Mini Split systems - comfort ?

[cbc58]

I have read some good reviews on mini-split systems, but would like to find out how comfortable they are vs. units where the heat/cool flows up from the floor.  I live in a house which has heat/AC coming from the ceiling on the second floor, and don't like it when it blows down (plus it can be somewhat noisy).  Since these mount on the wall - perhaps it's a different feel.   Guess the question is: is there a noticeable difference from a system that is mounted high on a wall vs. floor vents -- or is it just a matter of getting used to it?

[Adam Roby]

My last house had a wall mounted unit.  It was located in the stairwell upstairs.  It took a while to get the main floor to cool, whereas the upstairs bedrooms were freezing (we had to keep doors closed while we slept if we wanted the main floor to be cooled).  It was also quite loud, and quite annoying every time you would go up or down the stairs because you would be blasted with cold air.  They are no maintenance free either, mine used to collect dust like no end, and would start to vibrate shaking the entire house.  If enough dust blocks the drain, then it overflows and you get water damage on your wall and floor. 

That said, my current house has a furnace with a unit outside.  You have some control with the vents to direct more air in different rooms, but no matter what you do the basement is always freezing and the upstairs mostly too hot.  I am currently sitting in the family room directly over the furnace, and I can barely hear the TV.  I have come to hate furnaces now, they are simply too loud.

Something to chew one I suppose, but no definitive preference.  Just be aware of the differences.  For the split unit, the main factor is the location.  If it has to be placed over your kitchen table in order to cool the entire house, then it will drive you crazy. 

[jimvandyke]

I put a 1.5 ton Pioneer 22 Seer Mini split in my 16 x 24 builders cottage and it is amazing. It is very quite (both inside and outside) and I have had very low electric bills, like $35 or $ 40 a month since January this year.
The idea with mini splits is to use them like zones, buy more than one if you  have seperate large rooms or buy one that has multiple indoor units with one outdoor unit. Check out HighSeer's web site.

I wish I would have come across these years ago. I understand many European homes use these exclusively. For what I paid for my 4 ton unit for my house I could have put one of these in every room and saved a bunch of money.

Jim

[MushCreek]

We have two Mitsubishi HyperHeat units for our 1400 sq ft house. They are amazing! They are virtually silent; I often challenge new visitors to see if they can hear it running. The outside unit is also nearly silent. We have a 12K BTU in the main part of the house, and a 9K in the master suite. We run just the 12K during the day and leave the interior doors open. At night, the 12K shuts off, and the 9K runs at night. Our A/C adds about $20 a month to the power bill during the hottest part of summer, and about $40 a month during the coldest part of winter.

We have the vents on ours set to sweep back and forth, but you can program it in any direction you want, including up and down. I do feel a breeze when we sit at our dining table, which is right in front of it, but we could change the direction, or turn it off during dinner if it bothered us. We usually have ours on the lowest fan setting. We have the wall mounted heads, about 8' off the floor, as we have 9-1/2 foot ceilings.

Our house is very tight and well insulated (ICF), and I wonder how these small units would work on a less efficient structure. We go for long stretches without using heat or air, as the house is so stable. One of the reasons we went with the mini-splits is that our house is too efficient for a central system; they don't make them small enough! The Mitsubishi units are very high quality, and our total cost was about $4000, with me doing most of the installation, and hiring a licensed contractor to do the final commissioning.

[Dave Sparks]

There are different strategies for the mini-split. If you do not have grid power then you do not want zones and will use the solar to run the minisplit long hours to spread the cooling or heating out into the home. A 9,000 btu unit can easily cool an 1,800 sq ft home if run from sunrise to sunset. We have been doing this offgrid since 2007 with the same unit. At night during fire season we can run set at 76F and only draw 400 watts including the refrigerator cycling. No smoke, no dust, no problems. In the day when it is hot we set the differential to max cool at 72F.
Most of the time it is just set to auto and the temp we want.  Game changer!
4th best thing I ever did taking a chance that the variable speed compressor meant variable power use.

[upa]

I pretty much have to echo Dave's experience. We also have an off grid home and rely entirely on solar power. The 9K btu minisplit I installed in our main floor has been amazing for comfort, virtually silent on its lowest fan setting. On its lowest variable setting its only using 300 watts, very solar friendly. Mine was an inexpensive Chinese brand, $650 plus another $200 for incidentals including a new copper flaring tool. The install was pretty straightforward , fortunately I have HVAC gauges and a vacuum pump so I was able to do the complete install including shortening the line set and  the commission. As I did the commission myself I apparently voided the warranty. Nonetheless, if it fails it won't be because of my installation skills

[MushCreek]

Not to be argumentative, but a 9K BTU unit won't necessarily cool an 1800 sq ft home. It is very dependent upon the structure and climate. Our 1600 sq ft home in FL struggled with 2-1/2 tons, or 30K BTU's. You have to do a careful Manual J to determine what is actually needed. I bought a $50 program and did my own calcs. It has proven out to be very accurate.

