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  1. #1
    Join Date
    Sep 2019
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    Best way to determine ideal psi for freon recharge

    I have a 1/2 hp Tecumseh unit (compressor AKA4476YXA, r1324A) cooling a small utility closet. It appears that it has developed a leak after the unit shifted while some work was being done in the area. The leak appears to be very very slow - I have monitored the temperature and have noticed that it is taking slightly longer and longer over the last few months to keep at the set temp. I want to add freon and have the necessary manifold gauges etc. but do not want to overcharge.

    I know that the suction psi depends on ambient temp and have seen the related charts for the targeted psi at each temp. I am looking for some assistance as to what the running psi range should be and if there are any gotchas or things to consider in order not to overcharge. I know that this is not the best way to go about this but I would appreciate any pointers to get the right amount of freon in the unit.

    Thank you

  2. #2
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
    11,356
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    Whole lot of factors go into charging, there really isn’t a target pressure to be focused on.
    The leak should be found and fixed.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  3. #3
    Join Date
    Jul 2012
    Location
    WA
    Posts
    2,798
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    Do you have the tools to recover and weigh in a factory charge? I’d top it off, but topping off a charge is a bit of an art form. There’s a lot of factors to consider. If you have to ask how to do it, you’re much better off recovering and weighing it in.

  4. #4
    Join Date
    Jan 2010
    Posts
    17,323
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    Is there a sight glass ?

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    24,326
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    Quote Originally Posted by kapios View Post
    I have a 1/2 hp Tecumseh unit (compressor AKA4476YXA, r1324A) cooling a small utility closet. It appears that it has developed a leak after the unit shifted while some work was being done in the area. The leak appears to be very very slow - I have monitored the temperature and have noticed that it is taking slightly longer and longer over the last few months to keep at the set temp. I want to add freon and have the necessary manifold gauges etc. but do not want to overcharge.

    I know that the suction psi depends on ambient temp and have seen the related charts for the targeted psi at each temp. I am looking for some assistance as to what the running psi range should be and if there are any gotchas or things to consider in order not to overcharge. I know that this is not the best way to go about this but I would appreciate any pointers to get the right amount of freon in the unit.

    Thank you
    Suction pressure depends on
    Air Flow
    Temperature
    Design Delta
    Refrigerant flow


    Id like to see this chart!

  6. #6
    Join Date
    Jan 2012
    Location
    Missouri, USA
    Posts
    1,448
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    No diy.

  7. #7
    Join Date
    Sep 2019
    Posts
    3
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    Thread Starter
    I understand that I am not going about this the proper way and should turn to a professional to fix the leak and recharge. Because of my location it is cost prohibitive to do that at this time and would probably make more sense to replace the whole unit at some point (it is old) vs pay for over a day's wage for someone to attend to this issue (I'm not kidding). I would like to add some freon and extend the life of this unit until I get to the new year and be in a position to replace it.

    I have basic tools but not a vacuum pump - that is why I am hoping to use psi as a guide. There is a sight glass.

    I know some of you pros are reluctant to offer advice with my approach. I'm only doing it this ways as I am backed into a corner. If anyone can help steer me in the right direction I would appreciate it.

  8. #8
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
    11,356
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    We are not permitted to give diy instruction here. It’s listed clearly in the rules above.
    Something to consider here is the unit may not be low on refrigerant and could have another problem causing poor performance.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  9. #9
    Join Date
    Jan 2010
    Posts
    17,323
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    Quote Originally Posted by kapios View Post
    There is a sight glass.
    Google this ^^^^^^^

  10. #10
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    24,326
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    Quote Originally Posted by kapios View Post
    I understand that I am not going about this the proper way and should turn to a professional to fix the leak and recharge. Because of my location it is cost prohibitive to do that at this time and would probably make more sense to replace the whole unit at some point (it is old) vs pay for over a day's wage for someone to attend to this issue (I'm not kidding). I would like to add some freon and extend the life of this unit until I get to the new year and be in a position to replace it.

    I have basic tools but not a vacuum pump - that is why I am hoping to use psi as a guide. There is a sight glass.

    I know some of you pros are reluctant to offer advice with my approach. I'm only doing it this ways as I am backed into a corner. If anyone can help steer me in the right direction I would appreciate it.
    If you cant afford to fix it can you afford to screw it up?

    Pay to fix the leak. Several things begin to break as the charge runs short.

  11. #11
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
    Posts
    1,439
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    Thought I can't help you too much, I can tell you this.

    The way to "charge" a unit is to put enough juice in it to get it to where the pressure tells you the correlating saturated temperature of that refrigerant. So if the space is supposed to be 72*F or whatever, then a coil of about 50-55*F would be expected, that's pretty common.

    So you have to know what you are doing a bit, if you do it wrong it can be catastrophic failure in the next couple of weeks.

    What do you know how to do? We are restricted here as DIY is prohibited, though I think most of us DO want to help, we simply aren't allowed to.

  12. #12
    Join Date
    Sep 2019
    Location
    Houston, Texas
    Posts
    2
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    Yes....he is correct.

  13. #13
    Join Date
    Sep 2019
    Location
    Houston, Texas
    Posts
    2
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    Dirty coil, perhaps.

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