Slowing a Capacitor-Start pump motor

Discussion in 'Electrical Forum discussion & Blog' started by nooboo, Jun 8, 2012.

  1. nooboo

    nooboo New Member

    Messages:
    1
    Location:
    Willow, AK, United States
    I bet someone here knows how to do this:

    Picture a water transfer pump, a Tsurumi LB480, submersible, 2/3hp, 230v, 1ph, 60 hz, capcitor-start...I want to slow the GPM it delivers and I am thinking that slowing the frequency will slow the motor and slow the GPM flow rate.

    I have checked around with my friend Google, but after writing the manufacturer reps, I am told they don't have a device. I asked at Davis for AC Drive / Frequency Inverter, 200-240 VAC single or three phase input with 3 phase output, 2.4 max. ; not suitable, 3 ph out..
    Tsurumi says it is possible and OK to use a VFD on the pump, just not above 60hz. The VFD's I reviewed are not suitable for the capacitor-start.

    The motor has blk, wht, green wires, to be used in the US, 110/220/1ph,60hz.

    b
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,636
    Location:
    Cave Creek, Arizona
    Install a valve on the DISCHARGE pipe from the pump and you can throttle it to any GPM you want. It would not work on the inlet to a pump, even if there were a way to do it.
  3. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    It would need to be a permanent,split, capacitor motor to be slowed down. Cap start and other single phase motors need to reach full speed quite soon or the starting winding will fail.

    Hj has a good idea. An added benefit of clamping down on the water is the extra back pressure will be easier on the motor.
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,978
    Location:
    NW Ontario, Canada
    +1
    A dole valve is a common and acceptable way to reduce the GPM output. Did you want to reduce the GPM or vary the GPM and why?
  5. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    As long as it is a centrifugal pump, that would be fine. That could even reduce the current the motor will draw; less GPM transferred means more water just spiining around inside the pump body, using less work to get stationary water in motion.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,636
    Location:
    Cave Creek, Arizona
    As long as there is some flow. Completely stopping the flow would cause the water to heat up and turn to steam, then cavitation would damage the impellers.
  7. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    That makes for a really bad day.
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