start capacitor size

Discussion in 'Pumps and Tanks Well Forum & Blog' started by dragnuts, Jan 21, 2012.

  1. dragnuts

    dragnuts New Member

    Messages:
    5
    Location:
    australia
    have a Davey 3hp single phase submersible pump but the control box is missing the start capacitor. have been to davey dealers but the model numbers do not match apparently a limited model.Wondering if anyone has any information this model. The model number for the control box is #cp4h07-d, and for the pump motor #m4h07b-d-03.
  2. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Take a look at a franklin box and match that capacitor. There is plenty of slack in the exact size of a capacitor.
  3. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    That Pump Motor may have a centrifugal start winding switch built in, so a start capacitor would not be needed.
    Last edited: Jan 22, 2012
  4. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    If a pump has a control box, it requires a start cap. And no sumersible motor has a centrifugal switch in it, thank god. Not even the 2 wire ones. They have a biac switch and a split phase induction motor with HD start windings.
  5. valveman

    valveman Moderator Staff Member

    Messages:
    4,461
    Location:
    Lubbock, Texas
    I think DonL said that because he doesn't think it is a submersible pump. I don't think Davey makes a submersible either. Still can't find that they do. All I see is the pond type submersible pumps, no well pumps. Can't find that model number anywhere either. When you Google any of those things, this thread is the only thing that comes up. Are you sure it is a Submersible?
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,126
    Location:
    Houston, TX
    The thing about start capacitors is that they need to be close to the Winding to be most affective.

    Add a bunch of wire in series with the cap and it decreases it effectiveness. 3HP is a nice Load.

    What is the formula for that ?
  7. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I suppose the formula is how Franklin winds its motors and oversizes its caps. Take a look at the Franklin "AIM" manual for a start on their very particular type of motor.
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