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  1. #1

    Grundfos CU 200 Always Pumping

    I have a solar setup with a generator backup. CU200 SQFlex with a IO 101 SQFlex Switchbox.

    I recently found the tank overflowing. The CU200 is showing a full tank, is indicating water flow and the power switch is ON. The power switch is unresponsive. It will not shut off. To stop the water pumping I have to shut off the IO 101.

    I've checked all the connections. Disconnected the Float Switch. No changes. My take is that the circuit board is fried and I need to buy a new controller.

    Does anyone have any suggestions? I'm at a bit of a loss here.

    Thanks in advance.
    Last edited by patbob; 03-10-2017 at 02:04 PM.

  2. #2
    Pump guy speedbump's Avatar
    Join Date
    Jun 2005
    Murphy, NC. USA.
    I am not familiar with that pump. I know what it is, just never worked on one. I do know you can substitute the controller for a pressure switch or some other type of switch

  3. #3
    Quote Originally Posted by patbob View Post
    The power switch is unresponsive. It will not shut off. To stop the water pumping I have to shut off the IO 101.
    I believe you said you have three wells on this property that you are house sitting, I'm inclined to say if the on/off switch or button does not work the box is bad. But since you have two more, swap it out with one that is working to confirm.


  4. #4
    Senior Member
    Join Date
    Dec 2009
    , SE Texas, .
    Yep, it sounds like the control board is bad, but please post back up to let us know if that fixed the problem. About the worst thing I have found with solar is keeping the bugs and ants out of the electronics.

  5. #5
    Join Date
    Apr 2017
    Gottenborg, Sweden
    Unfortunately I do not have experience with this particular model, but from your description it sounds like it might be POWER ON button issue...

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