Reversing the way a fan turns

Discussion in 'General Electronics Chat' started by t00t, Sep 18, 2015.

  1. t00t

    Thread Starter Member

    Jan 22, 2015
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    Hi Guys,
    I am looking to reverse the way a huge ducting fan system to change it from a pull to a push . Is there anyway to change the polarity by changing the wires ? I know if it is a 3 phase motor i just change the polarity of the wires .

    But what about fans ?

    Thank You .
     
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Is the fan motor AC or DC?

    You don't give us much to go on....
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If it is squirrel cage impeller it is designed for one way, the blades of most fans are designed for a certain air flow direction.
    Max.
     
  4. t00t

    Thread Starter Member

    Jan 22, 2015
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    Wish I could give more information . But all I have is the picture of the control panel that powers the fan .
    fan panel.jpg

    seems like a 3 phase ac fan
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The control does not mean anything at this point, you need to show the fan design.
    Max.
     
  6. t00t

    Thread Starter Member

    Jan 22, 2015
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    sorry i do not have the fan design.

    does it mean even if it is a 3 phase AC fan , if the fan design is made so that the polarity can't be reversed then it cannot be reversed just by changing wires ?

    thank you.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You can easily reverse a 3ph motor by swapping any two conductors, but it is pointless if the fan impeller is not designed to run in reverse.
    Max.
     
  8. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Your best bet would be to physically remove the fan blades and put them on backwards (which probably isn't an option).
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Although a large duct system generally has a squirrel cage impeller.
    Max.
     
    DerStrom8 likes this.
  10. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Yep, good point. Missed that earlier.
     
  11. dannyf

    Well-Known Member

    Sep 13, 2015
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    Many of the fans are designed to be reversed: you take the two end plates off, take out the shaft and reverse it before putting it back in. Done.

    Others have different wires to reverse directions without taking the fan out.
     
  12. t00t

    Thread Starter Member

    Jan 22, 2015
    55
    1
    Thanks for the replies .

    If i try to swap any 2 conductor and the fan is not made to run in reverse like that will it damage the fan ?

    Thank you .
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Pretty difficult to reverse if it's like this.
    Won't damage the fan, just no air flow.
    [​IMG]

    Max.
     
  14. dannyf

    Well-Known Member

    Sep 13, 2015
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    Nothing special about it from the motor's perspective. Only the fan blades are different.
     
  15. dannyf

    Well-Known Member

    Sep 13, 2015
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    Here is a video of what it takes to reverse a motor:

    The motor in question happens to be an electronically reversible motor but they treated it like a non-reversible motor. All it does is to take out the shaft and reverse it before putting it back - as I indicated earlier.

    Hope it helps.
     
    Gdrumm likes this.
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    No one is disputing the ease of reversing the motor, it is the feasibility of whether the fan is a suitable type.
    Max.
     
  17. #12

    Expert

    Nov 30, 2010
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    One more point of interest: If you try reversing the armature, be sure the field windings are centered in the case. Sometimes, they aren't.
     
  18. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    I was going to say you can't so easily reverse a shaded pole motor, but then I saw the pic of the controller....
    If you cannot show us a picture of the fan itself, can you at least show us a picture of the plate on the motor that drives the fan?
     
  19. #12

    Expert

    Nov 30, 2010
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    Running a squirrel cage backwards unloads the motor because it will not move much air, so the answer is, "no".
     
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