[Dave Sparks]

Florida is harder that is for sure. I have several clients there.  They use a 12,000 btu unit and have a spare because it is so humid.
The concept still works and remember I am not saying that you cool down a hot home with this strategy. The key is you never let it get that hot because you live there. The home will need decent thermal properties but not excessive.

The Offgrid concept here is you are not paying for electricity and so the heat pump is on all of the time when it is hot. It just is running at low power at night and max during the day. For Florida you will need east and west arrays, or a tracker and a decent size battery for over night. It does work!  I know it is hard to believe !
There is so much less loss without ducting and the heat calcs never account for a home that does not get hot. They are made for someone who needs to cool down a hot house fast.

[Dave Sparks]

I pretty much have to echo Dave's experience. We also have an off grid home and rely entirely on solar power. The 9K btu minisplit I installed in our main floor has been amazing for comfort, virtually silent on its lowest fan setting. On its lowest variable setting its only using 300 watts, very solar friendly. Mine was an inexpensive Chinese brand, $650 plus another $200 for incidentals including a new copper flaring tool. The install was pretty straightforward , fortunately I have HVAC gauges and a vacuum pump so I was able to do the complete install including shortening the line set and  the commission. As I did the commission myself I apparently voided the warranty. Nonetheless, if it fails it won't be because of my installation skills

Even if you hired a pro to pull down the line set and test, many manufactures will only give warranty to units bought by the pro and not on the internet or telephone. Good Job!  They are almost all Chinese now with the difference being a name brand is manufactured in China at the name brands plant and not a third party manufacturer.
Third party manufacturing can be scary as the quality is a variable.

[misspriss]

Do mini splits do good in humid environments? How well do they stack up to forced air in a mixed hot humid climate? (I'm in central AR)

We have a 2.5 ton in our 1300 sq ft house and it is inadequate. It runs constantly and can't keep up during the summer. And it is SO. LOUD. We had planned to go with a mini split in the VC we plan to build, because we hate the forced air so much, but I have heard they do not handle humidity as well.

[MushCreek]

I'm no expert, but if 2-1/2 tons won't cool 1300 square feet, it is either a very inefficient building, or there's something wrong with the system. Our very efficient 1400 square feet uses 9,000 BTU (3/4 ton) in hot, humid SC. Our minis do a good job of reducing humidity, but again, it is a well sealed and insulated building. I hadn't heard about minis not handling humidity well, but I can't imagine that they wouldn't work any different than any other A/C system.

[MountainDon]

Mini  split's work on the same principle as the traditional US central A/C and window boxes.  They all have to be sized to the space and climate to be efficient. It does help a lot to start with an efficient building, good air infiltration sealing and insulation.

[Dave Sparks]

Do mini splits do good in humid environments? How well do they stack up to forced air in a mixed hot humid climate? (I'm in central AR)

We have a 2.5 ton in our 1300 sq ft house and it is inadequate. It runs constantly and can't keep up during the summer. And it is SO. LOUD. We had planned to go with a mini split in the VC we plan to build, because we hate the forced air so much, but I have heard they do not handle humidity as well.

Something is wrong! I would look in the attic or crawl and check the ducts. Then hire a pro check the system. That is incorrect about the humidity. A mini-split is only different from your 2.5 ton in that it is a variable speed compressor and with SEER's up around 30, extremely efficient. It still forces air into a room but it does not have the 30% duct loss. You may have more than 30% it sounds.

[misspriss]

Something is wrong! I would look in the attic or crawl and check the ducts. Then hire a pro check the system. That is incorrect about the humidity. A mini-split is only different from your 2.5 ton in that it is a variable speed compressor and with SEER's up around 30, extremely efficient. It still forces air into a room but it does not have the 30% duct loss. You may have more than 30% it sounds.

We actually had the entire system replaced 2 years ago. The guy assured us 2.5 ton was the correct size (we were replacing the 2.5 ton that came with the house). He checked the ducts, enlarged our return, and has been out to check it since. On days when it doesn't get above 90, it does fine (although it does run almost all day) but once it gets over 90 it's a crap shoot.

The house was poorly built, cheap material, fast cheap labor, bare minimum standards, huge windows in the wrong places, high ceilings, not enough vents, and no trees in the neighborhood. This was our first house and we knew nothing about owning a home. We learned a lot. We live in a cave in the summer because opening the insulating shades and blinds lets in so much heat it is awful.

