Powering Grundfos A/C Pump in off-grid application

[MichaelK!]

OK, well I guess I can give you more information: I know that that's where the water comes in (i.e., the location of the perforations) per the well report and when they were drilling the well. This information combined with my visual inspection and the transition from dry to wet on the pipe that I extracted tells me where the water level is.
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This is the third very, very dry year in California, and a historical report is not likely to be accurate for "right now" For my own well, the static water level was at -70 feet when the well was first drilled in 1980. In 2010 when the well pump failed and it needed replacement, the static level had dropped to -100 feet. My well's bore hole is supposed to cross three aquifers. I'm assuming they are located at -70, -100, and ~-180 feet. So, the upper most aquifer had totally dried. I monitor the well's pumping rate on a minute by minute basis, and what I see is that in wet years the well is putting out about 6.5 gallons per minute. Now, the well puts out about 5.5 gallons per minute at start-up till about the first hour. After that the pumping rate drops to 4.75 to 4.25 gallons per minute.

I interpret this as follows. In a wet year, the upper most aquifer (-70) is hydrated, and has a refresh rate of > than 6.5 gallons per minute. So, I can pump as long as I please with no drop in water level/pumping rate. Now, because of the drought, the uppermost aquifer is gone, and I start pumping from the second aquifer (-100), which has a refresh rate < 4.25 gallons per minute. As the water level drops towards -180 feet, the pumping rate drops, with the pump then stabilizing at a refresh rate of 4.25 gallons per minute, which appears sustainable.

I think that is what is happening in your well also. Your static level has dropped significantly lower that what it used to be, and drops even lower as water is pumped out because the static level is dropping.

[cjb80]

That inverter say 50/60 HZ. is it selectable? if it run on 50 cycle the pump performance will be cut significantly.

I am going to check on this the next time I am out at the site. Thanks for the suggestion.

Also, I am going to try and add a 10w light bulb to the circuit to see if that helps "wake up" the inverter from sleep mode. I will report on the results in about a week or so.

[cjb80]

I guarantee you cannot tell the water level in the well at 30' just by looking. There is no point of reference. I've been doing this for 20+ years and I can't do it accurately. I'll bet your level is deeper than you think.

OK, well I guess I can give you more information: I know that that's where the water comes in (i.e., the location of the perforations) per the well report and when they were drilling the well. This information combined with my visual inspection and the transition from dry to wet on the pipe that I extracted tells me where the water level is.

I agree that it is difficult to tell how far down it is by visual inspection alone. In fact it took me about a minute of staring into the darkness before I even realized what I was seeing.

[inetdog]

I guarantee you cannot tell the water level in the well at 30' just by looking. There is no point of reference. I've been doing this for 20+ years and I can't do it accurately. I'll bet your level is deeper than you think.

You can often tell by looking as you lower a sounding weight and see it hit the water.
As long as the level is not hundreds of feet down, that is.

[Texas Wellman]

I guarantee you cannot tell the water level in the well at 30' just by looking. There is no point of reference. I've been doing this for 20+ years and I can't do it accurately. I'll bet your level is deeper than you think.

I called the pump shop and the feedback that I got was that I did not account for the pressure in the line or any sort of elbows, couplers, etc in the line when calculating the head. This does not make much sense to me as the pump is pumping water into an open tank; hence the pressure should be negligible. I would also be astonished if the PVC connections were that much of a restriction. In any case, to achieve the amount of head that I am observing, I would need to have something on the order of 20 PSI of pressure in the line. When the water comes out of the pipe it is similar to water flowing out of a gallon junk, not like it is spraying out of a garden hose. So it is my judgement that the pressure is not anywhere close to 20 psi....

In response to Texas Wellman, I know the water level from looking down in the well. Also, when I took the old well pump out there was dry pipe and wet pipe, and I measure the length to the wet pipe.

Anyways, the question that I have is: Does the SQ series of pump always run at full speed (besides start up?). The pump curve says that it is at something like 10,000 RPM, but how do I know that it's actually trying to work at full speed?

Chris

[paulcheung]

That inverter say 50/60 HZ. is it selectable? if it run on 50 cycle the pump performance will be cut significantly.

[cjb80]

A MPPT controller will only "create" power from extra voltage, if you have 19V panels, MPPT might get you another 20 watts. If you have 35V panels, MPPT will more than double your harvest from the extra voltage over 12V. (I'm assuming a 12V system, every 12V needs about 19V to charge with, 24V batteries need 38V ....)



I'd consider the drop from 3.9 to 3.33 ignorable. But the discrepancy from expected 6gpm to 3.9gpm a issue. Call the pump shop.

I called the pump shop and the feedback that I got was that I did not account for the pressure in the line or any sort of elbows, couplers, etc in the line when calculating the head. This does not make much sense to me as the pump is pumping water into an open tank; hence the pressure should be negligible. I would also be astonished if the PVC connections were that much of a restriction. In any case, to achieve the amount of head that I am observing, I would need to have something on the order of 20 PSI of pressure in the line. When the water comes out of the pipe it is similar to water flowing out of a gallon junk, not like it is spraying out of a garden hose. So it is my judgement that the pressure is not anywhere close to 20 psi....

