Need a Deep Well Pump Solution [RE-wrenches]

[Brad Bassett]

Allan,

The Grundfos SQ pump has had some problems on generator power, but I 
have not heard of any problems on sinewave inverters, and even some 
sucess on mod square wave inverters. They are also great for powering on 
inverters since they have virtually no surge to start.

You might also consider the Grundfos SQFlex solar pump. There's a reason 
it's called Flex for flexible, with input of 30 to 300 VDC and 120 or 
240 VAC, especially set up to make sure it runs on generator power, so 
it will take almost any description of power quality (it all gets 
rectified I think). At your head of 350 ft +, you would use the 3-SQF-2 
pump which is a progressive cavity positive displacement pump. You could 
use it with 4 SP75 modules (or equiv.) to give you about 300 to 500 gal 
per day. Unfortunately it will not run on less than 30v DC so you can't 
run battery direct in your system. 

Since it will run on AC you could run it off your inverter at 120 or 240 
volts, or off your generator. My calculations indicate it would draw 
about 350 watts, with no surge, giving a flow of 2.2 gal per minute. It 
may draw down the water level and would then shut off with it's built in 
low water sensor, restating when the water level rises again. There is 
no provision for controlling the flow rate with a control (reducing the 
voltage would on DC, but they rate it at 120v min. on AC). In the future 
you could always change and use it with DC if you wanted.

The only drawback to the SQFlex is that it is new and not so proven, 
though Grundfos has a very good reputation for making reliable equipment 
and they have been testing it in the field for the past year. Grundfos 
also stands behind their pumps and have for many years. Many of the new 
solar pumps on the market have attractive advantages that may make it 
worth trying them.

If you want to try a DC-DC converter, I recommend the Wilmore brand. We 
have had great performance from these, and no problems. They are telecom 
quality so a bit on the pricey side. It might be hard to find a single 
DC-DC converter with the capacity needed to run a pump. The Wilmore's 
can be paralleled, but then you're looking at even more bucks.

Brad


Allan Sindelar, Positive Energy, Inc. wrote:
> Wrenches,
> Here's a tough one. If any of you have solved this, or can suggest a 
> good
> option, please do so.
> 
> We put in a system last year for a good client. 24V, PS2524 (our last), 
> 850W
> PV, SB50, etc. The water system was a SunRise 5218 with SC1B battery
> converter and Booster Pump. The power system has worked well; the water
> system hasn't. The SunRise pump has failed three times, and neither we 
> nor
> the customer want to continue using it.
> 
> The well is 500' deep, with weak (1+ gpm) flow at 330-350'. The SunRise 
> was
> originally set at 300', which the client knew was our recommended limit 
> for
> the hand installation method. When the pump started drawing air, we 
> lowered
> it to 350', which worked, but means a crew of 3-4 to pull it out, plus 2 
> 1/2
> hrs of RT travel time.
> 
We could use a
> 24-48V step-up converter, but don't want to until it has a proven track
> record in this application. The client can't afford an array-direct PV 
> array
> to run the pump. A conversion to a 48V home system is likewise pretty
> expensive, as it would mean adding two more modules (10 now), dropping 
> from
> 12 L16s to 8 @ 48V, changing SB50 to SB3048, and various other changes.
> 
> The only alternative I can see is a standard AC sub. The Grundfos SQ 
> won't
> work at an estimated 350-400' of lift, as that would require the 
> 5SQ-320,
> which has a 1.40 HP motor, almost certainly too much for a PS2524 with a
> T240. This leaves a standard 3/4 HP Grundfos 5S07-18 or equivalent with
> T240.
> 
> One alternative is a bigger 240VAC pump to run directly off of his 
> backup
> generator, which is a Subaru 5.1 kW at 7,000'. The problem with a
> bigger/faster pump (to minimize run time) is the slow recharge rate of 
> the
> well--it would quickly run dry.
> 
> Who has a better idea?
> 
> Allan at Positive Energy
> 
> 
> 



Brad Bassett
Schott Applied Power 
Tumwater, WA office
bsbassett at earthlink.net

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