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Condenser copper refrigerant lines were cut by vandals. They stayed open for several days. Before recharching with r-22, i know the repairmen will have to braze the copper lines and remove all the old oil because it was exposed to the ambient and oil absorbs water from the humidity of the air. Im gonna be watching the repairmen closely and want to know about the right way so i will have an educated opinion and be able to question the procedures. How should they purge the old oil? How to add new oil, as i understand the r-22 refrigerant (freon) does not come with oil mixed in?

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First you will need a new filter dryer. With the copper repaired Pull a high vacuum below 500um on the system for 24 hours or longer this will remove the moisture. At first you may not be able to get below ~3000um because of the moisture outgassing increases the pressure. Once a good base is achieved keep it there for 24 hours and the moisture will be gone you will also want to do an acid test, if positive you will need to flush the system, I like Qwikshot acid flush. I would probably upgrade to a newer refrigerant that might not cost much more than a recharge since R22 can run 100$ per pound a 5 ton unit the Freon alone could cost you over 1k and you still have an old system.

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  • Good info, Ed - out of curiosity, would a vacuum pump be attached at running for 24 hours?
    – JPhi1618
    Sep 11, 2019 at 17:10
  • Should mention that the legal refrigerants may vary by country, but your point about compatibility with an old compressor is well-taken. Sep 11, 2019 at 17:53
  • The pump would run until you get to 30"wc, what we do after that is fill system with nitrogen at about 350psi for 24 hours to check for leaks.
    – Gunner
    Sep 11, 2019 at 18:14
  • The 30” is Hg wc would not be enough. 500 millitor I think ~.3 pascal. If a good vacuum level is not maintained the moisture will not be removed so yes the pump should be going for 24 hours , I have left it over night or about 12 hours before and it was fully evacuated of air and moisture. It is not a legal requirement but a recommendation in the U.S. I personally have a pump that will reach 3 millitor if I can hit 50 and isolate the system for 5 minutes with no rise in pressure I know it will be ok. If you get a base pressure and turn the pump off you may find it close to atmosphere later.
    – Ed Beal
    Sep 11, 2019 at 18:45
  • Then removal of the old oil and refilling with fresh new oil is not an option? Using a refrigerant recovery pump does not pull out the oil along? Sep 12, 2019 at 3:12

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