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  1. #1
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125

    Add a return grill near a supply grill?

    Hi,

    I have a beast of a room, 450 sq ft, 14 foot ceilings. 4 supply grills on the floor, and an inadequate double return, placed 10 foot high.

    I would love to add more return flow. The only way I can see it (without tearing up drywall), would be to use the minfridge/closet that is 1 foot off the ground. I would be easy to have someone attach a return duct to it, and put a grill on the closet door. The problem is the return would be at floor level, about 9 feet from a floor supply. The supply grill feels like it blows straight up, and I also have a ceiling fan on low, 24/7. In short--the supply is very close, but at least not pouring air directly where the return would be sucking in air.

    Would a floor return significantly disrupt airflow/ be a terrible idea?

    Thanks,

    Steve

  2. #2
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    It would not disrupt the airflow.

    Why do you feel that you need more RA. Do you think you need more to that room or just more RA overall?

  3. #3
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    Thanks for the post. If I described the inadequate return of my system it would move you to tears. I need 2000 cfm apparently, and have 3 crappy sources.

    If it wouldn't disrupt the airflow, I wonder why they fairly competent fellow who saw it (and will eventually do the work) was so against it. We talked about increasing the 2 8-inch ducts servicing the double return, increasing them to 10 inches (but it wouldn't increase the grill or the part of the duct in the wall). When I told him about my idea around the minifridge he didn't like it.

    Steve

  4. #4
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    Quote Originally Posted by central nj View Post
    Thanks for the post. If I described the inadequate return of my system it would move you to tears. I need 2000 cfm apparently, and have 3 crappy sources.

    If it wouldn't disrupt the airflow, I wonder why they fairly competent fellow who saw it (and will eventually do the work) was so against it. We talked about increasing the 2 8-inch ducts servicing the double return, increasing them to 10 inches (but it wouldn't increase the grill or the part of the duct in the wall). When I told him about my idea around the minifridge he didn't like it.

    Steve
    I've been doing this HVAC "thing" for more than 30 years. From installs to sales. I would like to think that I have seen it all, but I'm sure there are some "new" crappy stuff going on since I've gotten out.

    You're right on........changing the 8" to 10" won't help much. Adding a RA, as you discribed, makes more sense. I would recommend, if that is the only place available, to go with a floor RA grille under the mini-fridge (if the MF is elevated, of course). They will allow much more airflow than a standard wall cavity or two.
    Or, if you have a new house that has a "open" floor plan, you can put the RA anywhere. Even in the basement.

  5. #5
    Join Date
    Jul 2012
    Location
    Near Chicago Il.
    Posts
    125
    When you say 3 crappy sources, is the third source at least a substantial one or the same as the 2 8" runs in this room?
    Also, how well opened up is this room to the rest of the house? (big 8' or more openings?)

    Is this room problematic in the winter as well?

  6. #6
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    George2--thank you!!
    Eddie:

    4 return Grills:

    9x30 inch grill with 2 8-inch ducts

    9x30 inch grill
    2 8x15 inch grills
    These three with a common 12x15 duct

    A big open floor plan.

    Any help would be appreciated.

    Steve

  7. #7
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    Eddie--there is no problem in winter, or really any time. The house is comfortable. I'm interested in making the system more efficient and appropriate.

  8. #8
    Join Date
    Jul 2012
    Location
    Near Chicago Il.
    Posts
    125
    Without seeing the house first hand, it's real hard to access online. But, from what you said so far, you do seem to be short on return air best I can tell.
    George is correct on what he said. Changing only part of the duct is not going to help much if at all.

    By my standards, your ductwork on the return side do not add up to the 2000 cfm you say you say your system is calling for. As far as your guy not loving the idea....That's hard to say why, he may be seeing some things that make that idea very challenging down below and have other ideas for getting air back to the furnace, so try and keep an open mind.

    Glad to hear the system is working well as it is, at least it's not an emergency. You have time to do some research.

    For that large room, with the high ceilings, check the rotation on that fan, no point in blowing hot air back down. Attic ventilators may help you out a bit there. Your HVAC contractor should be able to help you out there as well if you don't have one already

  9. #9
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    Quote Originally Posted by central nj View Post
    George2--thank you!!
    Eddie:

    4 return Grills:

    9x30 inch grill with 2 8-inch ducts

    9x30 inch grill
    2 8x15 inch grills
    These three with a common 12x15 duct

    A big open floor plan.

    Any help would be appreciated.

    Steve
    The size of the grille(s) doesn't matter (per say), it's the "feed" that counts. If your walls are the standard 2x4 then "that" is the real amount of air you'll be getting back to the furnace.

    I've never seen grilles that size. I think they are 30x8 and 6x14 or about 2 tons short of RA.

  10. #10
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by George2 View Post
    The size of the grille(s) doesn't matter (per say), it's the "feed" that counts. If your walls are the standard 2x4 then "that" is the real amount of air you'll be getting back to the furnace.

    I've never seen grilles that size. I think they are 30x8 and 6x14 or about 2 tons short of RA.
    The mains alone are a little over two tons short

  11. #11
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    As I said, ...to cry.

    Any problems putting the new return near the floor?

    Would a single grill (6x14 or close to it) with a 10 inch round duct be enough?

  12. #12
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    The ten inch will give you an additional 325 cfm increase it to a 14 inch will allow 750 and then change one of the others. The location of the return will not be a problem

  13. #13
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    George2--thanks again.

    Second opinion--big big thanks. I looked, and between the rafters a 12x12 square would fit, which i see would be close to 700. I'll increase the 2-8inches to 10s for a little bit more, and call it a day.

    This forum is wonderful!
    Steve

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