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Capacity of Ceiling-Mounted Minisplit

NotAnExpertByAnyMeans | Posted in General Questions on

I’m attempting to have another ductless mini split installed in the back of our home. Place was built in 78 and isn’t the tightest ever built. Since I don’t have the time/money to reinsulate, reside and install new windows I’ve chosen to install inexpensive heating solutions.

We have a Fujitsu in our living area that keeps the front of the house conditioned well. Now I’m looking to do a unit in the back of the house to condition the bedrooms.

Just had an estimate yesterday and the guy is trying to talk me into a ceiling unit to heat the back. Problem is the unit would be in a hallway that the 3 rooms are accessed by. I’m having a hard time believing that the unit will move heat in 4 directions up to 20′ away around corners to get the bedrooms warmed up. Do these units work? What are the limitations? I’m also concerned with having a condensate pump in my attic with all that AC water moving to the outside…

My other option, which I had come up with on my own, is placing a wall unit in the master bedroom. This would face the opening to the same hallway and hopefully push air 15′ through a short 3’x5′ bedroom entrance into the hallway to the other rooms that are directly across the hall. Would this be reasonable to expect? I understand doors need to be open and we are ok with some difference in temps room to room since currently the bedrooms get down into the 50s at night in the winter. Anything is better than that.

I’m just looking for some info on what other people would consider. The wall unit would be a lot easier and cheaper to install. I’m also not looking forward to have those guys have to go from one side of my attic to the other to install/service the ceiling unit… And what if it backs up and starts raining in my hallway?

Thank you in advance for any help!

Edit: added a crude sketch of my setup, the proposed location of the ceiling unit and where I’m thinking of putting the new unit in the master bedroom. Arrows indicate direction of airflow.

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Replies

  1. NotAnExpertByAnyMeans | | #1

    Nobody has any experience with these ceiling units?

  2. Expert Member
    AKOS TOTH | | #2

    Ceiling units are very hard install and you still end up with a point heat source. They are also a huge hole into your attic which is the last thing you want. They can be installed properly by building an airtight cubby in the attic, can't see an HVAC tech doing that. If you do want to put the effort into it, it can be made to work with one of the units that has branch ducts like this LG:

    https://ashp.neep.org/#!/product/29607/7/25000///0

    The square knockouts on the side are for ducts you can use to divert part of the flow. You can run these to each bedroom to get more even distribution. This does mean lot of ducting in the attic which takes a lot of care to install properly.

    I think the simplest is a single wall mount in the hallway. If there is a bathroom near by, you can drain into the overflow of the tub or into the sink drain (you can get a tailpiece with a drain connection for easy install). With doors open, the bedrooms should get reasonable amount of heat, you can always add a panel heater in each room if you need a bit more heat.

    Wall mounts are quiet but not noise free. You'll also definitely hear it going into defrost, not something I would want in a bedroom.

    1. NotAnExpertByAnyMeans | | #9

      Thank you! I agree and I'm not excited about a huge hole in my ceiling!

  3. kyle_r | | #3

    I don’t see a ceiling mount performing any better than a wall unit in a hallway. Some models allow you to duct some of the discharge a short distance. If you want to evenly distribute the conditioned air I would look at creative ways to install a ducted mini split.

    The air handlers are small and the ductwork could possibly be hidden in soffits above doorways. If you want to consider this route, I would post a sketch of your floor plan and let the community suggest ideas.

  4. mjhil | | #4

    I have a 1971 ranch house that is not well insulated and leaky where I haven't done work (75% of the house). I have a mini-split wall head in the main living/kitchen area and in the master bedroom. I'll say that It is nice to have a head in the bedroom for A/C and sleeping in the summer. In the winter I find that I don't get a lot of warm air down low and therefore get a layer of cool air on the floor, it seems, mostly from the two bedrooms I don't heat. My bedroom unit doesn't face a doorway, but I do notice a difference in the hallway when I have it on and the door open - though again it feels noticeably stratified. I don't think you should expect it to warm spaces by pushing air through doorways given how I understand your layout - especially with reasonable fan speeds. Instead you will be warming your bedrooms by keeping their adjoining space (hallway or whatever) at temp... as long as you have the doors open.

    I didn't put this system in, but if I was putting a new one in I would go from the basement with a ducted mini-split for that part of the house for better distribution, mixing, noise, etc. - though going from below might not be an option for you. A wall cassette in the bedroom can definitely be noisy (especially if you are sensitive to sounds) with defrost cycles, and DON'T put it above a bed or you may get a cold "waterfall" of air when it defrosts. In the summer it's much more civilized, though It's been said on GBA that even the smallest mini-split heads are oversized for bedrooms. My bedroom is a 6K head and yet I'd say it sure isn't undersized for a 12x14 corner room.

    I'd echo looking into a ducted unit- if it can work for your situation. Otherwise the ceiling or wall unit in the hallway might be the way to go.

  5. mr_reference_Hugh | | #5

    NotAnExpertByAnyMeans, you might notice less activity in the Q&A on the weekends and that might be why you did not see an immediate response.

    I would encourage you to hand draw a very rough sketch of the layout of your house, take a picture of it and upload the sketch as an attachment to your post. It could help a great deal in providing recommendations.

