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  1. #1
    Join Date
    Apr 2005
    Location
    Virginia
    Posts
    176
    what is the best way to check for leaks in lineset before initial charge. I was taught to pull a vacuum and if the gauge shows no drop after about 30 min. everything is fine. This is a lie I have found leaks.

  2. #2
    Join Date
    Oct 2004
    Location
    Texas
    Posts
    1,174
    Pressurize the lines with nitrogen
    Saddle Up!

  3. #3
    Join Date
    Oct 2004
    Posts
    3,400
    From a recent Trane installation guide:

    "...the indoor unit and field refrigerant lines with dry nitrogen to 350-400 psi.
    Use soap bubbles or other leak-checking methods..."

    Then in the next column:

    "...Evacuate until the micron gauge reads no higher than 350 microns..."


    Please realize this is BEFORE opening the service valves.





    [Edited by bwal2 on 04-28-2005 at 07:35 PM]

  4. #4
    Join Date
    Jun 2000
    Location
    NC
    Posts
    108
    Add nitrogen to 100 psig. and test with soap bubbles or leave over night.

  5. #5
    Join Date
    Apr 2005
    Location
    Virginia
    Posts
    176
    Not so much a follow-up but another question. Does outside temp cause vacuum pressure to flucuate like air pressure. i set 2 units today pulled vacuum down to 29.9 hg. Question is should they still have same vacuum pressure say tommorrow before we charge them.

  6. #6
    Join Date
    Oct 2004
    Posts
    3,400
    Wrong tool to use to measure vacuum.
    There are 25,400 microns in one inch.
    You need a micron guage.

    To answer your question, yes AND no.
    If you have a complete vacuum, than slight temperature changes temperaure would have little or no effect on the pressure.
    However, you probably still have some noncondensables and moisture in the system at 29.9" HG, so the guage could show a rise in pressure with a rise in temperature.

  7. #7
    Join Date
    Mar 2005
    Posts
    65
    I shouldnt think that it affects a vaccume, I have pulled vac on many units and let stand, came back later on in the eve and even though diff temps were apparent, the vaccume gauge read the same as wehn I left it.... thats just my personal exp, and the temp ranges were only in the -30deg ballpark, so maybe more extreme drops or increases will effect????? anyone care to share factual data on this?

    Although, I know that when pulling the vaccume, I have ran into longer times in hotter weather than in colder temp days.

  8. #8
    Join Date
    Apr 2005
    Location
    Virginia
    Posts
    176
    What type of micron gauge would be suggested. And can they be just as accurate at telling if there is a leak as the suggested use of nitrogen?

  9. #9
    Join Date
    Oct 2004
    Posts
    3,400
    Originally posted by hvac7
    What type of micron gauge would be suggested. And can they be just as accurate at telling if there is a leak as the suggested use of nitrogen?
    Everybody has their favorite.

    And yes, they can be very accurate.
    Plus, it can tell you if the system is dry.

    However, you should employ both nitrogen & micron guage.

    Search for a thread calle "Micron guage wars"

  10. #10
    Join Date
    Mar 2005
    Posts
    65

    Elaborating on the above post

    as for what gauge you use is personal opinion, but for the second question I would say to never just use one leak checking device, I ALWAYS charge the lines w/ nitro and then after 30 mins to 1 hr I blow the nitro and place the systems lines under a vaccume until your gauge shows good. As long as the nitro holds, then the vac holds, you shouldnt have any leaks. I have found that vac alone will hold in that little piece of dirt or solder that makes it "appear" all good and tight, but upon starting up, you will find that leak because the stoppage blew out.

    One more thing I have learned in brazing is there isnt anything wrong with the good ol visual inspection of your joint, if it looks like a good quality braze, it probably is but never rely on just one method.



    [Edited by craftyone on 04-28-2005 at 08:38 PM]

  11. #11
    Join Date
    Apr 2005
    Location
    Virginia
    Posts
    176
    Thanks so much for all the helpful advice. I have tons more questions, but I do not want out wear out my welcome. Thanks again!!

  12. #12
    Join Date
    Mar 2005
    Posts
    65
    ask away bud, thats what this site is for...

  13. #13
    Join Date
    Apr 2005
    Location
    Virginia
    Posts
    176
    O.K. Maybe 1 more question if I may, since the president seems to be on all channels of the tv (lol). I just purchased a Sight glass for my gauges (aka liquid eye) can anyone tell me how this thing really works. I installed it on the liqiud side of my gauges just like directuion say and at times I have seen no liquid in the sight glass even after weighing in correct charge.

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