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Zoning a Forced Air System

Crissie
Crissie Member Posts: 122
edited October 2021 in THE MAIN WALL
Does anyone know, do I need to have a variable speed AC and a separate Zoning (ComfortSync) piece of equipment or technology to adequately zone my house?

I got a quote for this, it included a really high end Armstrong 2 ton AC, a ComfortSync A3 Zoning System and another ComfortSync thermostat control. Seems like a lot, is this overkill? I have never installed a zoned system before. Thanks!

Comments

  • mattmia2
    mattmia2 Member Posts: 5,512
    What are you trying to do would be the first question. Is this a new system or some sort of retrofit?

    2 systems might be a better idea with 1 per floor. Forced air doesn't like a varying size system so modulating equipment makes zoning work better. There are ways to do it without modulating equipment but they don't work very well. An even better way would be mini splits or a couple conventional split systems for cooling and a hydronic system with TRVs for heating.
  • Crissie
    Crissie Member Posts: 122
    mattmia2 said:

    What are you trying to do would be the first question. Is this a new system or some sort of retrofit?

    2 systems might be a better idea with 1 per floor. Forced air doesn't like a varying size system so modulating equipment makes zoning work better. There are ways to do it without modulating equipment but they don't work very well. An even better way would be mini splits or a couple conventional split systems for cooling and a hydronic system with TRVs for heating.

    It is a new system I plan to put into a 44 yr old tri-level house. I am replacing the ducts that would be needed to support this, having an engineer design the ductwork. The Manual J by room has already been done. I need to select the equipment before the ductwork can be designed. Seems a little backward to me, but that is the way it has to be done. Each level is very different in terms of temperature needs and my use of the space. I would love two or three separate systems, just don't have room for them and that would make the loads for each so small.

    I was planning for a single conventional AC and furnace for two levels, then either a mini split or something else for the lower level. Can get the ductwork through lower level. Thought about Mits mini-splits, heard the good and bad, concerned about mold growth and the need to clean the heads, and also availability of parts. I was planning to put hydronic heat throughout the house and using the furnace as a back-up and to provide AC. What is a 'conventional split AC system' just two separate conventional AC's? Is zoning even successful these days? I tried in 25 yrs ago and it did not work at all. Thanks so much.
  • HVACNUT
    HVACNUT Member Posts: 4,591
    I'm not familiar with that particular system, but usually a barometric bypass is installed along with a Supply Air temperature sensor to prevent over heating or over cooling. Sometimes a Freezestat is needed as well.
  • pecmsg
    pecmsg Member Posts: 2,881
    2 Systems.

    the basement below grade gets a small ducted mini and dehumidifier.
  • Crissie
    Crissie Member Posts: 122
    pecmsg said:

    2 Systems.

    the basement below grade gets a small ducted mini and dehumidifier.

    What about the Upper Level and main level. A zoned conventional forced air furnace / AC system?
  • pecmsg
    pecmsg Member Posts: 2,881
    1 system for each level. 
    mattmia2SuperTech
  • Crissie
    Crissie Member Posts: 122
    pecmsg said:

    1 system for each level. 

    So you are saying a zoned forced air heating and cooling system will not adequately zone, so I should get a separate system for each? I have always wondered why there are homes with two separate systems if zoning was truly an effective viable option.
    bburd
  • pecmsg
    pecmsg Member Posts: 2,881
    If done properly they work. That’s maybe 5% of the time. 95% of the time too hot or too cold. 
    2 systems give you the benefit WHEN one breaks you still have an operating system 
    Crissiemattmia2
  • Crissie
    Crissie Member Posts: 122
    pecmsg said:

    If done properly they work. That’s maybe 5% of the time. 95% of the time too hot or too cold. 

    2 systems give you the benefit WHEN one breaks you still have an operating system 
    Has anyone else had experience in zoned forced air for either heat or AC? Does it really work on different levels of a home? I had one HVAC 'salesperson' tell me zoning works. Then I asked him what type of home he had and what HVAC equipment did he have in it. Answer was 2-story home and 2 furnaces / AC's.
  • mattmia2
    mattmia2 Member Posts: 5,512
    You need someone that really knows what they are doing to both design and install it. That rarely happens.
  • dopey27177
    dopey27177 Member Posts: 873
    In some commercial zoning installations thermostatically operated register are installed. This can only be done in large systems, because, when a zone closes down the forced are pressure increases and more air is forced through the remaining registers which can cause whistling and wind increase in other open zones. The fan motors would be needed to be variable speed with sensors in the duct work to monitor the air pressure and slow or increase the air pressure as needed by the system.

    The best and most economical way to do a two story house is two separate units.

