Central air vs. mini split ?

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Hello all -
I may be buying a house before too long, and a few questions about installing air conditioning into a home that lacks it. House will be ranch-style, 1600-1900 sq. ft. I have no house in particular picked out yet, but some I'm interested would be fine -- EXCEPT for the fact that they were not built with air conditioning.
I'm wondering about the pros/cons of installing a "mini split" system (with multiple "room units" or perhaps more than one mini split unit), vis-a-vis going for central air...?
Just from casual browsing, it looks like mini split would be considerably cheaper and easier to install than a full central air system with ducting, etc. (the latter probably involving a LOT of wall/floor work as well).
Is central air worth paying the extra $$$ and installation work? Or can mini split do as good a job, have equal reliability, etc.?
I'm also wondering if pre-existing ducting in some homes that have either oil or gas hot air, could also be used with a central air system?
Actually, if I found the right place with pre-existing ducting, I might even consider going to a full geothermal system. But that's a different topic.
Thanks, - John
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On Friday, August 23, 2013 12:52:36 PM UTC-4, John Albert wrote:

It depends on the house, what it already has, and how easy or hard it is to run ducts. If the house has forced air heating, then generally no new ducts are required. If it has hot water heat, then a lot of ducts are required. How much work that is depends on the layout of the house, ie basement, crawlspace, etc.

MS is good for areas. One room or a few rooms. If you need and want to cool the whole house, as most people do, then central is what's needed. MS or even window AC can be used as a supplement to central AC. If you have a room that has a lot of sun exposure, isn't being cooled adequately by central, or a room you spend a lot of time it, etc.
But if you're in an area with periods of high humidity, nothing beats central air.

Yes, they always are. Another option you should look at is the new high velocity systems. They use air under pressure through like 1.5" hoses to deliver it. They are more expensive, but might be viable for a retrofit, because they use those hoses, not ducts.

Yes, it sure is.

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Per snipped-for-privacy@optonline.net:

My parent's place had a system where the air was delivered through what looked tb 1.5 or 2" hoses. It was a retrofit.
I found the noise to be irritating enough that I would never have one installed in a house that I had to live in.
We recently re-did our system so that it has three zones: bedrooms, living room/kitchen, and rec room.
If I ever built a house, I would have a zone for each room and doors to enforce the zones.
My thinking is that hard times are coming fuel cost-wise and more zones would allow one to cut back heating/cooling to just a couple of rooms - or even just one - if the need arose.
--
Pete Cresswell

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wrote:

Unless the system were designed like a mini-split, I doubt you'd ever pay back the initial cost. I do shut vents off to rooms we're not using and have the upstairs unit on a "Nest" (we don't use the upstairs rooms much in the summer).
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Per snipped-for-privacy@attt.bizz:

Considering that the cost to zone our rec room was well over a grand, I'd have to agree with that.
In retrospect, now that I know what a mini-split is, we would have been better served by installing same for the rec room - which is at ground level. I would think that the install would have been about as simple as such installs get.
--
Pete Cresswell

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On Saturday, August 24, 2013 10:35:43 AM UTC-4, (PeteCresswell) wrote:

Only drawback is that the minisplit would have cost 2 to 3X.
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wrote:

I was thinking about a mini-split for the attic in our previous house. It had an air handler in the space I wanted to heat/AC but it would have been more work to use it than add a mini-split. OTOH, the solution ended up being to move. ;-) I my put a mini-split in our basement here. Like you said, installation would be a snap.
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On Friday, August 23, 2013 7:47:46 PM UTC-4, (PeteCresswell) wrote:

I've only seen one in operation. It was during an open house for a house being sold. It was an old colonial style house and it was a hot summer day. The house was nice and cool, air was coming out of the vents and I did not notice any noise. But, can't say what level it was operating at either. They could have had it cranking before the open house, and cut it way back during, etc.
My understanding is they have a design with special outlets that reduce the noise that you would expect. But how well that works probably varies from one manufacturer to the next. I would definitely want to see a few of the ones I was considering before having it installed.

I don't know about a zone for each room, but I agree that it's shocking that zoned systems, even doing just two, are not common on a single system. You do see a lot of new big two story homes with two zones via two separate systems, one in the basement, one in the attic.

