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  1. #1
    Join Date
    Mar 2007
    Location
    S. Central PA
    Posts
    45

    Fujitsu mini split Dry Mode fails to dehumidify in basement setting

    I have a Fujitsu 15RLQ mini split located in a 1500 sq ft walk-out basement. I attempted to use it in "dry" mode this summer and it did not reduce humidity nor did it produce any condensate. I kept a container under the output tubing to verify if it was actually doing anything for several weeks. Nothing came out.

    In dry mode the temp setting was 72 and the RH went up to 65%. In dry mode the unit seems to run intermittently along with the fan. I turned off the mini-split and used my dehumidifier to get the humidity back down to 50%.

    Service man / installer looked at it and could find nothing wrong. Put a coil cleaning solution through the indoor coil and solution came out the condensate tubing line indicating it wasn't blocked. Checked temperatures and it seemed good. When the unit is turned to AC mode it puts out lots of cold air, and will start generating condensate, but it cools room down too far. I thought dry mode was intended to dehumidify while stabilizing room temp.

    The serviceman will be returning to check it out again. It will soon be out of warranty. Any ideas on what they should look for, or have you found the dry mode (that they advertise) to be a worthless gimmick? I never use dry mode in my upstairs units. Thanks.

    PS: I have a 3300 sq ft ranch in PA with a Fujitsu 12RLE, Fujitsu 15RLQ, Mitsubishi 18FE, Mitsubishi FE12 single, and a Mitsubishi FE12-NA / GE6 / GE6 on 24NA 3-split system. I've often thought about writing a review on these mini-split units from a user perspective. Initially got some good info reading this forum.
    Last edited by Surferman; 09-14-2012 at 12:13 PM. Reason: Added PS

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,761
    basement probably just does not have enough load for the unit to run long enough to dehumidify the area.

    use the dehumidifier to control the humidity and the a/c to control temperature.

  3. #3
    Join Date
    Jul 2003
    Location
    Kingston, NY
    Posts
    74

    Check the Owner's Manual

    [QUOTE=Surferman;14192661]I have a Fujitsu 15RLQ mini split located in a 1500 sq ft walk-out basement. I attempted to use it in "dry" mode this summer and it did not reduce humidity nor did it produce any condensate. I kept a container under the output tubing to verify if it was actually doing anything for several weeks. Nothing came out.


    If I recall correctly.....the "dry mode" function is meant to dry the internal workings of the unit at the end of a use cycle to keep the indoor coil from promoting mold growth. So you would run the dry mode when turning the unit off after running it in a humid environment.

    To control the humidity in a space, just run the cooling at a comfortable temperature for you. They do a good job of humidity removal in my experience.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,474
    Usually dry mode is an overcool feature like on a Vision Pro. They may also vary blower speed and compressor capacity. But it is not a dehumidfy mode. It can't lower humidity without cooling and as 527 said, if you don't have a cooling load, it won't do any good.

  5. #5
    Join Date
    Mar 2007
    Location
    S. Central PA
    Posts
    45
    Thanks and appreciate the info.

    I was looking for any feedback by those who had experience or customers or who might have had similar questions about the "dry mode" because it doesn't work in a basement. There is both a "coil dry" mode and also a "dry mode" and that may cause confusion.

    The manual for "coil dry" says.....The Indoor unit can be dried by pressing the COIL DRY button on the Remote Control Unit so as to avoid going moldy and restrain the breed of bacterium. The COIL DRY Operation will operate for 30 minutes after pressing the COIL DRY button and it will stop automatically.

    My original question had to do with "Dry mode". The manual states it is for use for gently cooling while dehumidifying your room.  You cannot heat the room during Dry mode.  During Dry mode, the unit will operate at low speed; in order to adjust room humidity, the indoor unit’s fan may stop from time to time. Also, the fan may operate at very low speed when adjusting room humidity.  The fan speed cannot be changed manually when Dry mode has been selected.

    Dry mode may work where there is some cooling load, but not in my walkout basement as an example where the natural room temperature in summer might be 70 degrees or less. In this condition it removes no humidity. Some have said these units are not a dehumidifier and they are right. I would bet that some prospective customers may not be so informed.

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