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  1. #1
    klonoa's Avatar
    klonoa Guest

    About the deadband



    Hello,

    I am working on a university project related to domestic refrigerators, and I have something I really need some help here (I did my research for quite some time but cant seem to find my answer from google). I wonder if any one has the idea how big a deadband is within the freezer and fridge compartment of a typical domestic top-mount refrigerator??

    I think the deadband should be about 2 degree celsius (+/- 1 C from the setpoint), am I overestimated this value?

    And I absolutely have no idea what is the deadband range within the freezer compartment, from somepaper I read on internet , it seems to be a bigger value compare to that of the fridge compartment.

    Thanks in advance.

    -klo



  2. #2
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    Re: About the deadband

    .

    It deepends on the stat or controler.

    If it is a normal domestic fridge freezer with one stat controling
    the temp then it controls the temp of the evap not case temp.

    so it lets the fridge evap go down to about -5 / -7degC and then shuts down the comp.
    It then lets the evap warm up to +7degC before cutting in.

    This wide temp differance alows the fridge to remane ice free.

    If it is dual stat then the fridge works as above and the freezer works with a diff
    of abot 3degC.

    If it is on electronic controlers then it works on dual probs and has about
    a 2 or 3 deg C diff.

    All the best

    coolrunnings

    .

  3. #3
    klonoa's Avatar
    klonoa Guest

    Re: About the deadband

    hey coolrunnings,

    Just a quick question, when you refer to 1/2 stat controlling, you mean 1/2 compressor system do you?

    -klo

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    Re: About the deadband

    Quote Originally Posted by klonoa View Post
    hey coolrunnings,

    Just a quick question, when you refer to 1/2 stat controlling, you mean 1/2 compressor system do you?

    -klo

    Some fridge / freezers have one comp and the stat controls the temp of the fridge (if the fridge is down
    to temp then the freezer will be at temp also).

    Some fridge / freezers have one comp but 2 temp stats and they then control the temps accordingly.

    Some fridge / freezers have 2 comps and each is controled by their own stat.

    Some fridge / freezers have electronic controlers and they use probes in the evap and also air temps.

    Some fridge / freezers have air circulated over the evap and the system then requires fans
    to blow the air and ducts to travel the air through. These are normaly electronicaly controled.

    There are too many permatations in the design, configeration and layout that it is imposible
    to generalise.

    If you are refering to the bog standard fridge / freezer that only has basic natral convection cooling
    (the type where the shelves in the freezer are the coils of the evap and the fridge evap is a plate on the back wall of the fridge)
    then they generaly use one stat on the coil of the fridge evap.
    The fridge evap is an extention of the freezer evap and when the fridge is at the correct temp then
    the freezer is at the correct temp so the stat cuts the power to the comp. It then warms up to about +7 degC
    and then cuts in the comp.
    This wide diff alows the fridge evap to stay free of ice.


    All the best

    Coolrunnings

    .
    Last edited by cool runings; 29-04-2011 at 09:19 AM.

  5. #5
    sumit.dpfoc's Avatar
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    Re: About the deadband

    Dead Band is a range through which an input signal can be varied, upon reversal of direction, without initiating an observable change in the output signal. One of my friend told me this thing about dead band. I hope this will help you.


    _______________
    Display Fridges

  6. #6
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    Re: About the deadband

    Sorry, but the question was 'how big is the deadband'. Coolrunnings answer was right on spot.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  7. #7
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    Re: About the deadband

    Very informative Coolrunnings.
    They say you learn a little every day!
    Thanks for the info.
    Grizzly

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    Re: About the deadband

    Grizzly, thinking of expanding into domestics any time soon?. Plenty of tricky situations there... And Klonoa, just to clarify a section of coolrunnings description, "evaporator warms up to about 7c", this does not mean fridge product also warms to this temperature, contents warm and cool slower than the air so product is kept safely within range of 0 to +4c..Mike.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

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