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  1. #1
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    To charge or not to charge?



    Recently while working on a roof top unit for a walk in cooler, I came across the question of wether to charge or not to charge. R-22 *****. Ambient air outside @ 23 degrees. Hi side @ 155#. Lo side @ 12#. Sight glass is full. Cooler room temp is @ 39 degrees. Unit seems to recover rather quickly. I suspect a slight low charge. What would you do?
    thanks-Fire and Ice



  2. #2
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    Re: To charge or not to charge?

    I would measure superheat, subcooling and temperature difference of evaporator and condenser, also compressor current and discharge temperature.

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    Re: To charge or not to charge?

    I'm with Nike, I'd audit the system then determin where to go from there with certainty.

    Is it cappilery tube or txv, this will tell you the most usefull messure.

    Evap clean and all that sort of thing?

  4. #4
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    Re: To charge or not to charge?

    Why do you think it needs more refrigerant?

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    Re: To charge or not to charge?

    Only at the two extremes (grossly undercharged and grossly overcharged) does the amount of refrigerant in the system have anything to do with the head pressure.

    Between these two extremes, the head pressure is almost entirely determined by the temperature and volume of air flowing through the condenser.

    On a cool day, the head pressure is down. On a hot day, the head pressure is up.

    Increase the airflow and the head pressure is down. Decrease the airflow and the head pressure is up.

    Head pressure (aside from the extremes) is not about charge.

  6. #6
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    Re: To charge or not to charge?

    Hi, Gary

    Quote Originally Posted by Gary View Post
    Only at the two extremes (grossly undercharged and grossly overcharged) does the amount of refrigerant in the system have anything to do with the head pressure.

    Between these two extremes, the head pressure is almost entirely determined by the temperature and volume of air flowing through the condenser.

    On a cool day, the head pressure is down. On a hot day, the head pressure is up.

    Increase the airflow and the head pressure is down. Decrease the airflow and the head pressure is up.

    Head pressure (aside from the extremes) is not about charge.
    Very nice and clear.....

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  7. #7
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    Re: To charge or not to charge?

    Hi, MRcoolingMAGIC

    Quote Originally Posted by MRcoolingMAGIC View Post
    Why supprise ,Gary is one of the top guys in our refrigeration field.Thanx to him and O'Brien we can learn something ,that the books can not offer.
    ....it is in the books for sure, but you have to read many many books to extract it in the way Gary did.....simple and clear....

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  8. #8
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    Re: To charge or not to charge?

    Quote Originally Posted by Josip View Post
    Hi, MRcoolingMAGIC



    ....it is in the books for sure, but you have to read many many books to extract it in the way Gary did.....simple and clear....

    Best regards, Josip
    Many many books... or one of Gary's books.

  9. #9
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    Re: To charge or not to charge?

    Hi, Gary

    Quote Originally Posted by Gary View Post
    Many many books... or one of Gary's books.
    why not, but my statement is ok....not only one book, but books

    it is not easy to write down all, in only one book, I know that.....

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  10. #10
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    Re: To charge or not to charge?

    what is the name of your book gary? It was once on Xtreme systems but the name has drifted off forever into cyber space!

    I'd be interested in it.

  11. #11
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    Re: To charge or not to charge?

    See the man's signature
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  12. #12
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    Re: To charge or not to charge?

    Last edited by Gary; 20-01-2008 at 04:02 PM.

  13. #13
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    Re: To charge or not to charge?

    Ya I noticed that a bit after posting the question, thank you gary.

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