Grundfos CU 200 SQFlex and 25 SQF-7 Low power.

Robert_WRobert_W Registered Users Posts: 14 ✭✭
Howdy. Haven't posted here in over a decade. Glad this forum is still around!'s my question(s).

Ive been using a CU 200 controller with the SQF-7 pump now (bought from NAWS) for over a decade. For the most part zero issues. I am quite happy with the set up. About 80 feet of head total to a 1500 gallon water tower. About 45 feet of head to spigots.

Recently we expanded orchard / garden and the need for more water became evident. So I have added 600 more watts to the system. I planned for this years ago to make sure all was expandable.

The original setup was 3 - 190 watt (570 watt total) 24v panels run in series to the CU 200. Multimeter showed roughly 100 to 120 volts and 4 to 5 amps give or take in full sun. All works fine but just barely keeps up with current water needs. CU 200 would show roughly 400 watts with pump running in full sun. Always thought this a bit low but acceptable. All is grounded with 4 seperate rods as we have quite sandy / clay soil and have had issues in the past but worked that out many years ago. 10 gauge wire run to the pump from controller is under 200 feet. last week I add 3 more 200 watt 24v panels for a total now of 1170 watts. Again all run in series. Multimeter is showing roughly 240 volts and 5 amps output from the panels to the CU 200. (Roughly 1200 watts of panel output as expected.)

However the LED readout on the CU 200 has only improved from 400 to 460 watts or so. And I am flummoxed as to why. I have checked each individual panel and M4 connector plus diodes / wiring and all is fine. I cannot put the meter on the output of the CU 200 as it throws an instant fault and shuts down. Thankfully it reset. Don't want to continue to try this as I'm afraid to fry something and right now its over 100 degrees and I'd be screwed without water.

The CU 200 is rated from 30-300 volts DC and 8.5 amps ...So we're well within specs. The pump curves are here.

At the original setup of 400 watts given the head the system was roughly matching the 10 gallon per minute as shown in the pump curve. But now with the upgrade its only showing 460 watts on the CU 200 controller even though the panels are outputting close to 1200 watts. (240 v @  5 amps). I expected at least in the 800 to 900 watt range on the LED of the controller...accounting for some loss... after having more than doubled the panel output.

The pump does seem to be outputting more water but according to the chart it should have more than doubled output if not almost tripled. Have not been able to take an exact measurement yet (need heat to subside first) but I don't think it's anywhere near tripled.

So why is the CU 200 controller power LED only showing 460 watts when its receiving 1200? Pump is rated to 1400 watts. Shouldn't it be showing a much higher wattage?

Thoughts? Am I missing something obvious?

Much appreciated .


  • Robert_WRobert_W Registered Users Posts: 14 ✭✭
    So this has been sitting for a week. If no one has any ideas on the issue may I at least ask if any one can supply any contact info for Grundfos Support?

    Their website is completely geared towards higher end corporate and I've searched and searched with zero luck to find support for these SQFlex systems.

    Would sure appreciate it.

  • JRHillJRHill Registered Users Posts: 115 ✭✭
    edited August 15 #3
    I have an 11SQF-2 that's been in service for 14 years. For household use I used a bank of Trojan golf cart batteries for nominal 48vdc power to the pump through a CU200. The panel and charge controller are irrelevant to this conversation but I'll say it is sufficient to run the pump full out and still put a few watts into the batteries. So for practical purposes voltage to the pump would've been in the area of 53 to 58vdc with the sun out and depending on the charge status of the batteries during the day or 49 to 51vdc at night and running strictly off the batteries. The 10ga run to the pump from the batteries is approx 160'. Making up a conservative value, lets say I have a 5% voltage drop so at the pump I should have 44 to 53VDC available. With the above numbers the CU200 reports pump draw of approximately 720 watts max. Regardless of pushing into pressure tanks or free flowing the system through the hydrants the pump wattage stays about the same at the same: 720 watts.

    But I also have the IO101 in the system so with the flip of the switch I can change from battery power to 120vac into the CU200 and on to the pump. So when connecting 120vac the pump has better than twice the voltage going to work for me. The 11SQF-2 would then draw around 780 watts and of course it pumped a very little bit more volume. But certainly the wattage didn't double nor did the work being done (volume and pressure).

    So if you are sure than the integrity of your connections throughout the system are good with zero corrosion, tight and with our friend the dielectric grease, I'd say you have what you have. I am curious about you getting 240vdc with the 6 24v panels in series. That must have been measured with the pump disconnected and open circuit?  My CU200 doesn't have a safety interlock that would do anything with the cover off so something doesn't sound right. As I recall any fault code is generated by the pump and set to the CU200 for display through the power leads. What error or Fault Code is displayed on the CU200? 

    Oh, lastly, the AC or DC that goes into the CU200 is what does out. All the CU200 does is give you a nice little display for some information and the ON/OFF button for manual operation or automatic shut down if a fault. I don't even use mine anymore and have bypassed it since I use the well tank pressure for on/off, the IO101 as a disconnect for DC and can shut the AC down by just unplugging it from 120vac. The CU200 is a rather expensive little box for what it does.
    Two systems: 1) 2925w panels, OB VFXR3648, FM80, FNDC, Mate3s, 240 xformer, four SimpliPHI 3.8; 2) 780w, Morningstar 30a, Grundfos switch, controller and AC/DC pump, 8 T105. Honda EU7000is w/AGS. Champion 3100. Miller Bobcat.
  • Robert_WRobert_W Registered Users Posts: 14 ✭✭
    There is no error code shown. It just shuts down and needs to be reset if I try to take a reading at the CU200 with the multimeter.

    And yes the 240 (241 actually) volt reading was open circuit. All panels run in series.

    I have a breaker disconnect that is used to shut power off to the system when needed in addition to the CU200 on or off.
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