+ Reply to Thread
Results 1 to 10 of 10
  1. #1
    Join Date
    Oct 2008
    Posts
    2

    Default Location of Registers vs. Return?

    My home looks like it originally had a whole house heating system that use a main trunk line that runs under the hallway with the vents located at the baseboards. The heating and air system has been updated with flexible pre-insulated duct work that runs to each room individually and the registers are placed in the floor along the outside walls. The blower is in the crawlspace under the house but the unique thing is the new system is using the old trunk line as the cold air return. The trunk is not insulated and should be but before insulated it I was wondering if this configuration is suggested? I love the fact that each room has its own cold air return but both the registers and the cold air return is at the bottom of the floor. It seems like one should be located in the ceiling for proper air circulation? I was thinking about removing the old trunk line and build a chase to place the return in the ceiling. Would this be recommended or is it best just to seal and insulated the main trunk line and leave the return and registers at the floor.

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Location of Registers vs. Return?

    Personally I would leave the return trunk.

    The return vents should be located at floor level for heating and they definately should be in every room .... exceptions are bathrooms and kitchen.
    In a heating system the cold air return should be at floor level. That's not to say in the floor but usually they will be mounted on a vertical wall at floor level.

    Warm air from the heat vents will rise toward the ceiling leaving cooler air settling down toward the floor.... the law of nature. The term "cold air return" is for that reason to draw the cooler air from the floor level and return it to the furnace to be heated. If the return ducts are at ceiling level this will draw warm air returning to the furnace.

    The other reason to have the cold air return vents down toward the floor level is to help with circulating the heated air coming from the warm air heat vents.
    Since warm air rises you don't want all the warmth at the ceiling .... most people don't live on the ceilings .... you want it at the level of the room where you are.
    This helps preventing stratification where you would have a cold zone at floor level then different layers of warmer air rising with the warmest being at the ceiling.

    The cold air return at the lower point of the room will help draw the warm air down providing the heat where it's most desired.

    If you will be adding air conditioning one method that's being done is adding two return air vents ... one at the floor level for heating and one at the ceiling for A/C with dampers that allow you to close off one of the ducts and open the other so that the system can work to its maximum in each season.

    Hope this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,836

    Default Re: Location of Registers vs. Return?

    To add to Canuk's post, insulating the cold air returns is a waste of time and money with little chance of payback.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
    Join Date
    Oct 2008
    Posts
    2

    Default Re: Location of Registers vs. Return?

    Thank you both for the information.

    The system already has A/C. I will look into placing return air vents at the top of the wall also, I think it will be fairly easy because most of the returns are already between studs so I just may be able to knock out the top of the current return and use the stud cavities as the duct.
    JLMCDANIEL, I am confused by your reply that it is not worth insulating the returns. The trunk is approx 40ft long and runs through the uninsulated / unsealed craw space. I can feel a noticeable difference in the temperature of the craw space when the AC is on during the summer and the heater is on in the winter. Even though this is in the return line isn't it still conditioned air? We keep the house approx 74-76 degrees during the winter and the crawspace gets down to approx 60-65 degrees, wouldn't it be best to keep as much heat in the system as possible before it passes through the blower?

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,836

    Default Re: Location of Registers vs. Return?

    My point was that the insulation and labor involved to do the returns usually does not pay for itself. The heat loss actually helps to heat the floor . Thats just my opinion.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6

    Default Re: Location of Registers vs. Return?

    I don't want to jack your thread, but it seems that your question was answered and I have a very similar question.

    Right now my heat runs from the attic, down a central trunk to the floor, where it splits and runs to the outter edges of the house. The air return isn't much of a return, it is in the cieling of the hallway. The furnace sucks (probably already warm) air from the center of the house, at the cieling, then through the furnace and back down the central trunk.

    Now, I saw a TOH project house (Boston? It had a flat roof...) where Rich had high-velocity nozzles installed instead of regular duct work. The nozzles were located at the upper edge of the wall and really mixed the warm air in the room.

    What's to stop me from eliminating the "central trunk" design of my furnace and converting to a different approach?

    The furnace is located centrally in the attic of my one-level ranch. Why can't I just go directly from the furnace to a high-velocity vent in the cieling or upper wall of each room?

    Instead of the air traveling through 25' of duct work and coming out luke-warm and barely noticeable. I'm thinking that I can route the air directly from the furnace and into each room. It'll be fresh-out-of-the-furnace hot and have plenty of oomph.

    Is this possible?
    Last edited by Will Mahoney; 10-24-2008 at 04:08 PM.

  7. #7
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,836

    Default Re: Location of Registers vs. Return?

    You would need a high velocity fan unit to do this. Standard furnace is low velocity high volume fan.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  8. #8

    Default Re: Location of Registers vs. Return?

    Hmm, ok.

    But, would a smaller volume duct area speed up the airflow?

    What I mean is, the replacement duct work would be substantially smaller. So I'm thinking that the same amount of air moving through a smaller series of ducts would have higher velocity. No?

    The system is already a good 15-20 years old and I don't want to put undue strain on the blower - BUT - if I can boost the efficiency with a new design and customize the system to make my house more comfortable, what's the harm?

    Maybe I can even use the existing floor vents and central trunk as a new air return and scrap the useless one in the cieling.

    UPDATE:
    Ok, I looked up the TOH project that installed the high-velocity system. It was the Cambridge house. I looked up the products and found a link to the manufacturer of the high-velocity system. http://www.unicosystem.com/

    Their website says that while a typical furnace might move 400-500 CFM, their system only moves 200-250 CFM.

    I am way into modding things to be better or more efficient. Perhaps there is a smaller, higher-velocity blower I can retrofit to my existing furnace? Maybe it'll even use less power?

    Let's get outside the box on this and see what we can figure out - the current setup isn't worth the gas I'm wasting running it...
    Last edited by Will Mahoney; 10-24-2008 at 04:08 PM.

  9. #9
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,836

    Default Re: Location of Registers vs. Return?

    Replacing the blower would be one choice, using the existing blower would lose efficiency however the flame size, heat exchanger, and controls are set up for the full airfow. The back pressure from the reduced size could double the load on the blower. Think of it this way if you blow with nothing in front of your mouth then put a plate in front of your mouth that only has a pin hole in it. Your lungs will still put out the same amount of air but compare the amount of work to get it done. If not enough air is flowing through your current unit, the heat exchanger over heats and the controls would shut it down.
    Jack
    Last edited by JLMCDANIEL; 10-24-2008 at 06:36 PM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #10
    Join Date
    Nov 2008
    Posts
    25

    Default Re: Location of Registers vs. Return?

    Why not reverse it? Have flexible duct hose direct the fresh hot heat to each room through ceiling vents, then use the floor vents to return air to the attic.

    We reversed our system and it has worked for more than 25 years.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •