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  1. #1
    Join Date
    Jun 2007
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    walk in cooler EVAPORATOR coil icing up


    walk in cooler is kept at aound 38 degrees F. ....

    clean evap. coil every year, and every year after running for 6 or 8 months i go back and check it and the ball of ice is slowly getting bigger and bigger.

    its been doing this for few years now.

    its running on mp-39 or (r-401a) refrigerant.

    checked psi on suction line and its running at about 15psi. witch i belive is to cold, way below freezing.

    so evap. coil is clean, it must be low on
    mp-39 refrigerant ?????????????? any guesses?



  2. #2
    Join Date
    Oct 2006
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    England
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    Re: walk in cooler EVAPORATOR coil icing up

    Quote Originally Posted by kurt854 View Post
    walk in cooler is kept at aound 38 degrees F. ....

    clean evap. coil every year, and every year after running for 6 or 8 months i go back and check it and the ball of ice is slowly getting bigger and bigger.

    its been doing this for few years now.

    its running on mp-39 or (r-401a) refrigerant.

    checked psi on suction line and its running at about 15psi. witch i belive is to cold, way below freezing.

    so evap. coil is clean, it must be low on
    mp-39 refrigerant ?????????????? any gue
    R401a has temps very similar to R12 so the back pressure is not excessivly low.
    Does the thing have a sight glass?
    Every six or eight months is ok!!!
    Just adjust the defrost so it defrosts longer or hoter?

    taz.

  3. #3
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    Post Re: walk in cooler EVAPORATOR coil icing up

    thanks for the idea taz, it is a walk in cooler, not a freezer.... so do you think defrost is needed just for evaporator coil than? is that a normal aplication? it seems to run fine other than the slow icing of coil.

  4. #4
    Join Date
    Aug 2005
    Location
    USA
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    Re: walk in cooler EVAPORATOR coil icing up

    If you have ice or frost forming on the coil, then the coil temperature is below freezing. Say, you have a room at 40F (4.4C). The coil temperature may be operating at 30F (-1.1C). Over a long period of time this could slowly accumulate frost/ice (especially during the summer).

    An application similar to what I have described above is a candidate for an air defrost cycle. In this instance, the a defrost timer would lock out the compressor for say 30-40 minutes twice a day to allow the frost/ice to melt. The evaporator fans would still be running during this defrost cycle to help melt the frost.

    One thing to remember, frost is easy melt but once the frost melts and re-freezes on the coil it becomes ice. Ice takes a lot longer to defrost because it has a higher density that frost.
    Last edited by US Iceman; 14-06-2007 at 07:40 PM. Reason: added SI units because I forgot to...
    If all else fails, ask for help.


  5. #5
    Join Date
    Oct 2003
    Location
    Belgium
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    Re: walk in cooler EVAPORATOR coil icing up

    Are the fans running all the time?
    When is it frosting up: in winter or summer?
    Or the old trick, 2 thermostats.
    The room thermostat with the bulb located in the room is set to the desired room temperature and controls the fan (DT set to 1 K)
    A second thermostat is placed with its bulb in the coil and controls the compressor, set at start 2C (see, if you're not used to work with F, then this is difficult to read a post in IP units) and a DT of 10K.
    Your coil will never frost again.

    You repleid to Taz "it's a cooler not a freezer" Well, even a cooler needs defrosting from time to time
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  6. #6
    Join Date
    Aug 2005
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    Re: walk in cooler EVAPORATOR coil icing up

    Quote Originally Posted by Peter
    (see, if you're not used to work with F, then this is difficult to read a post in IP units)
    Sorry Peter. I fell back on old habits again. I'll try to remember not to do this the next time.
    If all else fails, ask for help.


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