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  1. #1
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    Question Thermostat cut in and cut out



    Hello guys.

    I am an engineer but I've never worked with refrigeration before so I would like your help understanding a few parameters.

    I've got a Ranco VT-9 thermostat that from info I found over the internet is specked at

    Cold In +3.5C
    Cold Out -26C
    Warm In +3.5C
    Warm Out -11C

    It also says Defrost termination +3.5C (constant cut in).

    I've viewed other posts on this forum and my understanding is that the cold in and cold out relate to the lowest setting on the thermostat (setting 7) and the warm in and warm out relate to the highest setting on the thermostat (setting 1). Is my understanding correct?

    Are the parameters mentioned above correct. i.e. I find it strange that the cold in and warm in are the same. I expected that cold in to be much lower than the warm in.

    I do not know how the defrosting thing changes the behavior of the thermostat. Can someone explain this to me?

    Where is the end of the capillary tube placed in a two door fridge? Is it somewhere between the freezer compartment and the fridge compartment?

    Any type of feedback is welcome and appreciated.

    Kilini.



  2. #2
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    Re: Thermostat cut in and cut out

    A VT9 thermostat is designed for a static Fridge/freezer combination. Not frost free.
    Cold in and out is what the VT9 will most likely achieve on coldest (7) setting.
    Warm in/out = setting (1)

    The last few inches of the thermostat capillary tube will be attached to the fridge compartment evaporator plate where manufacturers have positioned a clamp. Once the thermostat senses set point, it turns off the compressor and must not restart refrigeration cycle until capillary tube reaches +3 degrees C. This is called Cycle Defrost.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  3. #3
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    Re: Thermostat cut in and cut out

    Thanks for your feedback Mikref.

    So also from your feedback, my understanding is that irrespective of the thermostat setting the cut in will be always be at +3.5C

    Kilini.

  4. #4
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    Re: Thermostat cut in and cut out

    Yes. The VT9 is a thermostat that reacts to bellows pressure verses spring tension.
    Spring tension is variable, meaning the dial location adds or subtracts tension on the spring and will delay or increase the compressor run time.
    Either way, this thermostat cannot close it's contacts until the capillary tube connected to the fridge section plate reaches + 3 or so degrees C.

    (If this is you ....... ..., ) Karma will surely take it's revenge
    Last edited by mikeref; 03-08-2014 at 09:39 AM.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  5. #5
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    Re: Thermostat cut in and cut out

    Hello Mikeref. Thanks for the explanation. Appreciated.

    God bless you and nice weekend.

    Kilini.

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