Propane A/C refrigerant

[Stuart Hastings]

> >"Thermodynamic Properties of Refrigerants", as published by ASHRAE.
>  Propane is a _VERY_ good refrigerant, thermodynamically speaking.<
> 
> Hey, what I want out of this discussion is how I can flush out my R12
> system and replace it with propane. What would have to be changed in the
> system? How I'd love to thumb my nose at the massive government mandated
> taxes that have driven the cost of R12 into the stratosphere. I can't
> imagine a couple of pounds of propane up front would be that much more
> hazardous than a couple dozen gallons of fossil fuel in back.

It had to happen eventually. For once, *I* can answer a question on
this list. Please excuse my too-long rambling.

Short answer: Change nothing, use a 79%/21% mix of propane/butane,
make sure your gases are dry, and use less than half of the R-12
charge (use system operating pressure to determine correct charge).

Here is the definitive paper, explaining exactly how to do this,
complete with warnings about exactly which laws you break to do it,
and humor to boot. The part about mixing your own refrigerant is near
the end:

	http://www.vettenet.org/acfaq.txt

I urge anyone with an interest in this subject to make your *own* copy
of this document, in case the original disappears. This paper hasn't
been updated since 1996, so the comments there concerning R-406a and
R-414a are out of date (both are now EPA certified, and the
cheaper-and-better R-406a has rendered R-414a obsolete).

For those too lazy to look this up, be aware that, in the USA, it is
illegal to convert an ozone-depleting (i.e. R-12) automotive A/C
system to a hydrocarbon refrigerant. It is not explicitly illegal to
convert a a non-ozone-depleting refrigerant system (i.e. R-134a) to a
non-certified (i.e. propane) refrigerant. Go figure.

Of course, all bets are off if the A/C system isn't "mobile." If it's
stationary, I guess you can use whatever you like. If you're outside
the U.S., sanity prevails, and anything goes.

U.S. EPA won't certify hydrocarbon refrigerants for cars because
"nobody has proven them safe." Of course, why would anybody spend $$$
to prove that an extrememly cheap refrigerant is safe when they can
make money selling R-134a?

I understand that you can buy this stuff premixed now. Try

	http://www.es-refrigerants.com
	http://www.duracool.com.au

If you're interested in U.S. EPA "certification," you can do this
online:

	http://www.epatest.com

For those afraid of the U.S. EPA, the best non-hydrocarbon R-12-like
refrigerant is almost certainly R-406a; all of the other blends have
oil-return problems. See www.autofrost.com for details. I have R-414a
in two of my cars (an early, flameproof variant of R-406a), and the
claim of "better than R-12" is valid in my experience.

I also understand that propane/butane mixes are widely used in
Australia. Perhaps some of our contributors there can comment.

For further reading, check out the bulletin-board discussions at
www.aircondition.com .

stuart hastings

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