Ductless mini-splits have a
Ductless mini-splits have a place in mechanical design but more often than not, they’re mis-used due to a lack of understanding of their limitations. Limitations that include…

a) The minimum capacity of ductless heads is way oversized for most rooms in a home that meets current codes. On a 1:1 system, the min. capacity is typically several to many times more than all but the largest rooms, even worse on multi-splits.

b) One head for multiple rooms or entire floor MIGHT be acceptable in a way-beyond-code home with an open floor plan in a cold (read non-cooling) climate, assuming occupants don’t mind wide temperature swings (for example, bedrooms 4 or 5 degrees cooler than main area), BUT you can’t get away with this in a cooling climate.

The following limitations apply to ducted mini-splits as well..

c) There’s a reason why multi-splits have significantly lower SEER ratings than 1:1 mini-splits, just as there’s a reason why larger systems have lower SEER ratings than 9k, 12k, and 15k systems (same is true for non mini-split systems). Likewise, ducted mini’s have lower ratings than ductless for same model series since it takes more fan power to push the air through ducts.

d) Ducted mini’s have wider application than ductless (see a & b above). I’ve used them in a number of projects over the years. But as John P said, they have limited blower power compared to non-mini-split air handlers. Fujitsu and Daikin Skyair have significantly more available static than the Mitsubishi ducted ceiling head (SEZ). Daikin’s smallest ducted heads (less than 18k) units have barely enough static for the filter. A good designer can work within these limitations and select the most appropriate brand/model for the application. However…

e) Ducted mini’s are a poor choice for homes that require multiple zones on a single ducted head ( see (a) above, which applies equally to ducted mini’s). Unfortunately, you can’t (easily) do damper-based zone control with ducted mini’s due to proprietary controls. After-market zone control interfaces are available but you give much of what makes a variable system tick. In particular, the system can no longer track the delta-T in the zone(s). Daikin introduced an integrated zone control system for it’s larger (18k and higher) systems but I’m highly skeptical that it manages airflow properly when less than all zones are calling (see (f), below). I would be happy to be proven wrong if someone ever does a deep-dive research study on this system.

f) As Danny alluded to, the most serious downside with mini-splits in general is lack of latent capacity, depending on the specific model and size. The indoor unit (blower) doesn’t necessary (or ever) ramp down in concert with the outdoor unit, or the indoor unit that matches up with a particular outdoor unit is actually a re-labeled larger unit. Due to oversized indoor coil and blower, the latent capacity (ability to remove moisture) is reduced This is ESPECIALLY problematic with the smallest systems. Case in point, the Mitsubishi 30 SEER 6k system, which is the smallest 1:1 mini, and has the highest SEER of any air-to-air heat pump, has virtually NO latent capacity and not much at full load due to poor match-up between indoor and outdoor units. Ask Chris Laumer-Giddens how he knows this!

Sorry for so many words, but I’ll leave on this note: Anyone considering mini-splits for whole-house HVAC better make SURE the designer understands *all* these limitations. And be prepared to be told why you’d be better off with another solution.

Roy C. Just because some
Roy C. Just because some important group of entities do not want something does not mean they are against it being available. That said providing the information so people can start to become more educated seems positive to me.

In the early days of multi
In the early days of multi-capacity systems, some manufacturers did not adjust the indoor airflow rate in response to capacity changes, so latent capacity was greatly reduced at part load. I believe that all of the manufacturers do adjust indoor airflow rate to maintain latent capacity and some even provide manual user inputs or humidity sensor options that will reduce indoor airflow rate further when needed for additional latent capacity.

Manufacturers do not provide much performance information beyond what is required because the vast majority of their customers (dealers) do not want it.

Anyway – it taught me about things to consider when HVAC was required for a 16th century English manor (pre Willis). A great exercise in restraint and careful selection regarding both noise and air throws / velocities figured prominently.

HVAC etal can and should be invisible RE: practical sensibilities.

That term practical can often be wrestled with via cost factors where resistance to logic is running rampant.

Almost unseen is a good goal. Invisibility requires magic.

For example, a quick look around design critiquing sites (McMansion Hell being a great place to see what *not* to!) shows a motley assortment of badly placed outdoor units, gruesome diffusers and just plain ugly baseboard heaters. This http://mcmansionhell.com/post/171170635621/50-states-of-mcmansion-hell-washington-county is one of the worst to recently feature.

Even if you’re not a fan of mini-splits, good quality radiators and aesthetically pleasing diffusers made from better quality materials would have definitely helped the look of the rooms in this property. Oh, that, and not putting the outdoor unit on the front lawn by the entrance porch!

Well, here in Europe where
Well, here in Europe where wall mounted mini-splits are the norm, all the mainstream manufacturers have at least one, often several “design” oriented units which are available for a small premium. Mitsubishi, Daikin and Panasonic have some outstanding stylish units. The Daikin units I have installed are a real feature of each room and a talking point for first time visitors to the house. The motorised front panel which opens when the unit is switching on or off plus clever wide louvred flaps and horizontal airflow adjusters have an origami-like quality, and the plastic finish is very tactile. When I compare this to a dull off-white diffuser or, worse, a utilitarian plain grille which gets plonked randomly in most US houses, I don’t think we’re worse off. My unit in the kitchen/breakfast nook gets far more attention than any granite worktop would and the cost differential between than and a laminate counter almost paid for the whole-house installation I had done.

But you do have a point when it comes to bad or ill-considered unit placing (pipe runs in plastic conduit on the walls as rear piping wasn’t an option being a pet hate of mine). And a cheap horrid budget indoor unit will always look bad and most likely be noisy and show it’s age after a few years.

And ugly afterthought bump-outs for ducting make any space look compromised.

In short, it’s all just a question of what folks are used to, with getting used to the inevitable compromises for any air handling solution being a big part of that. And markets, along with tastes, do change

Good Point RoyC. BUT in my
Good Point RoyC. BUT in my climate (the rot belt), it is imperative that I know the SHR at those part load conditions. And when you ask many manufacturers what those numbers are, you get nothing but crickets. Who cares about efficiency when there is water dripping off the indoor unit because the latent removal capacity is nearly nonexistent. (Yes I have seen this several times with mini-splits.) Unlike sensible loads, indoor latent loads do not follow the same linear relationship. People still breathe, cook, take showers, wash clothes, mop floors nearly as much at 83 degrees as they do at 88 degrees.

Leigha — First of all there
Leigha — First of all there is no reason to have a return in your living room unless it can be totally closed off from the rest of the house. Second if it is noisy the return is probably too small for the airflow of the oversized HVAC equipment.