Solar well pump on / off control

Eric_R

Is there a way to control the solar well pump to turn off once the water tank is full?

Details:

The existing 5,000 gallon water tank is 350' higher in elevation than the well pump and 1,400 feet away as the crow flies. 

The existing system is run the generator till the tanks is full. There is no float or conduit running to the existing tank.

I will be adding another 5,000 gallon water tank on the other side of the property at the same elevation. 

Would manual floats in the tanks and a reverse pressure switch work?

Is there a wireless option? 

I dont want to waste water and let the tanks over flow.

mike95490

I used a conventional tank float switch, and wired it into the contactor for my AC pump.  Had to run 800' of control line wire from the tank to the pump controller, but it does work,  Wireless, has the problems of low battery and one end won't work, so you still end up doing it manually

Anawa

Looks like you've got an interesting situation Eric_r.

Yes, float switches as mike95490 will work, but since your tanks are separated they will probably have different water elevations. Thus, which float switch will control the pump? No problem if the tanks use the same amount of water and their respective water levels remain constant. Probably not reality. Is this a scenario that you have? If so, some very creative solutions will need to developed.

What is your current status in this endeavor?

Paul
in Georgia

vtmaps

Eric_R said:

Would manual floats in the tanks and a reverse pressure switch work?

In principle, I don't see why it won't work. 

As a practical matter, there may be some issues.   In a typical installation the pressure switch is at the pressure tank.  The pressure at the pump is higher than the pressure at the pressure tank.  

In the scheme that you propose, the pressure switch will be near the pump, therefore it will have to be adjustable to higher pressures.  Your pump needs about 150 PSI just to fill the pipe to your water tank...  the switch will need to turn off the pump at (at least) 175 PSI.  Note: the actual pressure setting is a function of the pipe diameter and length, and the desired gpm (assuming the pump can achieve the desired pressure and flow).

If you have too much pipe friction, the pressure difference (while pumping) between the pump and the tank will be greater than the 150 PSI that is due to the 350 ft elevation.  It may be great enough to shut off the pump.  When the pump shuts off the pressure difference will be due elevation alone and then the pump will turn on.  This can happen several times per minute and may wreck your pump.

Before I can say whether your scheme will work, I need to know the pipe diameter and the pump specs.  Then you will need to find a pressure switch that can work at the high pressure needed.

--vtMaps

Hill_Country

Eric_R, not sure if this will help you or not, but I read through the following link (http://forum.solar-electric.com/discussion/4157/pumping-to-a-storage-tank/p2 ) about a rancher that had multiple wells and multiple storage tanks and how he was trying to figure out how best to transport the water to keep his cattle troughs full.  I know it is a MUCH different setup that what you're facing, but perhaps it's another source of 'creativity' for your situation?  There were several proposed solutions, some of which might apply to your situation.

I do not claim to have any experience in pump/distribution design, but what if you did something that's time based, rather than pressure based?  Could you do something where you estimate how much time it takes to fill up a tank (from empty, or from 1/4 full, or whatever) and then put a timer on the pump to run it that long?  It would still be manual in that you'd need to be able to determine when a tank is empty/full to even know to turn it on...which begs the question:  If you can see the two tanks at all (line of sight via binoculars/spotting scope), could you put some sort of indicator when it's almost/completely full, or completely empty, or half way full or something like that?  If you knew it was half full (yes, I'm an optimist), and you knew about how long it takes to fill it from half full, you could run the pump for that length of time.  Just a thought...it's all about keeping it simple!

Hope this helps...

BB.

And figure out what could happen if something fails.

For example the stop switch fails and water pumps/over flows the tank. Would the water erode the dirt/support under the tank/flood your home.

-Bill

Anawa

A simple diagram of your current and a diagram of what you are proposing would be very helpful. You may have a "Ah-ha" moment by just laying it out on paper. I think it would also be helpful for the rest of us to be on the "same page", too.

Paul
in Georgia

Anawa

Apparently you manually shut-off the pump by visually monitoring the tank. Is this correct? 

Paul
in Georgia

Eric_R

Here is some more information regarding the project. This should really help to clarify some things and get a good solid design down.

