I currently have a 3 ton Trane that is on it’s last legs. We have 2 mini split systems in this house already, one just for our bedroom and one for an addition.
I am seriously thinking about ditching the ducted system and going for a 3 head mini split for the rest of the house. I would really like to get the duct work out of a 140 degree attic. This would also let me zone out the 2 bedrooms we seldom use.
This is an open plan with the living room dining area and kitchen all open. My thought was a compact cassette unit there and a wall head in the other 2 bedrooms. The cassette will accomodate a 4″ duct for the master bath. That may need to be the 18KBTU model
Am I crazy?
Replies
18K and go for it.
18K 'cause you can get 19+ seer in 18K but dont think so in 12K?
If you use for AC or humidity control most the time (yur geography?) you may want to stay with the 12K though.
I'd say it's time to stop 'patching,' clear the deck, and start over ... doing it right this time! Right now you have a hodge-podge of different systems.
You might be on the right track with the mini-split; that arrangement sure makes zone control a breeze! No more fussing with balancing ducts, powering VAV's, etc.
Not all mini-splits are created equal. Some can run at reduced speeds when under lighter loads - a good thing all around.
For all the hype given to mini-splits that can supply multiple heads, I'm against them. You've not only got an additional complication in the control design, you also pay a very real premium for the convenience.
Instead, I'd use completely separate units for the house. Three heads, each with it's own outside unit. Three 1-ton units cost far less than a single 3-ton unit and three heads.
Mini-split condensers are rated for their maximum load; there's no reason you can't use smaller fan units. You can upsize later.
Armchair calculations suggest your house will want 2 to 2-1/2 tons (24K - 30Kbtu) of total capacity. You're considering a 2-ton unit with 2-7K heads and a 12K head; this is more than the condenser can supply. Looking at the Fujitsu line, perhaps you might consider three separate units - two 9K and on 12K?
The configuraton (2 7k and 1 12k) is one of the approved configurations in the planning guide.
This is not really a hodge podge. The existing mini splits fulfill a need. The room in the back is seldom used and we want the bedroom significantly cooler than we allow the hoiuse to drift up to at night.
I am starting to think I will just replace the central system I have and keep the complexity down. Money is not that much different than the mini split solution and if the ductwork passes inspection it is a bit cheaper. One concern is the need for a condensate pump in the cassette.
You're right - it's not thart much of a hodge-podge :) I had mis-read the sketch; where you say "wall unit" I was picturing room 'window shaker' air conditioners.
I'm not going to put my fan units on outside walls. The main reason is because of the difficulty of feeding line sets into into the bottom of an outside wall; they usually sit right on the foundation wall. Then there are the issues of running the ndensate line (do you really want it dripping down the side of the house), nterference with the insulation / vapor barrier, and the chance that the siding crew will power-nail into your lines.
I'm finding that using mini-split(s) costs considerably more than just adding central air to an existing furnace. Still, you can't beat the efficiencies and ease of control. Chances are the mini-split will also be much quieter.
You'll still need your furnace, unless youlive next door to Jimmy Buffet Heat pumps do have their limitations.
What's a furnace? I have not heard of this thing.
I believe I can feed these Fujitsus down from the top and I already have line set covers going up that outside wall. All of my existing ductwork is in the attic. The existing TWE is in the hall closet shown on the picture (outside the 2 small bedrooms)
It is trivial to get to that ceiling from the attic
The construction is CBS, no siding, no vapor vapor barrier, no insulation. The existing system is cool only with 10kw of toastrer wire. I probably run it about 15-20 hours a year.
Welcome to Florida
BTW Jimmy Buffett is 250 miles north of me in the pan handle.
I got a quote on the hardware (labor and copper will be extra)
The 2 ton mini split with a 12k cassette and 2 7k wall units $3400
The 3 ton minisplit with 18K cxassette and 2 7kk wall units $4550
A 16 seer Trane $3340 after the FPL rebate.
Using my existing copper the Trane is a drop in, assuming they decide the ductwork is OK.
Replacing the ducts will make the new copper for the minisplits look cheap.
I guess I have to go up in that 140f attic and inspect the ducts some day soon before I make a decision ;-(