HVAC zoning questions

17 years ago

I am in the process of getting estimates to have my furnace replaced and I am i interested in installing a zoned system. I would like to have some knowledge on the topic before I make a contractor decision. I have been reading as much as I can about zoned systems, but am still left with some questions.

My house is a 4 story reverse floor plan. The lowest floor (4th down) is one room that is not connected to the heat/cool system; the 3rd floor has three bedrooms and one bath; the second floor down is comprised of living room, dining room, kitchen, family room and is an open floor plan, the 1st floor is the master bedroom suite and the foyer (which is open to the living room below).

Now, here are my questions regarding zoning. I originally thought that a three zone system would work, but now I am concerned about the fact that the foyer opens (overlooks) the living room (which is two stories tall). One of my issues is that the master bedroom is hot during the summer, even when I run the ac. Does it make sense to make he whole floor a zone even when it opens to the floor (zone) below? I can close the Master Bedroom door and make it it's own zone, but it is lacking an air return.

I read somewhere that having small areas in a zoned system to heat and cool is not good for the furnace, that all zones should be about the same size. My 1st floor (even including the foyer) is about 1/2 the size of the other zones. My total square footage is approx 3200 for the 3 zones. Would adding an outside air return help me in any way since I don't have an air return on the one level?

The furnace I have been shown by one of the contractors is a two stage, single speed 5 ton. Does this sound like it will fit my needs or should I be looking at a two stage, variable speed furnace?

Any advice would be appreciated. Thanks.

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Comments (4)

bob_brown
17 years ago
IMO, In a perfect world, in a far off galaxy, one system will be perfect.

For most people living in 2006 in this world; a house needs to be zoned with seperate systems, depending on room usage and floor. Typically, if you have 4 floors, you need 3-4 systems. If you do not use the entire house, you can sometimes turn off one unit, or program it for higher temperatures. There are vast differences from the top floor and the basement. Unless you have a miracle worker, you will only get a somewhat correct job using one system.
airsome
17 years ago
Furnace and indoor coil must be matched to outdoor unit.
For so many zones, esp when upstairs mbed is a zone by itself, a 5-ton system causes many problems.
1. The m-bed only needs 1 ton of ac. (1 ton is the amount of heat it takes to melt one ton of ice in 24 hours. For AC, this is how much heat you must pump OUT of the room.) If you zone this, you will force 5 tons of ac air into a 1-ton space. Pressure-wise, bad for furnace, bad for duct. Energy-wise, a waste of 4 tons of ac and blower capacity.
2. When a t-stat in a hot zone calls for AC, and no others call, you have short, frequent cycles loaded with fast pressurized air. Dehumidification is reduced. Condensed water on indoor coil has little time to drain, and then is re-evaporated and sent back to the air, leading to mold problems.
Best to have large zones or to have two or three small individual systems (furnaces and ac units) which are more easily balanced.
With your 5-ton system, suggest placing one t-stat (one zone) on each floor, regardless of tall foyer, and control temperature disparities with manual dampers.
The rest of the story: This can only work with certain houses, depending on the way the ductwork has been installed. If the ductwork is not right for such simple zoning modification, the ductwork may have to be reworked. This can be a huge undertaking. Often in such cases the contractor will walk away. Then your best bet is to try to install some manual dampers to restrict air flow to certain areas so that it will be increased to others.
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nicosa
16 years ago
This is interesting as my question pertains to the zoning system of HVAC.
I am in the process of building a house. The design is three level (walkout basement, main, 2nd floor). I requested for three zoning system instead of two. My builder is trying to convince me to have only two, and they are going to use dampers for the basement duct instead of another zone. I wonder why they want me to ppurchase two zone system which is cheaper than three zone system by $800.00? Any catch?
2. Is there any downside if the thermostat on the upper floor be located inside the master bedroom? All bedrooms on the second floor. This will cool all the bedrooms upstairs in less time than if it were on the hallway.
THANK YOU for your input.
energy_rater_la
16 years ago
You know Bob Brown..

Zoning is NOT multiple system installing.

We have been here before.

Zoning is one system, with multiple zones, each with its
own tstat.

Don't confuse the issue.

If you are not using one zone you simply adjust the tstat to provide less cooling or heating.

Having some air flow to lesser used areas is a much better
way to do this.

And OP..please hire someone who sucessfully has installed zoned systems for several years.
Remember one unit - seperate zones. This is zoning.

Best of luck.