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  1. #1
    Join Date
    Jun 2008
    Location
    South,Tx
    Posts
    331

    Leak test with nitrogen .......

    Went to a job after other people had installed this complete unit and guages went on , low on freon .
    Since the customer had enought of these " other" people , (i'm the # 3 man there ) i shut the Valves and proceded to test with nitrogen and left it for 1 Hr , even used soap to see "if" pinholes will show up . Nothingh .A course I finish the "other" problems ( bulb for expansion valve left hanging ) :
    Here is the rest of the story : what got me was i was called by the same customer after 5 days and said he had some one else that found the leak ???
    I would think that nitrogen would show up , even with the soap test , for pinholes, .............
    Where did i go wrong ??????????

  2. #2
    Join Date
    Jan 2008
    Location
    BAYOU LAND
    Posts
    697
    what did you pressure it up to with nitro? did you isolate the system? did you use a leak detector? sounds like the system was hacked in at first,lol
    The government works for me. I do not answer to them, they answer to me.

    we need a few more sheep dogs to keep barking at the wolves,and the stupid sheep

    A well-regulated militia, being necessary to the security of a free State, the right of the people to keep and bear arms, shall not be infringed.

  3. #3
    Join Date
    Jun 2008
    Location
    South,Tx
    Posts
    331
    Yes i isolated the system by the valves at condenser unit and tested the lines and coil only
    Got Low side up to "P" and high side up to 250 Psi.
    Yes it was a ........... when i go there.
    I would guess that nitro would expose that kind of leak ?

  4. #4
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49
    Valid point on the nitrogen pressure. I know that most reference books call for 150 psig maximum but what would be the maximum you guys would go if you had that problem leak that you just cannot seem to find? On a hack job install that would be risky I guess, especially if they are unskilled with a torch, you might just blow a entire joint or two or three or four LOL

  5. #5
    Join Date
    Jun 2008
    Posts
    8
    Is this Res. or Comm.?Low backpressure could also mean the blower is running too slow(or backwards)(take amp draw),a dirty filter or dirty evap if it was running during any construction.(sheetrock dust).Look for any sign of oil,I use up to 130# of nitrogen and listen for hissing.Install a sight glass on the LL ,just befor the condenser,so you can watch it when you add charge. Nitrogen is good but sometimes you need to add a little refrigerant for the leak detector to work.Also ,sometimes you fix the leak when you put your gauges on.Could be bad shrader vales.

  6. #6
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,970
    Quote Originally Posted by derbysr View Post
    what got me was i was called by the same customer after 5 days and said he had some one else that found the leak ???

    Where did i go wrong ??????????
    What makes you sure that you did anything wrong? Just because another person, in a long line of service techs that this homeowner has called, said they "found THE leak" don't automatically assume that you missed something or did anything wrong.

    Give this one a couple of months and then call the customer back to "check up" on how things are going with their air conditioner. You might find out that 3 more companies have also been out since and found more leaks.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  7. #7
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Quote Originally Posted by firecontrol View Post
    What makes you sure that you did anything wrong? Just because another person, in a long line of service techs that this homeowner has called, said they "found THE leak" don't automatically assume that you missed something or did anything wrong.

    Give this one a couple of months and then call the customer back to "check up" on how things are going with their air conditioner. You might find out that 3 more companies have also been out since and found more leaks.
    That is very good advice.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,702
    Did you pull your hoses off and check the schraders for leaks.
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    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Jan 2008
    Location
    BAYOU LAND
    Posts
    697
    Quote Originally Posted by firecontrol View Post
    What makes you sure that you did anything wrong? Just because another person, in a long line of service techs that this homeowner has called, said they "found THE leak" don't automatically assume that you missed something or did anything wrong.

    Give this one a couple of months and then call the customer back to "check up" on how things are going with their air conditioner. You might find out that 3 more companies have also been out since and found more leaks.
    happens too often
    The government works for me. I do not answer to them, they answer to me.

    we need a few more sheep dogs to keep barking at the wolves,and the stupid sheep

    A well-regulated militia, being necessary to the security of a free State, the right of the people to keep and bear arms, shall not be infringed.

  10. #10
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by Tsubaki View Post
    Valid point on the nitrogen pressure. I know that most reference books call for 150 psig maximum but what would be the maximum you guys would go if you had that problem leak that you just cannot seem to find? On a hack job install that would be risky I guess, especially if they are unskilled with a torch, you might just blow a entire joint or two or three or four LOL
    maximum pressure.......as much as it can hold.

    I also use a set of uniweld guages. The low side guage goes up to like 450 and the high side up to 800 I think.

    I have pressure tested systems to 350 and 400 before to find a pinhole or to isolate.
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    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  11. #11
    Join Date
    Jun 2008
    Location
    South,Tx
    Posts
    331

    Thanks for all replies ...............

    Yes i have the presure up to 350 Psi on other Jobs and you "will" listen to that hising , but for some reason nothingh for this JOB.
    My view is :"THE GUAGES NEVER LIE!"

  12. #12
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    The data plate on an evap is usually press tested to 150psig. It is not wise to surpass this point.

    Has anyone given thought to the fact nito has a heavier (denser) molecular weight than 22?

  13. #13
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    I use nitrogen with 22 as a tracer gas, which is EPA Ok, and one of my leak detectors usually my Inficon D-tek or my H-10. Use only the best leak detector so you can trust it, and look until you find the leak. On one system I was installing I set up the standing pressure test with nito and 22 tracer, found a small leak at one of the joints with the D-tek, it was late so I packed it in for the day and came back th next day, the gauge was still exactly at the same pressure as when I left, it showed me the benefit of using electronic leak detectors. Once it took me three hours on a Liebert system , the customer instead of being put out at the length of time said he was impressed with my thoroughness and tenacity, that I didn't give up and just charge it up and leave.

    I bought my D-tek after studying the posts on this site about leak detectors, it's the best advice you can get, and I've not regretted spending the extra money for the best product

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