[RE-wrenches] Design help for solar water pumping application

jay peltz jay at asis.com
Sun Jun 14 18:23:57 PDT 2009


HI Allan,

I would like to throw out that there are other options.

You could use timers with electric valves if you had some idea of how  
much water each system might use, set a timer for each system.

Or you could use float valves with relays and electric valves to fill  
each tank as needed.

Just depends on how important the water is.

jay

peltz power


On Jun 13, 2009, at 11:34 PM, Allan Sindelar wrote:

> I agree with Brian and Mark on most of their comments, but here’s a  
> bit more:
>
> Mark is right, there’s no way to separately control filling two  
> tanks at different levels. I didn’t read that section very  
> carefully. Brian’s float valve approach and sequential filling is  
> about the only approach. But given that a float valve failure could  
> be catastrophic (5,000 gallons flowing back down) you might want to  
> add a check valve on the line to the higher tank, if the line from  
> the well to the two tanks is shared.
>
> Remember, too, that the total dynamic head is measured from the  
> water level in the well, not the pump level. That means your tdh on  
> the far well is something less than 220’, or about 97 psi (plus  
> friction head). Assuming you don’t have 3,000 feet of signal cable  
> in the ground, the P2Flow approach would likely work well. Their  
> 0-100psi transducer has a resolution of 0.1 psi. Make sure to add a  
> check valve where the line leaves the well, so as to be unaffected  
> by fluctuations of the water level in the well, and put the pressure- 
> sensing transducer after the check valve, so that it only measures  
> head determined by the tank level. We’re working with a similar  
> application here in New Mexico, so I’m learning this too.
>
> One respectful disagreement with Mark: The 3SQF-3 Grundfos is  
> officially rated to 656’. I hear it will do well more than that, but  
> no direct experience. I would not recommend the Lorentz after  
> multiple failures back when Dankoff (now Conergy) was the sole North  
> American distributor. (We are in Santa Fe so do will call pickups  
> for most orders. Don’t ask me to describe seeing pallets of junk  
> Lorentz pumps outside their warehouse, waiting to head to the  
> recycler.)
>
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.positiveenergysolar.com
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> ] On Behalf Of Brian Teitelbaum
> Sent: Friday, June 12, 2009 2:18 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Design help for solar water pumping  
> application
>
> Hi Lee,
>
> I don’t know how the two tanks are laid out physically, but if they  
> happen to be installed in a way that you could run one pipeline up  
> to the tank at 200’ and go from there to the other tank, you might  
> try using a float valve in the lower tank and a float switch in the  
> upper tank. The lower tank’s inlet would just be “teed” off of the  
> pipeline going to the upper tank. The lower tank will fill first,  
> being the path of least resistance. When it is full, the float valve  
> closes sending water through the pipeline to the upper tank. When  
> the upper tank is full, the float switch would turn the pump off.
>
> The distance to the float switch in the upper tank is a bit far, but  
> you should be OK if you use a larger gauge wire than usual. I think  
> that 18 gauge would be fine, but 16 gauge would be better. If it is  
> line-of-site, you might look into doing a wireless control , but  
> that would mean that you need a small PV module and a battery up  
> there.
>
> Go with the 1 ½” pipe
>
> Not to contradict Mark (Ok…I guess that I am!) The Grundfos model 3  
> SQF-3 will do 600’
>
> As to Allen’s comment about array size, he is correct about the pump  
> drawing a max of 900W. However, if you only put a 900W array on the  
> pump, it will only pump at max volume at mid-day. If you put a  
> larger array on the pump, the array will produce 900W in less light  
> (morning and afternoon) and produce a lot more gallons per day  
> (GPD). The GPM figure of a solar pump is really only relevant for  
> making sure that you don’t over pump a low yielding well. It’s  
> really GPD that counts. That 1.36kW array might produce 900W at 9AM  
> and 3PM, giving you a solid six hours of max output pumping. No  
> problem over sizing the array – the pump will only draw what it  
> needs. If you have really good exposure to the sky, you can use a  
> tracker to increase GPD instead of over sizing the PV.
>
> According to my info, with 250” of head (220’ plus pipe friction  
