I have given some thought to having one installed in my woodworking shop. The problem with that is wood dust. I have a big ceiling mounted Jet air filtration system, but it doesn’t get all the dust particles, which would wind up in the AC filter and in the AC cooling fins.

Minis do not normally use standard type thermostats. The set point is more of a limit with a 4 degree swing.
Example. In cooling mode if the set point is 74 and the room temp is 78, the unit will operate at 100% capacity. As the room temp falls the unit will ramp down in capacity and power demand.

Once the room temp is is close to set point and stabilized, the unit ramps up and down in capacity and power demand.
Room temp will "float" at about 75 degrees. The outdoor unit will only stop completely if room temp falls below 74. Thr indoor unit operates at a very low speed sampling room air.

This method causes minis not to cool rapidily, but once a room is stable, humidity control is excellent.


The heating mode uses same method. As in any heat pump system, auxiliary heat will be needed when outdoor temps fall below 40 degrees. But I will admit mini applications require less aux heat than conventional heat pump systems.

There a a few considerations different conventional ducted systems but overall a good product.

There is a cassette model. The indoor air handler is installed in center of room above ceiling.

In regard to throwaway when needs out of warranty repair, probably correct. Often the mini is past its life expectancy and no repair parts are available or just not cost effective.

I have a 16 year old Mr Slim. Not a quiet as it was, but just keeps going.

Very interested in this thread. I have an old 3/1 farmhouse that has no AC and I need to redo the windows anyway, looks like a great option to cool that sucker.

They sell 'multi-zone' DIY ductless mini-splits (2,3,4,5 zone) for installs like yours - (one outdoor unit, multiple indoor units - NO DUCTING!)
example 3-Ton 3-zone system for under $3k: - https://iwae.com/shop/36k-btu-21-5-...mp-split-system-12k-12k-12k-ha21045.html
You can install the DIY series 100% yourself (if you can hook-up water to a fridge icemaker - you have all the tool & skills needed!)
There are non-DIY series of the same available, and cost is a bit lower, but you'll need HVAC Tech tools/skills or hire out.




Units I linked heat at FULL CAPACITY down to 5 degrees - they are 3rd-generation (inverter compressor) and don't have the old '40 degrees' limitation.
They use these units all over up north, where you normally wouldn't see 'regular' heatpumps. Sized right, you'll never need aux-heat.
The unit I linked has HSPF rating of 11 - that means in heating mode, 2000 watts of power put in gives over 22,000 watts (heatstrip equivalent) heating!!
(awesome for powering with portable generator in freezepocalypse like we just had!)

Let me explian my statement.

Yes minis provide often provide full capacity at low outdoor temps. But general rule of thumb, in north Texas, we need twice as much heat as we need cooling. A rule of thumb, with a ducted system, we match 3 Ton, about 36000 BTUs, cooling with an 80% efficient 70,000 BTU gas furnace or an air handler with a 15,000 KW heat kit.

70,000 x .80 = 56,000 BTUs net heat.
15,000 x 3.4 = 51,000 BTUs net heat.

A 36,000 BTU mini or ducted heat pump produces about 36,000 BTUs heating or cooling.

A layman explaination.
Regular 3 bedroom 2 bath home . 36MBTUs cool mode or heat pump mode will maintain a 25 degree split indoor vs outdoor.
100 degree day. 100 degrees - 25 degrees = 75 degree indoor temp.
Conversely for heat mode
40 degree day. 40 degrees + 25 degrees = 65 degree indoor temp. Acceptable
30 degree day 30 + 25 = 55 indoor temp. Probably not acceptable.

Just rule of thumb numbers. Construction of building and geography will cause variances. Not a substitute for a real load lost calculation.

Not sure of this number??
22000 x 3.4 BTUs = 74, 800 BTUs. This is twice the capacity of this unit. What am I missing.

One more ...

With muti head units, you can over shoot set point in one area in heat. If some one wants an explantion i will be post later.

oops - I grabbed the wrong unit watts - it uses ~ 1000 watts 11,000 watts heatstrip equvalent (~36,000 btu)

Thanks. It is easy to get crossed up looking at web pages, at least for me. I download spec sheets or make screen shots. Put in a folder, then I can thumb through them.

But, you are correct, they have a much lower energy appetite compared to resistance heat. This technology is now used in high ducted systems.

Everytime the HVAC equipment makes a major change, cost of upgrades drives the alternative market. When 13 seer equipment was usher in, new equipment was not compatible with older equipment. The result was complete upgrades were required. Often these upgrades required significant finacial planning for us regular folks. I saw a surge in window AC usage.

We are about to transition from R410A refrigerant to a more environmental friendly refrigerant, R454B. Just as when we transitioned from R22 to R410A, nothing was compatible, including our tools.
I guess it takes a lot of green to be green.

Minis will be our new alternative climate control systems to ducted systems. Just my opinion.

Thanks for all the great feedback guys. Almost everyone has been very pro minisplits. I got a bid and the price was way more than what I expected. I went back and most of y’all didn’t really talk price but other friends outside THF said they were cheap too. The price was $3060 installed(may need electric ran separate) and I can’t imagine a more basic and simple scenario than mine. One single room 20x22.
I already have ducts for a broken central unit so 4655 to put new central system in.
I’ll get another opinion but pretty sure how I’m leaning but wanted this info out there for y’all cause so many seemed interested.

$1,600 cheaper, more efficient, and better warranty? Sounds like a good call.

Installed a 2 ton Gree last summer and for everything mentioned in your bid mine was $2000 for parts, labor and installation.

Thanks Stompy, thats the kind of info I need. The AC company I got bid from is very reputable so maybe that means expensive. Of course, covid seems to of driven up price of almost EVERYTHING so maybe theres that.

That unit on Amazon runs about 1400. When I put one in a tiny house I did the electrical and paid a AC man 200 to install it. Have you got any other bids.

Not yet, I will.

Your bid says requires 220V circuit. Is that included in the bid? Or something needed in addition to the bid?

If it is included depending on how far it is being run and through what could have a big impact on the bid price.

Here is that same Daiken system for $1317 delivered - just so you know what you're paying for labor. - https://iwae.com/shop/18k-btu-17-se...p-split-system-wall-mounted-ha18409.html

You should already have sufficient 220v running outside where your current condenser is (unless mini-split condenser will be in substantially different location).
The supply power for a mini-split is ran to the outside condenser, not the inside unit.

The heatpump minisplit will save you a ton of money on heating, compared to the straight-cool central system with electric heatstrips.
17seer cooling is also way more efficient than 14seer.

Very helpful guys. The electrical is not included in bid.
I’m getting a bid from more of a mom pop type AC guy so figuring I’ll save on labor.
FYI, I will rarely use the room so I’m not too worried about efficiency. I just need to keep it from being too hot/humid for my deer mounts.

I’ve installed two. Previous house we built and the one we built about 4 yrs back. I bought cheap online both times and they have worked fine. The first one I used for my office/shop for 10 years and it worked great. The one I have now has been running for 4 years. Installing them is not for everybody. I’ve got it down pretty good. Drilling a 3 inch hole with a diamond hole saw in brand new house is not for everyone.

Freerange, where is this located?

I can discuss installed prices due to the many variables required to install correctly.

But the mini can be fed from existing 240 volt supply to old condenser unit but it will need to fused on a 20 amp breaker or fused disconnect with 20 slow blow fuses. If the out door unit is located where old condenser was located. Replacing extisting disconnect with a fused disconnect is probably best option. Of course, sight unseen, just guessing.