Grundfos SQFlex Solar Panel Question

I have a SQF12 pump in my well, currently powered by AC, manually switched on when I need to fill my tank. I have a bunch of solar panels laying around though.

So, my question is, can I effectively hook a couple of panels straight up to it without a controller? Practicality of switching on/off etc aside, I'm just wondering if I can directly wire one or two of my 345 watt panels directly to it.

Thank you.

chetwynd said:

I have a SQF12 pump in my well, currently powered by AC, manually switched on when I need to fill my tank. I have a bunch of solar panels laying around though.

So, my question is, can I effectively hook a couple of panels straight up to it without a controller? Practicality of switching on/off etc aside, I'm just wondering if I can directly wire one or two of my 345 watt panels directly to it.

Thank you.

Click to expand...

Yep. The Grundfos control boxes are wayyyy overpriced. I built my own with analog meters, a wind-up spa timer, and a big toggle switch.

You can get the pump performance curves from Grundfos and figure what panel capacity you will need vs. static level and GPM you want.

SQF's are very cool. I call them "convertors of sunlight to water."

I just tried a quick lookup of SQF 12 specs and I am not seeing a SQF 12 model in the solar series.

Typo in your original post? Maybe one of the 1.2XXXX series?

v_green57 said:

I just tried a quick lookup of SQF 12 specs and I am not seeing a SQF 12 model in the solar series.

Typo in your original post? Maybe one of the 1.2XXXX series?

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Sorry -

Grundfos SQFlex 11 SQF-2 Solar Submersible Pump​

v_green57 said:

Yep. The Grundfos control boxes are wayyyy overpriced. I built my own with analog meters, a wind-up spa timer, and a big toggle switch.

You can get the pump performance curves from Grundfos and figure what panel capacity you will need vs. static level and GPM you want.

SQF's are very cool. I call them "convertors of sunlight to water."

Click to expand...

Cool! That's beyond my skillset for sure, but very interesting. I agree, their controller decides are cool but expensive.

v_green57 said:

Yep. The Grundfos control boxes are wayyyy overpriced. I built my own with analog meters, a wind-up spa timer, and a big toggle switch.

You can get the pump performance curves from Grundfos and figure what panel capacity you will need vs. static level and GPM you want.

SQF's are very cool. I call them "convertors of sunlight to water."

Click to expand...

The constant pressure controllers are expensive but you can just run a regular spring pressure switch if you want.

As long as you don’t mind the pressure dropping to 40 before pump comes on.

If my CU301 ever goes out again I’m converting to a regular pressure switch and then adjust the on/off.

Ah, that's better...


Back in 2008, I did a "proof of concept" first run on my well with two 175W Suntech panels, some wire, and an empty milk bottle. No fancy controls needed.

v_green57 said:

Ah, that's better...

https://product-selection.grundfos.com/products/sqflex/11-sqf-2-95027335?pumpsystemid=2364665785&tab=variant-curves

Back in 2008, I did a "proof of concept" first run on my well with two 175W Suntech panels, some wire, and an empty milk bottle. No fancy controls needed.

Click to expand...

Just pumps whatever power it gets while the sun is up eh?

You pumping into storage tank?

Nobodybusiness said:

Just pumps whatever power it gets while the sun is up eh?

You pumping into storage tank?

Click to expand...

Yup. I wind up the spa timer for a few hours so I can safely go do other stuff and not worry about overfills, and it does its thing.

I have two 1200 gal. underground potable tanks and one aboveground ag and yard use 2500 gallon. The potables are pumped to place of use by Shurflos. The ag tank is gravity.

Nobodybusiness said:

Just pumps whatever power it gets while the sun is up eh?

You pumping into storage tank?

Click to expand...

Yes, that is exactly it. Actually I have three 8000 gallon tanks that I used to irrigate my property.

Nobodybusiness said:

The constant pressure controllers are expensive but you can just run a regular spring pressure switch if you want.

As long as you don’t mind the pressure dropping to 40 before pump comes on.

If my CU301 ever goes out again I’m converting to a regular pressure switch and then adjust the on/off.

Click to expand...

That is basically my plan for the pump that comes out of my giant storage tanks and sends water to my orchard. I have 350 fruit trees, and approximately 550 boysenberry and Blackberry plants. It’s a handful.

I guess what I’m trying to figure out and accomplish is using my extra solar panels to power the pump to keep my storage tanks full, without having to flip the breaker on which just feeds directly to my well pump (sq flex) without any other mechanism in between. I don’t really need protection in case the well goes dry, because that is definitely not happening. It would be nice to have an on off switch like one of the controllers they sell, but I drilled this separate well which is 200 feet deeper than my house well, specifically because I want to Use a lot of water and not really think twice about it.

Anyway, my only experience with solar is micro inverters. Is it just a matter of running a handful of panels in series? Positive on panel one to the negative on panel two, and the negative on panel one to the positive on panel two and those two going directly to the pump? I realize that is not the best set up is that effectively how it should work? It was home I’d post a quick drawing of what I mean.

It looks like my panels are 345 W, approximately 40 V or whatever. I’ve read that the pump likes to run at over 100 V, so is it just basically three or more panels in series? Do I need to increase the amperage by running any in parallel?

Use the pump curve chart on the link I sent to figure apx. what yield you will get from a given power input to the pump, given a known static water level. That should get you started.

All those trees...do you have any ballpark idea of how much water daily you need in growing season? That will also figure in. What you would like to do for completely unattended operation is pump daily what you will need that day (+ a little extra). That can be regulated by choosing the appropriate input power to the pump.

With such a big operation though, you might need to implement some kind of float switch to stop the pump when the tanks are full in order to keep them full year-round as your "solar day" will always be changing.

I have a very similar setup, i have a Grundfos 11 sqf 2 and the cu 200 controller, running solar direct, it is pumping to a tank that feeds everything by gravity flow, I have a float valve in my tank, when full it turns off the pump via the cu 200 controller.
I also have 120v power at my pump from my off grid solar system, if I am low on water and i don't have enough sun or it's dark, I switch the input power to the cu 200 with a simple plug and I am pumping water. I just switch it back when the sun comes up.
This setup requires float valve wires to be ran all the way to the tank.
The cu 200 is expensive but it works,
I saw growatt has a solar pump controller but I have no experience with it.

"This setup requires float valve wires to be ran all the way to the tank."

Yep, I ran some 6C wire with the PEX btwn. the well and the place(s) of use about 800 ft. away with the intent of using it for control purposes. Haven't used it yet. It's about a 5 minute walk down the hill to the well to turn the spa timer, and the dogs love it as do I. I also prefer to watch the gauges as things start up "just because". Have never had a problem, but the SQF I am using can pump to 500' head and that equates to 200+ PSI +/-. I blew up a hose once with that pressure due to an unanticipated restriction downstream. Lesson learned. Now have a PRV installed that fires off at 100PSI.

A pressure relief valve is a smart idea, I am going to add one to my setup