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Thread: poor airflow

  1. #1
    I'm looking at getting a new furnace & a/c to replace my old units. One room of my house receives very poor air flow, even though it has 4 registers, and is only about 300 sq feet. I've had a couple of techs (who have serviced my units in the past) say part of the reason is there are several 90 degree angles the air must go thru b4 it reaches the room. In addition, 3 of the walls in this room are exterior walls, so needless to say the room stays too cold during a Nebraska winter. One tech said when I replace my 4 ton furnace with a new one of the same size, I use a 5 ton blower on it to try and push more air. Any thoughts ?

  2. #2
    Senior Tech Guest
    There are probably several things that could help, but without knowing the design of your house and hvac system it would be hard to pinpoint a solution. One thing you can try is to go to the rooms with ample air flow and damper the register down a bit, this will force more air to the room your having trouble with. Experiment in adjusting the registers until you find the best positioning and see what happens

  3. #3
    Thnks for the response- The house is a multi-level, with this room being the entry to the home, exposed on three sides, and the rest of the house is either up or down from this room-No rooms directly above it, but a sub-basement below. I believe my old furnace is around 100,000 btus. To make matters worse, in the summer, the main bedroom above the garage stays too warm. With an 85 degree day and average humidity (a typical summer day), my old 3 ton a/c runs non-stop from 11 a.m. until 2 a.m., when it finally is able to start cooling the house. I've never had much luck adjusting registers to help these other rooms, either winter or summer.

  4. #4
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    Closing diffusers in other rooms can work. But in my experience you have to close a lot of them. Too many homeowners close a couple and then declare that the idea didn't work. You have to close more than that.

    But of course certain tradesmen have coronaries at that idea. The reason is that while some of it is diverted, some of it is also lost to the increase in static pressure. The lost airflow may translate into higher internal furnace temperatures. And even if it doesn't, the closed diffusers aren't fully closed so they might whistle.

    The proper solution is most likely to increase the duct sizes to that room and/or straighten the duct runs out. If you install a more powerful blower and do nothing else you'll end up having to close registers anyway. The bigger blower will just increase airflow to all of the diffusers. The increased blower power may be a good idea for other reasons. But to balance the airflow is not one of them.

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