DC pumping from deep well to cistern...

[BryanB]

Ok, this is my first post, except for my introduction. I live in the mountains of Puerto Rico and have a newly installed PV system that I don't think is working properly but that is the subject of another post. I have a 160' deep well with a 220v 3/4hp Grundfos pump that takes from 1000-1200w when it is on, which really drains my batteries (this is the pump that I have always used with grid energy). What I would like to do is replace it with a DC powered pump with dedicated solar panels and use the low flow when the sun is shining to fill a 3000 gallon cistern, which can then provide gravity fed water to the house. The following is what I think will work for me, but would appreciate any comments or advice!!!

1. Submersible Grundfos SQflex 3-SQF-2 (30-300VDC, 100-340w, 360' head, 3gpm) - The well is 160' deep, so this gives me plenty of vertical distance to move water to the cistern. I like that the pump will work with different voltages, just pumping less with a smaller voltage. Although it is pricier than some other pumps, the 15-20 year without service is a big advantage, as it is a hassle and costs me $225 every time I have to pull the pump. I also like that in an emergency I can use AC from the power company, the inverter or a gasoline generator.
file:///C:/Users/User/Desktop/SQF_Brochure_L-SQ-SL-010.pdf
https://thesolarstore.com/grundfos-s...ump-p-522.html (I'm not sure if I can post a commercial website, but it is just for the equipment details)

2. Three panels REC 240w, 8a, 29.9v in series for a total of 717.6w, 8a, 89.7v (is the excess in watts a problem?). These panels are available locally.

3. CU200 Interface box with water level switch, to turn off the pump when the cistern is full.

https://thesolarstore.com/grundfos-sqflex-cu200-interface-box-pump-controller-p-534.html

There is another possible component, but I'm not sure if this is necessary to switch over to AC, or if I can just use some simple manual control, like a transfer switch?
4. IO101 Interface box - Supposedly changes automatically to AC when it is available, but I would want to switch manually, because I want to preferentially use DC.

Thanks for any help you can give me and Happy New Year!!!

[bwkemp]

1. The grundfos pump is a good pump very few will argue with that. I would consider going to the sqf-6 or 11 to get you the most gallons a day.

2.those panels would work fine. The pump can use up to I belive 1200 watts (not the 340 you have listed. That might be a number for how many watts it takes to get 3 gpm from 160') but anyway even if you go over the max watts it will not hurt it and is okay.

3. Yes you can use that box with a separate switch to turn it off when the tank is full.

4.the cu101 box you can use to put power to it (in your case use a switch that when the tank is almost empty would turn it on for a few inches then shut it off and go back to solar) , or use some kind of a transfer box if you don't need it to be automatic. (you can plug the pump directly in with a 120 volt plug in but it isn't rated for dc to connect the panels with)

[MichaelK!]

I have a cabin in the mountains watered by a system similar to yours. It has a 1.5hp AC Grunfos pump that I power by solar. My running watts is about 2400W, and I have 4500 watts of panels to support that. Like you, I pump into a 5000 gallon storage tank positioned up the hill. However, I chose to go the AC route, and I'm very satified with the performance of my system. Basicly, I pump water only on bright clear days into the tank, then have on-demand running water because there's a one-way valve to keeps water from draining back into the well. I pump water 6-8 hours per day every two weeks or so in the summer when irrigation water is in high demand.

Rather than pulling the pump (which I can tell you is not something to look forward to) I'd recommend simply adding enough panels to support your pumping rate, which I'd say should be around 2400 watts or so. What kind of inverter do you have, and what's your system voltage.

[BryanB]

Thanks for the responses. The system voltage is 48v and the inverter is Schneider 4048. I had some problems with a newly installed photovoltaic system, but it turns out that the installers just didn't program the charge controller and control panel properly. Now is producing a lot more energy. I have used the pump when the sun is shining and the system is producing 2000-3000w, with no problem, so I could maybe just keep this pump and fill the cistern manually (and save a few thousand dollars), but at the same time I like the idea of making it totally automatic. What I don't think will work for me is to use the pressurized tank, because with that the pump can turn on when the sun isn't shining.

The well guy only charges me $225 to replace the pump, so that isn't too bad. What would be even better is to have the solar dc pump hanging above the ac pump, and have the option of using either. I have a friend in Australia who does that, but I do need to have enough standing water in the 160' deep well to have both submerged, and I don't know how much standing water there is. But I can get 500 gallons/hour in the cistern with the ac pump, so the well definitely has a decent amount of water.

[Mike90250]

I use a standard intermatic clockwork timer, and it is set to run in the sunny part of the day, I have a manual override to leave it off for winter, when sun is less reliable and I don't need to pump daily
I pump to elevated tanks and have pressure all night long.

