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Best work-around for oversized HVAC?

Dorothy Prowell | Posted in Energy Efficiency and Durability on

My house has a 5 ton AC which was oversized for the house even before weatherization. However, the unit is only 5 years old and I don’t want to replace it yet. Below are some suggestions to get the unit to run longer to increase efficiency and moisture removal.

1) Run a duct from the plenum to the air return to cool down inflowing air faster so moisture is removed sooner.

2) turn blower speed down so unit runs longer (and less often per unit time?).

3) add duct to make attic conditioned space so some unit will run longer (the attic rafters & gable areas are insulated).

Are any of these worth doing? I live in the seasonally hot, humid climate of Baton Rouge, Louisiana. Thanks for advice. Dorothy

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  1. GBA Editor
    Martin Holladay | | #1

    You can reduce the airflow to improve latent cooling (dehumidification), but only up to a point.

    As a rule of thumb, air conditioner manufacturers recommend that a residential cooling system should provide 400 cfm of air flow per ton of cooling capacity. However, lower air flows (less than 350 cfm per ton) will provide more latent cooling.

    Reducing the air flow to improve a unit’s latent capacity only works up to a point, however. If you slow the air flow too much, the coil can freeze.

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