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View Full Version : Anyone running multi-zone HVAC?


wiltok
04-01-2007, 09:51 AM
Building a house - wondering if it is worth the extra $3500. The house is a relatively small 2 story (2000 sq feet), but has high ceilings in both lower (12 feet) and upper (13 feet) levels. Thanks.

bigmac
04-01-2007, 10:06 AM
We do, but our house is larger. It works pretty well but we have had problems relative to too much heat building in the plenum when only one zone calls for heat. It periodically (and at the worst possible time) burns out the overtemp limiter relay putting the whole system offline until it's replaced. We recently derated the furnace and that seems to keeping the temps more consistent. The furnace runs more, but even that has the benefit of more even temps in the house.

We've also had problems on the cooling side using only one compressor. When only one zone calls for cooling, the plenum coils tended to freeze up, which created too much pressure and eventually blew the valves which meant the compressor had to be replaced. We added a bypass that reroutes the cooled air back to itself and haven't had problems since. In retrospect, one compressor for each zone would have been a better choice.

We've also had to replace the control circuit a couple of times - once as upgrade, the other due to failure.

Bottom line, IMHO, multi zone HVAC for a 2000 square foot house may be more trouble than it's worth. If your going to do it, make sure it's designed and installed by someone who really knows what they're doing. My recommendation would be to skip it and rely on ceiling fans to distribute the air better. Also, I highly recommend a whole-house fan - a high volume fan on the second story that draws air from the whole house into the attic.

SkiDog
04-01-2007, 10:23 AM
Another thing that I WILL do when I build another house is, use spray foam insulation! Open cell or closed cell, you might want to check in your area to see which one is the best, But I promise you, you;ll love it!

bigmac
04-01-2007, 10:46 AM
Another thing that I WILL do when I build another house is, use spray foam insulation! Open cell or closed cell, you might want to check in your area to see which one is the best, But I promise you, you;ll love it!I really agree with that, although it's pretty expensive. My son did that for several months between educational endeavors. It not only has much better insulation per volume, it adds something like 80% more structural integrity to the building, is far more soundproof, and allows for a much tighter structure than could ever be achieved by conventional insulation techniques.

TNH2oSkier
04-01-2007, 11:21 AM
Have you considered seperate units for each floor vs the zone units.

bigmac
04-01-2007, 11:31 AM
Have you considered seperate units for each floor vs the zone units.

Well, that's a good question. Was the $3500 for one-furnace/one-AC with zone dampers, or for separate heating and cooling sources for each zone? If the latter, try pricing the former.

I still think that the cost/benefit ratio would be too unfavorable for a 2000 sq ft house given the other (cheaper) air distribution methods available.

JohnnyB
04-01-2007, 01:08 PM
I really agree with that, although it's pretty expensive. My son did that for several months between educational endeavors. It not only has much better insulation per volume, it adds something like 80% more structural integrity to the building, is far more soundproof, and allows for a much tighter structure than could ever be achieved by conventional insulation techniques.

What % adder is this to the total cost of a home??

Leroy
04-01-2007, 01:18 PM
We have furnace and compressor for downstairs and basement and another set for upstairs but this is for 6000sqft+. Around Indianapolis seems like 2500-3000 is the breaking point to add second unit.

For our first house similar size we had to run the fan in the summer to get even temperature.

SkiDog
04-01-2007, 01:19 PM
What % adder is this to the total cost of a home??
It will cost you a little more than double to have it foamed rather than traditional fiberglass batts. But trust me, its WORTH every dime! Just make sure you get a reputable foam contractor. It usually runs around $2.00 per sq. ft. of wall and ceiling space.

Workin' 4 Toys
04-11-2007, 10:50 AM
It will cost you a little more than double to have it foamed rather than traditional fiberglass batts. But trust me, its WORTH every dime! Just make sure you get a reputable foam contractor. It usually runs around $2.00 per sq. ft. of wall and ceiling space.
Have you had this done? I have heard the "noise" is higher with this type of insulation. As I was told it does not have the same sound deadening characteristics of fiberglass or cellulose.


On the multizone HVAC unit. I would think it would be much more efficient to have two seperate systems than to try and seperate zones via auto dampers. In a 2000sq ft home, this may be hard to accomplish.


Leroy, in a 6000sq ft home, you should have several fan coil units and a Chiller system, you know like a commercial building...8p

Ric
04-11-2007, 11:09 AM
Another thing that I WILL do when I build another house is, use spray foam insulation! Open cell or closed cell, you might want to check in your area to see which one is the best, But I promise you, you;ll love it! point me toward an example of this before I assume that I know the type of insulation you're talking bout pleasssseee

Workin' 4 Toys
04-11-2007, 11:33 AM
point me toward an example of this before I assume that I know the type of insulation you're talking bout pleasssseee
You want an example...It comes in a can called "Great stuff"....

djhuff
04-11-2007, 11:33 AM
I'm currently in a 2 story about 2000 sf house and have two units, one for each floor. This should be cheaper then the zone system.

are the high ceilings due to 2 story rooms, or just vaults on each floor. If they are 2 story rooms, you are going to loose heat and cool from each floor in winter and summer respectively. IMO, it it's two stories, run two units period. I've got either a 1.5 or 2 ton (can't remember)unit for each floor and the house stays pretty constant.

The major cost of the HVAC installation is in the tonnage, and by running one system for the whole house, you might save .5 ton, the cost of the zone kit is almost 3 times the cost of that .5 ton. There will be more in the electrical bid for the two units though (that adds alot of copper).

Ric
04-11-2007, 11:55 AM
You want an example...It comes in a can called "Great stuff".... how do you tell the difference between closed cell and open cell?

Workin' 4 Toys
04-11-2007, 12:21 PM
how do you tell the difference between closed cell and open cell?
Closed cell foam is rigid and open is flexible and light.