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  1. #1
    Join Date
    Mar 2006
    Posts
    1,029

    To use sight glass or not

    ISo the other day I had a walk in cooler low on gas. R22 to be exact, I found and fixed two leaks. Had a coworker bring me some more r22. After installing a new fan cyce control begain charging the unit. Got the box to 42 with a 20 superheat and then box was down to 38 when I left.

    Ive always been told to keep a full glass to ensure all liquid to txv. Manager says to charge to the correct superheat and not worry how full the glass is and coworker says only with R22 you should charge to a full glass

  2. #2
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,595
    First of all, does this have a headmaster or just a fan cycling control? Also remember a sight glass is a tool, like any other tool you need to know when to use it and and what it's telling you.

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567
    A TEV MUST have a solid column of liquid to it in order to properly meter refrigerant.

    I would install a sightglass on any equipment with a receiver.


    I would NOT "charge to superheat" This is incorrect procedures for any walk-in that I've ever worked on.

  4. #4
    Join Date
    Mar 2006
    Posts
    1,029
    No headmaster just fan cycle and yes it does have a sight glass

  5. #5
    Join Date
    Jan 2009
    Location
    IRELAND
    Posts
    47
    Problem with fan cycling on single units is it plays havoc with sight glasses .if fan speeds up quickly its drops condenser pressure quickly and pulls liquid back into condenser and bubbles in the sight glass,very easy to overcharge system using sight glass on this scenario.Most of the fan controls on single units i come across tend to ramp up and down very quickly

  6. #6
    Join Date
    Jan 2006
    Location
    DFW Metroplex
    Posts
    4,910
    Quote Originally Posted by marter View Post
    Manager says to charge to the correct superheat and not worry how full the glass is and coworker says only with R22 you should charge to a full glass
    If the TXV does not have a solid column of liquid to work with, how is it supposed to maintain a 'correct superheat'?
    "The problem is the average person isnt tuned in to lifelong learning, or going to seminars and so forth. If the information is not on television, and its not in the movies they watch, and its not in the few books that they buy, they dont get it" - Jack Canfield

  7. #7
    Join Date
    Mar 2006
    Posts
    1,029
    I understand this but he signs the paycheck.

  8. #8
    Join Date
    Mar 2006
    Posts
    1,029
    A field installed unt no weigh in charge, you would have to have some type of head pressure control to handle low ambient tempreture though.

  9. #9
    Join Date
    Jan 2006
    Location
    DFW Metroplex
    Posts
    4,910
    Quote Originally Posted by marter View Post
    I understand this but he signs the paycheck.
    You don't have to prove a flashing sight glass via a picture, I would hope. Why can't you properly charge the unit (clear the sight glass) AND keep the boss happy by simply saying you charged the unit to XX superheat?

    Quote Originally Posted by marter View Post
    A field installed unt no weigh in charge, you would have to have some type of head pressure control to handle low ambient tempreture though.
    Headmaster would be the way to go.
    "The problem is the average person isnt tuned in to lifelong learning, or going to seminars and so forth. If the information is not on television, and its not in the movies they watch, and its not in the few books that they buy, they dont get it" - Jack Canfield

  10. #10
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567
    Quote Originally Posted by markettech View Post
    You don't have to prove a flashing sight glass via a picture, I would hope. Why can't you properly charge the unit (clear the sight glass) AND keep the boss happy by simply saying you charged the unit to XX superheat?
    Bingo!

    Do the right thing and tell the bossman what he wants to hear.

  11. #11
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,595
    There's a way to respectfully argue your point to the boss who you work for. Have your facts straight (which you are trying to do by being here) and just state your disagreement and back it up with why. Explain you will make him more money by doing it the right way the first time.

  12. #12
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    430
    If fan cycling is throttling my pressure up & down, first I make sure the fan control is set up as accurately as possible for the refrigerant being used. Then I try and maintain a head pressure of 180 (R22) maybe using a piece of cardboard to partially cover the condenser and then can watch the sight glass and clear it at this point. If I still see bubbles at a lower head say 160psi, I might add small amount more but being careful not to over charge. I don't even call the boss. I am the boss...

  13. #13
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,587
    Quote Originally Posted by marter View Post
    I understand this but he signs the paycheck.

    and when the call comes back in you were the tech who worked on it last...

    Try blocking off the condenser like Capz suggested
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

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