well pump sensor failure

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by rob brunkow, Jun 10, 2008.

  1. rob brunkow

    rob brunkow New Member

    Jun 10, 2008
    i am new to wells. just bought property with new installed well and house bib off of well. the control panel is a grundfos cu 301. the panel shows sensor failure indication. the sensor is down inside the 4" well pump pipe. i can see it if i shine a light down the pipe but can not figure out how you are supposed to remove and replace the sensor? a very long wrench perhaps? can i install a new sensor to test without it being connected to the well itself? thanks everone!! rob
  2. valveman

    valveman Cary Austin Staff Member

    Mar 15, 2006
    Pump Controls Technician
    Lubbock, Texas
    The Grundfos CU301 is the controller for an SQE pump. This is a variable speed pump and the sensor that is faulty is in the motor. I recently heard that Grundfos was changing the programming to let the pump cycle on and off 1000 times at 15 PSI differential, to allow time for the controller to "find the signal". This apparently happens a lot, since letting it cycle 250 times was not enough. The signal travels on the power wires that go down to the motor. This signal can be lost for several reasons. The length of wire can be a problem. Improper grounding can be a problem. The Harmonics or Stray Voltage created by the variable speed controller can be the problem. Or you could be getting a disruption of the signal from a different source such as a variable speed motor in your washing machine or something else in the area.

    You will continue to have problems with that type pump. I would recommend doing away with the CU301 controller and hooking it up as a standard SQ type pump. Of course you will need a larger pressure tank than the one gallon size that came with that pump, or you can use a Cycle Stop Valve and keep the small tank.

    Another customer of mine had several problems with his SQE not shutting off when it should, and the pressure would just blow off the pressure relief valve. Make sure you have a pressure relief valve. After nearly 4 years of these problems he had to purchase a new Cu302 conrtroller for about 800 bucks. The tech at Grundfos told him that the pump had already lasted nearly 4 years, and didn't understand why he was unhappy. That seems to be about the average life expectancy of those type pumps, which is crappy. A good pump should last decades.
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  4. rob brunkow

    rob brunkow New Member

    Jun 10, 2008
    hi valveman, the pump is the only thing on the temporary power pole as no house has even been built so washing machine or other electrical noise problem is not possible. there is no pressure tank installed unless it is downinside the pump casing or buried? the set up is brand new and used maybe 4 times. the only thing hooked to the well is a frost free faucet that comes up from the ground and i assume over from the casing and pitless adaper. it appears from the manual for the controller that the error is for the pressure sensor as per the lighted LED on the circuit board. i followed the wiring from the contoller circuit board sensor inputs down to the top of the pressure sensor so i know it can't be down in the motor as i can see it terminate at the top of the sensor. i see from the manual that the sensor should have been installed downstream from the pressure tank but no pressure tank exists? how would one hook up the pump as a standard SQ pump. thanks for your help!! rob
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