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  1. #1

    Closing cold air returns

    Greetings all. We live in Wisconsin and our home was built in 1994. It's a 1700 sq. ft. ranch with AC. There are cold air returns near the floor and near the ceiling. However the ones near the floor are the only ones that can be closed. Is this right? Or should the closeable ones be near the ceiling? To me is seems to be backwards. It just seems to me that you would want the ones near the ceiling closed in winter so you aren't pulling warm air back into the furnace. What do the pros think?

  2. #2
    Join Date
    Oct 2002
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    1,248
    Warm air rises so you would nbe right. But, be sure you will have enough return air before closing anything. It could be a second return air was installed to fix return air problems.

  3. #3
    Quote Originally Posted by timjimbob View Post
    Warm air rises so you would nbe right. But, be sure you will have enough return air before closing anything. It could be a second return air was installed to fix return air problems.
    Nope, we are the original owners and it's been like this since new. I guess what I am trying to say is this: Should both have the ability to be closed? And if only one can be closed, shouldn't it be the top one?

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,288
    Assuming your furnace is in the basement, the floor returns probably pull more air by proportion, year round. This is due to each one being closer to the blower intake than the ceiling return, so there is less pressure drop in the duct.

    I would leave the dampers fully open until it can be determined that the system has enough return air volume with one or more sets of dampers on the floor returns closed. I wouldn't do anything about it at all if the house is otherwise comfortable.
    • Electricity makes refrigeration happen.
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    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


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  5. #5
    Join Date
    Sep 2002
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    Northeast Ohio
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    With a properly sized air distribution system with high/low return grills the floor level grills should be open in the winter (heating mode) time and closed in the summer Cooling mode) time.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  6. #6
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    Leave them both open year round for increased airflow and increased life of equipment.

  7. #7
    Join Date
    Sep 2002
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    In Wisconsin, like in north east Ohio, gets pretty cold. The return air grills at floor level will bring the heat down to floor level from the ceiling, where you want it eliminating those pesky cold drafts. That's the reason for the high/low configuration other wise they would just cheap out and make them all high. It's done that way for added comfort. If it's sized properly, and odds are if they went to the extra trouble to do it in the first it is, then take advantage of the feature.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  8. #8
    Join Date
    Jan 2004
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    Lancaster PA
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    Leave them open year round.
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  9. #9
    Right. But is it right to have the ones with the closing flap near the floor? Or should the closeable ones be near the ceiling? See what I am saying? There are two vents but only one closes. Where should the closeable one be?

  10. #10
    Join Date
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    Anderson, South Carolina, United States
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    They should both be closable but it depends on heating or cooling climate which one you would do rather than the other. A primarily cooling climate the bottoms should be closable and primarily heating the tops should be closable, or both would be good or neither I think would be best.

    After thinking about it, if the furnace is below the space then if the return duct/grills are properly sized then most of the return air would naturally come from the bottom grills since they are closer to the unit unless you closed the bottom then it would pull more from the top due to air flow (energy) taking the path of least resistance.

  11. #11
    Join Date
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    Don't mater which ones have the dampers. leave them open year round, don't close off any of them.
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  12. #12
    Join Date
    Jul 2000
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    Northern Wisconsin
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    The lower ones having the ability to be closed was the "thinking" of the installing contractor and not something that is considered normal or standard installation practices in my opinion.

    A properly designed and functioning system for a home that has needs to both heat and air condition to opposite extremes can take advantage of both high and low returns year around.

    The only operational issue that might come into play with high and low returns is if they are using the same stud wall cavity. A standard interior studded wall has only 3 1/2" of space and if the damper from the lower register extends into this space when it's open it can block off the ability for the air to easily pass from the upper register. With some register designs (a single flap verses multiple small louvers) it can totally block off the air from the upper register. If the installer was "old school" from the days of gravity systems in 2 story houses, he could have installed the single flapper design to be able to block off the upper unit in the winter. I've seen plenty of these old style stacked systems here in wisconsin.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  13. #13
    Join Date
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    If the lower ones are single flap (as I guess they are), When they are "open", the flap extends into the wall cavity effectively "closing" the path of air from the upper grill. If they are of multi louver design, then closing that grill only limits the intake of that grill.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


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