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Thread: pressure switch wiring please help

  1. #1
    DIY Junior Member brenjake's Avatar
    Join Date
    Nov 2011
    cincinnati oh

    Default pressure switch wiring please help

    Hello I am trying to figure out how to wire a grundfos pump to the pressure switch. I have a 220 circuit red black and white with ground. The grundfos has three black wires and a green/yellow wire {ground?] Can you tell me what wire goes where? I have a square -D pressure switch mounted . I assume that the high voltage is the 220v diagram and the jumper bars Name:  DSCN0824.jpg
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Size:  36.5 KB are in place as per diagram. So from the pump the L1 which is U1 on the diagram goes to L1 on the pressure switch ? And the L2 from the pump whish is V1 goes to the L2 on the pressure switch? Where does the L3 orW1 from the pump go to? Thanks for any help. Any kind of schematic would be a great help.

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
    Join Date
    Jan 2008
    Land of Cheese


    You have a 3-wire pump, it must be connected to a control box which is matched to the pump motor. On a 3-wire pump the pressure switch and the pump are wired through the control box.

    Only a two-wire pump can be wired directly to a pressure switch.
    Last edited by cacher_chick; 11-06-2011 at 02:42 PM.

  3. #3
    General Engineering Contractor ballvalve's Avatar
    Join Date
    Dec 2009
    northfork, california


    But if you have three blacks coming out of the well, you have some careful ohmmeter work to do in order decipher what wire is which.

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