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  1. #1
    Join Date
    Jan 2015
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    Bellevue, Washington, United States
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    Ductless Ceiling Cassettes. How to run the drain?

    I've installed 100's of ductless mini splits using a wall unit. I just got a contract to install a ceiling cassette style ductless unit. I noticed in the literature that the unit uses a pump to take out the condensate water. I'm installing this unit in the attic and I was planning to run drain along with the line set that will lead back outside. Does anyone have any pointers for this? Thanks

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
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    The pumps have a limited lift keep it under that and run downhill from there.

  3. Likes jrbenny liked this post
  4. #3
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Some of those types, use a very weak pump for lift that run any time the cooling is on. The ones i installed, also had a regular drain port, that if you had the slope i used.
    UA Local 32

  5. #4
    Join Date
    Sep 2005
    Location
    Atlanta GA area
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    As noted above... the pump has limited lift... some of them are like 2 ft or less...

    As we all have learned... read the instructions...

    If it were me... I would determine if I could do a gravity drain... and if so do so.
    Remember that laying PVC pipe without insulation directly on a sheetrock ceiling... may result in sweat causing a ceiling spot.
    And remember to arrange a way to clean the drain line.

    If I relied on the pump... I would talk the HO into annual maintenance to keep the pump clean.
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

  6. #5
    Join Date
    Jan 2015
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    Bellevue, Washington, United States
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    Thread Starter
    I just found this instructional video on Youtube. The way they designed the drain looks pretty good.

    https://www.youtube.com/watch?v=rqEWpWnGOKI

    I was also thinking that since the unit is normally designed to be hung using all thread I might attach some channel to the roof trusses in the attic and hang it so that it's just even with the ceiling opening. It doesn't look like it can just be braced to the wood like a bathroom fan.

  7. #6
    Join Date
    Jun 2014
    Location
    Dover, DE
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    No, they need some support as they do have a little weight to them. Make sure to cut an access door in to the drywall ceiling for future servicing of the unit.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  8. #7
    Join Date
    Feb 2014
    Location
    Phoenix Arizona
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    If you have to use the pump, and it's possible, try to do your lift over a pan then gravity slope from there. If the unit doesn't have a overflow safety switch built in, I'd rig my own, but I think most brands cassettes do.

  9. #8
    Join Date
    Jun 2007
    Location
    Round Rock
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    I've installed one of those, but it was in a drop down ceiling. We used gravity for the drain as I recall. Nothing was visible except for the bottom of the unit. We used all thread to hang it.
    I like DIY'ers. They pay better to fix.

  10. #9
    Join Date
    May 2019
    Posts
    5
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    I was considering a 4 zone, mini-split system for a future shed/cabin project. (Best Barns 16' x 32' Richmond) I can't post a link or image.

    Do the wall units and the ceiling cassettes need to be installed on flat walls and ceilings, or can they be installed on angled walls or ceilings. The 2nd floor is semi-loft, and has a gambrel ceiling/roof. If the wall units need a straight wall, I could place them over the windows on the gable ends. Is there a minimum clearance to the ceiling?

    I'm in Houston, Texas, so heating is a much lower priority than A/C. Since there is no overflow pan, would it be better to plumb drain lines to exit near the foundation, instead of into the main waste line? I've used a Shopvac to suck slime out of secondary drain pan lines to great effect. Is there a big downside to placing all the lines and wiring in walls that will then be insulated with expanding foam? Since this is a larger, "tiny-home" guest cottage, trying to carve out space for an air handler and ducting would be a real challenge. Mini-splits are a bit more expensive, but seem like a more elegant, and a much more efficient solution than through-the-wall or window units.

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