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  1. #1
    Join Date
    Jun 2008
    Location
    Saskatchewan, Canada
    Posts
    6

    Microns and leaks?

    So, I haven't spent enough time with my micron guage, just wondering, how many microns do to have to pull to believe a system is tight? Will you get below 1000 with a small leak? I'm sure it depends on the leak but a rough idea?

  2. #2
    Join Date
    Jun 2014
    Posts
    32
    250-500-ish and let it stand for a bit (grab a sammich?) is what I use. Mostly just seeing if I get anything to bubble out of the oil. Sometimes I will hit the coils with my heat gun too.

    Did you already pressure test it with D. Nitro?

  3. #3
    Join Date
    Jun 2014
    Posts
    32
    Also, only 250 depending on the OEM if I can get it.

  4. #4
    Join Date
    Jun 2008
    Location
    Saskatchewan, Canada
    Posts
    6
    Yup, and I usually do but say if you didn't have time to leave a system pressurized for long and had a small leak. I guess I'm wondering if the micron guage would give it away.

  5. #5
    Join Date
    Oct 2001
    Posts
    6,945
    anything below 5K microns is moisture if your reading 1000 you can't have a leak it would of never got that low..sucking air in even on connections or hoses not holding the vac
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  6. #6
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    4,932
    Quote Originally Posted by maxster View Post
    anything below 5K microns is moisture if your reading 1000 you can't have a leak it would of never got that low..sucking air in even on connections or hoses not holding the vac
    If you run a pump long enough, you can drop below 1000 microns.
    Requires a pump that will pump bigger than the leak rate.

    Real life example:
    7 CFM pump.
    2-ton system, 15' lineset.
    Installer pumped down system. Tells me it took him 4 HOURS.
    "finally" got it down to 500 microns. Told him to let it sit for 15 minutes. Rose to 3500. Found a loose TXV connection.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  7. #7
    Join Date
    Nov 2004
    Location
    up in the hizzy
    Posts
    1,375
    Quote Originally Posted by hvacvegas View Post
    If you run a pump long enough, you can drop below 1000 microns.
    Requires a pump that will pump bigger than the leak rate.

    Real life example:
    7 CFM pump.
    2-ton system, 15' lineset.
    Installer pumped down system. Tells me it took him 4 HOURS.
    "finally" got it down to 500 microns. Told him to let it sit for 15 minutes. Rose to 3500. Found a loose TXV connection.
    maybe he had the micron gauge hooked to the vacuum pump inlet. I' have never been able to pull a leaky, big or small system down to less than 1000 microns with the micron gauge reading far from the pump.

  8. #8
    Join Date
    Jul 2014
    Location
    Boca Raton, FL
    Posts
    39
    Quote Originally Posted by maxster View Post
    anything below 5K microns is moisture if your reading 1000 you can't have a leak it would of never got that low..sucking air in even on connections or hoses not holding the vac
    I like that. going to keep that in mind.

  9. #9
    Join Date
    Dec 2005
    Posts
    1,909
    Quote Originally Posted by Shreadhead View Post
    So, I haven't spent enough time with my micron guage, just wondering, how many microns do to have to pull to believe a system is tight? Will you get below 1000 with a small leak? I'm sure it depends on the leak but a rough idea?
    It depends on the leakage rate VS the vacuum pump CFM rate.

    That's why we MUST turn the pump off when it reaches the (magic number or I call it BS number) and wait for 15 to 20 minutes. If the micron is NOT rising more than 600 microns, then you are good to go.

  10. #10
    Join Date
    Feb 2012
    Location
    EVERYWHERE
    Posts
    226
    Quote Originally Posted by maxster View Post
    anything below 5K microns is moisture if your reading 1000 you can't have a leak it would of never got that low..sucking air in even on connections or hoses not holding the vac
    BS I have repaired a leak on a 10 ton circuit pulled down to 490 microns turned off pump and in 5 mins it was at 6000 microns found sight glass leaking.

  11. #11
    Join Date
    Aug 2010
    Posts
    2,477
    Quote Originally Posted by FixItRight View Post
    BS I have repaired a leak on a 10 ton circuit pulled down to 490 microns turned off pump and in 5 mins it was at 6000 microns found sight glass leaking.
    Maybe he meant that if you're HOLDING 1,000 on blanking. If you blank out and it lingers in 1,000 to 5,000 range, it's moisture and if it keeps going up, it's a leak.
    Beer can cold bandit stoled my superheat.

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