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Ceiling Fan motor operation

  1. Nov 24, 2014 #1
    My husband asked a question earlier this evening, which has given me pause. I've looked everywhere I can think of and came across this forum. Maybe someone here knows the answer.

    Why do ceiling fans (and similar residential/box style fans) go from the off position to the highest possible speed setting before moving to slower speed settings?

    As an electrical engineer, I just couldn't come up with a response that was satisfactory to me.

    My postulation is that it has to do with the startup of the motor to begin with. Since the motor will overshoot upon startup anyway, it seemed logical to have the highest speed setting come first before slowing the motor to lower settings.

    Thoughts?
     
  2. jcsd
  3. Nov 24, 2014 #2

    RonL

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    I'm not an electrical engineer, but a quick guess might have to do with power through switches in a fashion that least likely will cause arc burn to the contacts.
    A mentor might move this thread to the EE forum for a better chance of getting the right answer:)

    Welcome to PF:)
     
  4. Nov 24, 2014 #3

    Danger

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    I'm not familiar with the concept. I don't have a fan in my house. When I lived with the ex- in a 4-plex, we had one installed in the kitchen. As with any others that I've seen, there were 3 bead chains hanging from it. One turned the light on or off. The other two toggled between high and low speed, depending upon which one was in the "pulled" position. The instructions specified, however, that we had to shut off the mains at the wall switch before changing speeds.
     
  5. Nov 24, 2014 #4

    RonL

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    I suspect that had to do with changing direction of rotation.
     
  6. Nov 24, 2014 #5

    Evo

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    I've had celings fans for decades and only had two switches, one for the light, the other for the speeds. The chain for speed was pulled repeatedly to get to the speed you wanted and there was no requirement to turn off the power between speed changes. Never seen a fan like the one you described. :)

    Moved.
     
  7. Nov 24, 2014 #6

    Danger

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    Now that you mention it... hmm...
    Maybe rather than changing speed, it just redirected the airflow in a less efficient direction. All I remember for sure was that there was a lot less breeze on one setting than the other. If that's the case, then I guess that I've never actually met a multi-speed fan. Sorry for the distraction.
     
  8. Nov 24, 2014 #7

    RonL

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    You might recall having a small slide switch up on the body of the fans ?
     
  9. Nov 24, 2014 #8

    Evo

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    No, never seen a slide switch. I've had ceiling fans since their renewed popularity in the late 70's.
     
  10. Nov 24, 2014 #9

    RonL

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    The fans I'm familiar with are "Hunter" and "Hampton Bay" they all have the two chains and the switch on the side, they range back to 1992.
    I'm sure there's someone that will pop in soon and answer the first post. :)
     
  11. Nov 24, 2014 #10

    Evo

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    What is the switch on the side for? Surely they didn't expect people to climb a ladder to switch the fan off to change the speed?
     
  12. Nov 24, 2014 #11

    RonL

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    The switches on mine, are for changing spin direction, the choice of moving air flow up or down can have a dramatic affect on room conditions, I really hate having air blowing down on a perfectly cooked steak:mad:

    Moving air up against the ceiling can have an affect of airflow to the sides of a room, instead of straight down in the center.

    PS. I do have to get a step ladder (3 step) to change directions, but that is just on very rare occasions, and only in a few rooms.
     
  13. Nov 24, 2014 #12

    Evo

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    ok, I could change spin directions by the sequence of pulls on the speed cords, but I'd have to test the cheap ones i have now to see if they do that
     
  14. Nov 24, 2014 #13

    RonL

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    Just to make sure I was clear about my fans,....they have one chain to turn on the lights, one chain to turn on and off and give the three speeds, and the slide switch that changes directions.
     
  15. Nov 24, 2014 #14

    Evo

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    Seems you're right, there had to be some switch somewhere or a remote that switched direction.
     
  16. Nov 24, 2014 #15

    RonL

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    I have far too many TV remotes to even want a fancy fan with yet another remote:eek:
     
  17. Nov 24, 2014 #16
    The switch on the side reverses the rotation of the blades. This is supposed to bring warm air down from high ceilings in the winter. I don't use it. In addition to reaching the switches they just seem to kick up all of the dust that settled in nooks and crannies with the fan running the other direction.

    As far as the fans always starting on high speed it probably goes back to the time when fan blades were much heavier. The high current draw to get the heavier blades rotating would put an unwanted load on the motor. Times and technology have changed and with the newer lightweight fans it probably wouldn't matter. The fan manufacturers may keep it the same just to avoid confusion.
     
  18. Nov 24, 2014 #17
    Yep a remote for the cable box and a second one for the TV, perhaps a third for the VCR, then bring in the cordless phone plus a cell phone in a pocket. Now just try to find the blasted fan remote with two phones ringing and a annoying commercial blasting on the TV.
     
  19. Nov 25, 2014 #18
    Yes, any fan, not just ceiling fans, that has three speeds, starts off in high speed and has to be switched down to lower speeds, in my experience. However, I happen to have a fan that has three separate buttons for the three separate speeds. It can be started in any speed. Therefore, I think starting in high speed is nothing more than a convention that might have had a purpose at one time, but is now just convention.
     
  20. Nov 25, 2014 #19
    Typically these are shaded pole motors - but that really should not be an issue for needing to start at high speed.

    As for direction - my understanding is they should blow "up" in the winter to force the warm air near the ceiling out and down along the walls, and then blow down in the summer - to move the air past the people for max cooling.
     
  21. Nov 25, 2014 #20

    Averagesupernova

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    I suspect it has always been convention since fans are often switched by a wall switch which of course will make no guarantee what speed it starts on.
     
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