SQFlex configuration options and their effects

Ravemind

Hi All,
I'm putting in an SQFlex pump for my off grid eco retreat center. We had been using a gasoline pump to fill a 5000 gallon tank 30 feet up on a tower. We are oh-so-tired of the noise and the hassle of pulling the starter a few times a day. 
I already have pump, cu200 and io101 control boxes and 1500 watts of panels. 
I was originally going to connect the panels direct for daytime pumping with AC from our facility solar as a backup. The AC is manual start and I'm worried having to turn it on will happen more often than I expect. So plan number two is to go with the added 48 volt battery bank option using the load terminal on a charge controller (Midnite Solar Kid) for a completely autonomous system. 
In the brochure they show the battery connected option feeding a pressure tank rather than going straight into a tank. Will it still work fine going into a tank rather than a pressurized system? I've read that the pump will be 20% less efficient at 48 volt vs 100+ volt, but are there other ways it will perform differently? Will it it still pump at 80% of the calculated gpm? Or is it limited in some way to fewer Amps or something?

The Midnite Solar Kid makes the full 30 Amps available to the Load terminals.

Thanks,
Jon

18 x 250 panels, 2 x Flexmax 80s, Schneider Electric 4024 inverter. 

mike95490

1) Are you using a pressure tank, or simply Gravity feed ?
2) Do you need to refill the tank at night ?  Will it last you through a cloudy day?

If you need to, increase the tank size so it has no need to run at night.   Otherwise, why use the SQFlex off battery, just run it off it's own solar array. 

BUT  I caution you, triple check your pump curves.   If you are starting the gasoline pump "a couple times a day" to fill the tank, a single solar pump may not be enough.   You may be better off with a beefy inverter, VSD controller, and a standard, cheap well pump.

jonr

I'm curious - are you really using > 10,000 gallons/day in an eco retreat?  Yes, pumping into an open tank is fine.  48V will limit the pump power to 403W (vs 1400W) or about 40% of the GPM.

Anawa

I assume that you are currently distributing the water via a piping network from the tank that you "manually" pump a couple times a day. How are you pressurizing from the tank to the outlets, or is it all gravity using the the 30 foot head?

Paul
in Georgia

Anawa

If you're either using some pumping mechanism (i.e. booster or diapham pump) that draws water from the tank and then pressurizes it or simple gravity, you will need to purchase the float switch option for the SQ that shuts-off and turns-on the pump at a predetermined levels. It's wired directly into the controller.

Paul

Ravemind

Hi, thank you all for the information. I recieved the answer I was looking for.
My main question was about how the pumps behave when connected to a battery bank so I didn't double check the numbers I was putting up. I did all the calculations a while ago and forgot the details.
The tank is actually 5000 liters, not gallons. So 3 to four of those depending on how much we water the palm trees. Sorry if that threw some of you for a loop. I was too lazy to go back and check.

Even with the reduced gpm I will be fine. I should get around 15 gpm with the sqflex 25 sqf 3 I bought from NAWS. Total head is around 50 feet. In a pinch we can use AC to get the full capacity for filling a pool etc.

We are entirely gravity fed and it works well. 40 people using the bathrooms and showers throughout the day.

Increasing the size of the tank isn't really an option since it is so high. We may switch to pressure in the future, but for now we are happy with the raised reservoir.

For the pump I want to experiment a bit and am looking at some slightly used electric car batteries with a BMS. The Grundfos calculator said I need 250 Ah of lead acid batteries in order to have a couple days backup. That's a lot of lead. Let's see if I can use 80 pounds of Tesla battery instead. Maybe I'll post that experience elsewhere in the forums.

Thanks again for your responses.