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Thread: Variable speed or std. air handler?

  1. #1
    DIY Member estone's Avatar
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    Mar 2008
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    Default Variable speed or std. air handler?

    Our 2100 sqft. ranch style home has hot water baseboard heat. We are looking at putting an air handler in our attic to add a/c.
    I have the opportunity to get a new "York" air handler for $225, I think it is around a $1000 unit new?. It is a standard 5-speed multipose.
    I've read about variable speed air handlers and they look like they would be more efficient.
    Should I pass this one up and spend the money on a variable speed unit or is the std. one o.k.?
    The guy said that I would run my fan on speed 4 for our size of home.
    Any advise would be greatly appreciated!

  2. #2
    Engineer Furd's Avatar
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    With a little bit of creative control work you could utilize all five speeds for various purposes. You could have continuous air circulation (and continuous filtration) on the lowest speed, you could use the highest, or next to highest speed for "normal" A/C with the next step down used for additional humidity control. All this is assuming that the ductwork is properly designed and installed and also that the A/C unit itself is properly sized.

    A downside is that the variable speed motors are definitely more energy efficient than the multi-speed motors. Whether or not that would play a part over the life of the air handler would depend on how, and how much, the unit was was used. In my area $750 will buy a lot of electricity.

  3. #3
    DIY Member estone's Avatar
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    I live in Colorado where humidity is not a problem. We generally would use the a/c 3 months out of the year. So do you use the dip switches to do the "creative control" work? Are the variable speed motors quieter? Do the variable speed motors last as long? I know with variable speed submersible pumps for wells, they don't last as long as the std. ones.
    If the variable speed ones are quieter and more efficient I might lean that direction.???????

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    The benefit of a variable speed air handler is that it can match the heating or cooling needs more accurately. A fixed speed motor comes on with a bang and may give you a shot of hot or cold air depending on whether you are cooling or heating. A variable speed one slowly ramps up. At the end of the cycle, it also ramps down. On a mild day, it may never reach full speed and with the ramp up/down, you would rarely notice it turning on or off. Coming on at the fixed speed is usually noticed. If dehumidification were an issue, Trane used to say in their adds that with identical systems, one with a variable speed and the other with a fixed speed blower, the variable speed would pull enough extra water out of the air over a season to fill the average back yard swimming pool. Running the air slowly over the cold coils draws much more moisture out than running it by faster.
    Depending on how the speed is adjusted on that one, you might be able to change it with a properly wired switch. If it is done with logic, you probably don't want to do it while on. If it is done with belts and pulleys, I doubt you'd ever change it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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