From: John De Armond
Subject: Re: A/C Vacuum pump
Date: Tue, 30 May 2000 16:58:41 EDT
Mike Fairleigh wrote:
> I'd like to do a bit of A/C work on my '88 Grand Voyager, including
> replacing the compressor & receiver/dryer. I could handle the job, if I had
> some way to pull the vacuum on the system. Is there some way for a DIY'er
> to get ahold of one? Thanks.
If you have an air compressor, you can get a venturi vacuum "pump"
for about $60. They're noisy, don't pull a good enough vacuum for
drying but they will get the job done if all you need is to get the
air out of an otherwise clean system. I have one that I've owned
for a couple of decades. Believe I got it at NAPA. JC Whitney also
If you don't have an air compressor, the compressor from an old
refrigerator will work fine. Since these compressors rely on the
refrigerant flow for cooling, you must be careful not to overheat it
in vacuum service.
These pumps are also good for recovering refrigerant. For the small
quantities involved in auto systems, simply hooking the discharge of
the compressor to a recovery jug does the trick. The walls of the
jug serve as the condenser. this has an added advantage of not
trapping any recovered liquid refrigerant in the recovery system.
Important, considering how expensive refrigerants are these days.
Silver solder shraeder valves on the inlet and outlet of the
compressor and then you can hook it up with refrigeration hoses.
For a cheap recovery tank, use a 20# propane tank. Either remove
the valve and fit a refrigerant valve with a shraeder (1/4" flare)
fitting or make a POL to 1/4" flare adapter. Propane's vapor
pressure curve is very close to R-22 so the tank can be used for
either 12 or 22 or 134a. Be sure to label them so as not to mix
X-Source: The Hotrod Mailing list
Subject: A/C thoughts
Date: Thursday, Jul 21 1994 12:00:20
From: John De Armond
>> One project I'd like to build would be a Freon recycling unit. I've
>>tried to rent recycling units before, but _even_though_they_all_rent_
>>vacuum_pumps_ (at the current time), nobody will touch recycling units
>>due to fear of the EPA Nazis coming down!
>If you do get into recycling Freon then be sure that you capture
>all the nasties that can exist in used Freon. In addition to water
>you may find HF, a product of decomposition of Freon. Depending
>on the failure mode of the system there can be lots of other nasties
>in there too.
My "recycling unit" consists of an old hermetic compressor from a
refrigerator, a large suction line dryer (10 ton rebuildable)
and a tank. I test the freon for acid using the convenient acid test
kit available from, among others, Sealed Power. This involves nothing
more than spraying a little mist on a test strip and observing the color
change. Acidic freon somehows manages to just leak away... :-)
What I do is pump the freon from the system into a tank. When the tank
has a decent inventory, I distill it by inverting the tank, connecting
a gauge set to the tank and to the suction of the pump through the
dryer so that I can use the valve on the gauge set as an expansion
device, and connect the outlet of the pump to another cylinder.
I invert the "source" cylinder and draw off liquid which I allow to very
slowly expand through the gauge valve. Any non-condensables are trapped
in the source tank vapor space. Dissolved impurities are carried
to the filter/dryer and absorbed. The purified freon then collects in
the receptacle tank, condensing on the walls of the tank. Properly done,
it takes several hours to distill a 30 lb tank of freon. Right before
the last liquid is drawn from the "source" tank, the process is stopped,
the tanks disconnected and the residual allowed to er, escape.