Grundfos CU 200 and pump doesn't shut off

Robert_W
Robert_W Registered Users Posts: 14 ✭✭
in Solar Water Pumping #1
Hey folks, this spring I installed a Grundfos CU 200 controller with an 11 SQF-2 pump and one of their floats. We use them to supply a 1500 gallon tank for orchard and critters. Have 3 - 190 watt panels. All worked fine for about a month and a half of VERY light use. The system puts out way more than actually needed but I plan to utilize the excess power and water in the future.

Any way a couple of weeks back the system, even though shut off, just started pumping away and would not stop. This is really bad because the tank is up on a hill side on top of a 15 foot tower that we built. The excess water was eating away at the foundation of the tower and almost caused it to fall. Could have been catastrophic had we not been home. So I drained the system, rebuilt and reinforced the foundation and chalked it up to a fluke. Turned it back on and all worked fine. But I make sure now that the system is shut off when I don't need it.

So tonight I walk out to the garden and sure enough it's spewing water every where down the side of the tank again. Looked like it had been running for hours.

I walked to the CU 200 and verified that it was indeed in the off mode. It was. I also verified that the tank level indicator was full. There were no green arrow pump indications and no service light but it was showing .32 kWatt and pumping away.

A check of the manual and trouble shooting doesn't quite have this scenario. These are my choices:

12.Pump does not stop when water reservoir is full.

Fault indicator light on CU 200 is off.
Level switch is dirty or defective.
• Clean or replace the level switch.
Cable on level switch is damaged.
• Replace the cable.


I'm really hoping that this is just the switch. But it's only 2 months in use and probably only been though 20 cycles of on and off. And the cable is in prime brand new condition too. All splices were made with heat shrink and crimps and verified working.

Do the switches / floats have a reputation of failure? Or the CU 200 itself?

I'm really flummoxed. If it wasn't showing full I'd say it was a switch / float. But it does. That and it not showing that it was pumping when it was makes me lean towards the controller.

Right now I removed the fuse to make sure it won't kick on again but I need to find a solution. Any help would be appreciated.

Thank you.
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Grundfos CU 200 and pump doesn't shut off

    Mechanical contractors and many electronic switches can fail shorted... DC is very hard on relays and mechanical switches. So I would suspect your controller too.

    Check for good electrical connections at the controller (if electronics are powered separately).

    And and some sort of overflow control/drain to direct flow away from critical areas (foundations, slide/erosion prone areas, etc.).

    Need to assume anything electrical can fail (on or off).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Robert_W
    Robert_W Registered Users Posts: 14 ✭✭
    #3
    Re: Grundfos CU 200 and pump doesn't shut off

    Bill, by controller do you mean the switch in the float itself? Or the CU 200? I would think that the ball float switch should be pretty bullet proof...no? They seem to last in septic systems for a long time. So does DC really make that much of a difference? I mean 2 months of light use? That's why I was wondering if these things had a history of failure. But there aren't to many Google search options for them.

    I guess everything can fail but I'd hate to have to warranty the Cu 200 after so short a time. Was hoping to come up with a definitive something.

    And yes, I have to come up with some sort of fail safe to re direct the over flow.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Grundfos CU 200 and pump doesn't shut off

    Disconnect the switch line at the controller and simulate the switch action there. If it turns on and off as it should, the problem is with the tank switch or wire/connections. If it doesn't shut off, the controller is at fault.
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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #5
    Re: Grundfos CU 200 and pump doesn't shut off

    Never heard the final details, but we had the same problem at a customer's house. Her pump was running 24-7 for months probably. We insisted on doing an energy survey before designing the solar system, and found the pump problem quietly blowing about $125/month. Not sure I trust the Grundfos system. Was the second time it had to be fixed under warranty. Like my tech used to say - "must be electronic".
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  • Robert_W
    Robert_W Registered Users Posts: 14 ✭✭
    #6
    Re: Grundfos CU 200 and pump doesn't shut off
    Cariboocoot wrote: »
    Disconnect the switch line at the controller and simulate the switch action there. If it turns on and off as it should, the problem is with the tank switch or wire/connections. If it doesn't shut off, the controller is at fault.

    Excellent idea. Thanks.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    #7
    Re: Grundfos CU 200 and pump doesn't shut off

    The Grundfos systems I have experience with are excellent systems if installed correctly and if the BOS parts are good quality.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • burningmom
    burningmom Registered Users Posts: 1
    #8
    Re: Grundfos CU 200 and pump doesn't shut off

    I too installed a Grundfos 11SQF-2 pump and a CU 200 (V03) controller- four years ago- and have had an intermittent overflow problem at my water tank (also on a tower.) I THINK I'VE SOLVED THE PROBLEM! My problem was that on occasion, the pump would not shut off when the water tank was full, which was very problematic for me, because I wouldn't always notice this was happening. I have two solar panels that are dedicated only to the water system, nothing else. My neighbor who installed a similar system in the past year was experiencing the same problem. I had my installer test everything. I obtained a second CU 200 controller under warranty. The problem continued. Finally, someone at Grundfos sent my neighbor a new "field test" CU 200 (VO6), with new software. Note that these field test units are "version 6", not "version 3." I was able to obtain the only other field test unit, and neither my neighbor nor I are experiencing the overflow problem any more. I will copy in what the Grundfos guy wrote me when I asked for an explanation of the problem. Bottom line is, all new CU 200 controllers will have the new software. If you have a CU200 V03 controller and are experiencing this problem, I expect you could get a new CU200 V06 to replace it. Below is the Grundfos guy's explanation of the problem, and its solution.

    "Regarding the situation which allowed the pump to come on and run when the float switch was indicating a full tank, that problem has been corrected with a software upgrade. All new CU200 units produced after December 2012 have new software to prevent this from happening. I was not directly involved with the determination of the problem or the software solution. We have some very sharp software engineers that do that stuff. I just helped to coordinate a site visit where the problem was happening and also the testing of the prototype units.

    "When I say the issue wasn't widespread I mean as a percentage of CU200 controllers that we sell is was a small percentage. Obviously, for those of you that have experienced the problem it was critical. Therefore, Grundfos was very interested in determining the problem and getting it corrected.

    "As you may know, the CU200 and the SQFlex motor communicate via high frequency Mains bourne signaling. This is message packets that are transmitted over the power wires between the motor and the CU200. Messages from the CU200 to the motor must be "acknowledged". The instability of solar power first thing in the morning would allow the CU200 to power up and signal the motor to "stop" because the float switch was closed. Solar power is very unstable when the sun is at a steep angle on the panels. Due to this instability the motor could receive enough power to "wake up" and acknowledge the message from the CU200. After this happened the CU200 would no longer signal the motor to "stop". If the power from the solar array dropped below the minimum for the motor electronics and then came back up the motor would "awaken" in its normal condition which is run. This was primarily seen in systems with low voltage solar arrays. The new software has been designed so that the CU200 will periodically query the motor for its current status and will reissue the "stop" message if the motor is in "run" mode. This has proven to eliminate the problem."
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Re: Grundfos CU 200 and pump doesn't shut off

    Thank you BurningMom... I am sure this will be helpful to some folks out there.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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