Eric_R

The current situation is this. I go and check the existing water tank for the water level and see how many gallons are in it.

I then calculate how many hours I need to run the generator and fill the tank to full capacity.

The current 220 volt well pumps about 11 gallons per minute. So I get about 700 gallons per hour of run time.

Eric_R

I think I may have figured this out. Let me know what you guys think.

The existing water tank is at an elevation of 1750 feet and the proposed new tank will be at an elevation of 1800 feet.

The grundfos 6 SQF-3 pump can pump with a total of 800 feet of total dynamic head. The pump should only see about 418 feet of total dynamic head.

I will put float valves that will shut off the inlet port on each water tank. The lower tank will fill up first and the float will shut off from allowing it to fill. Then the upper tank will fill to the top and the float valve will shut off and stop that tank from filling.

I will put a reverse pressure switch down at the well pump near the solar well pump controls to turn the pump off when high pressure is reached.

I will put a pressure tank on the inlet pipe at the upper water tank to give me a higher pressure reading down at the well where the reverse pressure switch is.

I would then calibrate it so that the solar well pump will turn on when the pressure is low enough that the tank has dropped to 4000 gallons or so.

I would then calibrate the pressure tank to pressurize the system high enough to activate the reverse pressure switch at the high pressure setting.


Does this make sense?

Option 2

My other idea was to add a 500 gallon tank up higher in elevation to act as a pressure tank with no float. When the pump feels That tank up it will then read higher pressure at the pressure switch and turn the pump off and when the water draws out of that small tank down to the bigger tank it will sense the pressure drop from head and then turn the pump back on.

Does this make sense?

Eric_R

I think I found my wireless option.

http://fuelminder.biz/Images/gallagher/gallagher/wireless_pump_controller.jpg

vtmaps

Eric_R said:

I think I may have figured this out. Let me know what you guys think.
<snip>

My other idea was to add a 500 gallon tank up higher in elevation to act as a pressure tank with no float. When the pump feels That tank up it will then read higher pressure at the pressure switch and turn the pump off and when the water draws out of that small tank down to the bigger tank it will sense the pressure drop from head and then turn the pump back on.

Does this make sense?

I don't understand why you want either a pressure tank (option 1) or a 500 gallon tank higher up (option 2).  Just put a float valve on the main tanks and when the tank is full the valve will close and the pressure will rise at the pump and shut off the pump.  Of course, if you are drawing water (or have a leak) from the storage tank, the pump could start cycling on and off too fast... is that why you want a pressure tank?  The solution is to have the pressure switch shut off the generator rather than the pump.  It seems to me that would be a better solution because you don't want the generator running after the tanks are full and the pump has shut off.

--vtMaps

Anawa

Thanks for the images, your piping layout helps me better understand what you up against and what you may be planning.

I like simple stuff and I agree, in part, with vtmaps. I have an adversion relying on mechanical devices that rely-on electronics that rely-on other mechanical devices that rely-on enviromental conditions, etc. Obviously, greater the number of these connections, greater is the number of potential failures and since your installation is in the "boonies", you may want to consider as few of these as possible.

I would suggest that you install a float valve at tank 1 (elev 1754) to shut-off the water flow when that tank is full. Hopefully, you are filling from the top and the valve can be fitted onto the outlet. Image starting with "6EOM..." that you attached shows this installation. Then, I would install a float switch at tank 2 (elev 1800) to shut-off the pump when that tank is full. If you have not started construction, you can lay a signal cable in the pipe trench to tank 2. Note: I would lay a cable to tank 2 during construction just in case you ever want a float switch option.

The devil is in the details. To begin, the attached images suggest that you intend to install a solar array to drive the pump. Is this correct? Have you settled on the Grundfos SQF pump? If so, this is an excellent choice. Do you intend to install the solar array as you install tank 2?

Paul 
in Georgia

Eric_R

The problem with the float switch in this situation is that it is limited to 1600 lineal feet in distance away from the controller.

Is there not a limit to the length of wire for a float switch?

For the construction of tank number two the new pipeline trench will be about 3,500 lineal feet.

I intend to install the solar well pump this year and then the second tank next year.

