Ceiling Fan Wiring

Discussion in 'Electrical Forum discussion & Blog' started by David D, Mar 28, 2008.

  1. David D

    David D New Member

    Messages:
    3
    I have a SMC fan motor with four wires,by pairing two sets of wires I'm able to run the motor CCW, changing the pairing will run the motor CC.
    I'm wanting to add the capicator to increase the speed.
    Where would the capicator be incerted t odo this

    David D
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    cap won't increase speed
  3. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    Some celling fans will run faster if you shorten or flatten the blades.

    Try running it without the blades to see what it's unloaded speed is.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina

    by doing this to gain more speed will the fan move more air or will the air flow be about the same
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The POWER (Watts) required by a fan varies approximately (theoretically) as the third power of the speed. Therefore, increasing the speed by only 10% increases the power requirement by 1.1 cubed = 1.331; or an increase of 33 percent. Since power= Volts x Amps, that means you need 33% more Amps.

    Now resistive heat loss in the windings varies as current squared x resistance. The resistance is approximately constant, (actually increases slightly with temperature), so the heating increases as Amps squared, or 1.33 squared = 1.77. That means that a 10% increase in speed will increase the heating in the windings by 77%.

    If you increase the heating in the windings by 77% you will eventually cause failure of the insulation of the windings. That will produce a short circuit - much sparks and smoke - until it (you hope) trips the circuit breaker.

    Now, you are the one to decide if you really want to increase the speed of the fan motor.
  6. David D

    David D New Member

    Messages:
    3
    The capicitors ,1.5 and 3.0 UF were initially in the circuit through a three position switch. I don't know how to wire them back into the circuit.


    David D.
  7. David D

    David D New Member

    Messages:
    3
    Bob,
    This fan came with a three position pull switch. when I received it the wiring was already dismantled. I can pair the fan wiring to made the fan run CW or CCW.
    I don't know how to wire the capicator in to chane the speed
  8. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Your first post on 3/28 said that you wanted to insert a capacitor to increase the speed.

    My post on 3/30 was in response to that first post. It explained why increasing the speed beyond the maximum speed for which the fan and motor were selected or designed will result in destruction of the motor and could cause a fire.

    If you are simply trying to replace capacitors to restore the fan/motor to an original factory condition, we don't have enough information to give you that answer.
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    I do!

    Throw the junk away and buy a new fan.
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