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scaffnet

Mini split debate

scaffnet
10 years ago

Hi,

I am about to get a mini split system installed in two of my upstairs bedrooms, no debate there. However up for discussion is an additional 12,000 BTU unit in the dining room downstairs, suggested by our HVAC installer. Here is the crux of the debate:

We own an 1847 house. Well insulated, restored windows, high efficiency storm windows. There are three rooms in the main house downstairs (DR, LR, Parlor). DR is the central room. It has three doorways - double french door to LR, door to hallway upstairs, door to kitchen. It is a large room that everyone walks through every day to move about the house. It's a hub.

HVAC guy says a unit here will make the downstairs much more comfortable, especially in the three rooms named above. However the kitchen is off one end of the DR, and there is another room off the kitchen.

Wife is concerned that we are going to spend money on an imperfect solution, and that the kitchen will not be positively impacted by the unit in the adjoining DR (a standard door opening separates these two rooms).

We have no plans to add another mini split zone in the kitchen ell of the house - no room for the unit, no finances. I think the DR unit will be better than nothing, and will definitely help keep the downstairs from hitting 85 degrees like it does during these heat waves, and it will knock down the humidity which is a big plus for me, an asthma sufferer.

So the question comes down to: how much air recirculation will a 12,000 BTU unit prompt? Will it draw hot air from the entire downstairs, even the rooms not directly adjoining? Will it be "worth it"?

Thanks for any thoughts or suggestions!

Comments (16)

  • stoveguyy
    10 years ago

    Could u put in a window a/c unit downstairs and see how it performs? Buy a used 10k unit for $100 and try it. Its not permanent.

  • scaffnet
    Original Author
    10 years ago

    I did put a window unit downstairs, it certainly helped quite a bit.

    My assumption is that the mini split, located on the ceiling, will actually cycle the hot air through better, and perhaps eventually draw from the more distant rooms, setting up circulation, as opposed to the window AC, which basically just dumps cool air on the floor. Is that fair to say?

  • ionized_gw
    10 years ago

    The relative performance of the window-shaker vs, the minisplit in cooling adjacent rooms might depend more on the direction the air is being thrown in.

    Are these two or three indoor units going on a single outdoor unit either way? The proposed downstairs mini is ceiling-grate type unit or high-wall mount?

  • ionized_gw
    10 years ago

    The relative performance of the window-shaker vs, the minisplit in cooling adjacent rooms might depend more on the direction the air is being thrown in.

    Are these two or three indoor units going on a single outdoor unit either way? The proposed downstairs mini is ceiling-grate type unit or high-wall mount?

  • ionized_gw
    10 years ago

    The relative performance of the window-shaker vs, the minisplit in cooling adjacent rooms might depend more on the direction the air is being thrown in.

    Are these two or three indoor units going on a single outdoor unit either way? The proposed downstairs mini is ceiling-grate type unit or high-wall mount?

  • scaffnet
    Original Author
    10 years ago

    All three will run off one unit. There will be two 9000 BTU units upstairs.

    There is a significant price increase if we go from 2 to 3 units (all high wall mount) as 3 requires a larger heat pump outside.

  • SaltiDawg
    10 years ago

    Are these mini-splits going to also be used for heating?

  • scaffnet
    Original Author
    10 years ago

    No, not for heating. Cooling only.

  • stoveguyy
    10 years ago

    What is cost difference? 2 units up vs 2 up/1 down? So u have nothing downstairs now? m

  • ionized_gw
    10 years ago

    You can get small, "minimally-ducted" air handlers that couple up with the same type outdoor units that you are considering installing. I can 't say where you might put it, but they are sometimes used to cool two or more rooms.

