Central air vs. mini split ?

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On Mon, 26 Aug 2013 04:42:33 -0700 (PDT), " snipped-for-privacy@optonline.net"

That's really the problem. It's fine during the day when the unit is working pretty constantly, or at least evenly. At night it pretty much coasts, or at least has this year. To keep it comfortable, I have to drop the temperature after sundown. I keep forgetting to tick it back up in the morning.
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Wonder if leaving the stat set to "fan on" will help?
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/26/2013 12:37 AM, snipped-for-privacy@aol.com wrote:

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On Mon, 26 Aug 2013 08:16:21 -0400, Stormin Mormon

Thought about that. Nest has a new setting that allows the fan to cycle for so many minutes per hour (don't remember the specifics).
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On Sunday, August 25, 2013 12:34:28 PM UTC-4, snipped-for-privacy@attt.bizz wrote:

The problem is it freezes quickly. It's similar to having a system that is oversized for a house. The house gets cooled off so fast that if it's a more moderate day with high humidity there isn't enough run time to get the humidity out. Two stage systems are good at that.

Might it be oversized?

Yes, I close a few depending on the season. You just have to have some common sense and not close off a lot of them. I think it's probably hard to get in to trouble if you're just balancing. But very easy if you're trying to close them off to avoid heating/cooling large areas of the house to save some money because they aren't used.
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wrote:

We have a 2 zone two stage system with a single compressor (dual stage) and air handler (dual speed). There are dampers to open/close each zone, and a central control box to take the inputs from the 2 thermostats, decide when to turn on the common system (and which stage, as the thermostats can call for stage 1 or 2) and which damper to close (if any).
This was profesionnaly installed, by the book; they did have to carefully balance the zones -- our upstairs zone is significantly smaller, so they enlarged a couple of upstairs vents and set the downstairs damper to not fully close. I think the controller we have can theoretically handle 3 zones, but balancing the minimum airflow would be a bigger challenge of course.
It works pretty well; upstairs and downstairs are able to be kept roughly at the same temperature (or different per the thermostat settings -- we are never upstairs during the day, and it's just the master bedroom, so we let that zone go higher then).
Josh
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On Sunday, August 25, 2013 11:53:31 AM UTC-4, bud-- wrote:

Yes, from what I've read, that is one problem. Some zoned systems apparently dump the unneeded cool air to the basement or other unused areas where the temp doesn't matter much to avoid the above problems. However, it's obviously a very inefficient strategy. I guess if you had plenty of ducting so that the system had sufficient air flow regardless of the zoning, then it would work. But that has it's own problems, like where to run all of them, cost, etc. Two stage system would seem to be better idea.

Yes they do and I would think they would be ideal for a zoned single system.

I do that at my house.
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On 8/23/2013 12:18 PM, snipped-for-privacy@optonline.net wrote:

You beat me to it. Johnstone Supply was carrying the units but all I see on their site are the parts for it. O_o
http://spacepak.com/
TDD
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On Fri, 23 Aug 2013 18:48:06 -0500, The Daring Dufas

They can drive you nuts - some are terribly LOUD, at an irritating frquency.
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On 8/23/2013 7:51 PM, snipped-for-privacy@snyder.on.ca wrote:

The units remind me of the AC systems on passenger planes. ^_^
TDD
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On Fri, 23 Aug 2013 20:12:11 -0500, The Daring Dufas

Or the Motel-sex.
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wrote:

I have been researching the same thing myself. If you already have forced air you might be able to use the existing duct work by adding A/C registers in the ceiling but it all depends on how the ducts are run. In a retro fit, if you need extensive duct work a minisplit ends up being competitive or even cheaper. Then the question becomes, how many condenser do you want. There are multi head systems but they end up being almost as expensive as using a one to one setup with multiple condensers and heads.
The first thing you have to do is create a scope of work on the particular house to see what is necessary to do the install.
Equipment alone
2400 BTU 3 head Fujitsu Mini Split $3400 3600 BTU 3 head Fujitsu Mini Split $4550 3600 BTU Trane 16 seer central (air handler and condenser) $3980 with a $585 rebate from FPL.
That does not include duct work, copper or labor.
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On Friday, August 23, 2013 1:36:04 PM UTC-4, snipped-for-privacy@aol.com wrote:

Agree with your overall points. But that cost for the 36K BTU central eqpt is way high. It might be Tranes price, but you can get good eqpt from a company like Rheem for more like $2500. I bought a Rheem 5 ton/60K btu a couple years ago for about that price. It was 14.5 Seer though. Don't know what the price curves look like today, but 2 years ago, it didn't make sense to shell out the extra money for higher seer, the payback was just too long. That was for me here in NJ. If you're in AZ or FL, it could be different.
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On Sat, 24 Aug 2013 07:00:45 -0700 (PDT), " snipped-for-privacy@optonline.net"

Are you talking about an air handler or just dropping an "A" coil in an existing furnace? Big price difference.
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On Saturday, August 24, 2013 11:07:38 AM UTC-4, snipped-for-privacy@aol.com wrote:

