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Central Air Handler in Basement?

In a few years we'll have to put in a new hot water boiler and central ac. Both systems are very old. we'll probably add an ERV into the AC mix, and foam the attic eaves and walls and rim joists; already have blowin in insulation in walls.

In order to free up floor space in the attic from the air handler and ducts currently all over the floor, we'd like to move the AC to the basement and use the inside chimney--which will then be empty since we'll direct vent the new boiler--for the AC ducts. (boiler's already in basement.)

Does this make sense? we really could use that attic space.


  • furnacefigher15
    furnacefigher15 Member Posts: 514

    Can the ducting be in the basement? If not, then you may be chasing your tail running the duct to the attic from the basement, and then distributing the ducting in the attic anyway.

    Most ducting takes up a good amount of space, unless you have a unico or space pak type system.
  • D107
    D107 Member Posts: 1,774
    AC in basement

    Thanks, yes ducting/manifolding from basement would be tough. If the manifold for a three ton unit could fit inside the 7 x 11 chimney and then branched off within that perhaps it would work--have to chop through brick sideways into existing room registers.My guess is that more than 7x11 would be needed for main trunk line. Unico as you know requires multiple registers per room which gets into work....maybe original plan was better: to live with the manifold and handler in the attic but bury the room ducts under the floor.

    thanks again.
  • furnacefigher15
    furnacefigher15 Member Posts: 514

    7 by 11 is way to small for 3 tons of air

    for 3 tons you need 1200 cfm which is 10 x 20 or equivalent in cross sectional area of 200 square inches.

    Remember you also need return ducting.

    My advise,

    reconfigure ducting in the attic to run around the perimeter of the attic, and move the air handler to a corner, that would leave the middle area free.

    If the attic is rather small, the effort may not be worth while.
  • D107
    D107 Member Posts: 1,774

    Great idea. Makes sense too since the perimeter of the attic is too shallow to use for anything else anyhow.
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