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1300 microns!

Timco
Timco Member Posts: 3,040
in A-C, Heat Pumps & Refrigeration
I can't seem to draw a system down below 1300 microns. Swapped a condenser on a 3 ton system and can't get a good vacuum. Can't find any leaks either. How long should it take a 5 cfm pump to bring a system with 75' of lines down to 250 microns?
Just a guy running some pipes.

Comments

  • Ironman
    Ironman Member Posts: 7,538
    Leaking Somewhere?

    Have you tried to see if it will hold pressure or vacuum? If it does, then you either have a lot of moisture or your vacuum pump is worn. Are you sure your micron gauge is reading correctly?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Techman
    Techman Member Posts: 2,144
    edited July 2011
    Microns

    How many systems have you used the same vac pump oil on ?What color are the evac hoses? How old are the gaskets in the hoses? What size is the hose attached to the vac pump? How long does it take?As long as it takes! There is no answer to that question.
  • Timco
    Timco Member Posts: 3,040
    More cfm

    with a second pump I am down to 350 and falling slow. Yellow hoses larger size to pump. Must just be lots of moisture.
    Just a guy running some pipes.
  • Techman
    Techman Member Posts: 2,144
    Hoses

    Those yellow hoses are not for pulling deep vacuum's. But if you are at 350 microns,something is working.
  • Unknown
    Unknown
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  • Timco
    Timco Member Posts: 3,040
    simple standards

    Thanks for your reply!



    Yes, I swept with compressed nitrogen while braising. I did in fact pressurize with nitrogen, but just to 100 psi to check for leaks. I did not read in any text book about getting up to 425 and I appreciate the advise.  As per Goodman's install manual, I pull down to 250 microns. Is this too far or a waste of time?



    When a different system I just did got down to 300 microns, it slowly rose back up to over 1000. I assumed leak, and re-pressurized. No leak. When I pulled down again, it got down to 300 and made an odd noise, and then the microns jumped to 800 with vapor at the pump outlet, then it settled back down. Water boiling out?



    At every AC service call, I examine the indoor coil and outdoor coil every time. I pulled a sheet of dog hair off of a indoor coil on a under-performing system last week.



    Last week, I had a system that would not pull down normal at all. I went

    to lunch (30 min) with the vac pumps running. When I got back, I was

    still at 800 microns. When I killed the pumps, the pressure DROPPED to

    400 microns and held fine. What happened there? Gauge issue?



    Thanks for the discussion. This is my first season offering AC and I am confident I can do this reliably. So far, great results.
    Just a guy running some pipes.
  • Unknown
    Unknown
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  • Timco
    Timco Member Posts: 3,040
    thanks!

    Great advise! Thanks for sharing!! Going to clean them both tomorrow!!



    Tim
    Just a guy running some pipes.
  • Techman
    Techman Member Posts: 2,144
    edited July 2011
    Hoses

    Get a set of hoses made for pulling deep vacuum's.! Are you using a 4-port manifold?
  • Unknown
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  • Timco
    Timco Member Posts: 3,040
    Barry

    My manifold (I call him Barry) is indeed a 4-port. Are you referring to the black hoses that are double the size and cost? A set of those and a nice vac pump tree will be next!



    No offense at all taken on the suggestions for the nitro! I need and appreciate all the advise I can get since I did not apprentice for this and have learned from text books. Can't wait to clean those gauges. My pumps are 5cfs and are good for 40 microns.



    Is 250 too low to pull each job down to?
    Just a guy running some pipes.
This discussion has been closed.

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