Mini split or central air? Be gentle, I'm a newbie

pjs755February 15, 2013

Okay, pretend you're talking to a moron and this will work fine.

We live in CT. The house is 27 yrs old, and has baseboard hot water heat. There is no duct work. The house is a colonial, with the main structure 2200sq feet, and a 500 sq foot great room above the garage. Basement and attic are unfinished. We will be installing Low E windows this spring. The lot is heavily treed.

We got a quote right when we moved in for central air 21k to 24k, depending on the equipment we chose. We saw a guy at a home show who said he'd do it for 13k, one unit, ducts run thru the closets.

And where do mini splits fit in? Are they a viable option?

I need an education is what this all boils down to. Tell me what I need to know to make an intelligent choice


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Two story colonial?

Generally, mini splits are used when installing ductwork is not a viable option.

If comfort is important to you and you are able to install ductwork system, then two separate systems would be best if you have two stories which I suspect you have. I will assume ductwork could be installed for downstairs zone in the basement and ductwork could be installed in the attic for upstairs system. In your situation, that would be best if practical.

Tell us how much you would use AC cooling in the summer. Do you bave window units now or just perhaps a whole house attic fan or maybe nothing?

Post back.


    Bookmark   February 15, 2013 at 11:54AM
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Yes, two stories except the great room.

We have window units and a wall unit in the great room.

Duct work could be run through the attic and the basement.

It's Connecticut, so even during the week June, July, August we'll at least run the A/C in the great room so the dogs don't roast. Absolutely they A/C is on while we sleep during those months.

The first quote we got was for two systems.

    Bookmark   February 15, 2013 at 12:04PM
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I would prefer two properly sized split AC systems over mini splits.

You need a load calculation performed for both floors as well as someone experienced in good ductwork design and sizing. R8 ductwork insulation minimum.

BTW, what is your electric rate?

Post back.


    Bookmark   February 15, 2013 at 12:37PM
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The larger the number of rooms that that you install mini splits in the higher the cost in comparison to a central system.

Remember that you need returns for a central system. The choices are to have one in each room, install grates in between the rooms, install jump ducts or under cut the doors.

Mini-splits have advantages in some situations. They are inherently zoned, so you don't have to cool the whole house for the dogs or you. Depending on your lifestyle, this might or might not save you money.

What is installed in the USA is almost all variable-speed (inverter) equipment so it throttles well to control humidity under low load conditions. If you are on the costal plain, that is more important. It is humid down there.

Typically, if a system fails you have lots of other areas to stay comfortable in. That also means that a modest generator will run parts of your system.)

For me, a duct system that is outside of the house envelope is a drawback. First, ducts always leak even when new and they never improve themselves. That means everywhere you have a leak it equals a power vent either drawing in outside air into a return or blowing air outside. Keep in mind that also induces pressure differentials in your house so air is sucked in or blown out to balance that.

Take a look at the Mitsubishi, Toshiba and Sanyo web sites and see what the mini split kingdom looks like. Keep in mind that in addition to the sterotypal high-wall indoor units, small ducted units (that handle more than one room) ceiling cassettes, horizontal ceiling units are available. You should see them on the web sites. They do cost more and are a little less efficient. Check out the different brands for how their controls thermostats) work if you decide to seriously consider mini splits.

You obviously need more quotes given the difference between the two you already have.

    Bookmark   February 15, 2013 at 3:26PM
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Another great option is a high-velocity system which uses flexible ducts which are fished through your walls. The two big companies are SpacePak and Unico.

What they would do is put the air handler (blower) in the unfinished attic and run a big, long duct across the attic floor. Then they'd connect the flexible hoses to that main duct and branch out to different rooms. They can usually tuck the ducts into the corners of bedroom closets to feed down to the first floor.

The registers (outlets) in the ceilings are round, not rectangular like conventional A/C. The air that comes out of the registers travels faster than regular A/C and is somewhat noisier. But still much quieter than window units! Usually, the registers are placed so they don't blow directly on where you'll be sitting on furniture, so you won't really feel the airflow.

What I don't like about mini-split systems is those bulky units that have to mount on the inside walls of each room. Ugly, noisy, yucky.

My 1800 sq. ft. house was built in 1931, has no ducts and we put in a SpacePak system in 2003. Back then it cost about $12,000 for everything. It took the guys about seven business days to install, but it wasn't disruptive at all. Most of those days were spent measuring and planning, and that's a good thing because you don't want them making any unnecessary cuts in walls. They made no wrong cuts.

They did have to cut a small rectangular hole in two bedroom walls in order to reach two first-floor rooms that stick out from the house. But they patch the walls and you'd never know the cuts are there.

Lastly, the system uses a regular condenser than sits outside the house, just like conventional A/C units.

Here is a link that might be useful: SpacePak

    Bookmark   March 8, 2013 at 12:43PM
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"What I don't like about mini-split systems is those bulky units that have to mount on the inside walls of each room. Ugly, noisy, yucky."

You appear to know little about mini-splits. They can go on inside walls or outside walls. Most would not consider them noisy. If you don't like high-wall units, you can install floor models, ceiling register-like models, hidden ceiling models, or minimally-ducted models.

They are not a universal solution, but will work for many. The especially nice thing about them is no ducts with their associated leaks and pressure differentials. Inherent zoning is nice too.

    Bookmark   March 8, 2013 at 2:48PM
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True, I wasn't aware there are so many variations for the inside units. But, for me, it still comes down to aesthetics. SpacePak is a very elegant solution for homes that don't have ducts.

    Bookmark   March 8, 2013 at 4:51PM
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Went to a home show this last weekend and actually saw a mini split demonstrated in a HVAC booth, and in my midwestern state this was rather shocking. I'd never heard of the system until I started looking into build options in a more "green" part of the country. The folks at the booth were rather shocked I recognized the system, but it gives me hope that the systems are starting to get a bit of notice!

    Bookmark   March 11, 2013 at 5:15AM
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