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  1. #1
    Join Date
    Aug 2003
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    Want to install a split system in a house that already has forced hot air. Because the duct system is already installed, how would the return work? When I bought this house it never had A/C before,It is 1850 sq feet with 2 equal floors. I would like to use the existing ductwork as much as possible. Service tech suggested probably 4 ton. Any suggestions would be appreceated. Subject of return never came up. Thanks

  2. #2
    Join Date
    Mar 2002
    Concord, CA
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    I don't understand the focus on the return. Why isn't there a concern (or at least consideration) of all the ducts? The return is typically the best place to start because upgrading it will give you the biggest bang for the buck. But the supply ducts are important too.

    In fact, if you don't address the upstairs supply ducts I can almost guarantee you'll be disappointed with the upstairs. A HUGE portion of the summer heat load will be upstairs. The odds of your current ducts sending enough air up there in the summer is slim to none. If they did the upstairs would be scorching hot in the winter compared to downstairs. So you'll need to upgrade the upstairs ducts to get enough air up there in the summer. And you'll need some sort of zone control (manual or automated dampers) to adjust that back down for the winter. Check the sig links for more.

    Make sure they perform a proper heat load calculation. Not that the tech suggested otherwise, but "probably 4 ton" is a bad way to surmise the heat load. MANY homes your size could easily be cooled by something smaller.

  3. #3
    Join Date
    Sep 2001
    Vancouver Canada
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    Don't know where you are located but I would say unless you are living in a glass house 4 tons is way oversize. I would have grave concerns about the ductwork in a 1800 sq. ft. house being able to handle 1600 cfm of air. Make sure your supplier is doing a heat loss to get the correct size. Even with the worst "rule of thumb" guess you would not be above 2.5 tons.
    "Go big or Go Home"

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