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Multi-"zone" without dampers

I have a basic single zone gas+AC forced air system in my 2-story home. We spend the days on the first floor, and nights in the bedrooms on the second. I have the idea of controlling the temperature measurement from downstairs during the day, and upstairs during the night after we go to bed. I don't want to go through the trouble and expense of adding dampers to the existing duct work, but I should think controlling the system based on where the people are would make us more comfortable and the system more efficient.
I haven't been able to find any thermostats that accept a second temperature input, that you can program when the different thermocouples are active (I have seen some that take the average of the tempreatures).

Any products out there fit the bill? Any feedback on the idea?


  • ratio
    ratio Member Posts: 3,403
    I think I heard the EcoBee can do that. I also saw that application described in the manual for this stat. I don't know about availability, however; the part number I'm using is part of a ZigBee-connected BMS. The Honeywell RedLINK stats can be programmed control to a handheld remote control, you'd have to remember to take it up with you (or get it from the teenager's room!).

    That said, I'm not sure you'll see much gain in efficiency, likely a loss. The hot air wants to go upstairs, the cold air downstairs. The only way to balance this is to adjust the airflow based on what the system is trying to do, otherwise you end up overconditioning the opposing space.

    John Mills_5
  • Jamie Hall
    Jamie Hall Member Posts: 21,105
    Another approach, if you can run two wires for the thermostat upstairs, is to just use two programmable thermostats, wired in parallel. Then program the downstairs one for a good setback at night, and the upstairs one for what you want as a night time temperature, perhaps with a day setback. That way, whichever thermostat is calling for heat the system will run. Might do what you want.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 13,437
    Can't be done without dampers. Your system is one zone and will stay one zone unless you make it two zones by installing dampers. Lets say for instance that you want the upstairs 64 and the downstairs 70

    If you don't want to install dampers, balance the airflow to all rooms until you get the temperatures in each room as close as you can to what you want.

    If you want the bedrooms cooler than downstairs you can do that, you can also use two thermostats as @Jamie Hall suggested. I would use a relay and a "day-night" switch as a selector switch to choose what thermostat you are using

    But, it's still one zone...no energy savings and while your upstairs thermostat for example is controlling at say 64 degrees at night you will still be heating the downstairs at 70 deg.

    Since you have AC in the same system it won't work at all, all bets are off unless you rebalance the air flow every spring and fall.