[BryanB]

Thanks, Mike. The problem is that I live in the mountains in a tropical rain forest and sun isn't always reliable at the same time every day. What would be nice for me is to have some kind of "timer" that turns on when the charge controller is receiving 2000w or more.

Let me ask a newbie question: If my submersible pump uses 1000w and the charge controller is receiving 3000w, is the submersible pump running 100% off direct solar electricity, without using the batteries?

Another question: How do you get your system specs to come out under your posts? I tried to do it in settings but don't think it worked.

[Mike90250]

Thanks, Mike. The problem is that I live in the mountains in a tropical rain forest and sun isn't always reliable at the same time every day. What would be nice for me is to have some kind of "timer" that turns on when the charge controller is receiving 2000w or more.

You would want to trigger when the charge controller switches from ABSORB to FLOAT. The Midnight Solar "Classic" controller has an AUX output that can trigger on this. Other controllers may have that too. You want battery charging to be priority, you don't want the pump to suck enough power to prevent the absorb cycle from completing.

Let me ask a newbie question: If my submersible pump uses 1000w and the charge controller is receiving 3000w, is the submersible pump running 100% off direct solar electricity, without using the batteries?

Depends, If the batteries are charging with 2400 watts, there are only 600 solar watts left to run the pump. Later in the absorb cycle, the batteries are consuming less, and then there is more power to run the pump or other large loads

Another question: How do you get your system specs to come out under your posts? I tried to do it in settings but don't think it worked.

That's the Signature Line

[BryanB]

You would want to trigger when the charge controller switches from ABSORB to FLOAT. The Midnight Solar "Classic" controller has an AUX output that can trigger on this. Other controllers may have that too. You want battery charging to be priority, you don't want the pump to suck enough power to prevent the absorb cycle from completing.

Depends, If the batteries are charging with 2400 watts, there are only 600 solar watts left to run the pump. Later in the absorb cycle, the batteries are consuming less, and then there is more power to run the pump or other large loads

Ok, so DC energy from the panels can be directed by the charge controller either to the batteries or a load, and the charge controller preferentially directs it to the batteries?

And DC energy goes directly to the load via the inverter without entering or affecting the batteries if the system is already in FLOAT? In other words, if the batteries are charged and the system is in float, any excess DC energy from the panels gets converted to AC by the inverter without any chemical reaction in the batteries?

What happens to excess DC energy from the panels once the batteries are fully charged? It obviously gets wasted, but where does it go? Sorry for all the questions, but I don't know much about electricity.

[BryanB]

That's the Signature Line

It won't let me post more than 50 characters... you definitely have more than that!!!

[SunEagle]

It won't let me post more than 50 characters... you definitely have more than that!!!

For some reason Moderators are allowed more characters in their signature.

[littleharbor]

For some reason Moderators are allowed more characters in their signature.

It is frustrating and I don't understand why it needs to be so limited.

[SunEagle]

It is frustrating and I don't understand why it needs to be so limited.

I guess it is a reward for all of the abuse we get from the forum members.

[littleharbor]

I guess it is a reward for all of the abuse we get from the forum members.

Stop it some more, It hurts so good.

[Wy_White_Wolf]

I run my well solar direct for watering the orchard. You never mention how much water you need in a day. How much of the cistern will you use daily?

My setup uses a Shurflo 9300 series pump with a 120 watt panel and a LCB. There is a float switch in the 350 gallon cistern. I use only about 80 to 100 gallons daily in the summer. Pump is set 160' down with a static water level of 66'.

Originally I figured this would pump just under 2 gallons a minute. It has far exceeded that when the girls covered an old stock tank into a swimming pool. It fills the ~500 gallon tank in about 3 hours on a sunny day. Summer time there just needs to be enough sun to slightly make a shadow for it to pump. Cold winter days on a fully overcast day it will still pump at a slow rate.

WWW

solar1.jpg

[Mike90250]

Ok, so DC energy from the panels can be directed by the charge controller either to the batteries or a load, and the charge controller preferentially directs it to the batteries?

Not quite, The charge controller output is directly connected to the batteries. Lets call the 3kw inverter the load. The Load is also directly connected to the battery. The charge controller merely controls the voltage coming out, and if the battery is discharged, it soaks up the power. If the load calls for power, it also takes power, and the battery charges slower.

And DC energy goes directly to the load via the inverter without entering or affecting the batteries if the system is already in FLOAT? In other words, if the batteries are charged and the system is in float, any excess DC energy from the panels gets converted to AC by the inverter without any chemical reaction in the batteries?

Well, mostly, the battery is in float, and if a load comes along and pulls power from the system, the controller simply adds more power to the keep the float voltage stable.

What happens to excess DC energy from the panels once the batteries are fully charged? It obviously gets wasted, but where does it go? Sorry for all the questions, but I don't know much about electricity.

The controller simply does not pass the power on to the batteries, it never leaves the solar panels. and no harm is done