Replies

1. 
   Dave421 | Oct 12, 2021 10:18am | #1

   Just checking if the mini split experts had any thoughts on this?

   Thank you

2. 
   kyle_r | Oct 12, 2021 11:02am | #2

   Is the closet next to the bathrooms up for grabs? Could you steal some of it to put either a Fujitsu or Carrier slim duct unit that can be mounted vertically like this? https://www.greenbuildingadvisor.com/article/getting-the-right-minisplit

   Have a central return to the living room. A very short supply run to the living room and bedroom and then run a duct in a soffit through the bathroom to the kitchen.

   What online calculator did you use? Your loads look high.

1. 
   Dave421 | Oct 13, 2021 10:48am | #4

   Thanks for the reply, Kyle. I don’t think the closet is up for grabs,
   doubt I could win that battle as we have limited closet space.
   But that is a good suggestion. I didn’t know they could be mounted like that.

   As far as the calculator I used one from the ecomfort site. It seemed
   pretty detailed for all the information you could enter. The front room
   of 368 sq.ft. and the north wall of the bedroom is old construction with single pane windows and only R13 or so insulation. So maybe they came in at a higher load.

   I added a rough look to my floor plan of how I thought the duct could run if I have to
   go with the concealed unit. The unit would be in the crawl space in the middle
   of the two rooms. Runs are 8’ to 12’. 6” flex duct into
   6x10” vents. With the red boxes being a return in each room going straight up
   to the return plenum. Maybe a 10”x10” return box? Any thoughts on this?

   Maybe I am way off base on this. I have just be trying
   to do research on my own and talking to a few friends about it. There is
   a lot more involved than I realized.

   Any suggestions are much appreciated!
   Thanks

   
3. 
   jameshowison | Oct 12, 2021 11:36am | #3

   One thing to consider with a "multi-split" (ie multiple heads on a single outdoor compressor) is the over-heating/over-cooling possibilities. Check out https://www.greenbuildingadvisor.com/article/multi-zone-heat-pump-issue as a starting point.

   When the outdoor compressor is selected, be conscious of the minimum output levels, think about how that production will be divided between the indoor units. This is particularly a problem if the loads are unbalanced due to sunlight through windows or woodfires that only run sometimes.

   If there's any chance of using 1-1 units I would definitely price those out, it's definitely not the case that multi-zone is always cheaper. Especially your "A" unit seems a candidate for a 1-1 system (if there is a possibility outside the wall there).

   Finally, if considering ducted then don't get exclusively focused on the "slim-line" "concealed" "pizza box" or "horizontal ducted" units, also check out the "multi-position" air-handler units. These are the small versions of the traditional air-handlers and they can be quite small. They also service from beside the unit and not underneath the unit. e.g., for Mitsu the 12k btu/h SVZ-KP12NA measures 17 x 22 x 40 where as the slimline one measures 39 x 28 x 8 ... but the 8 dimension is deceiving because service requires ~24" under the unit (directly, or disconnect all ducting and raise). Also adding filters etc for the slimline requires creative duct building.

   http://www.mylinkdrive.com/USA/M_Series/R410A_Systems-1/Indoor_Equipment-3/Multi_Position_Air_Handler-2/SVZ_KP_NA_Models/SVZ_KP12NA?product

   Also consider whether you want to clean three filters and risk three different units making noises if they get dust in their wheels :)

   btw, take these just as things to ask around about, I don't do installs just suffered through figuring this out with a multi-zone install in my house that we had to convert to a central ducted system due to multiple issues. So I read a lot of stuff here and on hvactalk.

1. 
   Dave421 | Oct 13, 2021 11:09am | #5

   Thanks for replying and sending the links, James. The multi zone discussion was
   very informative. I didn’t realize multi-splitsystems would have those issues.
   I would only have two units so I guess I didn’t think that would be too bad. A few contractors I had look it over suggested 3 indoor units on 1 condenser. I don’t think another
   condenser near the A location to get 1-1 system will work out.

   I looked for the minimum output levels on the Lg condenser but couldn’t find
   anything on it. Hopefully I can find something. I had been wondering what affects using the wood stoves would have on the system. I will also look into the air handlers
   you mentioned.

   Thanks for sharing what you learned through your own experience.
   I also have been reading as much as I can here. I had a few contractors look
   it over and they all had very different ideas and sizing figures so it
   just added to my confusion. Also their prices were pretty shocking.

   Thanks again for your help!