In my case, it was without the air handler. But you can get whole AC only system eqpt, including the air handler for $2500 or less. Here's some examples:
https://www.acwholesalers.com/Air-Conditioner-Split-Systems/cat1010.ac?mainCat=&subCat
I know some will say you shouldn't buy Goodman because it's cheap. Others say they've had them and they are fine. When I was shopping for mine, the Rheem prices were only a few hundred more than Goodman. My old system was Ruud, which is made by same company as Rheem. Since it was still working after 25+ years, I chose Rheem. Been very happy with it. I bought it from the above website, but looks like they no longer sell Rheem.
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On Sat, 24 Aug 2013 09:38:27 -0700 (PDT), " snipped-for-privacy@optonline.net"

Then the question becomes SEER, is that a variable speed A/H? Probably not. In a place with a 7 month A/C season, SEER will quickly eat up that thousand bucks you saved.
I also think there is a quality difference but that may just be me.
Although the complexity may be a factor, it is almost as cheap to get single head mini splits and have a bunch of them. That also gets you very high SEERs, up in the 20s. The one we put in the bedroom is 26 SEER. It also makes zoning an absolute thing. Each one is 100% separate.
The thing that is holding me back on the 3 head minisplit right now is the placement of the ceiling cassette and how I will deal with the condensate. I would like to avoid a pump.
http://gfretwell.com/ftp/house%20plan%20AC1.jpg
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A square evaporator that can go in the ceiling or even drop into a 2x2 T bar ceiling hole. Air comes out all 4 sides and the return is up the middle.
http://www.fujitsugeneral.com/comp_cassette.htm
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I already have a condensate line going out of that closet in the hall where the existing air handler is but you need a pump in the cassette no matter what.
I am really coming around to just swapping out the existing central system here. Mine is still running (knock wood) so this will be a fall project when we can live with the windows open and the attic is not so hot.
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On Saturday, August 24, 2013 1:09:01 PM UTC-4, snipped-for-privacy@aol.com wrote:

The one I bought was 14 or 14.5
is that a variable speed A/H? Probably

Yes it was.
In a place with a 7 month A/C season, SEER will quickly eat up

I'm in NJ, the house is in a shady location surrounded by lots of trees and I have mostly a 3 month season for AC. My electric bill for the AC is probably $400 a year. It would take a long time to make up the savings to justify going to a higher SEER. The total cost for the HVAC eqpt, 120K BTU 93% furnace, var speed blower, 5 ton 14 SEER AC, lines, condensate pump, compressor base, etc was about $4K.

Before I bought mine, I looked at Consumer Reports listings of reported repair history for the various brands. It was interesting. There wasn't much you could conclude. Some of what you would think would be the better brands appeared to be no different than any of the others. I think Ruud in fact had one of the better histories, but from the data as I recall, my overall conclusion was that there wasn't a lot of difference.
And with any of these, I'd rather have a correctly installed brand of less expensive eqpt than a poorly installed system using expensive stuff. In fact, you have to wonder how much of the perceived problems people have with certain brands may be due not to the eqpt, but the fact that installers using less expensive eqpt cut corners on the install to save money too. Like not flowing nitrogen during brazing, for example. Customer would never know, and few years later the crud causes the system to fail.

I think the big downside is where do you put all the outside units, hide them where they won't be heard, etc. When I did my replace 2 years ago, I was about to do monkey see, monkey do, ie just put the compressor where the old one was. Then, I started thinking. The old one was right outside my family room where we watch TV a lot. I quickly concluded that with maybe 10 ft more piping, I could move it to outside the master bathroom. The electric run was actually much shorter and I reused the existing cable. Doing that, combined with the fact that the new Rheem is a lot quieter made a big difference.

Yes, that's another problem. And if you have a central, at least it's only 1 pump, or possibly none, if you can route it to a sump pump pit, etc.

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On 8/23/2013 12:52 PM, John Albert wrote:

I don't have any technical knowledge about this. I can say that about 12 years ago, I had central AC added to my 1950s row house (basement plus 2 stories). The house had forced hot air, which the local utilities company used. At the time they warned me that the outcome would be that it would cool the 1st floor living area fine, but not so much the top floor. They were right, although it was definitely an improvement over what it had been like with no AC. I forget now how expensive it was, but they used the existing duct work and fan etc which helped to defray the costs.
Now I'm in a small 2 bedroom ranch that has central air. I'm almost positive that was an add-on as well since it's also a 1950's house. It does cool the house well, presumably because it's not trying to push air uphill. There is one floor vent in a bedroom that looks out of place and a return up on a hall wall, so they may have run some additional duct work, but I don't know.
FWIW, one of the houses that I looked at in this area (most of the houses in this neighborhood are identical) had been renovated and they'd put the AC (or maybe it was a heat pump?) in the attic. That seemed to work fairly well from what I could tell at the open house.
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On Friday, August 23, 2013 4:32:57 PM UTC-4, Lee B wrote:

Even in two story houses that had AC installed when built, it's typical for the upper story to be warmer. Around here, NJ, they are going to two systems for larger houses now. One in the basement, one in the attic. That can help solve it, but also the system in the attic brings it's own problems. In my experience, a difference of two or three degrees in a house with a single system isn't unusual.
This stuff isn't rocket science and you would think installers today could do a better job, but it is what it is.
I forget now how expensive it was, but

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