Am trying to decide on optimal placement of Minisplit in master bedroom. Wall behind bed is exterior. If you follow window away from bed leads to ensuite. At opposite side of room is doorway to hallway and other bedrooms. Ideally with door open I'd like some cooling / heating escaping yo that area. The bed is not centered in room, so centering on wall behind bed would look odd. Three locations we are considering. 1. Window wall beside bed; so blowing across bed. 2. On exterior wall behind bed but on window side. Centered between window wall and bed. This area would blow directly into ensuite and perhaps provide cooling there. If I go with this location how many inches from window wall. 3. On exterior wall on other side of bed. Set in from wall with twin bathroom on other side. I envisioned this area being best to blow through doorway into hallway.

is this an existing house or a new super insulated house? An older or poorly insulated house will have more heat loss from each room; a new well built house will stay close in temperature in adjoining spaces by normal air circulation. In general we place them where they will not be blowing on anyone.

Existing house. Minisplit will be used for both cooling and heating. I am wondering if location is merely aesthetics or is it actually better in center of room rather than near a wall, or pointed towards an open door. Cool air will drop and warm air will rise and eventually distribute.

Most minis have a number of options for directing the air flow. You can let it sweep, or aim in a particular direction. Some even sense the temperature in the room, and focus on the area that needs it most. In a room that small, unless it is very poorly insulated, you will be able to hang meat in there! Our lay-out is similar, and we have ours on the bed wall, centered in the room. That way, it blows out into the room and not on the bed. That being said, our house is very well sealed and insulated. We generally just run a single unit in the main part of the house, and only run the one in the BR at night or in extremely cold weather.

Does one feel a draft if you are sitting or lying (in bed) near a minisplit?

due to low ceilings and lack of wall space we had to install our main floor mini splits on a kitchen wall next to the table. (in an old house) We hope to move it some day when we remodel as it does blow on the table and can be irritating; especially if you are sitting under it. (sitting under the mini split, not the table, although that would help too). Even with that, we are very happy with the units. From 6' away you don't notice it.

Thanks, Bob. Good to know when deciding on placement.

Good info to consider when installing a minisplit. We put in a LG 9000btu 27 seer system in at the end of January in our living room on the first floor with a mostly open floor plan. The first floor is 1000sft with a conditioned crawl. It could use more insulation in the rim joists but the crawl walls are R30 at the moment. The rest of the first floor has R11 batts with foil faced polyiso on the exterior to that they used to bring it up to R13 code. Dont ask me why they did that. I guess they could get away with cheaper batts and not need to put plywood on. Anyway, we havnt used the first floor heat pump since February. Even then it was only two very very cold nights for VA. Feb was one of those months that most of my coworkers paid $400+ to heat their homes.

I mention this to do with placement because I measured heat coming out of the 9000btu split at 110deg F at one point and if I remember correctly even higher a few times. You do not want this over top of the head of your bed cooking you all winter long. Trust me... it would be horrible. Nice at first until you suddenly started feeling like you were in purgatory.

I'd like to bump up this thread as we are in a similar situation. Our 2100 sf one-level home is to be heated with 2 minisplits. In the preliminary consultation with the mechanical guy, he suggested having one in the master bedroom, which is at one end of the mostly-rectangular layout, and the other pump at the other end of the house.

The bed wall of the master bedroom is the eastern exterior wall. From a spot on that wall there is a corridor which, if the bedroom door is left open (which it always is, we have pets who come and go) allows for air flow right down the length of the home. But I'm concerned about air blowing on me. That spot, which lines up with the bedroom door and hallway, is just to the side of our bed. If you are just talking horizontal distance (i.e., not considering that the unit will be mounted high up on the wall), I'm not sure it would be 6 feet or more, as the previous poster suggested was a good distance.

I'm concerned not just about having air blowing on me while lying in bed, but also the noise. I cannot tolerate fan noises, especially at night when it is so quiet (we live in a rural area). However, given that we always turn the heat off at night except on the very rare coldest spells, perhaps it won't be an issue?

The lack of noise is one of the things I like about hydronic heating systems. There seem to be new heating systems coming out that have many of the advantages of minisplits, but can be used with panel radiators or so called radiant floors as well as with fan-based units that are like minisplit heads. The fan based units can be set on different fan speeds and can be very quiet with the fan on low. http://www.chiltrix.com/

What's your heating load?

At low speed a 3/4 ton mini-split is quieter than your refrigerator, not even remotely similar to a window air-conditioner.

It's generally not a great idea for comfort to have it blowing directly on you, since that introduces both a wind-chill factor and a drying factor into the mix.

As someone who turns off mini-fridges in hotel rooms in order to have it quiet enough to sleep, I note that 1) "quieter than your refrigerator" does not equate to "quiet enough that it doesn't matter for anyone," and that 2) I'm at the extreme of the noise sensitivity spectrum and so when I comment about liking the quiet of hydronic systems, that does not mean that a typical person would find the noise of a mini-split head problematic.

We've installed one in our kitchen, which has plaster walls, low ceiling, and tile floor so it can be a loud room. The unit is pretty quiet overall, but it does make some noise. If you are that sensitive, you might be better off with a ducted system.

Thanks, everyone.

A related question: do mini-splits work on a thermostat system, where you set the desired temperature and they go off and on as needed to maintain it? And if you have two mini-splits, as we will, do they work in tandem or as independent units with their own thermostats?

I'm asking because in our current home, which has a forced-air heating system, I always turn it off at night. It's rarely ever super cold here, and I prefer lots of blankets and cool air at night. So I'm wondering if I would just be turning it off at night anyways, so not really a problem unless we had a nasty cold snap, which don't last long. And there would still be the other one running so the house wouldn't be insanely cold (would that work?).

And then of course there is the wood stove, which we could light up before going to bed during a rare cold spell and not need to use the minis at night.

mini splits actually never go "off" unless you shut them off at the remote, but they do ramp up & down as necessary. The motors are not the old fashioned ON/OFF, but a newer type (ECM) which can run at a very low speed and use a small amount of electricity. It's usually less expensive to leave them alone at night.

Two minisplits could mean one compressor outside with two heads or two independent systems. But in either case, you can turn one off and keep the other one running.

As Bob notes, it's more efficient to leave them on all the time, but if you want to turn one off for the night to make it quieter, you can do that, and you won't lose a lot of efficiency.

The multi-split solutions are usually less efficient, due to the minimum modulation constraint of the compressor, which usually can't modulate down to the minimum output of a single head.

The part-load efficiency compared to full-speed efficiency is extremely high, especially at temps north of 25F. At 35F the older Fujitsu 12RLS2 delivered a COP of about 5 at minimum speed, but only about 2.5 at full speed in third-party bench testing- TWICE as efficient!

In-situ testing in MA also showed that people who turned them off or way down when they were away used substantially more power than similar nearby houses where the occupants used a "set and forget" strategy, letting the modulate.

Though some mini-splits have wall thermostat options, most sense the interior temp by the incoming are at the head/cassette, and will adjust the modulatation level accordingly. This leads to very real offsets in room temp vs. the setpoint temp, but as long as you're bumping it up or down a degree or two at a time they stay in an efficient modulating mode, and deliver stable room temps. If installed where the air-currents are too constrained they can short-cycle from that intake-air temp feedback, but that's usually soluble with a wall thermostat option.

Wow, you guys are great, thanks for all the info!

I believe the plan is to have two independent mini-splits (i.e., two compressors) rather than a multi-head system with one compressor, but if I understand correctly, in either case it's much better to just set a base temperature and forget about it than to fiddle with them, turn the thermostat up and down, or turn them off and on.

If this is correct then I will have to think carefully about putting one in my bedroom. There may be some alternative places to put it where the fan noise would not disturb me at night (and I get that they are very quiet, but I am sensitive to fan noises, and here in the country the nights are very quiet indeed).

Your understanding about modulation & not changing the set points is correct. A set & forget approach maximizes efficiency, and minimizes noise, since it'll be running at low speed most of the time, whereas during recovering ramps it has to run at mid to high speed.

If you really can't stand fan noise even at <30 dbA at a unit on the far side of the room, Bob I's suggested ducted mini-split solution would potentially be quieter, if somewhat less efficient than a wall-coil type.

If you are happy with the bedroom being a little cool, I think putting it in a different room and leaving it on is a good solution.

Posted By chrs on 07 Oct 2015 03:45 PM
If you are happy with the bedroom being a little cool, I think putting it in a different room and leaving it on is a good solution.

That works for one my relatives in WA with similar noise sensitivity and temperature preferences.

FWIW, we had Mitsubishi mini splits installed this last summer and when the fan is in whisper mode I cannot hear it at all.