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Thread: Setting up a 2-Zone System?

  1. #1
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    Setting up a 2-Zone System?

    We just had two new Daikin Fits installed with matching variable-speed 2-stage gas furnaces. A 4-ton unit services the first floor, which is roughly 2,000 square feet, and a 3-ton unit services the second floor, which is about 1,800 square feet. I'm trying to configure the units so we get even cooling throughout the house, but I'm having trouble because our family room is 19' x 21' x 20' high with an open loft adjacent to it. As a result, a lot of cool air drops down into the space below and satisfies the first-floor thermostat prematurely, which causes the study, kitchen, morning room, master bedroom, master bath, and sitting room to all run about 3 degrees hotter than the family room and downstairs hallway.

    I Googled two-story settings and the general rule is to set the first floor 2 degrees warmer than the second, but I'm sure that doesn't take into account the large open spaces that we have. Right now all of the vents are wide open, so so I can probably do some tweaking there. I've attached a copy of our builder floor plan for both floors. Our home has almost all of the options listed, except those I've crossed out.

    Any help and/or advice on setting this up is greatly appreciated.
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  2. #2
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    7-Tons of Cooling in New construction, Who sized this?

  3. #3
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    Quote Originally Posted by pecmsg View Post
    7-Tons of Cooling in New construction,
    Who sized this?
    This project is a REPLACEMENT ... ... ... ... previous thread
    ________________________________ DAIKIN FIT SYSTEM
    Fair Warning of oversizing was provided in Posts # 13 _ yours _ & #15 _ mine _
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    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
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    Quote Originally Posted by kcrossley View Post
    We just had two new Daikin Fits installed with matching variable-speed 2-stage gas furnaces. A 4-ton unit services the first floor, which is roughly 2,000 square feet, and a 3-ton unit services the second floor, which is about 1,800 square feet. I'm trying to configure the units so we get even cooling throughout the house, but I'm having trouble because our family room is 19' x 21' x 20' high with an open loft adjacent to it. As a result, a lot of cool air drops down into the space below and satisfies the first-floor thermostat prematurely, which causes the study, kitchen, morning room, master bedroom, master bath, and sitting room to all run about 3 degrees hotter than the family room and downstairs hallway.

    I Googled two-story settings and the general rule is to set the first floor 2 degrees warmer than the second, but I'm sure that doesn't take into account the large open spaces that we have. Right now all of the vents are wide open, so so I can probably do some tweaking there. I've attached a copy of our builder floor plan for both floors. Our home has almost all of the options listed, except those I've crossed out.

    Any help and/or advice on setting this up is greatly appreciated.
    SO how is this system different from the older system you had? Did you not have this problem before?

    The house layout is often the problem. One that can be hard to fix with ducted systems.

  5. #5
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    Quote Originally Posted by dan sw fl View Post
    This project is a REPLACEMENT ... ... ... ... previous thread
    ________________________________ DAIKIN FIT SYSTEM
    Fair Warning of oversizing was provided in Posts # 13 _ yours _ & #15 _ mine _
    Lets say a load calc was done and they sized the systems at 6 tons, or 4 tons, or whatever tons.

    How does it change the way the house is laid out? How does it change the way cold air drops to the bottom floor and satisfies first-floor thermostat?

  6. #6
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    Quote Originally Posted by kcrossley View Post
    We just had two new Daikin Fits installed with matching variable-speed 2-stage gas furnaces. A 4-ton unit services the first floor, which is roughly 2,000 square feet, and a 3-ton unit services the second floor, which is about 1,800 square feet. I'm trying to configure the units so we get even cooling throughout the house, but I'm having trouble because our family room is 19' x 21' x 20' high with an open loft adjacent to it. As a result, a lot of cool air drops down into the space below and satisfies the first-floor thermostat prematurely, which causes the study, kitchen, morning room, master bedroom, master bath, and sitting room to all run about 3 degrees hotter than the family room and downstairs hallway.

