Question about mini split AC systems.

7 years ago

I understand the basics of how these systems work but need to understand some details to assess a house we are considering buying. 12 room antique, about 4,000 sq feet. Currently the house has two exterior split units and 4 interior split units. As a rule of thumb, do you need 1 interior unit per room or can the interior unit effectively cool multiple rooms? Is it possible that 4 interior units could be cooling the whole house effectively or can I assume that we need to add more interior units?

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Comments (3)

klem1
7 years ago
It usually isn't necessary to have a unit in each room. One usually doesn't want to cool all 12 rooms at the same time so combined capacity of units need not be capiable either. So many factors play a part in how well it works/doesn't work,home can't be evaluated long distance via the net.
sjordan14 thanked klem1
sjordan14
Original Author
7 years ago
I am not following your answer. Sure you don’t want to cool whole house but what does it mean for the rooms without interior units? Are you saying that you only put units where you want cooling and that the others are not?
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armoured
7 years ago
sjordan, not answering for klem, just my point of view: when cooling with interior units only in some rooms, other rooms will be cooled indireclty from normal heat/air exchange within the house. Also a lot of how we perceive heat is the amount of humidity in the air, and a lot of A/C is removing the humidity, which can benefit other rooms (and then how tight is the house in terms of penetration of humid air). Heat rises within the house, so you get houses where upper floor bedrooms can get stifling - but possibly only need A/C for a few hours a day, to remove heat before bedtime, are nights cool where you are, etc. Plus solar gain - south facing rooms may get uncomfortably hot, rooms that don't get sun be okay much of the day, shade effects. Air flow within the house, can fans and ceiling fans help. Etc.

So, too many factors to generalize, your climate matters, and also depends on how demanding you are about temperature differences. If you focus first on rooms where you spend the most time (usually kitchen, main recreation room, occupied bedrooms), the rest may work itself out. Some households want 72f year-round, others are tolerant of quite a bit warmer during hot summers.

The thing with at least some older houses - it was considered normal e.g. to have bedrooms quite a bit colder (more blankets!) or warmer (sleep with a fan, no sheets or blankets) in tune with the time of year. During summer, wasn't uncommon to have outdoor kitchens. Getting to the modern ideal of identical temperature everywhere may be a tall order - possible but a lot of work and expense (or lots of heating / cooling units).
sjordan14 thanked armoured