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Old 19-11-2006, 20:42   #1
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Refrigerant

Any fridge experts here?
This may (hopefuly may not) be a really stupid question. Can Propane be used as a refrigerant in a compressor type system. I realise it may not be as efficient as the proper gas, R22 is it?? but would it still work??
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Old 19-11-2006, 21:21   #2
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Absolutely!

Yes, propane would work as a referigerant. I do not know what its merits would be relative to ammonia or to the lesser efficient refrigerants in "legal" use today.

Although most people might gasp at the thought it actually might be practical to design such a system that would be relatively safe, well at least as safe as propane use is today as we know it with heaters and stoves, etc. Just because it gets compressed and released in some expansion device as a closed system does not mean that it could not be done safely.
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Old 19-11-2006, 22:26   #3
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Check out http://www.kollmann-marine.com/ go to the Technical Forum
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Old 19-11-2006, 22:51   #4
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Well as I see it, Propane should be "safe" because there is no oxygen in the system. It would only be "unsafe" if it leaked out and sat in a confined space.
But actually I am being a little off topic here. This is actually a car airconditoner not a boat refrigeration system. My car unit has lost it's cool and I wanted to top it up. But to get the experts to do it, they are going to charge me $400.00. I said, "ya what!?!?!"
So I had one of those Brain fart moments when I suddenly thought, "hey I wonder if I can charge it with LPG ?" It may not be totaly as efficient, but if it kept the car a little cooler than me winding down the window at the mo, I am all for it. Besides, the window down dries out my hair ;-)
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Old 20-11-2006, 00:53   #5
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Old 20-11-2006, 05:37   #6
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nz??? and airconditioning you need to come and live in cairns for a while when you return to nz ittl be the heater youll need not the aircon, 400$ PROBLEM FIXED
SEAN
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Old 20-11-2006, 06:03   #7
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Wheels, what kind of refrigerant is it supposed to use? I would NOT put just any old gas in, even though in theory any old gas can be used as a refrigerant. Why? Refrigeration systems have lubrication oils in them that are specifically compatible with certain refrigerants. Introducing a foreign chemical into the system could severly damage it. $400 is a lot to rechage a system. Does it use R-134a, or what type of refrigerant?

Are all refrigerants strictly controlled in NZ?

Shame you're not around here. When I bought that broken fridge last year, I had to buy nearly $1000 worth of stuff to fix it. I have everything needed to do refrigeration repair right on the boat. I could pump down the system, recharge it, hang a 2nd expansion valve off it, etc... ha ha ha

Don't use propane though. There's no telling what it might do with the compressor oil, plus, it has different properties than the known refrigerants, so you'd need a new expansion valve, etc...
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Old 20-11-2006, 11:59   #8
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Ummmm, I might damage the aircon?? how can I make it any worse than it not working at all??? :-)
The reason why I was willign to think this, is the car is a 1995 model commadore and it has done 300,000kms. So I figured the compressor is possibly worn out. The cost of repair would be more than the car is worth. So one reason for LPG was that if the compressor is slowly leaking gas, it doesn't really matter. It does if I am going to spend $400 on gas only to find it lasts one summer or even less.
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Old 20-11-2006, 14:01   #9
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Ahhhh.... I see. So it already has one foot in the grave. I still am not sure you would get the performance out of propane. Take a look at R-134a or R-12 evaporation and boiling points (for a given temperature and pressure). Next, compare these with that of propane to see if your system has a prayer of running with propane.

While you're looking into that, maybe you'll find a gas that more closely matches the physical characteristics of a refrigerant?
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Old 20-11-2006, 15:45   #10
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I definitely wouldn't use propane. The fact that it is leaking should be enough reason not to. Propane is heavier than air, if the leak is in the evaporator (inside the car) it could pool in the floor of the car overnight, and you could blow yourself up in the morning.

