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Thread: How to determine low speed flow of 2 speed pump?

  1. Back To Top    #1

    Join Date
    Jul 2007
    Location
    Portsmouth, Virginia
    Posts
    17

    How to determine low speed flow of 2 speed pump?

    Looking at Pentair Dynamo 2 speed 3/4 hp pump. They give flow chart for high speed but no low. How can I determine if this pump can handle my pool on low speed without the flow dynamics of the pump at low speed? (I have already calculated total head and flow needs of my setup)

    Head 25
    100 sqft cartridge-flow30-35
    15000 gallons 15x30

    Thanks
    15 x 30 Sharkline AG pool, Pentair cc100, Pentair 1hp 2-speed, Liquidator.

  2. Back To Top    #2

    Join Date
    Jul 2007
    Location
    Portsmouth, Virginia
    Posts
    17
    Actually found another thread saying that flow is cut in half on low speed. Guess this answers my question.
    15 x 30 Sharkline AG pool, Pentair cc100, Pentair 1hp 2-speed, Liquidator.

  3. Back To Top    #3
    That's my understanding.

    I belive head loss is too.

    Fyi, I recently emailed Pentair for the flow chart on the 2 speed dynamo, they told me they don't have it for 2 speed, only one speed.

  4. Back To Top    #4
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    9,928
    From pump affinity laws:

    GPM Low Speed = GPM High Speed / 2
    Head Loss Low Speed = Head Loss High Speed / 4
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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