Mini Split Engineering Recommendation

[Mage182]

I had a home energy review done during a renovation a few years back that included a mini split implementation design by a Mitsubishi cooling engineer. However, it is contradictory to everything I have read here about microzoning or oversizing. Does anyone have any opinions on the design or how it can be improved before I start shopping for equipment? It's an expanded cape with a full second floor. The recommendation is 5 heads with 1 outdoor unit. My concern is that the small rooms on the first floor won't function efficiently with a head in each of them. But placing one larger head in the living room won't cool those rooms adequately due to the layout and those rooms being south facing with zero shade on that side of the house. Any thoughts you have would be much appreciated.

 

[Stuff]

You've got forced air heating so normal recommendation would be to add a/c to that. Then 2nd floor could have problems cooling due to inadequate duct work but many are just fine.

 

[Sponsor]

 

[Mage182]

You've got forced air heating so normal recommendation would be to add a/c to that. Then 2nd floor could have problems cooling due to inadequate duct work but many are just fine.

I have hydronic heating.

 

[Stuff]

OK - the doc shows a 85% efficient system with 1000 cfm so thought that was existing.

Yes, 1st floor bedroom units are oversized but since you have no air circulation between them and the living room you need a head in each. Other option would be to get a single horizontal ducted unit (basically an air handler) to cover the two bedrooms.

 

[Mage182]

Can I mount one ducted unit to the ceiling in the unfinished basement below and run a feed up through the floor to each room? Is that an acceptable install?

 

[Stuff]

Those are advertised as either ceiling or under floor so basement should be fine. A bit of duct work. Note you need both a supply and return.

 

[Mage182]

What is best practice for placing the vents and return for this since the documentation doesn't give any guidance?

Can the return be an existing hole in the floor in one closet? Can I run one duct up the wall in between the two rooms and put a grate on either side for output up near the ceiling?

 

[Stuff]

Best practice for a/c registers and returns is to place them high on the wall. You need a return in each area there is a supply; otherwise trim the bottom of doors or other work-around.
With bedrooms you generally don't want a back-to-back as noise travels easily.