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  1. #1
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    Half frozen evaporator


    Hey everyone I could use a little help with a problem that is driving me crazy. The problem is with a walk in cooler. Its a 404a system. The evaporator freezes up on the upper half. It is freezing up overnight. I have replaced the TEV. I have not been able to check the proper super heat due to the customer goes in and out all day long. Shortly after the unit is running I begin to notice frost build up on 2 of the 3 lines coming out of the distributor going into the evaporator. The two that are frosting up go to the middle and top of the evaporator. The third line does not frost but just sweats. After running all night the suction line if froze up back to the compressor. The sight glass is full with refrigerant. My head pressure is 225 and suction is 45 with an ambient temp of 70. The walk is running at 42 with these pressures.

    If anybody has any ideas that could help me I would greatly appreciate it.



  2. #2
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    Re: Half frozen evaporator

    .

    Obvious faults are defrosts and defrost heaters, are they all working?
    and refrigerant charge, is there enough refrigerant?

    Once that is proven you need to look at the distribution of liquid through
    the distributor after the valve.

    If there is an uneven share of the liquid for any reason then some of the
    distribution passes will get preference to the liquid and other will appear to
    starve of liquid.

    Check the angle of the dangle

    The distributor needs to be positioned so it shares the liquid evenly.

    It is possible that there is a restriction (blockage) in one or more of the passes.

    Regards

    Rob

    .
    .. ... -. .----. - / -- --- .-. ... . / -.-. --- -.. . / --. --- --- -..

  3. #3
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    Re: Half frozen evaporator

    The working pressures seem to be within range, have you been trying to charge the system whilst the staff have been in and out of it all day and accidently overcharged it?

    Is the evaporator fan working properly and the XV phial strapped to the suction line?

    You need to tell them you need to lock the door for an hour to check superheat and for potential over charge.
    50 hertz but 100s worse

  4. #4
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    Re: Half frozen evaporator

    First you need to check for air distribution at coil! Is it uniform?
    Last edited by nike123; 03-10-2013 at 05:33 PM.
    Now, when I am officialy citizen off EU, I am looking for decent job! For any job offer please check my profile!

  5. #5
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    Re: Half frozen evaporator

    Quote Originally Posted by jscorb1 View Post
    Hey everyone I could use a little help with a problem that is driving me crazy. The problem is with a walk in cooler. Its a 404a system. The evaporator freezes up on the upper half. It is freezing up overnight. I have replaced the TEV. I have not been able to check the proper super heat due to the customer goes in and out all day long. Shortly after the unit is running I begin to notice frost build up on 2 of the 3 lines coming out of the distributor going into the evaporator. The two that are frosting up go to the middle and top of the evaporator. The third line does not frost but just sweats. After running all night the suction line if froze up back to the compressor. The sight glass is full with refrigerant. My head pressure is 225 and suction is 45 with an ambient temp of 70. The walk is running at 42 with these pressures.

    If anybody has any ideas that could help me I would greatly appreciate it.



    Hi yes I know what is wrong with your system, you've already replaced the TEV, hoping you then put in the correct size seat back in and not reused the same one? Also was the filter clear? I had this issue the other day and replaced the seat and filter, it turned out to be moisture in the system. I'd pump down the system lose whatever gas is in the line, and put on an half hour vac and get some moisture control and put into the suction, the moisture is restricting the tev which is why your getting liquid sitting in the sight glass and why your suction line is icing back to the compressor. And that's why only half of your coil is icing, also make it practice to change the drier at the same time bud… hope this helps! Any more info you want give me your number and we can talk it thru…

  6. #6
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    Re: Half frozen evaporator

    ???
    MrStevee,
    You got me confused now, how can pumping a system down and just vaccing out the suction side and parts of the liquid line get rid of moisture? Surely most of the moisture will be in the highly hygroscopic oil that goes with R404a and most of that oil will (hopefully) be in the compressor...

    My personal diagnose from a couple of thousand miles away?
    Flows...
    You are either looking at a problem with the airflow or with the refrigerant flow, it could be as simple as dust in the airside of the coil or oil in the refrigerant side.

    Just my 4p


  7. #7
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    Re: Half frozen evaporator

    Quote Originally Posted by The Viking View Post
    ???
    MrStevee,
    You got me confused now, how can pumping a system down and just vaccing out the suction side and parts of the liquid line get rid of moisture? Surely most of the moisture will be in the highly hygroscopic oil that goes with R404a and most of that oil will (hopefully) be in the compressor...

    My personal diagnose from a couple of thousand miles away?
    Flows...
    You are either looking at a problem with the airflow or with the refrigerant flow, it could be as simple as dust in the airside of the coil or oil in the refrigerant side.

    Just my 4p

    Because the moisture is stilling in the tev so vaccine out changes the boiling point of the moisture, that's why we vac out to remove moisture. And the thawzone that's added will help remove anything that might be left in with the liquid, I've had this problem many times with walk in freezers and if it isn't that it's normally a poor pumping confessor chucking out its oil into the suction line. Dust wouldn't cause half the coil to ice up and not the rest if anything then dust in the coil will give a high back pressure, there is no way it's poor air flow or the pressures wouldn't be as they are, the tev is trying to push all the gas possible thru but it can't because of a restriction… hence the suction line icing, if it was poor air flow the whole coil would ice up and that's not the issue it's half the coil…

  8. #8
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    Re: Half frozen evaporator

    Quote Originally Posted by MrStevee23 View Post
    Because the moisture is stilling in the tev so vaccine out changes the boiling point of the moisture, that's why we vac out to remove moisture. And the thawzone that's added will help remove anything that might be left in with the liquid, I've had this problem many times with walk in freezers and if it isn't that it's normally a poor pumping confessor chucking out its oil into the suction line. Dust wouldn't cause half the coil to ice up and not the rest if anything then dust in the coil will give a high back pressure, there is no way it's poor air flow or the pressures wouldn't be as they are, the tev is trying to push all the gas possible thru but it can't because of a restriction… hence the suction line icing, if it was poor air flow the whole coil would ice up and that's not the issue it's half the coil…
    Wow...as they say, you learn something everyday
    I'm back on the Pale

  9. #9
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    Re: Half frozen evaporator

    Sorry about the poor grammar btw typing on my phone so it's hard, but I'm only giving my experience and what I've found out from hours scratching my head. But that's my opinion and I hope it makes sense and I hope it helps at least one person and I hope I don't come across as rude just trying to help

  10. #10
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    Re: Half frozen evaporator

    Not coming across as rude Steve...welcome to our little world.

    Lots of info and experience on here...looking forward to your input
    I'm back on the Pale

  11. #11
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    Re: Half frozen evaporator

    Good I read it back and thought it sounded a little arrogant, and thank you I've been meaning to sign up for a little while for when I get stuck, and I look forward to helping, thanks frank

  12. #12
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    Re: Half frozen evaporator

    your head pressure appears low,with these walk in freezers defrost is critical the interval time and the stop temperature,are there curtains on the door if not fit some,over here i put the defrost interval every 2/3 hours and if its heater elements rather than reverse /hot gas the defrost end temperature 12/15 degrees c with a max time out of 30 minutes.

  13. #13
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    Re: Half frozen evaporator

    Just a point is your distributor in the vertical or horizontal position. If it is in the horizontal position you might be starving the passes at the top of the distributor. I've always put the distributor in the vertical position so as all the passes get an even flow of refrigerant if I have had the issue you are having now and it always seems to work.

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