From: John De Armond Subject: Re: A/C Vacuum pump Date: Tue, 30 May 2000 16:58:41 EDT Message-ID: <39342B8B.5C5FC02F@bellsouth.net> Newsgroups: rec.autos.tech 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 sells them. 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 refrigerants. John 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. John |