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R-12 substitutes

This thread came up last December on rec.autos and rec.autos.tech; I
have appended one of especially thorough posts.  Another alternative
to R-12 is a refigerant called GHG-12 which was invented by George
Goble (thus the GHG) of Purdue.  If you email him at
ghg@noose.ecn.purdue.edu he can give you all the info on it.
Unfortunately, it is not an alternative.

~From rec.autos.tech Thu Dec 16 00:12:33 1993
~Path: panix!cmcl2!rutgers!gatech!howland.reston.ans.net!europa.eng.gtefsd.com!emory!rsiatl!jgd
~From: jgd@dixie.com (John De Armond)
~Newsgroups: rec.autos.tech
~Subject: Re: Car air conditioner using BBQ gas
~Keywords: air-conditioner, auto-gas, BBQ-gas, R12
~Message-ID: <aky2kmc@dixie.com>
~Date: 15 Dec 93 18:10:20 GMT
~References: <9334713.3996@mulga.cs.mu.OZ.AU> <schless.755916135@bart.ecss.iastate.edu>
~Organization: Dixie Communications Public Access.  The Mouth of the South.
~Lines: 92

schless@iastate.edu (P C Schlesselmann) writes:

>In <9334713.3996@mulga.cs.mu.OZ.AU> yang@mundoe.maths.mu.OZ.AU (Yang Yu-shuang) writes:

>>Hi Net Friends,
>>I remembered there were some discussions about using the auto gas and BBQ
>>gas to replace the R12 in the car air-conditioners. Unfortunately, I lost
>>my files on this subject. I would appreciate if you could send me a copy
>>of your file or your article posted on the subject.



>Break down and spend the $20 bucks for the R-12
>or use DuPont Suva MP42 (aka R-401C) after TOTAL evacuation of the old R-12

Now that we've heard from the bozo brigade, here's how to do it.  From
an article I posted awhile back:

~Date: Tue, 22 Jun 93 19:05:41 GMT

elkins@remus.rutgers.edu (George Elkins) writes:

>> use 21% isobutane and 79% propane.. makes a good
>> match for R-12..

>But where would this mixture be likely to be sold?   A welding supply store?

No one will sell the mix for A/C use because EPA has made its use
illegal.  When you use it you will be engaging in the finest form of
civil disobedience.  Means you gotta roll your own.  isobutane is
available as the fuel used in Gaz brand camping stoves.  Read the label
to make sure you are getting isobutane and not n-butane.  isobutane is
generally used in stoves designed for low temperature use.  Gaz sells
both plus a propane/butane mix so read the label.  Propane is
conveniently available in propane torch cylinders.  The odorant does not
harm its use as a refrigerant.  Don't use gas grill propane.  This stuff
is generally fairly wet.

An empty propane torch cylinder makes a very good mixing container,
particularly the large fat ones.  An old torch valve fitted with a
refrigeration flare fitting lets you use it with A/C equipment.  The
procedure is simple and requires only a scales of some sort.  A postage
scale will work fine.  Evacuate the propane cylinder if you have a
vacuum pump.  Then using a side tapper for blow-off cans (the type that
punches a hole in the side of the can), introduce the correct weight of
isobutane from the Gaz cylinder.  Then top the cylinder off with the
required weight of propane from another propane torch cylinder.  Warming
the donor cylinder will drive the process.  A second torch body fitted
with a refrigeration flare will let you hook the two cylinders together
with a refrigeration service hose.  Be sure not to overfill the
recipient cylinder.  Check this by slightly lifting the safety valve
with the cylinder sitting upright.  If liquid comes out (white mist,
real cold), bleed the cylinder until the liquid is below the bottom of
the safety valve.  Needless to say, do all this outside.

Before using the mix, double check the accuracy of the blend by comparing
the vapor pressure in the cylinder to its temperature.  This is easily
done using refrigeration gauges.  The vapor pressure should agree with
that of R-12 +- 10 psi or so.  

When you modify a torch body, you'll need to find and drill out all 
restrictions that limit the propane flow to the torch.  Typically there is
a restriction and/or a check valve in the barb that taps the cylinder 
and another one downstream of the control valve.

BTW, propane torch cylinders make convenient replacements for blow-off
cans.  They are much more gas-tight than the typical disposable 
freon cylinder so transfering valuable R-12, GHG-12 or whatnot makes 
real good sense.  And they are more reliable.  Instant sickness is dropping
a 30 lb can of freon onto something that punctures it :-(  Be sure to 
label the cylinder contents.

Oh, refilling used propane torch cylinders is illegal and if DOT catches
you, they'll cut your dick off or something.  Don't transport the refilled
cylinders and you'll be OK.

John De Armond, WD4OQC                   | For a free sample magazine, send
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