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  1. #1

    Walk in cooler trouble

    Once a week, a call will come in that the cooler temp is at 50 degrees. It is a longer run walk in so add just a touch of refrigerant (404) to keep it from short cycling.

    Everything runs fine for 45 minutes and all of a sudden, suction pressure drops and will not rise. Jump out low pressure switch and let it run for a few seconds, and again pressure does not rise, like it is in pump down.

    Removed the TXV bulb and held it in my hand for a minute, no rise in pressure. The workers were moving the items out of the way when my shift was up, but I'm thinking the TXV maybe clogged or stuck closed as I have gotten this call 2 times, but never enough time to troubleshoot it.

    But I have heard from co workers that the pressure will all of a sudden rise and the system will work normal again. Just not sure if it is the TXV or the Liquid line solenoid that is failing as I never have enough time to access the panel to check out the components.

    Any thoughts?

  2. #2
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    2,586
    Temperature drop across the LLS will tell you if that is the culprit. Is the LLS even being energized? Remove solenoid (unwire to prevent it from being energized and destroying it when it is off) and throw a magnetic solenoid tester and see what happens. Could be faulty coil or voltage drop somewhere causing not to be fully energized. Thermostat or defrost on the fritz?
    During that 45 minutes when everything seems to be running fine, what are you getting for SH (at compressor and at evap unit), SC, TD's, etc? This will help distinguish if it SEEMS FINE, or if it IS FINE...big difference.
    Coils all clean in and out?
    Fans all operating properly at proper rpm?
    Oil Logging?
    Single evap or multiple?
    Piping engineered and installed properly with traps, slope, etc?
    Keep touching her off with 404, is there a leak? Or are you possibly over-charging. Being a blend, your glide could be way off. Maybe fix leak, for giggles replace LLS, LLFD, and TXV, thermostat (if old mechanical), new oil, deep vac, and virgin refrigerant...nice system over-haul if cond and evap units are in decent condition.

    Just some thoughts.

  3. #3
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,754
    Nobody ever has enough time to diagnose/fix things properly the first time, but they always have time to keep returning to the scene of the crime.
    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

  4. #4
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Wonder how many times that touch of 404A has been added to keep it from short cycling?

  5. #5
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,459
    It sounds to me like it could be a moisture problem. At least, I'd eliminate that first.

  6. #6
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,754
    Quote Originally Posted by icemeister View Post
    It sounds to me like it could be a moisture problem. At least, I'd eliminate that first.
    BINGO!!!
    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

  7. #7
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    Quote Originally Posted by 2sac View Post
    Nobody ever has enough time to diagnose/fix things properly the first time, but they always have time to keep returning to the scene of the crime.
    Haha, I've heard this a few times...

  8. #8
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,559
    Found a wire broke inside the insulation on the temp control. One of those now you see it and now you don't.

    Quote Originally Posted by Matango02 View Post
    Once a week, a call will come in that the cooler temp is at 50 degrees. It is a longer run walk in so add just a touch of refrigerant (404) to keep it from short cycling.

    Everything runs fine for 45 minutes and all of a sudden, suction pressure drops and will not rise. Jump out low pressure switch and let it run for a few seconds, and again pressure does not rise, like it is in pump down.

    Removed the TXV bulb and held it in my hand for a minute, no rise in pressure. The workers were moving the items out of the way when my shift was up, but I'm thinking the TXV maybe clogged or stuck closed as I have gotten this call 2 times, but never enough time to troubleshoot it.

    But I have heard from co workers that the pressure will all of a sudden rise and the system will work normal again. Just not sure if it is the TXV or the Liquid line solenoid that is failing as I never have enough time to access the panel to check out the components.

    Any thoughts?

  9. #9
    Join Date
    Feb 2011
    Location
    OH
    Posts
    149
    IF YOU HAVE MOISTURE IT WILL FREEZ AND ICE TAKE TORCH HEAT UP IF IT GOES AWAY YOU HAVE MOISTER IT WILL BREAK LOOS LIKE ICE PLUGG ;

  10. #10
    Thanks slctech, I posted this on my Friday night and have not been back to work since then, but I will get with the foreman tomorrow morning to see what was found "if info was shared". But you did bring up a good thought about temp drop across LLS, I would not that've thought of that (if I ever have the time to access that side of the panel).

    Hopefully I will get some sort of resolution tomorrow

  11. #11
    Join Date
    May 2010
    Location
    Oxford, UK
    Posts
    343
    Have seen a couple of solenoids with a faulty coil that is ok when cold but goes open circuit when it warms up, then cools and works again. One was a Danfoss and the other was hot water inlet on a wash system on a milk tank. Both times i noticed it while working on the system next to them which makes me wonder if this is a common failure path for coils, as we tend to only see thing when they have failed bad enough for the customer to notice...

    Though i think favourite would be moisture blocking the txv, any colour change in the sight glass? LP switch out of adjustment on pumpdown and a leak in the evap is a common way for the water to get in as i'm sure you know!

  12. #12
    Quote Originally Posted by Matango02 View Post
    Thanks slctech, I posted this on my Friday night and have not been back to work since then, but I will get with the foreman tomorrow morning to see what was found "if info was shared". But you did bring up a good thought about temp drop across LLS, I would not that've thought of that (if I ever have the time to access that side of the panel).

    Hopefully I will get some sort of resolution tomorrow
    Someone found the cooler was on a timer, huh? For a cooler? Timer? Set at 5am when bakery people are in and out? Oh my, time will tell if that call comes back, thanks for responses

  13. #13
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    2,586
    Everything you are explaining in your original post, just explains the common pumpdown procedure for most refrigerant systems. Liquid Line Solenoid is de-energized and closes, compressor pulls refrigerant back into the receiver until the low pressure switch shuts down compressor. That moment that the techs see the pressure spike and system starts to operate is the moment the liquid line solenoid is being energized and refrigerant is let loose.

    Need to see what is causing the liquid line solenoid to have power disrupted to it when the thermostat is calling for cooling. Again, could be the defrost timer, thermostat, valve solenoid, or as strange as it may be a timer. I am not sure here in this regular member forum your experience, is the timer simply a old style Paragon defrost clock? Never seen an actual timer in series with the system controls.

    More concerned about the extra juice you were pumping into this system. Would definitely go back and verify that you have not over-charged this system.

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