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  1. #1
    Join Date
    Nov 2011
    Posts
    9

    Walk in freezer defrost cycle question

    I posted this in the wrong section before maybe someone here can help me. I have a problem with a walk in freezer. The evap coils keeps freezing up, about 1-2" a week. The front freezes up really bad with soft ice on top and solid ice on the bottom. The back freezes up just on top. During the defrost when the arm first hits the pin, nothing happens. The pump down doesnt start until the second click, by then there is about 10 - 20 minutes left on the defrost. The defrost is set to 60 minutes. The heaters only stay on for a couple minutes after that. I've replaced timers before, but I dont know the actual sequence and what the terminals are associated with. Any help would be great.

  2. #2
    Join Date
    Mar 2005
    Location
    N.J.
    Posts
    149
    sounds like your'e in way over your'e head.Obtain a qualified repair person!!!!

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,426
    A good way to learn how the timer works is to remove it and examine it.

    Most defrost timers are very simple and easy to understand once you see the back side of it.

  4. #4
    Join Date
    Nov 2011
    Posts
    9
    Thanks richper for the useful advice. I was looking to get a breakdown of the defrost cycle. From my understanding the cycle goes as follows: The defrost timer activates the cycle, the solenoid valve is denergized and the condensing unit begins to pump down, the low pressure switch cuts power to the compressor contactor, the defrost heaters are energized, once the defrost time is reached the solenoid valve is opened and the indoor fans turn on once the coil reaches 30F. I do have an understanding of how this works but I am missing some key information.

  5. #5
    Join Date
    Feb 2010
    Location
    butler pa
    Posts
    1,073
    add in the dtfd also....and heater limits

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,426
    Quote Originally Posted by Maven445 View Post
    Thanks richper for the useful advice. I was looking to get a breakdown of the defrost cycle. From my understanding the cycle goes as follows: The defrost timer activates the cycle, the solenoid valve is denergized and the condensing unit begins to pump down, the low pressure switch cuts power to the compressor contactor, the defrost heaters are energized, once the defrost time is reached the solenoid valve is opened and the indoor fans turn on once the coil reaches 30F. I do have an understanding of how this works but I am missing some key information.
    I've gotta say that something isn't adding up here.

    Please post more information about this problem. Post specifics, not generalities and vague requests for information,

  7. #7
    Join Date
    Dec 2009
    Location
    Southern US
    Posts
    504
    We cant go into detailed info per site rules but does your compressor shut down shortly after defrost cycle is initiated?
    I'm good at making things cold...You can ask my first two wives!

  8. #8
    Join Date
    Mar 2005
    Location
    N.J.
    Posts
    149
    Sorry if I offended you but, from your original post it sounded like you are not very familiar with this type of system and well what J.P. said....Dito.

  9. #9
    Join Date
    Nov 2011
    Posts
    9
    No feelings hurt, its just a frustrating problem. The specifics of the problem that I see is that when the defrost timer first hits the pin and I can see the arm move, but nothing happens. Meaning that the system continues to operate. I know the timer motor works, Ive watched it go through a defrost cycle. When I manually turn the timer, I feel the first click and the second click. Its on the second click when the pump down is initiated. After the pump down is initiated there are no problems with the defrost expect that it lasts 10 - 20 minutes. The clock is set to 60 minutes. It seems way to short. There is no hi limit sensor, it was an optional part not installed. There is onlt a defrost termination switch.

  10. #10
    Join Date
    Nov 2011
    Posts
    9
    Another problem that I've noticed which is not associated with the defrost but I believe adds to the ice build up, is that they never keep the door closed to the freezer. Its always open about 12", not wide open. The door to the freezer is inside a walk in refrigerator and one of the evaps from the walk in refrigerator blows air directly into the open freezer. How much ice build up can occur from this.

  11. #11
    Join Date
    Dec 2010
    Location
    Central US
    Posts
    412
    Quote Originally Posted by Maven445 View Post
    Another problem that I've noticed which is not associated with the defrost but I believe adds to the ice build up, is that they never keep the door closed to the freezer. Its always open about 12", not wide open. The door to the freezer is inside a walk in refrigerator and one of the evaps from the walk in refrigerator blows air directly into the open freezer. How much ice build up can occur from this.
    Tons got to keep the door closed. Especially since you mentioned frost not ice. Frost indicates moisture infiltration in to the walk in. Fix the door problem after you completley remove any and all frost from evap coil. If you dont it just keeps coming back like the plague. As far as the timer when you manually initiate defrost by turning dial you are fast forwarding the defrost time need to let it operate automatically and then see how long the actual defrost is. but if the defrost ends before the 60 minutes it could simply be the early term sensor canceling defrost because the case got to warm before time expired.

  12. #12
    Join Date
    Dec 2010
    Location
    new jersey
    Posts
    364
    You have to start somewhere first, lets get back to the def. problem....

    I'm going to assume it has electric def...The timer motor may work, but may have a problem as it hits the tripper you can check this rather easily w/ ammeter,in any event,if the clock is bad, replace it, and set-up the same as the one you just removed as a starting point usually 1 or 2 a day is more than enough depending on area.

    Yes the open of doors does create a problem w/frosting but even less when the freezer is inside the cooler.

    in some cases, the door to the box must be closed to close the fan ,and ,or sol.circuit.

    and to be sure to check def. Term sensor/klixon that it is not kicking it out of def.

  13. #13
    Join Date
    Nov 2011
    Posts
    9
    I actually spoke to a supplier and he told me that it was probably the defrost termination switch, which doesnt make sense cause that doesnt affect the start of the defrost. I just wanted to get some more info on the defrost cycle. Thanks everyone for your posts.

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