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Not kidding. As a scientist I am required to have an open mind. I too once thought that hydrocarbon refrigerants were dangerous until I read some engineering papers by faculty at the University of New South Wales that proved otherwise. Below is a short review of the published literature.
Our cars have the expansion valve in the engine bay. This restricts a leak in the passenger compartment to about one minute to discharge a substantial quantity of refrigerant. If the ventilation system is on (do you ever turn yours off?) and the refrigerant charge is low (it is if you are doing it right) a flammable mixture can only be reached close to the leak, and is only present transiently (Maclaine-Cross and Leonardi, 1995, Maclaine-Cross 1997). In addition, switches, relays, and even cigarette lighters in our cars are unable to ignite an unlit butane/propane mix capable of sustaining combustion when lit with an ordinary striker (Razmovski 1994, Rajasekariah 1995). The ‘bomb in the passenger compartment’ accident is impossible due to the necessary slowness of any possible leaks and the unsuitability of any in-cabin ignition sources. Furthermore, due to the high pressures present in the condenser, flames have the opposite problem if tubing is pierced in the front of the car, as might happen in a crash. The jet from most such leaks only slows below the flame velocity when it has mixed with air below the flammable limit (Maclaine-Cross, 2004). The bottom line is that none of these practically possible leak scenarios produce mixtures of hydrocarbon and air in concentrations and velocities capable of sustaining combustion without a suitable external ignition source, of which there are none anyway.
The above research is the only real-world testing I can find, using realistic amounts of hydrocarbon refrigerant released at realistic rates in real cars using real car components as ignition sources. Yes, I am aware of the tests some fire departments and arson researchers have done, dramatically blowing the windows out of cars by releasing large amounts (600g to upwards of 1kg) of LPG all at once in a completely sealed vehicle with a flame as the ignition source. I think we can all agree on what these mean. Besides, you can do the same with gasoline. All that stands in the way of your 900 becoming a bomb is a couple of O-rings and plastic fittings on the fuel tank.
In a crash, propane-butane mix is quick to evaporate and leave the area due to air flow and the fact that it is under pressure. Gasoline leaks pose a far greater real-world risk. In addition to the literature above, real-world performance of hydrocarbon refrigerants in Europe, Australia, and Africa has shown them to be safe.
Finally, you know you can burn 1,1,1,2 tetrafluoroethane anyway, right? Not as easily as propane or butane, but if you're so worried about flammability, why don't you try a CO2 retrofit. Now THAT would be interesting! It could double as an automatic fire extinguisher in the event of an accident.
Nobody works on my air conditioning except me, so getting HC refrigerant in somebody's machine is a non-issue. I trust others will take the same precautions so as not to ruin someone's expensive equipment. I kind of figured DIYers would keep DIYing. After all, we are responsible humans, aren't we?
In your R134A instructions, you do not mention an oil change. From what I know, this is absolutely necessary due to the fact that R134A is immiscible with R12 mineral oil. Flushing even with large amounts of paint thinner and air will not, in my experience, remove the mineral oil completely, especially from the space next to the shaft seal of the SS170PSS compressor, where oil likes to collect. Using a conversion oil such as polyol ester is the current industry standard. I have had less than great experiences with R134A doing anything less than a full rebuild, manually changing oil in the compressor and flushing all the lines extensively with paint thinner and compressed air. And switching oils, flushing, and backflushing is a lot of work, with nasty chemicals! Hydrocarbons are easier, cheaper, about as safe (see above), and more environmentally friendly. What's not to like?
posted by 75.69.61...
, Wed, 12 Jul 2017 18:08:57
1, Thu, 13 Jul 2017 20:49:53, Mon, 17 Jul 2017 09:29:06, Mon, 17 Jul 2017 09:32:37
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