My inlaws have a similar sized house, a 3 ton (admittedly oversized, they went oversized on purpose), and a giant mature oak tree that shades the house all day long almost. They have strategic porches over the windows in the right places, and have reinusulated the entire house themselves. Their house stays perfect no matter the temperature.

Our in-laws will be helping us build our house, complete with the insulation and sealing and such. And I'm planting the fastest growing oak tree I can find, just as soon as we figure out where the septic lines will be.

[NathanS]

We actually had the entire system replaced 2 years ago. The guy assured us 2.5 ton was the correct size (we were replacing the 2.5 ton that came with the house). He checked the ducts, enlarged our return, and has been out to check it since. On days when it doesn't get above 90, it does fine (although it does run almost all day) but once it gets over 90 it's a crap shoot.

The house was poorly built, cheap material, fast cheap labor, bare minimum standards, huge windows in the wrong places, high ceilings, not enough vents, and no trees in the neighborhood. This was our first house and we knew nothing about owning a home. We learned a lot. We live in a cave in the summer because opening the insulating shades and blinds lets in so much heat it is awful.

My inlaws have a similar sized house, a 3 ton (admittedly oversized, they went oversized on purpose), and a giant mature oak tree that shades the house all day long almost. They have strategic porches over the windows in the right places, and have reinusulated the entire house themselves. Their house stays perfect no matter the temperature.

Our in-laws will be helping us build our house, complete with the insulation and sealing and such. And I'm planting the fastest growing oak tree I can find, just as soon as we figure out where the septic lines will be.

Are the ducts running through an unconditioned space? Even if they are sealed with mastic (which still leaks) if those vents are running through spaces that are 100F+ that would be your problem.

Ducts are supposed to be located inside of the insulation, air seals, vapor barrier.. simply put, within the conditioned space.

Ductless minisplits are nice in one sense, because there is no opportunity for someone to do something wrong.

[misspriss]

Are the ducts running through an unconditioned space? Even if they are sealed with mastic (which still leaks) if those vents are running through spaces that are 100F+ that would be your problem.

Ducts are supposed to be located inside of the insulation, air seals, vapor barrier.. simply put, within the conditioned space.

Ductless minisplits are nice in one sense, because there is no opportunity for someone to do something wrong.

Yes they are in the attic, the house is on a slab there really isn't any other place to put them. Where else would they go?

We plan to do a crawlspace in our new house.

[MountainDon]

Newer home designs on a slab would run the ductwork through an attic space but boxed in and insulated with the bottom of the duct "chase" not being insulated. That duct space is then a conditioned space. Much less heat loss or gain depending on season than the standard old way of ducts in the attic with a f-glass blanket or something like r 12 if you are lucky.  Much of your cool air is likely being lost before it gets from the A/C to the rooms. same thing with heat in winter.

Dave mentioned a 30% duct loss; common enough figure. A split mini eliminates that duct loss. If the duct joints are poorly sealed and leak air it can be worse.

[misspriss]

Newer home designs on a slab would run the ductwork through an attic space but boxed in and insulated with the bottom of the duct "chase" not being insulated. That duct space is then a conditioned space. Much less heat loss or gain depending on season than the standard old way of ducts in the attic with a f-glass blanket or something like r 12 if you are lucky.  Much of your cool air is likely being lost before it gets from the A/C to the rooms. same thing with heat in winter.

Dave mentioned a 30% duct loss; common enough figure. A split mini eliminates that duct loss. If the duct joints are poorly sealed and leak air the loss can be more like 50% in a bad case.

Well,it's a 16 year old house, so not "new". The hottest room is the one with the vaulted ceiling and not enough vents. The bedrooms stay quite comfortable, but we live in the living space most of the time. The kitchen might as well be all oven.

We plan to do a sealed/conditioned crawlspace in our build. Humidity is a big problem here. Your house can be a perfectly cool temperature but be clammy and uncomfortable. It gets that way when it's spring-ish and the air is moist, but not hot enough to make the AC run enough to take out the moisture.

Ah well, we aren't putting any more money or effort into this HVAC, we are trying to get rid of this house as quickly as possible. It's close to a good school, so maybe someone will want it for that...

[NathanS]

I have heard that Florida is on the verge of making it code to install a dehumidifier in a house in addition to an AC unit. With improved energy efficiency, AC units no longer run enough to dehumidify.

If you could at least get the insulation above the ducts that could go a long way to improving your comfort. I bet there is a ton of condensation on those ducts that could be leaking water into your attic insulation. Hopefully no mold. It might not cost much to get those ducts within conditioned space if you DIY.

[MushCreek]

Dehumidifying is tough during the shoulder seasons when it's too cool to run the A/C. Our Mitsubishi's have a dehumidify mode for that, and it works pretty well.