> loss) you can get about 2000 GPD (summer) with the Grundfos model 6  
> SQF-2 and about 700W of PV in a fixed array, with a peak flow of 4.5  
> GPM. Adding more PV will give you more GPD. With the model 11 SQF-2,  
> you can get up to about 4300 GPD with a 1750W array at that head. If  
> you needed even more water volume, and the well produced it, you  
> could even put two pumps in the well (with separate arrays). I had  
> one dealer who managed to put two Grundfos pumps down a 5” casing!  
> He said that it all went easy….but I don’t believe him. He did have  
> a curious issue though. He said that if he turned one pump off with  
> its CU200, both pumps would shut down, even though the other pump  
> was not connected to that CU200. He couldn’t just run one pump. I  
> never did talk to Grundfos about that.
>
> Cheers!
>
> Brian Teitelbaum
> AEE Solar
>
>
>
>
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> ] On Behalf Of Mark Dickson
> Sent: Thursday, June 11, 2009 9:40 PM
> To: 'RE-wrenches'
> Subject: Re: [RE-wrenches] Design help for solar water pumping  
> application
>
> Hey Lee,
> Allan is right in that the WINcaps software is a lifesaver and  
> FREE!  Not to contradict Allan, but I do not see a feasible way of  
> using two float switches in separate tanks with only one pump  
> controller.  Also, the 3000’ distance is a little far—they usually  
> recommend a max distance of 1600’ for the float switches.  Lastly,  
> if you are ever worried about the head, the Lorentz pumps can pump  
> up to 760’ --more than double the recommended for Grundfos.
>
> I highly recommend Genpro Energy Solutions as a pump distributor for  
> both of those brands.  They always answer the phone, are personable  
> and return emails (hint, hint Conergy)!
>
> Best,
>
> Mark Dickson
> Oasis Montana Inc.
> www.oasismontana.com
>
> www.grid-tie.com
>
> www.PVsolarpumps.com
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> ] On Behalf Of Allan Sindelar
> Sent: Thursday, June 11, 2009 2:28 PM
> To: 'RE-wrenches'
> Subject: Re: [RE-wrenches] Design help for solar water pumping  
> application
>
> Lee,
> You can get Grundfos’ WINCaps software from your RE or pump  
> supplier; some will run the sizing for you (Jeremy at Conergy does  
> for us). I didn’t check your head and flow, but I would expect  
> that’s about your only good pump choice at that head. Add a tracker  
> if you need greater summer output; don’t attempt batteries as a  
> solution. If usage occasionally exceeds output, add an IO101 control  
> and allow the pump to run off any AC source at night. A tiny 1,200W  
> inverter/generator will work at sea level. Use a CU200 controller to  
> allow a float or level detector switch to turn off the pump when  
> tanks are full. Mercury-based float switches last longer in signal  
> circuits that carry no current. If you can’t use a float switch  
> because the lines are already buried, look intowww.P2Flow.com for  
> pressure transducer-based control. Read the website info, then call  
> Britt there with your specific application. That array sounds  
> oversized, as the pump draws a maximum of 900 watts. Hope this helps.
>
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.positiveenergysolar.com
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> ] On Behalf Of Lee Bristol
> Sent: Thursday, June 11, 2009 1:26 PM
> To: RE-wrenches at lists.re-wrenches.org
> Subject: [RE-wrenches] Design help for solar water pumping application
>
> Solar Water Pumping Wrenches,
>
> We normally don't do solar water pumping but a friend asked for some  
> help designing his system.  He has one well and two 5,000 gallon  
> reservoirs to fill up.  The average usage is expected to be about  
> 2,000 gallons per day but may be higher in the summer.  The tanks  
> will have level detector switches to sense when the tank is full.   
> The site is near Leesburg, VA.
>
> The problem is to design a control system to turn on the pump when  
> one or both of the tanks needs water and to shut it off when both  
> are full.  The closest tank has a head requirement of 200 feet (pump  
> to tank) and is 300 feet from the well head.  The second tank head  
> requirement is 220 feet and it is 3,000 feet from the well.  The  
> pipes are expected to be 1.25 or 1.5 inch.
>
> A Grundfos SQFlex 6 SQF-2 pump with 1.36 KW solar was recommended,  
> 360 foot head, 360 gph.  I think that this would provide the lift  
> but not the quantity.  Hmmmm, what valves and controls would you all  
> suggest?
>
> Thanks!
> Lee
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