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    danpatm's Avatar
    danpatm Posts: 28, Reputation: 1
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    #1

    Jul 20, 2010, 04:44 PM
    Evaccuating system
    When you get a system in a vacuum @ 500 microns and let it set for over night how much lee way are you allowed on the micron gage up to 600 are more?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Jul 20, 2010, 10:50 PM
    Quote Originally Posted by danpatm View Post
    When you get a system in a vaccum @ 500 microns and let it set for over night how much lee way are you allowed on the micron gage up to 600 are more?
    When a system has been evacuated below 500 microns, the pump has been shut off and the micron gauge is connected, if the vacuum rises to 1500 microns and stops, there is moisture remaining in the system. If it rises above 1500 microns AND continues to rise, there is a leak. You should allow at least 15 minutes after the pump has been shut off to have this micron gauge reading be accurate. Most of the time when a system will not evacuate below 1500 microns there either is a lot of water or there is a fairly large leak. Regardless, a micron reading taken when the pump is running is useless unless the micron gauge is attached to a totally different part of the system and not connected in any way to the gauges being used to evacuate the system.
    mygirlsdad77's Avatar
    mygirlsdad77 Posts: 5,713, Reputation: 339
    Plumbing Expert
    		  
    #3

    Jul 21, 2010, 03:21 PM

    If you are saying you pulled to 500 and let set overnight with the pump off, and it only went up to 600, or a little higher, then you should be just fine. When I pull a vac, I pull to at least 250 and let it set for roughly half an hour. If it rises above 800 I re vac and go from there.
    danpatm's Avatar
    danpatm Posts: 28, Reputation: 1
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    #4

    Jul 22, 2010, 04:10 PM
    Comment on mygirlsdad77's post
    When you re vac do you add nitrogen to the system first and then re vac?
    mygirlsdad77's Avatar
    mygirlsdad77 Posts: 5,713, Reputation: 339
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    #5

    Jul 23, 2010, 03:10 PM

    Not always. If I'm in a hurry, I will purge the system again with nirogen, but if I have another job to go to I just leave the pump run while at the other job. I do however always purge the system with nitrogen before the initial vac. Its really amazing how much quicker it will pull a good vac.
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