    Note that I think that there are advantages to having some smaller outdoor units vs. one larger one. I think an example best illustrates the point. It looks like the variable-capacity inverter equipment can throttle back to about 30% of its rated capacity.0 If you have a 24000 BTU outdoor unit with 2 x 6000 BTU and one 12000 BTU indoor unit, you can throttle back the compressor to 8000 BTU. If you are running one indoor unit it will have to be shutting off and turning on. On the other hand, if you have a 1:1 6000 BTU system, you can throttle back to 2000 BTU and increase your dehumidification capacity and even out the cooling.

  • mojwnun
    10 years ago

    I'm in the Northeast too, have a 1915 Arts & Crafts "Foursquare" home, about 1800 s/f, no A/C, radiator heat supplemented with woodburning fp insert. Taking bids right now on ductless splits, and contractors seem to want to sell me on multiple compressor units running a couple of air handlers rather than a single compressor with four multizones. What's up with that? Are they upselling me? Is it worth the cost?

  • jackfre
    10 years ago

    You will be delighted with the downstairs units performance. I have a Fujitsu 12RLS unit (25 SEER and 12 HSPF) unit downstairs. It cools the kitchen, LR & DR very evenly. There is only one door to each of these rooms. Upstairs I have a dual unit. Usually, upstairs we run the ac for a few hours late in the pm to cool the space and then run just the fan overnight. You could also run the units in "quiet" mode and they will cool nicely and are very quiet. I chose to have the really high efficiency unit which we run frequently separate from the upstairs. I was able to purchase the 24k dual unit (16 SEER) as well as the downstairs 12 for about the same price as the triple 36.

    This was a few years ago and now you can run 3evaps off an 18 or 24 kbtu unit. When you consider that you will not run the upstairs and downstairs units at the same time, you may find that perfectly satisfactory.

    You will find that the heating performance of these units is excellent. In the Northern climates, the heating savings is what pays for these units.

  • mic111
    10 years ago

    I think your contractor is giving you good advice. Can you locate the high wall unit so that the vent can be aimed to throw AC into the kitchen? That is what we did. We have a high wall unit in our dining room and we permanently aimed the air flow into the kitchen. Our kitchen gets direct south sunlight but is more open to the dining room than yours. If you need to you might consider a small fan that will pull the cool air at the floor into your kitchen.

    We find our ductless mini-split does a pretty good job with adjacent rooms. In fact we installed a unit in an upstairs office that we don't use much because our ceiling unit (out in the hall) does a good enough job throwing air into the room.

    The problem with a kitchen is that the appliances throw off heat as well as the act of cooking. But I think you will be happy with a cooler downstairs. In the future you might still consider adding a unit to the kitchen.

    When you have the bedroom units installed be sure not to install them in an area where they are blowing directly on your heads. Pick a location where you will only get indirect cool air while sleeping.

  • klem1
    10 years ago

    I consider extra cost of 2 systems rather than one to be money well spent if and when one breaks down. Cost is recaptured if there are periods where one or the other is not needed.
    It isn't nessary to force air flow through the doorways in order to cool ajacent rooms. High placment of return air(mini-split evap) generates convection that improves distribution. If after useing the DR-LR-Parlor unit,you need more cooling in kitchen,do through wall,celing cavity or fur down supply enhancement. A grill near floor in cooled room and another near ceiling in adjoining room is inexpensive and can be eaisliy added any time. The fan need not move much air. Cost of fan is a matter of cheap and loud or increased cost and quiter. Cooling adjoining room plus room on other side of adjoining room can be accomplised via ceiling cavity or fur down. This would not require air supply in center room. Carful consideration should be given to fan in approved fire resistant inclosure.

  • samandjinna
    7 years ago

    Hi there, scaffnet. I'm curious what you decided to do. How is the system working out for you? Looking at options for our Boston-area home for heating and cooling.

  • ionized_gw
    7 years ago

    A great deal depends on heat transfer rates from room to room compared to through the home's envelope. If the house is well-insulated, room to room transfer transfer is pretty fast compared to heating from outside. If not well-insulated heat will enter through the kitchen outside envelope faster than it can be transferred to the dining room for removal.