In response to Texas Wellman, I know the water level from looking down in the well. Also, when I took the old well pump out there was dry pipe and wet pipe, and I measure the length to the wet pipe.

Anyways, the question that I have is: Does the SQ series of pump always run at full speed (besides start up?). The pump curve says that it is at something like 10,000 RPM, but how do I know that it's actually trying to work at full speed?

Chris

[Texas Wellman]

How do you know the starting level of the water? It would be difficult to measure with the pump in the well. Are you using an air-line?

[Mike90250]

A MPPT controller will only "create" power from extra voltage, if you have 19V panels, MPPT might get you another 20 watts. If you have 35V panels, MPPT will more than double your harvest from the extra voltage over 12V. (I'm assuming a 12V system, every 12V needs about 19V to charge with, 24V batteries need 38V ....)

2) The water level in the well is currently about 30 feet below grade, and it is pumping into a tank. The pump is ~120 feet down from grade. So there should be something on the order of 45 feet of head; which should yield about 6 gallons/minute. I am seeing about half of that flow rate right now; it started at about 3.9 GPM, and then dropped to 3.33 GPM after about 30 minutes of running.

I'd consider the drop from 3.9 to 3.33 ignorable. But the discrepancy from expected 6gpm to 3.9gpm a issue. Call the pump shop.

[inetdog]

Depending on how many hours per day your pump runs, and the difference in inverter power consumption (tare) between sleep and simple idle, you may just want to put a 40W or smaller light bulb in parallel with the pump on the output side of the pressure switch or other control.
Even a 10W light bulb will have a low enough cold resistance to reliably bring the inverter out of sleep.

If the switch is used only as a set of dry contacts for an input to the controller, you could look for a switch with two sets of contacts (as is required in some cases for 240V pumps) and use the second set to control the 120V light bulb.
If you are using a float switch and cannot find one with dual contacts, you may have to use a relay to drive both the controller and the light bulb.

[cjb80]

OK, so to follow up on this thread, I have finally installed an inverter and Grundfos pump.

The inverter is a Samlex 2Kw pure sine wave inverter and I chose the 5SQ05-90 pump. Everything is working but I have noticed a few 'issues' along the way.

1) The soft start does not trigger the "sleep" mode to turn off in the inverter, so I have to run the inverter with the sleep mode disabled. This causes a higher power draw when the pump is not running. I need to double check this, but I believe I tested it with 40W as the threshold to turn off the sleep mode. So apparently the pump is not even drawing 40W when it performs the soft start.

2) The water level in the well is currently about 30 feet below grade, and it is pumping into a tank. The pump is ~120 feet down from grade. So there should be something on the order of 45 feet of head; which should yield about 6 gallons/minute. I am seeing about half of that flow rate right now; it started at about 3.9 GPM, and then dropped to 3.33 GPM after about 30 minutes of running. If I look up the flow rate on the Grundfos charts to work backwards and determine the "observed head", it appears that I am starting at about 115 ft of head and then progressing towards about 125 feet of head (I assume this is due to draw-down of the well). I can't explain why I am observing ~120 ft of head (in regard to flow rate) but the with the water level I should only have about ~45 of head..? I have double checked the system and I don't believe there are any restrictions. The drop pipe is 1", so there shouldn't be any restrictions in the line...

3) My PWM charge controller is not keeping up with the additional draw on the line, so I am swapping out to an MPPT controller in the hopes that the panels are always producing more power than the pump is drawing... I estimate that the power consumption is ~600W including the inverter losses.

Chris

[russ]

Running watts is starting watts. There is no surge. Please post back up how you like the pump and set-up so others will know.

Yes! Please do - there are always questions about the solar pumps.

[Texas Wellman]

Running watts is starting watts. There is no surge. Please post back up how you like the pump and set-up so others will know.

I looked up the SQ pumps and the 5SQ05-90 looks pretty good. It looks like the normal running power consumption is around 500 watts. What should I expect the power consumption to be during start-up with this pump? Does the soft-start make the starting power consumption similar to the running power consumption?

Thanks,

Chris

[cjb80]

You have SQ confused with SQ Flex. There is a difference.

I looked up the SQ pumps and the 5SQ05-90 looks pretty good. It looks like the normal running power consumption is around 500 watts. What should I expect the power consumption to be during start-up with this pump? Does the soft-start make the starting power consumption similar to the running power consumption?

Thanks,

Chris

[Mike90250]

Here is the breakdown for you on what a submersible motor consumes by Horsepower:
1/2 HP = 600-950 watts
3/4 HP = 940-1300 watts
1 HP = 1200-1600 watts.
Source: http://www.franklin-electric.com/aim...l/page-13.aspx....

All I can add is that my 1/2 hp Franklin pump, logs 1Kw on my inverters' control panel. It's a 3 wire, 240v unit, and my 6KW inverter does just fine with it and other loads. I'm pumping about 160' lift.