Eric_R

Pressure switches typically have a wide range between the on-off psi settings. So by adding a pressure tank I would artificially increase pressure up at the tank to simulate the difference of 20 psi that the switch would use for the on/off pressure.

The 5000 gallon water tank is about 10 feet tall. So the pressure at the water tank from when the level is full to the level at empty is only 4 PSI difference.

So by the time the reverse pressure switch would be signaled to turn back on to fill the tank, the tank will already have been completely drawn down and empty.

Tumi 4 PSI is not a huge difference to expect a pressure switch to be sensitive enough to detect in such a short elevation change from the tank being full or empty.

This would then prevent the pump from wanting to cycle on and off easily or quickly if I am using water during the day while the pump is running and the tanks were full.

I figured this would be a way to create nice kind buffer to prevent over cycling of the pump.

I guess another way to do this would be to have a pressure switch down below and then install some type of time relay that would only allow the pump to turn on after 2 hours or so after receiving a signal that the tank is full.

Dave Angelini

Pressure switches can easily sense 4psi. The place I worked built them for Lockheed's Atlas rocket.

I like being outdoors and so I do not mind just setting a timer and controlling the pump the old fashioned way.

If I was doing this for unattended I might just set an electric timer and if it overflows a little, maybe I plant some romaine lettuce nearby.

I probably do not understand this application really well....Like if you have to run a generator anyway why be concerned with making this automatic?

westbranch

If you can see the tanks from a good distance, why not use a mechanical float gauge on the outside ad when you see it is full enough shut off the pump...  there is a thread about that item here somewhere, I think the solution is from NZ or Oz...

hth

Anawa

Eric, on one hand you state that the float switch is limited to 1600 LF, then you query about limitations on wire length. Where do you get the information that the float switch is limited to 1600 ft in "distance". Not sure what means. Perhaps someone will chime in with expertise in signal wire length. 

Anawa

I ran across a spec on the Grundfos float switch that states that using "...#18 2-wire conductor the switch is operable up to 1,640 LF". The spec states the float switch "uses only 15 mA". I would think you can overcome the the 3,500 LF distance by increasing the wire size. Maybe I'm wrong, but this should be worth investigating.

Paul
In Geogia

BB.

Here is the calculation (assuming 12 volt signal voltage, could be something else):

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=20.95&voltage=12&phase=dc&noofconductor=1&distance=1600&distanceunit=feet&amperes=0.015&x=38&y=4

18 awg, 0.015 amps, 1,600 feet (round trip)
Voltage drop: 0.31
Voltage drop percentage: 2.58%
Voltage at the end: 11.69

0.3 volt drop is not much--And, yes, if you went to 16 awg or larger wire, it go could go farther.

Or, you could do a signal repeater 1/2 way down the run--Or make your own signal sender and receiver (higher voltage, even more current for less possible interference, etc.).

Of course, the above assumptions depend on the actual pump interface (simple on/off switch, or one way/bi-directional communications line).

Or go with some other interface. RS 485 can send a signal upwards of 4,000 feet with only 1.5 volts.

https://en.wikipedia.org/wiki/RS-485
https://cds.linear.com/docs/en/product-selector-card/2PB_RS485fd.pdf

RS 485 has lots of parts you can by (voltage isolators, etc.) that would work nice.

Anawa

Eric, your piping layout for tank #2 reflects numerous switch-backs and a very indirect route from the well pump to the tank location. It does not seem to follow elevation contours, but rather routing to miss trees, rocks, or other(?). Can you explain some of the routing criteria?

What would prevent you from installing a tee at about sta. 2+50 (thereabouts) on the Ex. pipeline 2 and run it uphill to trough 2 on the new pipeline? Unless I'm missing something, I do not think you need to have separate effluent lines at the well pump to the two tanks.

Do you think this is doable?

Paul
in Georgia

Anawa

Edit: Trough #5 not Trough #2. 

Eric_R

I decided to us the Smart Water Wireless Monitoring sytem with the pump controller. I will let you all know how things work out. I will be documenting this process with photos and video.


http://fuelminder.biz/Images/gallagher/gallagher/wireless_pump_controller.jpg

Anawa

Eric, glad you came back. It seems I've had an Ah-ha moment. After studying the material you have provided, here is what I would attempt to engineer if I were you.

