Results 1 to 6 of 6
  1. #1
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    3,445
    Post Likes

    Mitsubishi dehumidify mode

    Have a customer with a Mitsubishi 1-1 hyper heat and the unit cools fine,,, he will put it into dehumidification mode for days (I believe, he gives conflicting info) and the coil will ice up. After weighing out charge it is within 4oz of nameplate. Info is pretty scarce on dehumidification mode... Will the unit in indefinitely? I can imagine if the load drops it would freeze but I would think it should kick off on sensor?? I have another customer which the unit cools perfect but in dehumidification mode the unit produces ritually zero condensate... That doesn't sound right either...ideas
    ...

  2. #2
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
    Posts
    4,965
    Post Likes
    Someone with great experience and knowledge should write a book on these things, explaining in detail all the sequences of operation, what to look for, possible problems related to conditions, codes and what is relative to those fault codes, and those things never described in any manual, but learned from trial and error.

    I hate working on them, because I don't work on more than 3 or 4 a year.

    Being 4oz low seems like it could be a lot compared to the systems total charge- I would look there first.
    Since the compressor runs 80% of the time ? to dehumidify with a slow blower speed, the charge it seems needs to be very close to specs.

  3. #3
    Join Date
    Mar 2013
    Location
    Windham, Maine
    Posts
    24
    Post Likes
    I work on these all the time, we're a diamond dealer.

    I have never known anyone to use them in dehumidify, but I can ask around.

    The Mitsubishi will not tolerate an undercharge, but is cool with a slight overcharge.

    Sent from my Motorola Electrify using Tapatalk 2

  4. #4
    Join Date
    Aug 2012
    Location
    Maine
    Posts
    180
    Post Likes
    I do alot of these mini splits. The charge needs to be spot on. If the unit lists 32oz I will shoot for 32-33oz. 4 oz low would cause your problems. Dehumidfy works by running the comp at medium speed and the blower at a very slow speed. Check your blower wheel. These are notorious for getting gunked up due to air bypassing the not so great filters. It doesn't take much to affect airflow on these things. I hit the blower wheels with compressed air yearly when I do pms on these. Dehumidify will funtion down to a certain temp. Check the thermistor on the evap. The evap thermistor should shut down the comp before the coil starts to ice. Hope this helps.

  5. #5
    Join Date
    Mar 2013
    Location
    Windham, Maine
    Posts
    24
    Post Likes
    If you think about it for a minute you'll understand why- the Mitsubishi has no minimum lineset length (at least in the 1:1) The receiver has to be able to accommodate the "extra" refrigerant in a condenser precharged with enough refrigerant to fill a liquid line up to the maximum allowable length. Therefore if you know a system is precharged with that amount of "extra" refrigerant (say .63oz/ft liquid line) you can actually determine how much it could possibly be "overcharged" and still function correctly.
    Sent from my Motorola Electrify using Tapatalk 2

  6. #6
    Join Date
    Mar 2013
    Location
    Windham, Maine
    Posts
    24
    Post Likes
    Quote Originally Posted by JDenyer232 View Post
    I do alot of these mini splits. The charge needs to be spot on. If the unit lists 32oz I will shoot for 32-33oz. 4 oz low would cause your problems. Dehumidfy works by running the comp at medium speed and the blower at a very slow speed. Check your blower wheel. These are notorious for getting gunked up due to air bypassing the not so great filters. It doesn't take much to affect airflow on these things. I hit the blower wheels with compressed air yearly when I do pms on these. Dehumidify will funtion down to a certain temp. Check the thermistor on the evap. The evap thermistor should shut down the comp before the coil starts to ice. Hope this helps.
    JD brings up a few good points- the blower wheel on all mini splits are almost always covered in thick black/green moulds. The filters on all mini-splits are a joke. I personally have worked on almost every mini split on the market and only the diakin and Mitsubishi have never frozen up without a mechanical/electrical issue. I bet you have a failed thermistor in your midst.

    I know the fujitsu, sanyo, Samsung, and comfort star? will freeze if undersized, uncharged, or have lack of airflow, but the diakin and Mitsubishi have never frozen up on me.

    Sent from my Motorola Electrify using Tapatalk 2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •