Water dripping from Mitsubishi Mr. Slim mini split unit

Discussion in 'HVAC Heating & Cooling' started by SkepticRae, Aug 2, 2011.

  1. SkepticRae

    SkepticRae New Member

    Aug 2, 2011
    Hello all,

    I have a bit of a problem and am hoping that someone here can help. I have a Mitsubishi mini split unit (MSZ-FE12NA) that was installed three months ago. It has worked beautifully up until very recently, keeping up with high outside temperatures/humidity with no problems. Recently, however, we came home to find that the indoor unit was spewing water out of the air exhaust.

    We have checked everything we can think to check and have scoured the internet with no luck. The drain line is clear and is draining well (it emits a steady dripping stream of water); we used 1.5" PVC for the drain. The drain is sloped properly with no possibility for entrapment of water. No water builds up in the pan-- we are able to dump water into the pan and have it drain with no problems. We have also ruled out the possibility of back pressure in the drain. We are just at a loss, and tech support seems only to want to suggest that we make sure the drain is not clogged-- which we have done.

    Our tentative guess as to the problem is this: There are coils along the wall side of the indoor unit; the condensate drips from them into the back pan, and then drips into the main pan that leads to the drain. For some reason, it seems that while some of the water follows this path, some of it does not, and instead ends up getting sucked into the squirrel cage/blower and out of the air exhaust.

    The unit is spotless and always has the cover on. The filters are kept clean, and there is no lint or dust on the inside or outside of the unit. If anyone has any idea as to what the problem could be, we would appreciate any and all input.

    Thank you!
  2. MAoilTech

    MAoilTech New Member

    Nov 24, 2009
    Oil Tech,HVAC
    u need to check where the drain is connected to might have a hair line crack or the seal is no good I would replace the whole drain where it connects from the unit hope it helps.
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  4. Hatch

    Hatch New Member

    Nov 18, 2011
    Texas Gulf Coast
    Did you resolve this problem?

    How did you resolve this?
    I had a similar problem with a Soleus 12,000 mini-split unit a few years ago and the solution taken was to reduce the amount of the R-22 charge. I don't know how much that reduced the cooling capacity, but it remained enough for that room.
    We are in a high-humidity area down here on the Texas coast and it seemed that the evaporator coils were not designed to handle the amount of moisture collected. It would spray water droplets out with the cooled air.
    I am considering a Mr. Slim replacement and I'd like to hear your experience.
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
    I would almost bet that the unit was improperly installed and not set level so the condensate is not draining
  6. bbecker56

    bbecker56 New Member

    Jun 14, 2013
    We had the same problem. Had everything checked and all was well- level, etc. After a call to Mitsubishi, the technician knew right away that the issue was the fan speed - we had the unit operating on silent cool. We were told there was too much humidity for the unit to handle on that speed and to put the fan on auto so that it could adjust as needed. After we did that, we have not had any issues.
  7. Lhayes

    Lhayes New Member

    Aug 22, 2015
    Beaverton, Oregon
    I have been having the same problem and when the tech came out everything was fine. He also suggested the fan speed. We set the fan on high and it quit dripping. I had it on auto but that is when it dripped.
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