Grundfos SQFlex MPPT function

mxsolar

I am about to install a Grundfos SQFlex submersible pump and I have a couple of questions about selecting the right PV modules to run it.

The pump has an internal MPPT circuit and according to its spec sheet, its maximum input current is 7 amps.

My questions are:

Can I use PV modules with a high current like the Evergreen ES-A-200 (Imp=11 amps) without damaging the pump?

Will the MPPT circuit convert any excess current into usable voltage or will it just be wasted power?

I understand a MPPT charge controller converts excess voltage (from I-V curve Maximum Power Point) to current thus increasing energy available to charge batteries. However, I don't know if a MPPT circuit, like the one in this pump will bring down the current and maintain power via increasing voltage.

Can anyone comment on this?

Thanks.

BTW, the reason I am considering these modules is because I am able to get them at a very low price compared to others.

mike95490

Re: Grundfos SQFlex MPPT function

I think the MPPT function works in down-converting a 70V array, to the motor voltage. Extra available amps from PV won't hurt, but you need to supply the minimum voltage the MPPT wants to see.
Excess amps would be wasted, but then again, your 11A panels will nearly always have 7A avaib to the pump, even with slight haze, clouds or off angle sun. A 7A panel would starve the pump in the same conditions.

Dave Angelini

Re: Grundfos SQFlex MPPT function

How deep and which model? It sounds like you are worried about the wrong parameters.

mxsolar

Re: Grundfos SQFlex MPPT function

I have two wells but at this time I am installing only one pump, the other one will come later. The first well is 200 ft deep and the pump model is 11-SQF-2. I will be pumping about 7 GPM.

The other well is only 70 ft deep, I am planning on using the same pump, and the water requirement is very similar.

Thanks.

westbranch

Re: Grundfos SQFlex MPPT function

DO you mean that those depths are the static levels or is that the depth to which you will lower the pump?
What is the recovery rate of the wells?

Eric

mxsolar

Re: Grundfos SQFlex MPPT function

These are the levels at which the pump will be lowered. The well yields way more than I will be pumping.

westbranch

Re: Grundfos SQFlex MPPT function

so then what is the vertical distance the pump has to lift the water?
this allows evaluation of the pump vs delivery vs power demand.
Why 7 GPM?

NAWS shows:
Model Type Max Head Max Flow PV Watts (Min-Max)
3 SQF-2 Helical Rotor 360 Feet 3 GPM 100-340
3 SQF-3 Helical Rotor 600 Feet 2 GPM 130-600
6 SQF-2 Helical Rotor 360 Feet 6 GPM 100-650
11 SQF-2 Helical Rotor 300 Feet 11 GPM 50-900

looks like you will easily get the 7 gpm you need as it will deliver 11 gpm @ from 300 feet... maybe more pump than you need.

What did Grundfos say about the power needed for your static level? their website is less than helpful..
HTH

Eric

mxsolar

Re: Grundfos SQFlex MPPT function

Eric,

I think I have the system sizing figured out. I think I have the right pump and I think I have calculated the PV wattage correctly.

My question, though, is if I can use a module that puts out way more amps that the pump's specs say it can take (refer to my first post).

Thanks!

mike95490

Re: Grundfos SQFlex MPPT function

mxsolar wrote: »

Eric,

I think I have the system sizing figured out. I think I have the right pump and I think I have calculated the PV wattage correctly.

My question, though, is if I can use a module that puts out way more amps that the pump's specs say it can take (refer to my first post).

Thanks!

It's ok, and the pump may run at a faster allowed speed, till it reaches it's max, as long as you stay under the Max Voltage Allowed.

PhilS

Re: Grundfos SQFlex MPPT function

mxsolar wrote: »

I think I have the system sizing figured out. I think I have the right pump and I think I have calculated the PV wattage correctly.

My question, though, is if I can use a module that puts out way more amps that the pump's specs say it can take (refer to my first post).

I had the 6-SQF-2 installed last fall and it's GREAT!! I find it simply amazing that you can put just about any voltage, AC or DC, to these things and they work.

To answer your question, mine is powered by a Xantrex SW2512. Just because the inverter will output 2500W, the pump only draws what it needs/wants. Yours would be the same. The pump will draw what it needs just like any other electrical load, as Mike said.

I also got the CU200 controller... all indications at a glance including watt draw, dry well and full tank. I had to engineer an easy relay addition since the Grundfos comes designed to shut off when a float signals that the 'livestock' tank is full. I needed it to shut off when my pressure bladder tank is full.

Windsun

Re: Grundfos SQFlex MPPT function

mxsolar wrote: »

Eric,

I think I have the system sizing figured out. I think I have the right pump and I think I have calculated the PV wattage correctly.

My question, though, is if I can use a module that puts out way more amps that the pump's specs say it can take (refer to my first post).

Thanks!

You can, but much better to use high voltage panels. The SQF will down convert high voltage, low amps to what the motor needs. It will not "up" convert high amps, low voltage - and you need a certain minimum voltage. Higher voltage also means small wire size needed.