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  1. #1

    suction pressure bouncing

    i pulled a vacuum for over 24hrs, unit stayed in a vacuum. charged unit to nameplate weight. unit pressures will look great at 68 low and 270 high. then all of a sudden suction will drop to 50psi then rise back up to almost 70psi, stabilize for a minute and do it all over again. any ideas for me? i appreciate your time.

  2. #2
    Join Date
    Nov 2006
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    We usually don't address technical issues in open forums. We have a Pro Technical forum for that. A few more posts and you can apply for that status.

    Speaking in the general sense, I would look at what variable is changing that could cause the reaction you describe. If no variable is changing, then something is changing without a changing input variable. I can only think of two possibilities right now.
    Last edited by timebuilder; 06-27-2010 at 10:29 AM.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  3. #3
    Join Date
    Apr 2010
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    East of Lyndon's
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    525

    Confused

    How about an improperly sized or malfunctioning TXV valve? How many microns did you pull the system down to? Is there a crankcase pressure regulating valve on the system or something like that?
    If you can't fix it with a hammer, you've got an electrical problem.

  4. #4
    well, at first thought TXV, but it is fixed orifice. 500 microns. i ran out of time yesterday and will dig deeper. i thought maybe a little blockage in the fixed? wendo, will look into what you have pointed out, much appreciated.
    timebuilder, two possibilities? thanks for your time y'all.
    i am new to this forum and did not realize there is a pro technical forum, excuse my etiquette.

  5. #5
    Join Date
    Nov 2006
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    Quote Originally Posted by h-to-the-vac View Post
    well, at first thought TXV, but it is fixed orifice. 500 microns. i ran out of time yesterday and will dig deeper. i thought maybe a little blockage in the fixed? wendo, will look into what you have pointed out, much appreciated.
    timebuilder, two possibilities? thanks for your time y'all.
    i am new to this forum and did not realize there is a pro technical forum, excuse my etiquette.
    No problem. If you are a working pro, get the pro status and we will see you in pro technical.

    We don't want people being able to search for info and get hurt trying to DIY, and the pro status is how we keep that from happening.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  6. #6
    will do see you in pro technical

  7. #7
    Join Date
    Jan 2004
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    Lancaster PA
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    68,599
    Sh and SC can tell you a lot about what is happening in a system.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    19,298
    Quote Originally Posted by beenthere View Post
    Sh and SC can tell you a lot about what is happening in a system.

    Ding, ding, ding, and we have a winner!
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  9. #9
    Join Date
    Aug 2007
    Location
    Winter Haven, FL
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    4,380
    Look around the air handler for the piston and put it back in.

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