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Air return issue: What is best approach to diagnose why I am not getting good return flow?

BlueMTN | Posted in Mechanicals on

House is about 3200 SQ ft. two story with a single air handler in the basement..
– (original contractor no longer living to question)
– air temp balance is hard to maintain both in summer and winter.
– Had two local companies visit wanting to add a second unit vs diagnosing existing return air paths.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Blue Mountain,
    It can be tricky to make sure that a single-zone forced air system serving a two-story house provides balanced comfort in summer as well as winter, especially if the house has air leaks or is poorly insulated. Your contractor's suggestion -- installing two furnaces or air handlers -- isn't crazy. This approach usually results in better comfort, as long as the units aren't oversized.

    One possible (cheaper) solution is to install a centrally located ductless minisplit to serve the cooling needs of the second floor.

    For further discussion of this issue, see this article (and the comments posted on the same page): Keeping Cool in a Two-Story House.

  2. GBA Editor
    Martin Holladay | | #2

    Blue Mountain,
    To assess the performance of your return air system, you need to double-check the design of your existing duct system and then you need to measure air flows through the system's ducts, registers, or grilles.

    For information on how to double-check the design of your existing duct system, see this article: All About Furnaces and Duct Systems.

    For information on measuring air flow through ducts, registers, and grilles, see this article: Is Your Ventilation System Working? (Although the article discusses ventilation systems, not forced-air heating and cooling systems, the air flow measurement techniques discussed in the article can be used to measure air flows through the components of a forced-air heating and cooling system.)

  3. Jon R | | #3

    Have you tried simply adjusting the registers in areas that are too hot/cold? I would expect that you would need to do it every spring and fall. Other lower cost possibilities are booster fans and/or zoning.

    It's likely that your existing system is over-sized. Be careful about making this worse by adding another one.

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