Question about Grundfos JPS4 1 HP Pressure Booster Pump

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I have a Grundfos pump type CU 301 that is running constantly 24 hrs a day. The manual switches are not responding at all....i.e. I can not turn it off or change the pressure setting at the box. The only way I can turn it off is to turn off the main power supply.

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  • aprilshouse Mar 26, 2011

    Thank-you so much for your prompt response, unfortunately, I am still waiting for one of the men in the family to come help me with this as I don't have the tools or the knowledge of pumps to continue any further. As soon as one of them shows up I will get back to you and let you know how it worked

  • aprilshouse Apr 01, 2011

    This model is solid state control. There is no pressure switch, it is controlled by a panel, 24v. controls. The sensor from the water line to the control box is a twisted pair, 24v., The control panel is in "locked" mode, and we can't get it un-locked so we can change the pressure settings on the control panel. Any advise on how to get it out of the "locked" mode? The water is runnng, the pump sounds good, the flow is going somewhere, not into the house, we closed the valve to the house, still keeps running. The pipe down into the well is sched. 80 pvc, and looks good, but have not pulled the pump to inspect all of it. Need to get the control box out of the"locked" mode first.... HELP!!! Thanks. Call 575-895-5631 if you can, Thanks, Dennis Franklin. email

  • aprilshouse Apr 02, 2011

    Thank-you again! I called my uncle and he is looking up the We live way out in the sticks here so takes awhile. Thank-you for being so patient!



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  • 43,501 Answers

There are two things that can happen to cause this...

First, check that the contacts in the pressure switch are not welded together...sometimes they arc and the heat welds the contacts and keeps the power on...
The other problem is that sometimes dirt or corrosion builds up over the hole where the pressure tubing hooks up to the pump... or the tubing it's self gets plugged with dirt...then the pressure does not change to the pressure switch.. this traps water in the tubing and hold the switch on...
Take the tubing off at the pump, take out the fitting and make sure that the hole is clear...also take off the tubing at the pressure switch and make sure the fitting at the pressure switch is clear and that the tubing is clear...
Make sure to turn off the pump and relieve the pressure first or you may get an unwanted shower!!

Any questions or comments please get back to me...


Posted on Mar 25, 2011

  • D. Floyd Kolb
    D. Floyd Kolb Apr 01, 2011

    Okay... sorry I was looking at the JPS4 pum that you had this posted under...

    Here is the manual for the control...

    Page 10 tells you how to unlock by pushing the two arrow buttons at the same time...

    After unlocking, check for alarms, it may tell you what is wrong...

    Also as a side note...

    There have been many problems with these pumps and controls, in fact Grundfos stopped selling them for a time to get them working better...but first make sure that it is not a simple problem that can be fixed easily..


  • D. Floyd Kolb
    D. Floyd Kolb Apr 02, 2011

    No problem...

    I know he left his phone number and email, but FixYa really frowns on us communicating other then through the website...

    Hope he can figure it out for you!!



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