    Regarding the equipment

    Option #1 Something that involves ductwork in the attic
    I would avoid a unit that would involve ductwork in the attic. It creates a lot of challenges.

    Option #2 The ceiling cassette as proposed by HVAC tech
    I would avoid the ceiling cassette - in the hallway 20ft away - that the HVAC tech suggested. It does in fact create a large hole leading to your unheated attic. Having a condensate pump in a cold attic is not making sense to me. I would be concerned that it would freeze.

    Option #3 Ceiling cassette below existing ceiling, boxed in with drywall
    The Mitsubishi ceiling cassette units are just 9" in height. I could see installing this below the existing ceiling gyprock right in front of your bedroom. Installing it below the existing celling, you don't need to cut a gaping hole into your attic. You would need someone to then to finish around the unit in the hallway with some minor framing and drywall work (or decorative paneling) - but this all costs money. Of course, you need to have a drain nearby if you don't want a condensate pump and tubing. If this is a bungalow with a basement then a drain might be something a plumber could install. In our area of North America, the building codes does not require venting for 3" floor drains and a 3" floor drain could inside the wall cavity of an interior wall with an access panel.

    Option #4 Wall mounted head in master bedroom as described
    I think that your idea for a wall mounted head in one room in front of two-bedroom doors that are across from each other would work well for those 2 bedrooms. I do agree that you would need to be prepared to deal with the sound as mentioned in other replies... sure I could handle the sound myself.

    Option #5 Wall mounted head in the other bedroom across the hall
    If the room across from the master bedroom is not occupied, maybe you could install the wall unit there and have it facing the doors (in the same way you intended from the master bedroom.)

    Option #6 Ducted mini-split head in hallway below existing ceiling (or in basement below the floor)

    There are ducted units that are just 8" in height.
    See the image attached. Source: https://cdn.agilitycms.com/mesca/mem-201908v3-e_mitsubishi_mseries_mrslim_catalogue_lr_fin.pdf (on page 27.)

    You could put this below the existing ceiling in the hallway (not in the attic) and have some very simple and short ductwork move air into the two bedrooms. This would require putting low profile ductwork under the ceiling and through a spot of your choice at the top of the bedroom walls. You would keep the ducting as short as possible because you would need to box them in and hide them - lowering the height of the ceiling. This would require some minor framing and drywall work (or decorative paneling). This has at least two other considerations:
    - Consider existing ceiling light fixtures and whether they would need to be moved by an electrician.
    - Consider how the unit would drain like with a condensate pump or whether a plumber would need to install a drain.
    Of course, this could most likely be installed from under the floor if you have a basement.

    Option #7 - Call other companies for quotes and recommendations
    Getting other HVAC companies to give you recommendations and a quote might allow you to discover the optimal solution.

    A final note. Remember that if you have a condensate pump as suggested by the HVAC tech, these things can fail and create a mess. It is that this is a common problem or anything like that. It is just that you need to know this when deciding to install a condensate pump.

    1. NotAnExpertByAnyMeans | | #8

      I like all your info, thank you. I think I'm going with option 4. Having that unit in my attic sounds like a nightmare waiting to happen.

      Added a crude sketch. Hope it can be read...

      1. mr_reference_Hugh | | #10

        I looked at the sketch and it is very close what I had understood.

        I understand that you want to keep things simple and that makes lots of sense to me. You understand your needs/wants better than anyone else.

        I agree with the other post above that you can always add a electric panel heater in other 2 rooms if you need a bit more heat. Some are really low capacity and can be plugged into a regular wall socket.

        Take care.

        1. NotAnExpertByAnyMeans | | #11

          Thank you again!

  6. Robert Opaluch | | #6

    Although mini splits are double to triple the efficiency of resistance electric heating...
    --Heat rises so a ceiling unit isn't the best for heating (better for AC), not to mention all the other problems you and others have noted with a ceiling unit
    --We have had success with a typical mini split wall unit blowing warm air directly about 40' down a hallway to three bedrooms in a 1979 ranch not well insulated or airtight, but only if the doors are left open (won't help at night if doors closed). But this is a mildly cold winter climate (Cape Cod, MA, average 23F low to 38F high Jan temps), you didn't mention your climate zone or location, which might be much colder. Also, the airtightness of the building is crucial, and given your description, I'm guessing this option wouldn't work very well but would help if you warmed rooms all day and drywall/plaster/etc would absorb some heat, warming objects, and keep rooms a bit warmer overnight.
    -- Radiant or resistance heating (even a cheap plug in portable electric heater or electric blanket) will be more expensive to run, but put that heat right where you need it most, when you need it most. (And cheaper to install with little maintenance headaches, and simple to replace.) Therefore you will use them for a shorter time, and tolerate a lower temp in some areas of the room. It also will allow more individual control per each room. And could heat only the rooms needed, when needed. Maybe you are doing this already, and don't like the higher electric bills or the focused heat and cold objects in the room? Or don't like kids playing with heaters? (Growing up, my younger brother was using one to dry his wet socks by hanging them on the heating unit safety screen! ;-)

    1. NotAnExpertByAnyMeans | | #7

      Thank you! The home is located in central Maine. We do have 1 single mini split (2nd smallest Fujitsu rs3 unit) so I'm definitely ok with the noise and operation of the wall units.

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