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  1. #1
    Join Date
    Apr 2006
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    61

    Dry Mode function on minisplit

    Mitsubishi minisplits have a "dry mode" operation in addition to Heat, Cool and Auto.

    The tech manual is located here

    When Dry Mode is engaged, the unit runs a timed interval On and timed interval Off while keeping a few degrees of variation from setpoint.

    No problem or question about any of that.

    My question is about the Infrared Remote Control, when placed in Dry Mode, then indoor unit continues to operate and outside unit runs based on the chart on pg. 8 of the manual link above. The LCD display shows only the waterdrop Icon image and the temperature display disappears.

    Thus, if one is running Dry Mode operation, how does one know what the setpoint fahrenheit value baseline is since it is not shown as long as the unit runs Dry Mode?

    To recap:
    Set IR Remote to Auto, Heat or Cool: The LCD shows the current temp setpoint and Icons for Auto, Sun(Heat), Cool(Snowflake)

    Set IR Remote to Dry: The LCD shows nothing but clock time, temperature disappears and Icon is Waterdrop.

  2. #2
    Join Date
    Jan 2004
    Location
    PA
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    68,759
    Your suppose to remember what temp you set it for.
    Page 32 has the temp diferences on it.
    Will vary the room temp from 1.8 to 1.3 degrees above set point in dry mode.
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  3. #3
    Join Date
    Apr 2006
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    61
    so if as an example, in Cool Mode the temp setpoint is 78F, then in Dry Mode it moves from 76.2 to 79.3 ?

    it apparently does this on it's 8 minutes ON and 3 minutes OFF automatic function so is it constantly switching from heat to cool, repeatedly?

    since there is no RH% target, if left in Dry Mode, it just keeps running, no matter how dry the indoor air may be or may become?

    thanks, just trying to understand how that works.

  4. #4
    Join Date
    Jan 2004
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    PA
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    In cool, dry mode, if the temp gets too low it shuts off.
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  5. #5
    Join Date
    Apr 2006
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    61
    setup a controlled test environment inside an empty office last evening.

    IR handset temperature setpoint adjusted to 77 F, OD temperature was 77 F.

    moved MODE selection from COOL to DRY (snowflake to waterdrop).

    outside compressor started within a couple minutes.

    this morning the office is 69.2 F and OD temperature is 76 F.

  6. #6
    Join Date
    Jan 2004
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    PA
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    What was the over night temp, and was it running when you came in this morning.
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  7. #7
    Join Date
    Apr 2006
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    61
    nightly OD temp was 74 F and outdoor compressor was not running when I arrived in the morning.

    in the evening, when I started the test, the dual green lights on the indoor unit were lit, indicating it was working and outside compressor was running.

    I am a bit surprised at how low it took the indoor temperature as I expected it to stop somewhere within a 72 F to 74 F range.

  8. #8
    Join Date
    Jan 2004
    Location
    PA
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    Me too.

    Do you still have it in dry for tonight. If so, see how it does now that the humidity is down.
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  9. #9
    Join Date
    Apr 2006
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    61
    tonight will be 80 F OD, dropping to 74 F OD at lowest point.

    while I can run a 2nd night test, I think that there is nothing new to learn here as the whole DRY mode is still a bit of a mystery, with the blank LCD display and no RH% indicator to show target RH%. during the day, the office was running in normal COOL mode at setpoint 77 F which kept temperature at around 75 F

    the Mitsubishi units are totally silent, that is the *amazing* thing about the compressors and airhandlers. one can stand next to the outdoor compressor without knowing it is running at full speed, it makes *no sound* when turning on, when running or when turning off. why can't there be resi units with those sound attributes?

    as to the running modes, COOL and HEAT work perfectly, overshooting by no more than 1 or 1.5 F degrees but DRY mode has me stumped.

  10. #10
    Join Date
    Apr 2006
    Posts
    61
    ran a 2nd night test in the empty office overnight, results as expected, indoor temp was at 70 F and setpoint on Infrared controller was at 79 F.

    it sure was dry but still a mystery what it is doing.

    OD temps were as posted previously.

  11. #11
    Join Date
    May 2006
    Posts
    312
    after watching the operation at an installation, what is the reason the mitsubishi turns on the "Powerful" mode LED while running a DRY mode operation?

    The first LED signals "Power is ON", the second LED signals "Powerful mode".

    When running COOL mode, only the first LED is turned on but DRY mode turns intermittently both of them on. What part of the DRY mode requires a "Powerful" mode?

    As to the temperature variations noted above, I've observed it maintaining a little over 3 degrees below the COOL mode setpoint, so I also suspect the temperature setting in COOL mode does not link directly to whatever number the temperature finds after running in DRY mode for 12-24 hours.


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