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  1. #1
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    Sep 2015
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    trenton walk in freezer ice issues

    hello, i recently accepted a maintenance position at a manufacturing plant, before that ive had 6 years of journeyman experience with light commercial hvac and refrigeration units. im needing some input on a walk in freezer I have been working on at my new facility, it is a 404 system has 2 condensers and 2 evaporators with 5 fans each, systems are individual but share the same space. each unit has its own thermostat, and defrost timers, box demensions are 20'x20' wide and 8' tall.
    the problem I am having is water droplets freezing on the outlet and the shroud of the evaporator fans. the drain line is trapped and clear, all the defrost element are making good contact with the back of the evaporators, I have 4 sets of defrost at 40 min, the defrost termination fan delay is terminating defrost at about 20 min and the evaporators will come on about 3 min after condenser starts. the freezer is on a shop floor with a temp of 74 and is opened and closed quite frequently 24 hrs a day. an air curtain will not work in this situation and they don't want plastic curtains because of slipping hazard from ice falling off. I am wondering if I increase the defrost cycle to 6 times a day for 20 min if that would help or any other ideas would be appreciated.

  2. #2
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    Jan 2010
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    Vancouver Island
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    I take it there is no door switch to shut down the evap fans when the door is opened?

  3. #3
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    Jun 2014
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    Dover, DE
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    What's RH% inside and outside the box?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

  4. #4
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    Quote Originally Posted by BALloyd View Post
    I take it there is no door switch to shut down the evap fans when the door is opened?
    No door is on hinges and is wide enough for a pallet to fit through, one thing I failed to mention is, the evaporator fans are on an auxiliary switch to the compressor contactor so once temp is satisfied everything shuts down.

  5. #5
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    Sep 2015
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    Outside is 55, 70 inside

  6. #6
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    Quote Originally Posted by midnightman View Post
    Outside is 55, 70 inside
    Is that RH?
    Also, how well does fan delay work after defrost?
    I'm not really sure on the reasoning for evap fan shutdown with meeting temp.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

  7. #7
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    misspoke on that, i was reading humidity. i dont know i havent seen a freezer wired that way, i dont know if that would have an effect if the fans are off and they open the door with heat rising?

  8. #8
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    Sep 2015
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    fans come on around 3 min after compressor starts.

  9. #9
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    Sep 2010
    Location
    miami,fl.
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    From what I was told regarding the evaporator fans shutting down once the set point is reached is for energy savings. The equipment is more efficient due to less energy consumption. I've seen a couple of reach in coolers wired the same way. They were made by true.

  10. #10
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    Sep 2002
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    Try moving the fan delay to another place on coil so the fans don't come on so soon

    If that dont solve it , get a delay that has a lower temp , yours might be a 20 deg , get a 15

  11. #11
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    Quote Originally Posted by Snapperhead View Post
    Try moving the fan delay to another place on coil so the fans don't come on so soon

    If that dont solve it , get a delay that has a lower temp , yours might be a 20 deg , get a 15
    I will try that.

  12. #12
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    Quote Originally Posted by Snapperhead View Post
    Try moving the fan delay to another place on coil so the fans don't come on so soon

    If that dont solve it , get a delay that has a lower temp , yours might be a 20 deg , get a 15
    Yes, your problem seems to be in the delay. Any water left after a defrost MUST have time to refreeze. If not the fan will pull that water off the coil. Your evaporators are facing the door opening ?

  13. #13
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    Jun 2014
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    Do the fans take 3 minutes to come on after a defrost, or when the thermostat closes?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

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