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  1. #1
    Join Date
    Jan 2010
    Posts
    19

    plenum splitter design & linkage

    Hi , new here. Been employed in the hvac industry for over 20 years.

    Iv been brainstorming how to install a easily actuated duct damper to balance, or isolate half of my split level house redirecting all the air flow to the other. Branch take offs located close to the plenum take off prevent me from installing a damper in the 8x14 duct. The 8x18 duct on the opposite side of the plenum is adequate size for 1st stage heating airflow. Thermostat wired only to W1.

    I think I can build a splitter damper in the top of the plenum. A damper which doesn't have the pivot axle in the middle. But only at the top located at the top of the plenum and blade. This will put allot of stress on the linkage and stops positioning the loose leading edge. But wont restrict any flow when neutral.

    Can I design something that will work if I beef it up to say a 16 gage blade and maybe two commercial grade linkage rods which would attach to the loose corners of the damper? Noise may be a factor as well..

    Thanks for your time

  2. #2
    Join Date
    Jul 2005
    Posts
    717
    A "leaf" type damper could be installed and could be operated manually or via the electronic method.
    Position the hinges of the leaf damper at the highest part of the plenum and a simple rod type lever could be brought to the exterior surface of the plenum and then either adjusted manually by a locking type ball joint or by the installation of an electrically operated lever arm control. You may have to relocate some of the supply takeoffs to acomplish this damper arrangement. And this damper does not need necessarily to be of a heavy (16 ga)material, It could be made from 24 or 26 ga but broke up in a "tear drop" shape for rigidity. if made from a heavier material such as 16 ga it could put too much strain on the electric control if you go that route.

    A photo of your present set-up would be of great help in actually pinpointing a location or design of this damper.

  3. #3
    Join Date
    Jan 2010
    Posts
    19
    Thanks Deejoe.

    Heres a pic. Its a typical residential install. I did raise the coil so I could see it from the bottom. 18x8 taken off the front and 14x8 off the back. I need to completely block the air to the 14x8 but not restrict it when open

    I googled leaf dampers and don't think it would work well. I probably misunderstood you though. The leaf dampers had multiple blades and a thick frame. The single blade Im talking about wont restrict any air when open.

    I did find the linkage I need. Duro-dyne splitter damper bracket 3034 srp40 and ball joint damper casting 8032 srp14. Over $ for the ball joint.

    You don't think a splitter damper will work?
    Heres a pic of a tee with a divider plate in the middle. Now imagine the divider plate with a hinge at the top and a rod to control the leading edge position. Then imagine that divider with the splitter hardware in the top of my plenum.
    http://www.jensenmetals.co.nz/compon...uct_image6.jpg
    Attached Images Attached Images  
    Last edited by beenthere; 01-18-2010 at 01:10 PM. Reason: Removed price

  4. #4
    Join Date
    Jul 2005
    Posts
    717
    Rebar;
    A leaf type hinged damper will work just fine, but then that all really depends on the locations of the takeoffs. Can you give a more descriptive drawing or a view of these takoffs
    Note; Just so we are both on the same page; A leaf type damper is hinged or pivots on one end only. A splitter damper has a central pivot point.
    Also, a leaf type damper will serve as an air stream diverter even when it is the open postion, .It can also act as a "turning vane" to greatly assist air flow into the duct opening.
    When this leaf type damper is closed, or even partially closed, it will not interfere with the airflow into the other duct opening.

  5. #5
    Join Date
    Jan 2010
    Posts
    19
    I guess I still dont see a leaf damper in there. Im just going with the images I find when I goggle leaf damper and splitter damper.

    Heres my first attempt with sketchup
    Attached Images Attached Images  

  6. #6
    Join Date
    Jul 2005
    Posts
    717
    Rebar; This should be a easy installation if you use a leaf damper. The leaf damper i'm referring to is just a flat piece of, say 24 ga galv, that will block off that 14x8 takeoff. The size required to cover this 14x8 opening would be approx 16x10
    Personally, I prefer to use a double tear drop shaped damper(The shape of an exclamation symbol like this !
    In this case because it is right in the main high air flow of the system,namely the supply plenum, a"teardrop shaped damper makes for less air turbulence in this main high air stream.
    But if you are still intent on using a 16 ga flat plate as a damper then simply put a couple of hinges along the top of this damper and fix it securely to the side of the plenum, slightly above the top of this 14x8 opening but WITHIN the plenum proper) Then secure an adjusting rod to the bottom of this damper and bring it out to the outside of the plenum and secure it with a ball joint type adjustment nut.

    Unless you use a "swing" type rod connector on the lower leading edge of the damper you may have to slightly "arc" this adjustment rod so that it can be pulled back and forth with ease.
    Obviously you will need an access opening in the plenum to work from.

    Note: a splitter type damper installed in the 14x8 takeoff would be much easierr to install, but you say that branch ducts are too close to this area.

  7. #7
    Join Date
    Jan 2010
    Posts
    19
    I think we are talking about the same thing except for the hinge location. The 16 gage was only a thought because I know it will want to flop around with the amount of air passing by it.

    Is this pic more what your talking about? With this design, I cant figure out where the linkage rod would exit well and be able to control it though..
    Attached Images Attached Images  

  8. #8
    Join Date
    Jul 2005
    Posts
    717
    That sketch showing the location of the damper will work just fine.
    If you are going to make this damper from 16 ga steel either use 2 - hinges on the top secured to the plenum and then secure the rod fitting to the lower center edge of the damper and extend this rod out the side of the plenum.(the same side of the plenum that this 14x8 collar is attached to)
    I don't think ANY amount of air flow in this residential system is going to make this damper "flop" around. If installed securely and especially with a 16 ga damper it could probably take at LEAST double the air velocity that there is in this plenum and still NOT come close to ever "flopping" around.

    Use either 2- 2" hinges, or even better, use a piano type hinge approx 12"
    long.
    Btw, I still can't fathom why you would not just simply install a splitter type damper in this 14x8 starting collar that is attached to the plenum. Even IF there was a supply takeoff within 8" of the plenum it would still not interfere in any way with the installation of a splitter type damper

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