Locating a High-Mounted Minisplit Head
Retrofit HVAC design was done a few years ago, manual J and all of the relevant stuff. 1400 sq ft first floor is simple, 9k and 18k ducted units with ducting in the encap’d crawlspace. Could likely also do a single air handler with zoning in the crawlspace. No work has been done yet.
The 2nd floor is our upstairs bedroom and a 8×9 master bath for a 440 sqft total. The bedroom ceiling is about 10.5ft in the middle, conceptually the same as a collar tie ceiling.
Equipment loads 4600 BTU heating, 3000 BTU cooling. 6k 1:1 ductless specified.
The only place for a high mount head is on the wall above the head of the bed, as there is a window at the other end of the room between the sloped ceiling sections. I think there is clear path to get the lineset down to the crawlspace and outside.
My concerns:
Noise from the high wall unit, either from the fan or from refrig in the lineset?
Air throw into the attached bathroom, with the doorway in one of the long perpendicular walls?
Cleaning and filter maint above the bed (move the bed to clean the filter)?
The only other easy-ish option is a cassette in the middle of the room, which would solve any issues with throw into the bathroom, but would need a rather oversized 7k cassette and a multi-split config. I’d probably need to make a dropped soffit to make that happen, with the installation depth and air sealing/access.
I have thought about a single phase VRF because of the different 4k/5k/6k ductless/ducted/cassette options (entire house on a 36k outdoor unit), but don’t have any intuition on how this would compare for price.
We’re already having problems with high quotes or getting quotes at all, because quotes are a serious struggle for anything around here. Business is very good, and getting anyone to followup is hard.
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My in-laws have a very hot attic with a Mr. Cool mini split head less than 30” above our heads when we stay over there. On the lowest fan speed the sound is just a light gray noise. We have toddlers so we are used to sound machines anyways. You can fix the movable vanes to point out above the bed so that it is not throwing air on you all night.
But the mixing and sending air over to your bathroom is a legitimate concern. I would strongly prefer a ducted VRF system if you can get an installer on board. You will have a quieter and more comfortable system with better room-to-room airflow. For such a large house load, please do not rely on a single outdoor unit. It won’t be able to modulate down low enough in the shoulder seasons and will cycle on and off a lot. And with two floors you will have very different loads by floor. The upstairs may call for cooling when the downstairs doesn’t need it, etc. Additionally, with two (or more) units you have some redundancy in case one is down for repairs. The other(s) can keep your house at a reasonable temperature.
Currently the plan is that all units are 1:1 (that was the as-designed spec), but the 9k and 18k for the first floor may turn into a single air handler for cost reduction. Every shred of ducting is getting replaced, so there's some flexibility there. I'm already balking at the quotes for the three 1:1 units and all the ductwork (I seem to remember $25k), and if the high wall unit will work effectively, I'll likely not explore a VRF.
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I think if your space is air tight and well insulated, the bathroom should be fine. In our master suite, the minisplit head is right over the bathroom door, so the throw is directly away. The bathroom stays within a degree or so of the bedroom temperature.
As for noise, if it turns out to be bothersome, just run the fan on lowest setting while you're sleeping. I don't bother doing that, but noise doesn't bother me as much as it might some people.
I built the bed, so I put it on casters. If your bed has the typical four posts, you could try that if standing on it to change filters isn't an option because it's too high off the floor.
Good to know that noise shouldn't be an issue. I've heard mention of people on this site being wary of bedroom installs because of noise, which is where my hesitancy came from.