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  1. #1
    Join Date
    May 2012
    Location
    Albany, Georgia
    Posts
    38

    Walk-In cooler freezing product

    I've had a problem with a walk-in cooler that is intermittantly dropping below freezing (usually around 18 degrees). The customer originally called with frozen product and by the time I got there it was cycling normally. Pressures were good. I checked the bulb on the TXV and there was no corrosion and it was in the correct position. I concluded that it had to be a thermostat sticking and changed the thermostat. A week passed with no problems and then the customer called back with the same complaint. I checked the system again with no visable problems. I marked the thermostat just to make sure no one was adjusting it (it is behind the coil and out of sight) 3 weeks went by and the same problem occured. I did adjust the position of the thermostat bulb on the evap coil, hoping that this will make a difference. I have never been able to catch it not cycling on and off. The customer is getting frustrated and so am I.

    Anyone have any suggestions?

    SAM

  2. #2
    Join Date
    Feb 2004
    Location
    Western New York
    Posts
    1,049
    Is this a pump-down system?
    Experience is what you have an hour after you need it.

  3. #3
    Join Date
    Oct 2008
    Posts
    784
    Once had a cooler doing that. As I recall on that particular unit, tstat was wired to break one leg of the 208v contactor coil (vice using a liquid line solenoid valve & low pressure control). Other side of the contactor coil remained hot (not a good setup by whoever installed unit).

    The tstat would open at proper temp, but contactor remained pulled in. Tested voltage @ contactor coil & still had 120v present (not 208).
    Therefore, that 120v kept the coil magnetized enough that it kept the contacts closed.

    Discovered the line routed through the tstat was grounding through moisture inside a junction box mounted to the exterior of that outdoor-installed walk-in cooler. The wet grounding wasn't a good enough "short" to trip any circuit protection. However, it was just enough to keep that coil alive.

    So...one thing you might look for as a possibility...now & later.

  4. #4
    Join Date
    Jan 2007
    Location
    Pittsburgh
    Posts
    181
    Quote Originally Posted by samservice View Post
    I've had a problem with a walk-in cooler that is intermittantly dropping below freezing (usually around 18 degrees). The customer originally called with frozen product and by the time I got there it was cycling normally. Pressures were good. I checked the bulb on the TXV and there was no corrosion and it was in the correct position. I concluded that it had to be a thermostat sticking and changed the thermostat. A week passed with no problems and then the customer called back with the same complaint. I checked the system again with no visable problems. I marked the thermostat just to make sure no one was adjusting it (it is behind the coil and out of sight) 3 weeks went by and the same problem occured. I did adjust the position of the thermostat bulb on the evap coil, hoping that this will make a difference. I have never been able to catch it not cycling on and off. The customer is getting frustrated and so am I.

    Anyone have any suggestions?

    SAM
    Did you set the temperature with a good probe ? Don't use the numbers on the thermostat... What about LLSV ?

  5. #5
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,150
    Quote Originally Posted by ECtofix View Post
    Once had a cooler doing that. As I recall on that particular unit, tstat was wired to break one leg of the 208v contactor coil (vice using a liquid line solenoid valve & low pressure control). Other side of the contactor coil remained hot (not a good setup by whoever installed unit).

    The tstat would open at proper temp, but contactor remained pulled in. Tested voltage @ contactor coil & still had 120v present (not 208).
    Therefore, that 120v kept the coil magnetized enough that it kept the contacts closed.

    Discovered the line routed through the tstat was grounding through moisture inside a junction box mounted to the exterior of that outdoor-installed walk-in cooler. The wet grounding wasn't a good enough "short" to trip any circuit protection. However, it was just enough to keep that coil alive.

    So...one thing you might look for as a possibility...now & later.
    One side being hot is common pratice.... Actually never seen it any other way on condensing units.

  6. #6
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,150
    Op, if it is on a pump down. Pump the system down and take the LLSV apart and clean it.

  7. #7
    Join Date
    Oct 2008
    Posts
    784
    Quote Originally Posted by Dchappa21 View Post
    One side being hot is common pratice.... Actually never seen it any other way on condensing units.
    Now that you mentioned that, I realize now they usually are. I work on a large variety of equipment other than refrigeration which generally breaks both lines. My bad on that.

    Unfortunately, with the problem being so intermittent - and if it's a pumpdown system - and no possibility of an electrical issue I'd recollected and shared - then the solenoid valve would be the suspect.

    If only you could catch it in the act.


    "You never know what others don't know." -

    If I can't laugh at myself...then I'll laugh at YOU! -

  8. #8
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    Change the entire solenoid assembly, if this is a high risk situation concerning product loss.

  9. #9
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Suspect the LL solenoid valve, if a pump down system.

  10. #10
    Join Date
    May 2012
    Location
    Albany, Georgia
    Posts
    38

    Not a pump-down

    Quote Originally Posted by baub View Post
    Is this a pump-down system?
    This is not a pump-down system. It does not have a contactor. Thermostat brings on the liquid line solenoid.
    I just got a call, it has frozen product this morning.

  11. #11
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by samservice View Post
    This is not a pump-down system. It does not have a contactor. Thermostat brings on the liquid line solenoid.
    I just got a call, it has frozen product this morning.
    If the temp control is only controlling a solenoid valve then its a pump down system. Temp control closes solenoid valve, when set point reached, system pumps down and low pressure switch shuts comp off. Then opens solenoid valve, on a call for cool, pressure rises on low side and low pressure switch closes and brings comp on. If solenoid valve is failing open system will not pump down so it will not shut off.

  12. #12
    Join Date
    Mar 2013
    Location
    Joplin,Missouri
    Posts
    310
    I agree with everyone else change the solenoid valve

  13. #13
    Join Date
    Jan 2013
    Location
    Wisconsin
    Posts
    23
    Yep. LLSV.

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