    I Googled two-story settings and the general rule is to set the first floor 2 degrees warmer than the second, but I'm sure that doesn't take into account the large open spaces that we have. Right now all of the vents are wide open, so so I can probably do some tweaking there. I've attached a copy of our builder floor plan for both floors. Our home has almost all of the options listed, except those I've crossed out.

    Any help and/or advice on setting this up is greatly appreciated.
    My down stairs thermostat is in the entry way and also has cold air drop down from main floor so the computer room, theater room, and bedrooms down stairs run 3* warmer all year round. Ill be moving my downstairs thermostat into my theater room soon as I get around to it. That should give all the rooms downstairs a closer range of temps.

    My house has 1 system but 3 zones. the downstairs is on its own zone. so the house functions similar to yours with 2 systems...

  7. #7
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    The new system is working great, aside from getting some rooms balanced. I personally think the deviation can be adjusted by tweaking the vents. No longer do we wake up to a humid house every morning during the spring and summer.

    The past 2 days, weve had outdoor humidity from 70-85%, but the Daikins have maintained a consistent 50% RH. So far. Im happy, but the true test will be several days of hot and humid weather.

  8. #8
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    Quote Originally Posted by jacob-k View Post
    SO how is this system different from the older system you had? Did you not have this problem before?

    The house layout is often the problem. One that can be hard to fix with ducted systems.
    Actually, in terms of maintaining a consistent temperature, yes, but only in the master bedroom, sitting room, and study, the last of which is all windows and south facing.

    The biggest problem we had with the old Janitrol systems was high indoor humidity in the mornings. When the new systems were installed, my HVAC tech had me fully open all the vents. I just havent repositioned them yet. Before I did I wanted to consult the experts on this forum.

  9. #9
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    Move the 1st thermostat to one of the rooms that is warmer. I would put it in the bedroom since, for me, that would be the critical temperature location on that floor.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  10. #10
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    Quote Originally Posted by jacob-k View Post
    Lets say a load calc was done and they sized the systems at 6 tons, or 4 tons, or whatever tons.

    How does it change the way the house is laid out? How does it change the way cold air drops to the bottom floor and satisfies first-floor thermostat?
    This is a good point. Id be interested in the answer too. 🙂

  11. #11
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    Quote Originally Posted by kcrossley View Post
    This is a good point. Id be interested in the answer too.
    I dont believe there is an answer to it.

    The current system you have now will operate at far less tonnage than it is rated for.

    For example. Today I was looking at my phone app with a customer since she is getting the same system as me. My upstairs zones where both calling for cool. Both zones where set to 76* and the rooms where 76*. The compressor was running at 32% capacity. It's a 5 ton system so probably around 1 1/2 tons.

    My downstairs zone was reading 73* and is set for 75*. But I'm sure the rooms downstairs where 3* hotter.

    For most systems one could argue that if a load Calc wasn't done and the downstairs was cooling way to much its because it's oversized. Essentially a single stage unit runs at full capacity all the time and could easily over throw the downstairs. But once you get it communicating equipment and the unit has 750 or so speeds it would be really hard to say it's because it's oversized.....

    HOWEVER. If a load Calc had been done you would know how many btus each area needed and you could size the ductwork and confirm airflow which would help the situation. But still not completely eliminate it.

    For myself the answer is to just mover downstairs thermostat into a downstairs room.

    Sent from my SM-G998U using Tapatalk

  12. #12
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    Quote Originally Posted by kcrossley View Post
    I Googled two-story settings and the general rule is to set the first floor 2 degrees warmer than the second, but I'm sure that doesn't take into account the large open spaces that we have.
    Hey everyone, here's a quick update. I changed the upstairs thermostat so it's now 2 degrees warmer than the downstairs thermostat, which is completely opposite of the general rule for 2-story setups, and that seems to have done the trick. Things are a lot more balanced and the 4-Ton big boy is now doing its share of keeping the house cool.

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