vacuum question
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Thread: vacuum question

  1. #1
    Join Date
    Jun 2004
    Posts
    43
    i just bought a supco vg64 miron gauge. i hooked it up to my vacuum pump as i ran it the bars where showing it was pulling down , after about a half hour still showing above 12000 microns i changed the pump oil before i started. then i took my gauges off closed pump valve still the same after an hour . dous any one know if there is a way to tell if there is an air leak using several fittings at this time
    any help would be appreciated

  2. #2
    Join Date
    Dec 2002
    Posts
    9,871
    Your pump or your hose and fittings are shot.

  3. #3
    Join Date
    Jun 2004
    Posts
    43

    flare fittings

    will flare fittings hold a vacuum, hoses are brand new got everything capped off except pump and micron gauge.

  4. #4
    Join Date
    Jun 2004
    Location
    s.c.
    Posts
    287
    get you some hose extenders w/ ball valves then you can test your hoses & manifold before starting on a system vacume. thats a good micron gauge for the money I have that model as well as the yellow jacket lab model.
    I can do all things...

  5. #5
    Join Date
    Jun 2004
    Location
    s.c.
    Posts
    287
    where is the flare fitting ?
    I can do all things...

  6. #6
    Join Date
    Jun 2004
    Posts
    43

    fitting

    i have a Titting the female end hooked up to the pump then top capped off the left one is male so i flared two female flare nuts one to that end the other to the gauge.

  7. #7
    Join Date
    Jan 2002
    Posts
    1,895
    If its holding.. It's probably the pump. 12,000 or 1,200 microns ?

  8. #8
    Join Date
    Jun 2004
    Posts
    43

    pump

    believe its 12000 the screen says atm

  9. #9
    Join Date
    Oct 2003
    Location
    South Carolina
    Posts
    1,241
    I bought one of those micron gauges a few weeks ago and have been having trouble similar to yours. I thought my hoses were leaking so I got new hoses, changed the oil in the pump and it still won't pull down below about 1650 microns when vacuuming a system. If I isolate the micron gauge from anything else and pull a vacuum on it, it'll read down to 350 microns most of the times. If I shut off the micron gauge for awhile when evacuating a system, when I re-energize it later, it shows different readings up to ATM with the bars moving from side to side, no consistency whatsoever. I know the system I worked on is leak free because it held 225 psig nitrogen for over a week. There ARE no leaks in that system! My hoses are brand new, the gauges were replaced on the manifold recently, I check all the threaded joints on the manifold and hoses with soapy stuff when under pressure and I can't get a reasonable reading to save my life. I even put a new battery in the gauge and checked it with a meter beforehand.
    I'm going to try one more thing which is, cleaning it out with some denatured alcohol. If that doesn't help, I'm taking it back where I bought it and getting a refund. I'll look for a different one rather than using that type again. It's too much trouble.

  10. #10
    Join Date
    Feb 2002
    Location
    Yuma, Arizona
    Posts
    924
    Charging hoses are not MADE for vacuums.
    They will pull a vacuum but only the heavy black yellow jacket hoses are made for a 75 micron vacuum (36" only).
    So if you are trying to get below 200 with charging hoses good luck.
    Look on the yellow jacket site for a lot of good info. http://www.jbind.com/ Look under deep vacuum.

    Yuma,
    What is snow? Is it that white stuff in a freezer?

  11. #11
    Hey fellas, this aint market refrigeration!!! Lets try and keep it all simple ... okay?

    The gage needs to be clean. If and when they get in contact with any contamination, like oil or something ... they begin reading wrong. They become a waste of time.

    So keep them isolated away from the vac pump.
    Keep the micron gage elevated above the level of the vac pump.

    Is there a tool for testing vacuum leaks? Yes. It is called an ultra sonic leak detector.
    AccuTrak makes one called the VPE.
    Amprobe also makes a model about the same price. $250-$280.

    But just doing a balnk off test is a simple method of determining whether or not your pump and gage are both working.


    This is a process of elimination.


    My opinion; when working on a tiny system, 20oz. or less of refrigerant .... limit your hose length to 36".
    This does not apply to service on a True or Bev-Air unit.
    With those .... "anything goes".

    On a system of greater quantity then 20 oz of charge, the shorter the hoses, the better and easier, quicker your work will be.
    However, you do have some greater flexibility than with the mini systems which are much more sensetive to how they are processed.

    Personally, I have never experienced bad vacuums using 60" black hoses on the 21oz. and above systems.


    Also, there is a sealant specially designed for temporary sealing of vacuum leaks at spots which cannot be sealed off while performing service to them.

    It is called; "High Vacuum Sealant". United sells it. It comes in a little can just like pipe dope.

    You can use it around service valve stems while they are mid way seated, etc.



    And guys, just remember... bigger isnt better! A vacuum pump will never take the place of what you lost due to age and saging physical conditions!
    A 1/4" hose can only pass one cfm thru it.
    So with two hoses, 1/4" each and a 3/8" center port hose hooked up to the vacuum pump... you can only pass 3 cfm thru that hose to the pump!
    Bigger isnt necessarily better.

    There are of course, exceptions to the rule when dealing with supersized systems. But on those, you would not be using 1/4" lines and gage manifolds!

    You would be welding copper tubing directly into large copper header pipes and running those lines into your pumps, PLURAL.
    And these pumps would be located at various points in your built up system.

    And that my friend is why they make bigger vacuum pumps!
    They were not built for your small to medium sized packaged A/C systems or beer boxes!!!


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