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  1. #1
    Join Date
    May 2005
    Posts
    47
    I live in a two-story colonial in Virginia built in 1947 that has a two-story addition on the back that was added in 1984. Last year, I had a Carrier Infinity system installed (3 ton A/C, 60k btu 95% furnace). It works great for A/C, but I’m having problems with heating. In a nutshell, the addition is always cold, which is odd since the airflow seems fine and it is better insulated than the rest of the house--it does not get too warm in the summer even though it faces SW and has large windows and skylights. But it is always 4-5 degrees colder than the rest of the house in the winter.

    I know the typical zoning setup is to have a zone for each floor, but because of the way the ducting is run in the original house, that is not feasible. (The main supply duct for the original house runs horizontally through the basement, alternating ducts that feed the first floor, second floor, first floor, etc. It could not be zoned without extensive ductwork.)

    But because the addition has the same cold problem both in the downstairs family room and the upstairs master bedroom, it seems as though I could zone the addition separately. The supply plenum has two main branches—one feeding the original house, and the other extending into the crawlspace under the addition, and then feeding the supplies on both the first and second floors. This seems to be a simple setup that could be accomodated by two dampers.

    Any thoughts on this unorthodox zoning? I requested a Carrier Infinity Zone thermostat with the original installation so I could upgrade later without ditching the $500 thermostat. The installer recommended against zoning this way when it was installed but said he would give me a good rate if I came back and requested it later. The reason the installer recommended against zoning was to give the Infinity system a chance to equalize the temperature by having the fan run on low continuously. This hasn't worked. The old system also resulted in colder temperatures in the addition.

    Thanks.


  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,641
    should be a simple zoning job with mains already split.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    If I understand correctly you have mutiple duct runs to each floor comingout in several places of a common trunkline,not a trunkline for each floor.


    Count how many for each floor and note which ones,if any, can be combined on one damper,ie they are next to each other.


    You can "slave " dampers with Infinity,just not sure how many per zone.Slave means the operate exactly the same same.Two dampers operating the same for one zone ,on one thermostat.

    Your cost would be more because of using more dampers,but likely less than reworking all the ducts.

  4. #4
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,641
    dash.. the way i read the op he already has mains split and wants to zone old house from new addition, not up-down. should be an easy one.

  5. #5
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    talk to the installer --
    usually, the air quantities are different for heating & cooling -- for a given room --

    one room may have lots of sunlight from south | west in summer so needs lots of cool air, yet not so much in winter.
    and vice- versa
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by kcb203


    I know the typical zoning setup is to have a zone for each floor, but because of the way the ducting is run in the original house, that is not feasible. (The main supply duct for the original house runs horizontally through the basement, alternating ducts that feed the first floor, second floor, first floor, etc. It could not be zoned without extensive ductwork.)




    This sonuds like one trunk to me.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    Originally posted by kcb203


    But because the addition has the same cold problem both in the downstairs family room and the upstairs master bedroom, it seems as though I could zone the addition separately. The supply plenum has two main branches—one feeding the original house, and the other extending into the crawlspace under the addition, and then feeding the supplies on both the first and second floors. This seems to be a simple setup that could be accomodated by two dampers.


    2 trunk lines ???
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  8. #8
    Join Date
    Mar 2005
    Location
    burlington county n.j.
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    9,641
    i read it as one trunk for old house, one trunk for addition. OP where are you????????? we need some clarification here!

  9. #9
    Join Date
    May 2005
    Posts
    47
    There are two trunk lines. There are also two small branch lines that extend directly from the supply plenum (is that the correct word?) just above the A/C coil.

    The first trunk line serves the original house, but in a strange way. It extends horizontally across the basement ceiling, and branches go up to the 1st and 2nd floors in a haphazard way. In other words, the first branch goes to the 1st floor, the second branch to the 2nd floor, the 3rd and 4th branches to the 1st floor, etc. Thus, there is no way to zone the first floor separately from the second floor without totally redoing the ductwork (which isn't feasible in a finished basement) or by putting a damper on each branch (which would be very expensive).

    The second trunk line goes to the crawlspace in the addition, where it branches into two ducts, each of which feeds a couple of first floor registers then goes to the second floor. Again, due to the design, it is impractical to separate the first and second floors.

    There are also two small ducts that extend directly from the main supply plenum--one goes to the original house, and the other goes to the addition. As I understand the way the Infinity zoning works, the installer can wire dampers on these in parallel with the larger ducts so they work in tandem.

    I would like to create two zones: 1) for the main house; and 2) for the addition. My real question here is that even though the "traditional" way to zone is by floor, that is impractical here. Furthermore, for whatever reason, both floors in the addition have the same temperature, which is colder in the winter than the main house. Accordingly, I think it would make sense to zone the addition separately to send more heat to the addition in the winter. Is it somehow wrong or inappropriate to zone this way rather than by floor?

    In an ideal world, I'd have four zones (floor by floor, for the main house and the addition), but it seems as though my two-zone solution should help keep the family room warm in the winter without totally redoing the entire duct system. And in the summer, due to the orientation and large windows, the addition is warmer than the rest of the house, so this would allow for extra cooling at that time. Finally, the kids sleep in the bedrooms in the original house, while the family room and master bedroom are in the addition. This would allow me to turn down the temperature in the original house at 8 pm, while leaving the family room and my bedroom warm until 10 or 11 pm.

    Thanks for all the advice I've received from this forum in the last year.

    [Edited by kcb203 on 03-09-2006 at 10:17 AM]

  10. #10
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    Typically you don't zone two floors on the same zone,because the second floor has an attic load,and heat from the first floor tends to rise.So the upstairs in too hot in the winter ,and the downstairs is too cold in the summer.

    Now if your home doesn't have these symtoms,your proposed zoning should get the results you want you want.If you have these symtoms,zoning by floor first and then ares ,will solve it.

    In any case,the temperature differences between floors won't get worse than they presently are,if properly done.


    If you have it done,try to increase the airflow to the addition.Large ducts, "turning vanes" in elbows,less restrictive regiters/grilles.

    [Edited by dash on 03-09-2006 at 11:07 AM]

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