Choosing a Ductless Mini Split Based on Sound
April 28, 2021 11:55 AM   Subscribe

How do we choose a mini split and make sure it doesn't make any stupid noises that will keep us awake?

Our 10,000 BTU window air has been great for our bedroom but it's reaching the end of it's life.
For both aesthetic and functional reasons we are looking to install a mini split. My wife and I are very complicated sleepers and our window unit provided a nice amount of consistent white noise the fan was very loud but also very consistent. It was loud enough that you could barely hear the compressor kick on and off. I know mini splits are generally pretty quiet by design and won't provide the white noise of the window unit, but I don't want to end up with a unit that makes some kind of inconsistent or annoying noise. I've stayed in hotels where the fan will kick on and off with the compressor with no option to stay on constantly. I've seen units that use the condensate to improve efficiency and you get a god awful watery sound. I just want to make sure whatever unit we choose meets our needs for either complete silence or consistent white noise.
posted by jmsta to Home & Garden (12 answers total) 4 users marked this as a favorite
dumb answer: put a small box fan in the bedroom. consistent white noise, regardless of whether the mini-split is going or not.
posted by ivan ivanych samovar at 12:00 PM on April 28

Here is my general mini-split advice, along with answer to your specific question: We have a Mitsubishi mini-split above our bed (ductless), and it does not make enough noise to disturb my wife, who is a very light sleeper. Mini-splits are awesome if you haven't had one before-- heat and cooling in one unit, quiet, energy efficient, with a host of settings.

I did a lot of research before buying ours, and received the good advice that Mitsubishi is a high quality (the best) brand, which I now agree with. Also, consider the fact that installation is a very important part of whether or not the unit is going to work well, so spend at least as much time choosing the installers as the unit itself. Both of these pieces of knowledge came from our realtor when we bought our house. So find a person who knows the local installation companies (again, probably a realtor is a good place to start) and go with one that has a good reputation. We paid more for both the brand, and the installation, but haven't regretted it at all.

Finally, and this may not apply to you, but may be useful to others reading about mini-splits-- if you are using a VA loan in the USA, you can by law add up to $6000 (this was 2018, may be a different amount now) to your loan for the installation of energy efficient heating/cooling units. We did this when we bought our house and it has made the difference between liking being our bedroom and loving it. It was a pain in the neck at every step of the way to insist that our lender/realtor/title company follow the law and offer this option to us-- none of them wanted to do the paperwork and all of them tried to talk us out of it to save themselves work-- but was totally worth it for us. I hope all that experience helps you with your decisions-- good luck!
posted by seasparrow at 12:09 PM on April 28 [1 favorite]

Apologies for stating what you might already know - the mini spit has the condenser unit outside, so the only noise the "indoor unit" usually makes is a fan. The only time the unit makes other noise is when coolant flow directionality reverses. This will only happen when you switch from heating mode to cooling mode (twice a year), or when the unit goes into defrost mode in the coldest parts of the winter. Even then, I just hear about 15 seconds of swooshing sounds as the coolant flow reverses. If you live in an area that regularly goes below freezing, you might consider getting a lower temperature rated unit to avoid that.

As for the indoor units, they're basically white noise because they're just a fan. If you want to minimize noise, you can get the dBa loudness rating of the unit. However, when I investigated this, basically all vendors had the same loudness. I just picked based on aesthetics.
posted by saeculorum at 12:09 PM on April 28

Our Mitsubishi is not in a bedroom but it's in a quiet room. It has slight whooshes on a cold start (i.e. from "off" to "on") but once it's running and cycling it's just... whisper-quiet with the fan on low, and quiet when it's on high. (And the AUTO settings are smart enough to do most of the work.) On low, it's quieter than a white noise generator set at a comfortable level for sleeping, so you could easily do what ivan ivanych samovar suggests to make your preferred level of white noise predominant.