First, you only need one storage tank at the 1800 ft elev. to supply water to your troughs. The site plan reflects that all of the new and existing troughs are below elev 1800, thus a completely separate and isolated pipeline to the new tank and troughs would appear to be redundant (according to the information that has been made available). I would tie into Ex. Pipeline #2 as noted above and run all lines to the new tank location and to the new troughs. Install a properly sized communication cable from the pump location to the new tank either in the new pipeline trench, or separately in-ground (or above-ground on poles) directly from pump-to-new-tank. I would then move the existing 5000 gal tank to the new tank location. Install the float switch, cap the pipeline at the existing tank and tee over to the trough at that location. You can water all troughs with this set-up and have to deal with only 1 switch that has a respectable service record. You can visualize this layout if you draw a simple schematic with a vertical axis reflecting the elevation differentials.  

Something that you may wish to consider. It's simple and you can start the process by immediately installing the Grundfos pump and operating it with your existing generator and the distribution system. Heck, you may even be able to run a temporary communication cable to the existing tank to switch-off the pump when the tank is full. Of course you still have the problem with the generator running, but you're not wasting water, just fuel. 

Paul
in Georgia

Anawa

BTW, just looked over the the wireless pump controller, very promising. Would seem to be a perfect fit for the kind of installation laid-out in my previous post (one-tank, one-pump). Would you have line-of-sight between the pump controller housing and the transmitter?

Eric_R

I have line of site from the cabin to the tanks but the pump controller will down in the creek bottom at the well. There are trees blocking the line of site to the well but its only about 700' away. I will try the standard antennas first. If they don't work. I will upgrade to an 2 mile antenna or a six mile antenna.

It was going to cost about $600 in conduit to run float to the tank. That doesn't even include the wire.

Anawa

Eric, couple of things. You may want to completely price-out and think through the Smartwater wireless system given the line of sight and other potential issues. Just because it has sexy and some "wow" technology, it may not be best for your situation.

It's looks like to me that you'll have well over $1k invested when you include the pump controller. The $713 is only for the monitoring system. As you already know, because of the pump being down in the draw, you may end up spending another few hundred on antennas etc. and a very complicated system. 

Then, you will need to have 120v at the pump house to make the connection between controller and pump. I thought you were going solar because you did not have grid power to the pump location? The Grundfos CU-200 pump controller (that you will need to purchase if going to use the Grundfos) is wire-ready for the float switch.

I must be missing something here, but $600 for buried conduit plus #16 controller wire does not sound like a bad deal when compared to the issues and the cost you will face with the Smartwater wireless. Again, I do not profess know everything about your situation, but based on the info you have provided it appears you may be a bit head-strong about things. Question: Why buried conduit for communication cable? Is this a code requirement? Do you have an engineer (or a vendor) that you're working with or what? 

If you're still determined to invest and ultimately use the Smartwater system, please keep us posted, I hope it goes well, and the best of luck.

Paul
in Georgia

jonr

For an "all on one end" system, I'd use two accurate pressure sensors, one slightly further up the hill from the other.  From one, you can calculate level in the tank (under no flow conditions) and from two, flow rate (based on the small dynamic difference between two sensors).  I'd use the former to turn the pump on and the latter (plus a float valve up at the tank) to turn off the pump/generator.    By looking at flow rate to turn off, you don't have to worry about the effect of dynamic head (ie, what vtmaps said on May 17).  But I expect it would be custom development with something like an Arduino.  Looking at pump motor current or power factor (off-the-shelf Franklin Pumptec?) should be another way to detect no flow and turn off the pump.

When dealing with long pipe runs, it's most efficient to use a small (or variable speed) pump and pump slowly.  But the use of a generator may suggest the opposite.

BB.

One thing that I worry about with long wire runs is Lightning--Understanding and protecting this long sense leads against a remote strike vs a wireless system--May be some advantages to wireless.

-Bill

Dave Angelini

Yes Lightning!  I never understood why the OP here did not just walk up to the tank? He has to start a generator so what is the big deal.
Simplifying offgrid life to the point of adding risks that have low rewards really does not make sense.
 It is cheaper to walk than going to the gym!