[RE-wrenches] Grundfos SQFlex

[Brian Teitelbaum]

Hi Ron,

What you describe with using a pressure switch and pressure tank, and just
running the pump with 240 VAC, is fine. You don't need the CU-200 to do
any of that, if all you are doing is switching AC. The diagnostics is
nice, but probably not worth the cost in this kind of simple setup.

One issue though. The SQFlex pumps are not exactly instant-on. There is a
slight delay between when power is applied and the pump starts. Just make
sure that you use a large enough pressure tank to keep the pressure from
dropping too far before the pump starts filling it. You may have to raise
the starting pressure on the switch a little above where you set the
minimum pressure, to let it fall some at startup.

When it becomes time to replace the pump (hopefully many years from now),
I would just go with a Grundfos SQ straight AC pump instead of the Flex
model. If you are not going to be using a PV-direct arrangement, there is
not much advantage in using the Flex pumps.

Brian Teitelbaum
AEE solar



-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Ron @ earthRight Solar
Sent: Monday, October 20, 2014 6:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Grundfos SQFlex

Hello water pumping Wrenches, I have a customer who has a Grundfos SQFlex
11 pump and he is getting connected to the grid. He will still have his
battery back up charged by PV and wants to look at the most efficient way
to operate the pump. It seems to me that neither the IO101 or the CU200
really is needed and he could just wire directly to the inverter output at
240v via a pressure switch on a standard pressure tank for most efficient
operation. Although this doesn't give any access to the Grundfos built in
diagnostics that display on the CU200.

Would you recommend keeping a CU200 in the system or is it overkill? With
the CU200 the max voltage is 120 whereas without it I can go with 240v and
a more efficient operation. unless I am missing something.

Ron Young
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