Not only that, but increased comfort, as it can be balanced automatically. I think the big problem here is who pays for all this? Easiest and cheapest time to install that kind of system is during construction. But most homes are being built by spec builders, not homeowners. So, the builder may say to himself, if I sink an extra $5K into this, will the house sell for $10K, $15K more. Will a prospective buyer really care, etc.
I see this kind of thing going on here in NJ all the time. Builders are building $700K - $1mil houses and doing lots of cheap things that are a long way from shelling out extra money for fancier HVAC. If I were a builder, I'd try doing some enhancements and then making that a feature that distinguishes me from the competition. Basically, yeah my house sells for $50K more, but look at x, y, and z, what I'm giving you. A good place to start would be bathroom fans. In those houses referenced about, they all use the cheapest, noisiest fan available. For just $30 more, you could get one that was much quieter. Then when you're selling it show that to the clients.
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On Sat, 24 Aug 2013 06:51:24 -0700 (PDT), " snipped-for-privacy@optonline.net"

It's quite common. My previous house had two, 2T for the second floor (in the unheated attic space) and 3-1/2T on the main floor (no basement). This house has 4-1/2T for the main and a 1-1/2 for the second floor. Both are in the attic. No heat or AC in the basement.
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On Saturday, August 24, 2013 3:06:11 PM UTC-4, snipped-for-privacy@attt.bizz wrote:

What's quite common? Three zones on a single system, like the poster is talking about? Or a two story house that has two entirely separate systems. The latter is common here too, but not zoning within a system.
My previous house had two, 2T for the second floor

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On Sat, 24 Aug 2013 12:30:32 -0700 (PDT), " snipped-for-privacy@optonline.net"

Two independent systems. One for the upstairs, another for the main floor. In fact, I think it's the norm, here in the SE (don't know of any 2-story houses with a single system).

Zoning is not common.
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On 8/24/2013 1:56 PM, snipped-for-privacy@attt.bizz wrote:

If you zone a conventional system you have less air over the evaporator. Less heat will be transferred to the evaporator. The evaporator can get too cold and freeze up. I assume this can be prevented by a 'freeze stat' on the evaporator to shut down the compressor, but it is added complexity and short-cycling also has to be avoided. I suspect dehumidification may not be as effective.
I haven't seen a zoned conventional system. One major company that adds air conditioning to existing forced air houses wanted existing zoning defeated for air conditioning so all zones were open and only one thermostat controlled the system. Do they make 2-stage compressors?
My understanding is that room outlets may have to be rebalanced between heating and cooling, particularly 2 floor. Outlets could be closed in rooms that are not used, but freeze-up may be a problem.
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wrote:

Good point about the freezing. I would think dehumidification would be better with a colder coil, though (until it froze).
The biggest problem with our current system is dehumidification. If it did a better job I'm sure I could bump up the temperature a few degrees. I'll probably have to replace the system(s) in a couple of years, though. I replaced one of the coils last year and the guy said the system wasn't long for the world (it's only six years old now).

I assume it's a matter of how many are closed. One or two bedrooms and closets(!) shouldn't cause much of a problem.
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Yep, humidity is a big factor in comfort. Had anyone look at the system, and try to improve the humidity?
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/25/2013 12:34 PM, snipped-for-privacy@attt.bizz wrote:

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On Sun, 25 Aug 2013 17:57:53 -0400, Stormin Mormon

We had someone in last year, when we first moved into the house. He changed the (leaking) coil and added a 24" return in parallel with one of the others (getting too cold - condensate rusting out the unit). that probably made the humidity higher but he said there wasn't nearly enough return size. It works a lot better, anyway. Of course it didn't work very well at all without coolant. ;-)
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Yes, lack of return air is a really common problem.
I'm trying to remember what helps lower humidity. Lower fan speed, perhaps. More time in the air handler.
Ah, well. Your man at the scene is best person to figure it out.
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/25/2013 6:47 PM, snipped-for-privacy@attt.bizz wrote:

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On Sun, 25 Aug 2013 19:21:40 -0400, Stormin Mormon

He doesn't seem to be the brightest bulb in the pack but I think he can handle the handlers. ;-) We signed a service contract with him. $200/yr which includes maintenance twice a year, (6) filters included. He threw in the service calls for outages, the additional return line, and grille, with the contract, but not the coil. ;-)
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It makes me wonder if the system is over sized. Perhaps a smaller orifice / piston, or a TXV adjustment will allow it to run longer.
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/25/2013 8:49 PM, snipped-for-privacy@attt.bizz wrote:

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On Sun, 25 Aug 2013 19:21:40 -0400, Stormin Mormon

The biggest factor in humidity is properly sizing the system in the first lace. Bigger is not better. It won't run long enough and you will be "cave clammy", cold but still with lots of humidity
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On Monday, August 26, 2013 12:37:18 AM UTC-4, snipped-for-privacy@aol.com wrote:

+1
And having a two stage can also help. If you have days where it's high humidity but not such high temps, it will run longer, allowing it to take out more of the humidity. I don't have that kind of climate here, but where it's common it can be an issue.
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