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Thread: ductless ac help

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  1. #1

    Default ductless ac help

    I have small bedrooms that would require 5000btu ac units. I notice the ductless systems start at 9000btu. Isn't that too big and would waste energy?
    Which brand would be best Mitsubishi, Fujitsu or LG? TIA.

  2. #2
    DIY Junior Member Rat's Avatar
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    Default

    How do you know it needs 5000 BTU? Did you have a heat load performed?

    If it does need 5000 BTU and you are looking for a ductless solution then a 9000 BTU would do nicely. The Mitsubishi M series uses VRF technology to modulate output capacity. IOW it modulates the speed of the compressor, outdoor fan and indoor fan to match the load of the room. It will modulate down to 20% of total capacity and the H2 will do a little better than that. Mitsubishi is made in Japan.

    LG has some models that will modulate as well. Made in Korea.

    Fujitsu has some modulating models and is made in Japan.

    Mitsubishi has the largest support network for parts and systems, Daiken is next, then LG then Fujitsu; in my area anyway.

    The Japan products are superior, I am a Mitsubishi dealer BTW, and parts are relatively quick to find. Korean and China systems are a nightmare and parts come from a china on a S L O W boat.
    There's nothing magical about it; it's all science, physics and math.

  3. #3

    Default

    I figure the 5000btu by the area of the room. Like when you buy a window unit from Home Depot. It does get full sun and get very hot in the summer. Thanks for the info.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Area is only one small part of determining what's needed. The size and quality of the window(s), the amount of insulation, and the orientation of the room have MUCH more impact on what's needed.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Member Lightwave's Avatar
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    Unlike window ACs, ductless minisplits are a fairly big investment. It's worth taking the trouble to size them properly.

    Get a copy of HVAC Calc or RHVAC (the demo is good enough) and do a heat gain calculation.

    Modern minisplits have inverter driven compressors and can throttle back to deal with reduced load conditions. There's no harm in buying a unit that's somewhat larger than you need. Undersizing, however, will mean inadequate cooling.

    Mitsubishi and Fujitsu make far better units than LG.

  6. #6
    DIY Senior Member chefwong's Avatar
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    Default Country of Origin.....Mr.Slim

    OT but there seems to be *consensus posts* that the Japanese units are far superior.
    Mitsubishi, then Fujitsu, etc.

    Are we talking about the engineering/design of the unit that makes them superior/better .

    Three Mr. Slims FE series 9K and 12K and a 18K GE series that are waiting to be installed all say made in Thailand. I was under the impression they were all made in Japan.

    Then again some of my Nikon PRO 2K++++ lenses are not even made in Japan anymore

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