Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

cruiser guy

We have a Grundfos 11-SQF-2 in a 90' deep well with about 75' of 1" pipe down to the pump. This is pumping through about 400' of 1" pipe to a water tank which is probably 50' - 70' above the well so a total rise from pump to tank of about 150' give or take. The system is powered currently by 6 90 watt SolarWorld panels with a 300' run of #8 wire I think from the controller to the pump. The panels are on the roof two stories directly above the controller. We are located in Sierra Leone about 7 degrees north of the equator and we have sun almost all day every day and the panels are at about 5-10 degrees sloped to the south on the south facing roof surface. The six panels are grounded as is the controller and pump. Ground is a 4' copper ground rod at the building foundation as well as the steel well casing which is a 6" steel pipe about 60 - 70' down. I have no lightening arrestors yet.

This system was installed by myself in July and it has worked great until we went on a short vacation in December. Since returning I have had a tough time getting enough water and water pressure. We have cleaned the solar panels of the dirt accumulation and I think but am not sure I've taken care of folks siphoning water off the system. The CU-200 controller only shows 0.33kw maximum going to the pump with full sun on the panels. That seems low considering we have 540 watts of panel connected. The buildings are about 60 - 70' below the tank so pressure should not be a problem.

There was considerable brushing and burning of vegetation in the area the pipes run but I cannot see any wet spots yet. I'm going to see if I can fill the tank today by shutting off everything else. If I can fill the tank I'll assume my problem lays in the distribution. If I can't fill the tank my problem is in the pump side and the accompanying piping.

Today I am going to add an additional 6 panels to the system and see what happens. Maybe with more power I'll get a geyser of water somewhere.

Any ideas where or what else to check?

Ralph Day

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Can you pull the pump and check for crud restricting the water inlet area? It wouldn't take much to restrict the intake of water if there's foreign material in the well. Good luck.

|Ralph

westbranch

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

If machinery has traveled over the pipe line there may be a spot where the pipe has been squashed but not broken. If it is conventional 160 PSI water pipe it is tough stuff...

Do you have any taps /drains mid way in the line to check pressure at that point? 300 feet of line is a long distance to check for a compressed spot.

hth

niel

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

can you verify the obvious, the wires? there could've been a break in the wiring. it is still best to pull the pump up to verify this as well as to verify the pump is fine.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

We added the remaining six panels I had yesterday morning for a panel wattage of 1080 watts all in series and the tank was full almost right away. I don't know if there maybe was something down in the well that was stuck on the intake and then fell away at night or if the added power blew out a blockage or expanded a squashed pipe or what but it seems to be working. Time will tell.

We initially had a 2000 liter storage tank but will be upsizing to 5000 liters in the next week or two so the additional panels were needed anyways. 2000 liters was too small to start with anyways. 5000 liters will be OK for the next while and the tank platform will be made large enough for an additional 5000 liter tank to be added later.

westbranch

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

It sounds like in the process of adding more panels you may have inadvertently "fixed" a loose connection or ? in the wiring as Niel said.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

The only questionable wiring connection is the one from the float switch to the controller. The silly little push in wire connector broke when I was wiring it. It must be good though because it was calling for water even when it didn't fill the tank.

I'm thinking with all the draw on the well that the locals drained it good while I was gone and it needed a little time to "recharge".

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

I have been lax in checking on this but since we had a team last week and were always low on water it has moved up the priority list. The water is barely dribbling into the larger 5000 liter tank. There are 1080 watts of panel available but it shows only 340 watts maximum going to the pump?!? With 300 watts I should be getting about 4 gpm and with 1080 watts it should be flowing in big time. There is no display of low water or any other problem right now on the controller.

Ideas?

pabloesguapo

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

It's strange to me that you would get great water flow from the pump when you added the new panels, and now you're not. You went from 333 watts to 1080 and then back down to 340. I doubt it's wiring. Wiring is either going to be good or bad, all the way, or not. Bad wiring usually doesn't go bad by degrees like that. My guess is perhaps there is something wrong with the controller itself. It can't seem to regulate things consistently.

BB.

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Sand filled the well?

-Bill

KeithNyst

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Newbie. Another possiblity is that the recovery rate of the well has changed and you are pumping it dry. If I'm reading the Grundfos pump chart correctly for a 11-sqf-2, it should pump about 7gpm at 400 watts and a 150ft head. 12 gpm at 600 watts is almost at the top it's pump curve for 150ft, so not sure the added panel wattage helps much.

If the well's recovery rate dropped to 2-3 gpm, it would not take long to pump it down. If you have a 4" casing, and the well was full to the surface with water, i'm calculating that you would have about 42 gals of water in the casing from 6 ft above the pump intake to the surface (intake is set at 75').

Also, assume you are running the pump on DC? The sqf supply volatage specs read 30-300 vdc, pe. Are all 12 panels now in series? If yes, and they are 30v, wouldn't that produce 360v? Not sure what the voltage drop would be by the time it makes it to the pump.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

According to my GPS there is about 30m of elevation from the well head to the tank and then an additional 70 or 80' down to the pump. for a total head of probably 180' or so.

This well could be pumped dry by the community in about 4 hours or so with a hand pump till we put in a better producing well nearby and took this well over for the hospital water supply. The thing is the CU-200 controller is not indicating a dry well.

This is a 6" casing driven down to the bedrock at about 90'. Sand is possible but doubtful as the overburden in this area is generally quite a bit of clay (not good for regenerating the well I know). I didn't drill this particular well but we do hit fissures in the bedrock that can give us a pretty good water flow at times.

