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  1. #1
    Join Date
    Oct 2006
    Posts
    4
    Does the motor speed in a multi-speed blower furnace increase and decrease as needed similar to a variable speed one?If so,surely a four speed motor will give very similar results to a variable speed....or am I missing something?

  2. #2
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    Multi speed motors are just that... like a car with say 4 gears. You are forced to pick a gear, hopefully it's close enough for what you need to do.

    A variable speed motor basically has an infinate number of "gears" if you will, and allows for proper RPM (and because of that, proper CFM in every condition). On top of that it ramps up and down to help reduce noise and wear on the equipment where a normal motor just turns on and gets up to speed as quick as it can.

    The best thing about a variable speed blower is the board can control the speed, this will allow you get get benifits such as greater humidity removal, lower CFM (if chosen) with the fan constantly on, hotter temps if you are using a heat pump... etc.

    I'm sure that's not the best explination out there, but hopefully it helps some.
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  3. #3
    Join Date
    Oct 2006
    Posts
    4
    thanks for clearing things up.

  4. #4
    Join Date
    Oct 2006
    Posts
    34
    the trane xv 90 for example removes 4 times the amount of water as a fixed because a slower motor speed will allow the evap coil to get colder, faster thus condensation will stick. also the weight of air is different so the variable speed can adjust to the weight and deliver the perfect amount of air. One more thing, the whole moter is expensive, $400+ but the dc drive head can be replaced seperatly from the motor saving the customer money

  5. #5
    Join Date
    Oct 2006
    Posts
    4
    You mean that the variable speed furnace electronic control board can integrate with an A/C condenser unit and adjust air volume accordingly?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,074
    On some brands yes.

    Not all manufacturers use the same type of control communication.
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