DIY HVAC zoning asking help


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Old 03-07-10, 07:41 PM
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DIY HVAC zoning asking help

I have a 2500sqft 2 story house and tend to use 3 zone system. Because most system offers 2200CFM max I normalized total CFM to 2200, with Z3=FL1 bed/bath(500sqft),Z2=FL2 (700sqft),Z1=FL1 rest(1000sqft).

What I want is turn on Z3 heating at night and Z2 cooling at summer - I seldom need cooling FL1. As no system can work at 20% I think may be I can use Carrier 58CVA-110 (plus a 3.5ton) and try to keep ~1400CFM because
58CVA spec says lo/hi/3.5ton/4ton having 1320/1475/1225/1400 CFM.

My understanding to variable speed furnace like 58CVA is that it offers constant CFM in wide range of duct. I'm not sure how many CFM for pure vent mode. Who can tell me?

I suppose to DIY zoning controller by logically combine Wx/Y/G requirements from thermostat from each zone. Z3 is always on, Z2 is on only when needed, Z1 is closed when not in use and Z2 and Z3 on (this close will still allow ~220CFM pass by), then the system will have CFM no less than 1400. This system doesn't close all unused zones, but try to keep CFM requirements so blower can work longer.

Of course I can use balance damper or return unused BTUH to return duct, yet then the system will have more on/off cycles.

If I can afford 3-stage or modulated furnace like 58MVC-100, keep CFM to 660+ can save more energy when only Z3 is used. Comments?

For 2 stage furnace, the gas works either at main=67%, and main+hi=100%, which means hi alone is 33%? I wonder anyway to use hi valve alone for 33% output - then get a 3-stage furnace. comments?
 
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Old 03-08-10, 04:04 PM
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Since you are trying to figure out what will give you optimum results floor by floor - have you ever thought if a whole house fan might work for you also?
 
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Old 03-08-10, 06:27 PM
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Zoning

I've never seen a zoned forced air system which worked properly. Don't waste your time or money.
 
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Old 03-08-10, 06:44 PM
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Originally Posted by ecman51`
Since you are trying to figure out what will give you optimum results floor by floor - have you ever thought if a whole house fan might work for you also?
I know little about it. What I know is FL2 must have cooling and FL1 must have heating. I do questioned myself whether should I add another damper to allow ext fresh air come in rather than open windows. Why no HVAC does this?
 
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Old 03-08-10, 06:51 PM
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Originally Posted by Grady
I've never seen a zoned forced air system which worked properly. Don't waste your time or money.
Thanks for comments, which I have little sense. I just feel that in winter I simply need 20% heat at sleeping, and in summer I need cooling for FL2 at most - FL2 currently is storage. But when I do sth I want 1st time right and last forever.
 
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Old 03-09-10, 08:20 AM
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I responded to your post last night and while correcting typos it froze and I lost the post. Then I got mad and quit.

Are you trying to heat and cool simultaneously? If so, will your system be capable of that? If you want that, I do believe you need 2 air handlers. One of the handlers would be the furnace. The other handler would be for just a/c.

If you had a water source geothermal system with a couple water-to-air heat pumps, you could have one heat pump putting out heat on one floor, while the other heat pump put out cool on the other. Heat pump return water would mix. The heated area would discharge cold water back to the ground while the a/c rooms would discharge heat back to the ground, and the two would mix.

The whole house fan system is pretty neat. A rich landlord I worked for had large dual furnaces, a/c, heated garage, heated driveway, low voltage lighting inside the house, etc., and also had a whole house fan. These are real large fans where a large square hole is cut in the top floor ceiling(right above is the attic). The fan is installed and has louvers. When it comes on, the louvers open and draws air out of the house, from open windows, and discharges it in the attic where it goes out the attic vents. These are more economical to run than the a/c during certain temperature conditions. You might want to read up on them.
 
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Old 03-10-10, 11:49 PM
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Originally Posted by ecman51`
Are you trying to heat and cool simultaneously?
No I don't. Thank you very much for spend time to re-post.
Yeah I'll study more on add circular fan, FL2 hot mainly because ceiling has no insulation nor have enough space for (only 3.5" for insertion and I can't access top flat area)

I just wonder why no HVAC system blows in air when it vent or circular inside the room. May be I can add a damper rather than install a fan.
 
 

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