    Jake
    Crissie
  • Crissie
    Crissie Member Posts: 122

    In some commercial zoning installations thermostatically operated register are installed. This can only be done in large systems, because, when a zone closes down the forced are pressure increases and more air is forced through the remaining registers which can cause whistling and wind increase in other open zones. The fan motors would be needed to be variable speed with sensors in the duct work to monitor the air pressure and slow or increase the air pressure as needed by the system.

    The best and most economical way to do a two story house is two separate units.

    Jake

    Thank you Jake. I don't have room for two systems. What about using ductless mini-splits on the my upper level. In Chicago, the heat might be a problem, not sure.
  • MLJ
    MLJ Member Posts: 6
    Have had good luck with zoning....did a lot more of them when the wireless stats came out....did not like trying to get a stat wire to the 2nd floor.

    For the older furnaces and a/c's would install a bypass damper...new variable equipment did not have to install bypass.
    If you do it without a bypass damper..... will have too much air pressure and air will leak around your closes dampers and then that's when you will get problems with being too hot or cold. Plus will have air noise from the supply grills

    When in business installed 20 or so of them, always use Honeywell dampers and controls.

    I don't ever recall getting a call from any of them complaining about being too hot or too cold...

    I do think zoning works.....
    Crissie
  • dopey27177
    dopey27177 Member Posts: 873
    Look into installing the unit in the attic.
    Duct work would only be in the attic blowing down to the rooms.
    Return air needs to be run down to the floor in a central location.
    The return air will pull the warm air to the floor.

    Jake
    Crissie
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited November 2021
    For a 2 ton total capacity system you might think of using Mini Split inverter technology. Some of the indoor sections can be ducted. I have installed a 42,000 BTU system with 3 wall mount units, and two ducted units. First floor kitchen was a wall mount with its own thermostat remote control. the front of the first floor was a "SlimDuct" unit with a duct feeding the front "Living Room" and another duct to the center "Dining Room" using a wired wall mount thermostat.

    Second floor was a wall mount in the front bedroom with remote control, and the Master suite and master bath used the ducted unit with wall mount thermostat. Top floor "Finished off attic Bedroom" used a wall mount unit.

    All 5 indoor units were connected the one outdoor unit.

    There are several brands like Mitsubishi, Sanyo, Carrier and Fujitsu among others. Technology has changed since I did my job years ago.

    The ductwork must be minimal on these units. basically they are "ductless" models with beefed up fans, but you can only do so much. Depending on your layout, this may be a more efficient alternative.

    This is the undoor section I used for the small duct work needed to connect 2 adjacent rooms


    You can find the info here https://www.fujitsugeneral.com/us/products/multi/indoor.html
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    Crissie
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited November 2021

    Look into installing the unit in the attic.
    Duct work would only be in the attic blowing down to the rooms.
    Return air needs to be run down to the floor in a central location.
    The return air will pull the warm air to the floor.

    Jake

    Attic ductwork must be super insulated, vapor barrier intact and still will use more energy than duct work that is inside the envelope of the conditioned space then, covered with decorative soffit. Your choice will result in years of operating cost. You decide now, if you want higher operating cost or lower operating cost.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    Crissie
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    A three story home with a 2 ton AC load, sounds like a townhouse, (or Row-home in Philadelphia). If you are in a place with high enough ceilings you should consider the multi indoor unit Mini Split inverter systems. A thermostat for each indoor unit will offer better temperature control for each zone. Also the indoor units are available in capacities as low as 7000 BTU cooling/8,100 heating nominal capacity. Ceiling mounted units with small duct to get to adjacent rooms are easily covered up with false ceiling panels or soffit
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    Crissie
  • Crissie
    Crissie Member Posts: 122

    A three story home with a 2 ton AC load, sounds like a townhouse, (or Row-home in Philadelphia). If you are in a place with high enough ceilings you should consider the multi indoor unit Mini Split inverter systems. A thermostat for each indoor unit will offer better temperature control for each zone. Also the indoor units are available in capacities as low as 7000 BTU cooling/8,100 heating nominal capacity. Ceiling mounted units with small duct to get to adjacent rooms are easily covered up with false ceiling panels or soffit

    No, this is a single family split level home) three levels in Chicago area. The design has main ductwork running through a finished bath and hallway in lower level with very limited space. I can't fit the ductwork needed so was considering the Mitsubishi Hyper Heat ductless units for a few rooms. Are these modulating? I didn't think they were, only the ducted unit are modulating. Definitely leaning in this direction, only draw back is our harsh Chicago weather. Thx to everyone!!
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 521
    @Crissie Mitsubishi mini splits (ducted and ductless) are modulating.
    Crissie