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  1. #1

    Zone Priority for Forced Air 3 zone system

    I currently have a home heated with forced air with 3 zones and a honeywell mini zone controller. In times when it is extremely cold, my furnace has a hard time satisfying all 3 zones at once. The 3rd zone was an add on for a basement and with all 3 zones going the system has poor airflow. As a work around, I have been turning off one zone until the other zones are satisfied but I am hoping this is only short term. I would like to only have 2 zones on at once and then the 3rd zone can come on after one of other zones is satisfied. Does anyone know of a way to prioritize the zones or another possible way to correct this? BTW, this is my first time posting so please bare with me. Thanks!

  2. #2
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,696
    Regarding the low airflow with all three zones going.........Do some balancing with the (manual) dampers on the duct or at the registers if you can't. Also, make sure, if you have a by-pass damper, that it's set properly.

    For the area that is not being used very much, set that stat a little cooler.

    P. S.
    I have a three zone system and never are they all running at once.
    80,000 btu for 2250 sq. ft. (2-story) in the mid-west built in 1946.

  3. #3
    Thanks George, I have done some balancing with the registers which has helped but not significantly. I shut a few registers completely on my first floor since there are so many (11). I havent touched any on the second floor. What would you suggest? Closing them half way? There are not any manual dampers but if needed, I can install. Also there is not a by-pass.

    With 2 zones running there is great airflow. But with all 3 I can hardly feel air coming out of the registers and the furnace will run for hours but never gets close to recovering. Its a 80,000 BTU and the house is 2200 sq ft2 story + the finished basement which adds another 700 and we are in Conecticut.House is about 5 yrs old Also, there is not a by-pass.

  4. #4
    Join Date
    May 2007
    Posts
    733
    A professional should inspect the system, including ductwork and zone controls, to determine if it is working at full capacity. If it is working at full capacity, it would be wise to determine what changes would be needed in the equipment, ductwork, and zoning to match the structure, or what changes would be needed in the structure to match the equipment.

    If the system was installed by a competent professional it was air balanced when installed. Air balancing thereafter is being done by the zone dampers. Doing experimental air balancing at the registers is not advisable. It can result in furnace overheating which will shorten the life of the equipment. The zone system should have a discharge air sensor that, if set correctly, will turn the furnace off when overheating starts to occur. But if the furnace cycles on discharge air limit too much it will affect the life of the furnace or make furnace components fail sooner than they otherwise would.

    If you are going to try balancing yourself, please check furnace temperature rise during all possible combinations of zone operation. If you don't know how it is time for an inspection by a professional experienced with zoned systems.

  5. #5
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    I would first open all three zones , and check heat rise and confirm it is within mfg, specifications. This will tell you if the furnace blower is delivering the cfm as per specs. There may be duct issues, like a bypass should be installed, but it is possible the heat loss in the structure is greater than the furnace capacity, even with zoning.

  6. #6
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,696
    Quote Originally Posted by 3zonehouse View Post
    Thanks George, I have done some balancing with the registers which has helped but not significantly. I shut a few registers completely on my first floor since there are so many (11). I havent touched any on the second floor. What would you suggest? Closing them half way? There are not any manual dampers but if needed, I can install. Also there is not a by-pass.

    With 2 zones running there is great airflow. But with all 3 I can hardly feel air coming out of the registers and the furnace will run for hours but never gets close to recovering. Its a 80,000 BTU and the house is 2200 sq ft2 story + the finished basement which adds another 700 and we are in Conecticut.House is about 5 yrs old Also, there is not a by-pass.
    Is your furnace a 80% or 90+% AFUE? Is it 80,000 btu input or output?

    I can understand low airflow with all 3 zones calling...that's a lot of ductwork.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,090
    Don't shut off registers in any zone. Because when that zone is the only zone calling, you have too low of an air flow for the furnace.

    There is a simple way to do what you want. Just site rules prohibit us from telling you how to do it.

    Do you have all 3 thermostats set to the same temp?
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    How many times must one fix something before it is fixed?

  8. #8
    Beenthere- the thermosats are at different temps, Warmest upstair, cooler on first floor and coldest down stairs. Delta from basement to 1st floor is about 5-7 degrees. Any help that you can provide without breaking any rules is apprectiated. Maybe some guidance on your easy fix?


    George- its a 80K BTU Input and is 90+ Efficiency.

    I will see if I can get someone to come in and perform the balancing and have them determine if there is proper temp rise and provide me with a recomendation. What would a resonable rate be for this? I have my doubts about the installer but someone else may not want to get involved.

  9. #9
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    It sounds like your furnace is undersized.

    The equipment should be sized as if all zoned would be calling. The bypass need to be sized to relieve the airflow of closed zones as if only the smallest zone was calling.

    Did you say the basement was finished after the fact?
    How tall are you Private???!!!!

  10. #10
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,696
    I agree with Gunnery, it sound like the furnace is too small or it's not firing to its full potential.

    Hard to believe for a new house. Maybe someone should check the attic insulation?

  11. #11
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,696
    How long have you been in the home?

    How does the A/C work?

    What size is the A/C?

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