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Member

Join Date: Oct 2010
Posts: 7

How to Design an Automotive A/C Recovery Machine

10/16/2010 10:56 AM

I've been working as an Instructor in toyota kuwait, and I want to build my own recovery machine because it is very costly. I bought a recovery tank a manchester 50 lbs dot 400, a 134a compressor 1/3 hp (1/2 hp, 50/60 hz is not available at the moment), I fabricated my 2 oil separator for the suction side & discharge side, I bought a condenser, but I am planning to custom my own heat exchanger to minimize space, my question are as follows.

1. Is it necessary to put a one way valve in my suction side and a gas/liq. regulator? (Needs suggestion & explanation)

2. How to design a compact heat exchanger in order not to use a huge condenser?

3. Since the compressor is discharging a minute amount of oil what is the right capillary orifice diameter to use to return the oil in suction side of the compressor(oil sep) or should I use a regulator using spring & ball instead of capillary ( needs suggestion & correct me if it is necessary to return it back the oil or discard it, if I am wrong please inform me ) if spring & ball, what is the right spring tension and pressure? ( Needs computation)

4. At the end of the condenser/heat exchanger what is the right diameter of the capillary orifice going to my tank? (Kindly explain)

5. Is it necessary to use a capillary tube from the vapor tank to suction side of the compressor as pressure equalizer or use a purge valve to maintain tank pressure? (Needs suggestion and explanation )

I really appreciate your relentless help and if you could share your computation and design.

Thanking you in advance,

Nathan

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Commentator

Join Date: Aug 2010
Location: VA
Posts: 76
Good Answers: 4
#1

Re: How to Design an Automotive A/C Recovery Machine

10/17/2010 8:37 AM

Your recovery tank costs about $100. In the states recovery machines for r12 or 134a and even r410 are only about $500 new and have a value that you could recover when you choose to sell it. Id suggest that you buy one on ebay or craigs list to save money and save your efforts at trying to build one.

Simply a compressor feeding directly into the recovery tank would work for cars and you dont really need a condenser; 50# tanks work, Ive done it and also had a company that made recovery machines prior to the need for U.S. certification rules on such equipment. Making one is a pain and lots of your time.

http://cgi.ebay.com/Oil-Less-Refrigerant-Recovery-Machine-MICRO-VAC-II-NIB-/140464866764?pt=LH_DefaultDomain_0&hash=item20b45bc5cc

http://cgi.ebay.com/Inficon-Vortex-AC-Refrigerant-Recovery-Machine-/120633002374?pt=LH_DefaultDomain_0&hash=item1c16498986

Woody

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Guru
Hobbies - CNC - New Member Canada - Member - Finaly got around to it.

Join Date: Feb 2008
Location: Canada
Posts: 503
Good Answers: 12
#2

Re: How to Design an Automotive A/C Recovery Machine

10/17/2010 12:02 PM

The big problem with using a standard oil filled compressor is that every time you use it some oil from the system that you are recovering from will contaminate the compressor oil. The first recovery units that I dealt with required the compressor oil to be changed every time that it was used. This rarely was done. Lots of cross contamination from one system to another and even more compressor failures. All compressors used today are "oil-less".

I assume that this unit will be staying at ground level and not need to be hoisted?

If this is the case, than weight is not a problem.

-a one way valve is required in case you connect to system with less pressure than the latent pressure in your unit.

-You will need some method to handle any liquid refrigerant. Liquids do not compress well in this universe. You can restrict the flow and allow it to flash into vapour or use a suction accumulator.

-The condenser; the bigger the better. Or go small and have the mother of all fans moving air over it.

-There a lot of other things I could list. But I not have the time.

Unless this is a hobby experiment, than get Toyota to pay for one. Japan did sign on to the Montreal Protocol.

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Power-User

Join Date: May 2006
Posts: 142
Good Answers: 3
#3
In reply to #2

Re: How to Design an Automotive A/C Recovery Machine

10/17/2010 8:35 PM

Icarus is right, you don't want to use a hermetic and what you really want is an oilless unit. You could not buy the necessary components for the price of a complete unit. I own a service company and we have tried all brands and models there is a model called a G5 twin that has outperformed all the others and costs about $500. They sell replacement parts at a reasonable cost although they are seldom needed. It's actually a pump where most of the others are using a cheap air compressor. Save yourself the money and grief I wasted and buy the G5.

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