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Community and Q&A

Choosing minisplits for a home

Versius | Posted in Mechanicals on

We are trying to size mini splits for a home. There is an area in the front that includes the kitchen (with commercial range and an 8ft hood that does not have makeup air; it just exhausts), dining room and living room that is 60’x20′ with 21′ high sidewalls and a cathedral ceiling that goes up to 34′. There is a large fireplace as well. It has 8″ concrete walls with no insulation (poured concrete with concrete finish inside and out). There are 16 windows that are single pane wood frame at 71inches high by 35 inches wide each and a 60inch oval stained glass window and 2 sets of 8ft high 6ft wide double doors that are made of 4inch thick wood, but are not particularly well sealed. Each set of doors has a large half oval window about 6ft wide and 36inches high above it and 22inch wide by 6ft high panes to the sides of the doors. The floors are stained concrete. There are several rooms off this room that comprise an additional 460sf that don’t have any heating or cooling of their own and this room has never had any cooling system installed. In the summer, this area gets to around 110F and has high humidity. Heating is not an important issue as its virtually never needed, but cooling this area is probably going to be an issue. I’m just afraid of oversizing the system. I was considering going with a 54000 btu system with 5 spaced outlets in the area placed at around 20ft up; does this sound about right? We also have a 736sf area that is built the same way, but with 11ft tray ceilings and only a few smaller windows that we were considering a 36k BTU unit for and 3 additional areas that are each 400sf with 11ft ceilings and 4 medium windows that we were looking at 18k but units for. So, we would end up with 1 54k BTU, 1 36k BTU and 3 18k BTU units. We are having a 40kw solar system installed over a canopy.  

Do these sound like appropriate numbers? We would like the house to be able to be cooled to around 70 degrees at the peak of summer.


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  1. user-2310254 | | #1

    What is your climate zone?

    Also... You may want to hire an engineer to develop an accurate load calculation. As for who can do that, see this article:

  2. walta100 | | #2

    To me it is not clear is the new construction you are planning or an existing building?

    I think it would be a mistake and a code violation to not provide make up air for that large a range hood.

    The first step in designing your system is an aggressive manual J calculation. I find a manual J calculation like most things are worth what you pay for them. If the guy bidding to install your unit is offering a free manual J it is most likely worthless.

    It may seem like having one outdoor unit running several indoor heads is a good idea but I do not think so because the large unit cannot slow down as much as single units can so it will cycle on and off killing your efficiency. I do not think you will find a large price difference for the install. Plus you get redundancy in that when something breaks only one unit will go down not the entire system so you will still have some heat.


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