won't take the chance. Now if I could run an ammonia system, would that be efficent or what?
 
Looking at the MSDS for the product on the above linked site, it appears that "Freeze 12" is still a chloro-fluorocarbon! Isn't that what the problem was with Freon 12 and it's chemical brethren, relative to wiping out the ozone layer? Sounds suspicious to me(and yes, it's been a while since my last organic chemistry class!).

J.R.
 
8) true, but freeze-12 is an hcfc and is considered partially halogenated, where as R-12 is just a cfc which is fully halogenated. freeze-12 is actually chemically similar to R-22(there are differences though).
 
To give you an idea of just how dangerous propane really is, here is a little story.
Last year, a fire broke out in guys house in my town of Rhine, GA (Pop. 243) He had a propane bottle in his closet, why, I do not know. But it was a bottle like the one you use on your grill at home, and it was full. Anyway, the fire soon reached the propane bottle and heated it up to the point that the propane inside the bottle started to boil. It exploded and leveled his house and 4 other houses. The explosion killed 4 volunteer fire fighters, one of whom was my FFA advisor :cry: and several bystanders. The moral of the story, propane is very dangerous so do not use s*#t that explodes for anything other than what it was intended for. Using propane on a 30+ year old car is just asking for. All it takes is one spark from bad wiring and you will never know what hit you.

P.S. I did not make this up!!
 
I too have converted 2 1990 Ford Broncos to Freeze 12 from R-12. Easy to do and as far as I can tell just as cold. One of them has been running just fine for two years, the other one 6 months.
 
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