return air on second floor - Page 2
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  1. #14
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    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Originally posted by hvac-tech-lane
    Originally posted by dash
    Common misconception but the location,high or low ,for returns has very,very little effect on operation or comfort.

    You do need a return on each floor and a return "path" from all rooms .back to the main return ,as a minimum .
    Dash, under the scenario of a second story with floor supplies and a floor return what supply grill face velocity do you set your system up for?
    You would size the registers for "throw " that's at least 6 to seven feet high ,so the conditioned air "covers" the "occupied"(where people are standing etc.) zone.Critical in cooling to prevent stratification of the air in the occupied zone.

    Keep the velocity below 600 fpm,per grille mfr. spec sheet.

  2. #15
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    Apr 2003
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    the Great Pacific Northwest
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    Quote from Dash

    "You would size the registers for "throw " that's at least 6 to seven feet high ,so the conditioned air "covers" the "occupied"(where people are standing etc.) zone.Critical in cooling to prevent stratification of the air in the occupied zone.

    Keep the velocity below 600 fpm,per grille mfr. spec sheet."

    I agree, but you must admit that's a perfect world scenario;proper duct design, prorer sizing of supply grills, proper placement of supplys, proper placement of home owners who won't put furniture or other items where it will block or impinge on the air flow, proper maintenance of the system, etc...etc.. etc.
    Back in the real world where most likely not one of the factors is likely to occur I've found that a high return is emensely helpful in limiting stratification and is why I use it in my designs and have installed them on retro and AC add-on jobs.I have won jobs because of proposing it to customers, one in paticular that wanted an AC add-on balked at the price of my system, I asked her if she knew anybody else with a similar house that had added AC and sugested she call and ask how it worked. The next day she called and scheduled the job. She later told me her mother had the same style house and the upstairs never really got cool but downstairs you could hang meat. After a period of using the system the customer reported that it worked wonderfully and her mother had noticed when she visited that the house was much more comfortable than her own. So that is why I say absolutly install a high return, besides whats it going to hurt but the up side is great.

  3. #16
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    Not that I doubt what you have seeen on other jobs ,But

    Supply grilles when properly designed,installed and not "blocked,etc., are the determining factor in comfort far more than the location of the return.

    The velocity at the return is about 1/2 the supplies,the return is large and has no throw,to create movement in the room,so little effect on stratification.

    There is nothing wrong with the returns bing high wall or ceiling.

  4. #17
    Join Date
    Apr 2003
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    the Great Pacific Northwest
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    607
    Originally posted by dash
    Not that I doubt what you have seeen on other jobs ,But

    Supply grilles when properly designed,installed and not "blocked,etc., are the determining factor in comfort far more than the location of the return.
    Thats what I said, I agree with you. However key word; Properly(Ideal world)
    Originally posted by dash
    The velocity at the return is about 1/2 the supplies,the return is large and has no throw,to create movement in the room
    Again, agreement, But.
    Originally posted by dash
    so little effect on stratification.
    Disagree.
    Originally posted by dash


    There is nothing wrong with the returns bing high wall or ceiling.
    The stratification is from the thermal properties of air, warm air being less dense thus lighter and migrating to the highest point of its enviroment. Now if at that point we draw that stratified warm air off the top and condition it and reintroduce it into the controlled space we will have a better mixing and comfort won't we. And I've never had a customer block a ceiling return by setting a couch over it.

    [Edited by hvac-tech-lane on 04-30-2005 at 09:08 PM]

  5. #18
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    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    We have thousands of manufactured homes in our area ,all with floor ducts a floor or low sidewall returns,They aren't all well insulated.We are in hot ,humid ,sunny Florida.


    With the proper throw,from the floor registers,theres not a problem.Of course ,no grilles can be blocked.

    Manual D ,states basically what i have,and we have found it to be true.

    It's likely you are doing a better job than your competion ,on the supply side design and install,so your jobs work better.I just don't think the credit goes to high returns.

  6. #19
    Join Date
    May 2005
    Location
    North Carolina
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    38

    returns

    Is this 2 stories plus basement? that is what I think you stated. Anyway, the most important issue that prevails is proper sizing and then location. Sometimes the size of ductwork required will dictate where it can be installed. Another factor to consider is whether you will be heating more than coolind and vice versa, this has a greater bearing on where you want your supplies/ returns. Warm air rises and cold air drops. For real comfort go with hot water heat unless it's to late.

  7. #20
    Join Date
    Jul 2008
    Posts
    17
    Quote Originally Posted by dash View Post
    Common misconception but the location,high or low ,for returns has very,very little effect on operation or comfort.

    You do need a return on each floor and a return "path" from all rooms .back to the main return ,as a minimum .
    I totally agree with dash. Every floor needs a return and path to the return.The location of the return air's are not that important. Good supply air flow is much more important.

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