The outdoor unit is separated from the indoor one by a windowless wall, and it's pretty quiet too. Depending on your home layout you can potentially place it at a distance or somewhere that's more insulated. (I'd agree with seasparrow that it's vital to have an experienced installer.) The outdoor unit may work a little harder at the extremes of your local temperature range but it's night-and-day different from a hotel AC unit or a whole-house heat pump.

It is a genuinely remarkable bit of kit, and has transformed the comfort level of the room in which it's installed.
posted by holgate at 12:21 PM on April 28 [1 favorite]

You can now get dual inverter window Air conditioners such as this LG model .. reviews say these sound more like mini splits
posted by soylent00FF00 at 12:32 PM on April 28

My bedroom mini split bothers me sometimes, although it looks like I'm in the minority. In theory it's like a fan making white noise, but the fan noise isn't consistent enough for me to filter out, and sometimes it sounds clunky or like it's making a higher pitched whirr. I also get occasional gurgles and the drain lines (outside the house) are very audible in certain situations. We have had the guy who installed them come check and there's nothing obviously wrong. Our mini splits are Fujitsu, and FWIW I'm a very light sleeper and am frequently woken up by all sorts of heating/cooling systems, so it might be a me-problem. It is also SO MUCH BETTER than a hotel room system, but I do notice the issue.
posted by zibra at 1:07 PM on April 28

All I'll say is don't let them do any install that requires a condensate pump. This is an unusual thing to do but that's how ours is and while the unit itself is quiet the pump can be loud. It helps to clean it regularly.
posted by potrzebie at 1:43 PM on April 28 [1 favorite]

I think one of the reasons our Mitsubishi mini-split is so quiet is that it has a variable speed compressor. This means that it can cool constantly at a low rate if need be. Other mini-splits I’ve experienced cycle frequently between loudish fan arctic blast and silence while the room gradually warms up, until the startle of the fan comes back. Definitely definitely prefer ours!!!
posted by wyzewoman at 2:02 PM on April 28

I've got an LG Art Cool in my workshop, and we've got a Mitsubishi mini-split in the house. The LG is just a quiet fan, the Mitsubishi has a mode where it waves it's blades around, if you are extremely super amazingly sensitive that rhythmic very slight variation in sound might possible kinda keep someone awake, but it doesn't bother my wife or me, or our cats.

It is not, for instance, nearly as intrusive as my wife's less than a year old Philips CPAP.
posted by straw at 2:08 PM on April 28

> dumb answer: put a small box fan in the bedroom. consistent white noise, regardless of whether the mini-split is going or not.

Well, for that matter, I'm pretty sure that on our Mitsubishi you can let the fan run all the time, regardless of whether the compressor is working, so no box fan is needed. Furthermore, the fan on its lowest setting is nearly inaudible, but can be turned up much higher if you want the white noise.
posted by polecat at 3:07 PM on April 28 [1 favorite]

I am almost exactly one-year into owning a Mitsubishi system throughout our house to replace a set of ancient window ACs and a gas furnace, and I actually found them to be TOO quiet (the sound of the sump pump running in our crawlspace or a vocal cat outside can wake me out of a dead sleep), but (fortunately?) also have terrible allergies, so using a fan or air filter has worked well for white noise while sleeping. Seriously. They're so quiet that when we first got them, I could hear the coolant circulating sometimes because there was no other noise and called out the installing HVAC company to check all the fluid levels and listen to the sounds and I think they thought I was nuts. VERY VERY QUIET. It's great, aside from the fact that now I'm able to hear every single other house sound and so I drive my spouse crazy worrying about the fridge noises or the sump pump sounds or stuff creaking and settling.
posted by bowtiesarecool at 2:21 PM on April 29 [1 favorite]

I've done a bit of listening to the Mitsubishi inside and out since this question was posted -- coincidentally, I was working in the yard right next to the outdoor unit when it was running -- and it is really really quiet on both sides. It is quieter than a ceiling fan set on high. So if you want white noise and have a ceiling fan and don't want to fiddle with the mini-split settings, that's an answer.
posted by holgate at 8:10 PM on April 29 [1 favorite]

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