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Thread: Mini split mold

  1. #1
    Join Date
    Dec 2003
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    Confused Mini split mold

    I am starting to run into heavy mold build up on the evap blowers on ductless air conditioners. The build up is so heavy it almost blocks the fins of the blower wheel. The brand of the units varies and the install sites have all been clean so I don't think it's a house keeping problem.
    We have installed these units for a number of years and have never seen this problem before. Most of the units are less than a year old with some only a few months of use.
    Has anyone else encountered this problem? And is a solution other than installing ultra violet lights?
    These things are very difficult to clean and of course the homeowners blame the equipment.
    Thanks

  2. #2
    Join Date
    May 2008
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    Southeast
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    I've seen this occur. Maybe mold can form more easily on plastic surfaces rather than galvanized steel or fiberglass...?

    And yes, they are a pain to clean. I would recommend making some custom attachments for a shop vac as well as some methods for applying a cleaning solution.

  3. #3
    Join Date
    Jan 2005
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    See it a lot in my area. Mainly the blower wheel. There not to bad to clean. They disassemble easier than you think.

  4. #4
    Join Date
    Feb 2009
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    Tallahassee, FL
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    Cleaned one today was so bad no air movement. Cleaned it in place on a Mitsubishi m series.

    Sure makes a mess.

    Have been wanting to try a Uv light kit and see if they prevent it or not.

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    A common problem with mini splits if the btu output is greater than the space load, and for the majority this is the case.

  6. #6
    Join Date
    Mar 2013
    Location
    Windham, Maine
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    I have this issue in almost every mini split here in the northeast. This seems to be more common in more energy conscious households that use the dehumidify mode only, or just use the split for cooling for a short period of time and then shut it off.
    My theory is that the unit is run for just long enough to cool the space and then shut completely off. The air louvers then close and the cold air then falls into the blower wheel causing it to produce condensate in this dark environment.
    This spring we installed a system from www.freshaireuv.com in the mini split above the service managers desk- so far so good, but still not enough to call it a success yet.

    If anyone else has tried any other system in mini splits I would love to hear about it- any input is welcome.

  7. #7
    Join Date
    Mar 2006
    Location
    Florida, jacksonville
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    I try to tell the customer to use the coil dry option when ever possible or set it up in the timer, some splits have the option others dont, as far as cleaning them, they have a little flex built into the coil to remove blower which just sit on rubber bushing most of the time, I had an LG one that will actually throw a code when blower is dirty, and it will not ramp up. It seems like all variable speed equipment has mold issues.

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by curdogg08 View Post
    I try to tell the customer to use the coil dry option when ever possible or set it up in the timer, some splits have the option others dont, as far as cleaning them, they have a little flex built into the coil to remove blower which just sit on rubber bushing most of the time, I had an LG one that will actually throw a code when blower is dirty, and it will not ramp up. It seems like all variable speed equipment has mold issues.
    All air handlers with cooling coils containing moisture from the cooling cycle need an air dry time for a couple airs every day. Any surface that is +90%RH for +24 hours is vunerable to growing mold. Fan "on" for a couple hours everyday when the a/c is not running will benefit. Also maintain <50%RH in the space will more quickly dry the system out during the off cycle. Green grass climates need supplemental dehumidification during the low/no cooling loads and +60^F outdoor dew points. In whole house ducted a/c systems, ducting a small whole house dehu like an Ultra-Aire 70H into the cooling ducts will dry the system during the more humid times of the season.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  9. #9
    Join Date
    Mar 2006
    Location
    Houston
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    Make sure the wall behind the the unit is 100% sealed also possible to get moisture infiltration through the drain hose. Rectorseal has some products to help with this. A wall sleeve to make it easy to seal and then they have this little check valve that you can put in the drain line to not allow outside air from coming back in. The UV lights do work but make sure you are not just treating the systems.


    Sent from my iPhone using Tapatalk - now Free

  10. #10
    Join Date
    Jan 2010
    Location
    Surprise, AZ
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    342
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