KeithNyst

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

6" casing would provide about 100 gals from 6 ft above the pump to the wellhead if the well was full to the top.

I don't known the output of a hand pump, but I'll bet it is a lot less than 7-10 gpm. If they were pumping this well dry with a hand pump in 4 hours, I'm suspecting your pump is oversized.

Any reocords of, or have you every measured the static fluid level and recovery rate?

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

It looks like it was just a simple air lock in the piping

We tested it at the well head yesterday and got full flow from it and it matched the pump curve. And there was no sand or solids in the pumped water.

When I looked at the water entering the tank it was like the flow from a garden hose, plenty to keep the tank filled.

Now I need an automatic air vent to avoid this in the future.

PhilS

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

I don't know if any of my experiences with our SQflex pump apply, but I'll mention them in case they might.

1) The sensor that tells the CU200 that the well is empty only lasted 6 months for me. That wasn't a big enough deal to have them pull the pump because I hadn't had a working sensor for decades (we had a "Coyote" that quit after a few years). I have learned to pump a fixed amount that is just short of emptying the well.

2) Mine will pump air when the water is gone. I can hear the bubbles in the pipe and then see them in the cistern. After a short while the pressure switch will drop low enough to shut the pump down.

Phil

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

I'm going to guess we're probably only at 3-4 gpm going into our tank due to head and friction losses. The GPS says the tank is 100' above the well head, I doubt it is that much but it is certainly something. It might be interesting to go up and measure it one day and see especially since there is a valve for a future second tank up on the tower already.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

We got around to pulling the pump the other day. The low water sensor is definitely NOT working as the pump attempts to start while it is laying on the ground. Anyone have ideas to fix this? Apparently it is caused by water entering the area of the pump where the level sensor connects.

The low flow/lack of water was due the well going dry. The low water sensor did not show that the well was low.

inetdog

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

cruiser guy wrote: »

We got around to pulling the pump the other day. The low water sensor is definitely NOT working as the pump attempts to start while it is laying on the ground. Anyone have ideas to fix this? Apparently it is caused by water entering the area of the pump where the level sensor connects.

The low flow/lack of water was due the well going dry. The low water sensor did not show that the well was low.

There are two different ways to sense dry (overpumped) conditions. With a conventional AC pump, it is possible to detect the change in load and power factor of the AC going to the pump. A centrifugal pump without water will consume almost zero power, but will still pull significant VA.

With a DC pump, the equivalent may not be as easy, requiring a sensor at the pump. That could either be a pressure or flow sensor, or a simple thermistor with resistive heating that will stay cool if immersed in water. You will need to find out what type of sensor is used in this pump.

If the well has a low recovery rate compared to the pumping rate, the simple solution is to put a timer on the pump so that it cannot run long enough to draw the well level down past the pump, and then another timer that keeps it turned off long enough for the well to recover. ( I have a 4" 300 deep well with 80 feet of standing water above the pump (approximately 80 gallons above the pump) and a recovery rate of only 1.3 gallons per minute. If the 10 GPM pump runs longer than about 10 minutes, I am in trouble.)

If on the other hand, the well just plain fails, you do have to have a working sensor.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

If there are only the three options you point out then it must be the thermistor that is a low water sensor. The Grundfos rep was saying that there must be some water ingress to the area where the sensor electrical connections are but his solution is to replace the entire pump. That sounds a little extreme to me.

I was going to simply throttle back the pump flow with a gate valve and see if I can slow the pump flow enough to keep it in the water.

Is there a flow sensor of some kind that, along with a timer, could be used to run the pump intermittently? This is really only a problem in the dry season if we have a large draw on the system. At any other time of the year there is no problems.

Blackcherry04

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Attach a 1/8 poly tube to the pump pipe with a pressure switch on the open end of the tube at the top of the well. When the water drops to the open end of the tube the switch will open and stop the pump. It will work like a gas nozzle in reverse. You need a micro switch, like this or something similar. Of course any flow switch would do the same thing at the top of the well. You can get a flow switch with a flapper that would open when there is no water flow.

http://www.pressureswitch.com/mpl500.html


I'd think you'd want to put in a delay timer so a switch would not short cycle your pump to death and would give the well a chance to recover.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

I like that idea. I've sent an e-mail off asking about contact rating on the switch. Up to 300vDC and several amps can be a bit demanding of the contacts.

Ideas for a DC powered delay timer of say a half hour minimum.

On second thought, would the time taken to build up pressure by the rising water level not give enough of a time delay?

Cariboocoot

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Got to point out that the proposed switching system is very much like the type use on certain septic digester pumps: water level rises sufficiently to cause an increase in pressure within a sealed tube by acting on rubber diaphragm thus actuating the pump. A second such switch is used as a low-level control to shut the pump off.

There is no reason why you couldn't vary the length of tube to adjust the minimum water level so that the well would have to rise above a safe amount before the pump was allowed to operate. This level would depend on two things; how fast the pump can drain the well and how fast the well can recover. You can't adjust that last item, but you can reduce the flow from the pump to prevent it taking the level down too fast. Flexibility is the key; make sure you can adjust level, pressure, and flow rate.

cruiser guy

Re: Lack of water with a Grunfos 11-SQF-2 serving a hospital in Sierra Leone, Africa

Unfortunately the contacts in the switch are not rated for the high DC voltages used by the pump. I'd need a relay along with the switch. That means running additional wires back from the well head to the CU-200 controller so I have a source of power to operate the relay.

When the rest of the work here slows down I'll pull the pump and see if anything can be done with the factory low water switch.