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  • Air Return Dilemma

    I have a 3 ton heat pump w/ two 12" x 24" air return grilles below my air handler closet. I had a Florida Room built 15 yrs ago that is the farthest distance room from the air handler. It has an 8" diam flex return that has to travel 50' back to the air handler area. I am sure the 8" return from the FL Rm is adequate. How do I overcome the 50' run and air friction restriction w/ the 8" diam flex return?

    Thanks!

  • #2
    Re: Air Return Dilemma

    The air follows the path of least resistance. If the return was added without changing the existing return, not much air will flow through the new return. Some calculations need to be made in order to change the existing returns to provide more draw through the new return.

    Comment


    • #3
      Re: Air Return Dilemma

      Everett,

      Thanks for the reply.

      I agree, that the 8" return from the FL room is overpowered by the two unrestricted 12" x 24" return grilles directly below the air handler. The 3 common options I have heard, are keep the doors open to the FL room and the main house, split pKg system just for the FL room or put a two-way pass thru grille above the French doors that lead to the FL room for constant air exhange.

      On person recommened possibly going to a 10" diam flex return from the FL room, but based on what I am hearing from you, it won't help.

      Glenn

      Comment


      • #4
        Re: Air Return Dilemma

        It's all about duct design. Without seeing exactly what you have, fixing it is difficult since no matter how many questions are answered something can get overlooked.

        The design CFM of your system is needed and then a duct design needs to be made with your current ducts kept in mind. Are there supply ducts in the sun room? How big are they?

        Comment


        • #5
          Re: Air Return Dilemma

          The two 12" x 24" air supply ducts are located just below the air handler 50' away from the FL room. My condenser unit/air handler are 16 y/o, so I don't want to sink a lot of $ redesigning my duct system b/c I was told it has to match the new unit I'll eventually have to buy before too long, so I was just trying to buy a little time and comfort until the inevitable.

          Comment


          • #6
            Re: Air Return Dilemma

            A low cost way that might help would be to place a small table fan near the intake of the 8" flex duct to push some air into it. This is pretty crazy but it may help some.

            See the pictures on this web site. They are inline booster fans for round air ducts. One of these should help.
            Contact HVAC contractors in your area. Someone that's most into repairs than new equipment should be able to obtain what you need and install it without too much fuss or big expense.

            http://www.airboosterfans.com/duct-fan.html

            AF-8 MODEL 420 CFM - For 8" duct
            Last edited by Woussko; 02-11-2009, 03:56 PM.

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            • #7
              Re: Air Return Dilemma

              block your 12x24return in half that should give more draw on the 8 inch
              Originally posted by RoseRx View Post
              I have a 3 ton heat pump w/ two 12" x 24" air return grilles below my air handler closet. I had a Florida Room built 15 yrs ago that is the farthest distance room from the air handler. It has an 8" diam flex return that has to travel 50' back to the air handler area. I am sure the 8" return from the FL Rm is adequate. How do I overcome the 50' run and air friction restriction w/ the 8" diam flex return?

              Thanks!

              Comment


              • #8
                Re: Air Return Dilemma

                block off your 12*24 less than half that will give more draw on the 8 inch.
                you may need a mini split system for that room.

                Comment


                • #9
                  Re: Air Return Dilemma

                  it will never heat or cool. get a mini split system for that room.

                  Comment


                  • #10
                    Re: Air Return Dilemma

                    Originally posted by RoseRx View Post
                    I have a 3 ton heat pump w/ two 12" x 24" air return grilles below my air handler closet. I had a Florida Room built 15 yrs ago that is the farthest distance room from the air handler. It has an 8" diam flex return that has to travel 50' back to the air handler area. I am sure the 8" return from the FL Rm is adequate. How do I overcome the 50' run and air friction restriction w/ the 8" diam flex return?

                    Thanks!

                    http://www.fieldcontrols.com/cart/in...=index&cPath=1

                    48 dollars and a half hour of your time your doing great!

                    Comment


                    • #11
                      Re: Air Return Dilemma

                      independent system is ideal.... if not it sounds to me like u need more supply air.... the return is plenty big enouph

                      Comment


                      • #12
                        Re: Air Return Dilemma

                        Coming into this late but here's a couple thoughts.

                        -why after 15 years is this an issue? Was your room comfortable when you first installed the ac to it?
                        -you can't oversize a return.
                        -why are you worried about the return? How much air is being supplied? Generally speaking, you have to distribute your returns throughout a well built house, good cents house for example. But if your air infiltration is high and 15 years old it may well be, you probably have good air exchange already.
                        -if the flex is 15 years old, replace it. The insulation is possibly collapsed.
                        Buy cheap, buy twice.

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