Also it probably wouldn't work, the pressures in the system would most likely be all wrong for propane so it either may not condense in the condenser, in which case the system simply wouldn't work, or conversely it could cause real problems, like condensing in the compressor and destroying it, for instance.

The system would hold a few kilo's of gas - a few kilo's of propane can cause a huge explosion.
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Old 20-11-2006, 18:35   #11
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Yeah good point 44. Although I hope I ain't breathing refrigerant either ;-).
This has been a very gradual decline in performance over the last 6months. It didn't just stop. I haven't really noticed it as we have just come out of winter. Although I use it most of the time even in winter to demist the windscreen and keep the air inside dryer.
But I still take your point and I will drop this idea.
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Old 20-11-2006, 19:36   #12
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Wheels, there are in fact "replacements" for R12 on the market which sometimes include propane, but pretty much everyone in the AC business or the business of regulating those systems will tell you not to do it, there's simply too much danger of explosion as the gas finds a way to mix with oxygen and heat.

On the other hand, R-134a conversions are common and R-134a is both cheap and effective. About 5% less coolling power when used in an older R-12 system, but aside from the riceburners (which had no excess capacity to begin with) it can be used in "Detroit" cars in general and you'll only see an extra minute lag before the system blows cold air.

R12 is still only about $30/lb. in the US, new or recycled, and unless that's a BIG car, you probably wouldn't need more than 3# of R12 to refill it. The big trick is, to leak test the system before you waste money on more R12. Leak testing is the hardest part of AC repair, at least in the US most AC folks are inept bozos. Even some of the car companies report that nearly 50% of the compressors returned to them as defective, are perfectly good. Their own dealer mechanics just don't know how to work on AC systems. DUH.

Leaks can be hard to track down, but if you use a dye kit, and clean the lines down before you start, even a 1/2 pound of gas should be enough for gas testing. And, you can use nitrogen or CO2 for the pressure testing. You'll have to rig fittings to get it into the system...but any inert gas with no air and no moisture in it will do fine. Both of these will be evacuated when you vacuum the system down anyway.

I'm no expert even though I'm EPA certified to work with these things, so feel free to ask.
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Old 20-11-2006, 23:07   #13
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I think we have several issues with why it is so darn expensive where I am. I wouldn't mind betting that it is much cheaper int he bigger cities due to competition. But here, we don't have many rfer guys and only one that does cars. Firstly, we are not allowed to just let the gas go here in NZ. Especialy the old gas. That has to be collected. If a system comes in with the old gas, it has to be removed and the system "converted" to be able to run on the new stuff. That costs and seeing as it all tends to be "smoke and mirrors" here, the few that do it charge big time and we as a consumer just presume that is the way it is.
I know that there has to be some problem due to age. If I get some wally to try and fault find, the cost would be prohibitive. Then I imagine the seals int eh compressor would most likely be the culprit anyway. So replacing or rebuilding would also be cost prohibitive.
I doubt I could even buy the gas from a refrigeration company. It was difficult enough to get one to just fill my boat fridge system.
However, I have had a very kind offer from someone on here with supplying some gas and so I may be able to sort this out myself yet. The leak is so slow, that if a top up gets it running efficiently again, I may just require a top up once a year which will last till we replace the car in a year or two.
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Old 21-11-2006, 05:42   #14
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Better just roll the windows down! lol
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Old 21-11-2006, 17:10   #15
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If the system is R12, then you can buy a cheap replacement in 134A, most auto part stores sell a direct replaceemtn with no oils drained. if the system is flat no recovery is needed. you should leak check with an inert gas such as nitrogen, as it is a dry gas, careful with the pressures. as mentioned before, you should not need much gas, largest system i have worked on was 4 lbs, and that was a suburban with rear air. propane in a car is not a good idea, nor would i think on a boat, since the unit is usually installed in confined areas adn the compressor uses contactors with spark or arc if you prefer, and since most leaks are usually in the unit, you are going to pool any leaking gas in the area of a potential spark.
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