Off-grid pumps [RE-wrenches]

[Kelly Keilwitz]

Jason, Windy and Todd,

Thanks for the suggestions.

New information I learned today is that the customer would like to be able
to pump at a rate as low as 1 gpm, if necessary, to reduce salt water
intrusion.

I, and our customer don't like the idea of needing to pull a pump every 5
years to rebuild it. Even if it might last longer than that because the
owner won't be living there year-round for some time, reliability is
important to me and owner.

The cost difference between a pos displacement pump and AC centrifugal pump
is quite significant. However efficency is fairly important as the owner
comes to stay for a month or two at a time, any time of year. Thus, the
design must be the same as for a full-time off-grid residence. He doesn't
want to run the generator unless he has to. And the PV size will be limited
by how much we can hang on a tree 50 feet up its trunk. So, spending more
for a pump might be justified in this case. Also, if we choke down a
centrifugal pump to 1 gpm I imagine that the efficiency gets even worse!

The suggestion about going direct from the well to the pressure tank was an
interesting one (and they already have an 80-gal pressure tank ready).
However, they already have the 1000 gal storage tank in and ready. And if
they need to reduce the flow to 1 gpm they might need that for recovery.
But, we might try it in the short-term just to get the system up and running
sooner.

So, now the choices seem to be whether to use battery 48VDC or 115VAC from
the inverter and the Lorentz or the Grundfos SQ. If any of you have personal
suggestions or warnings I would apprecieate them, on-list or off. Also, are
there any fairly efficient AC pressurizing pumps?

Thanks again for your suggestions,

-Kelly

Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd, 
Coupeville, WA 98239
PH & FAX 360-678-7131
sunwind at whidbeysunwind.com
 




On 7/23/06 9:16 AM, "Windy Dankoff" <windydankoff at mac.com> wrote:

> 
> 
> Todd,
> 
> You're right, Kelly said:
>      But, as this is a salt water intrusion area, we want
>      to pump at no more than 3 gpm.
> 
> He also said:
>      There is an existing 1000 gal concrete
>      storage tank in the ground about 20 feet from the well head
> 
>   I had lost site of the fact that there is already a storage tank in
> place.
> 
> Since they have surface water for irrigation, and it's only a cabin,
> it is feasible to directly pressurize from the well pump using <3
> GPM. This has worked fine for old customers of mine using even less
> than 1 GPM, provided:
> 1. They must understand the inherent limitation (taking time to
> recover if they draw > about 25 gal. quickly),
> 2. they use at least one 80 gal. pressure tank, set up in the normal
> way,
> 3.  raise the pres. switch's cut-in pressure so, for example, the
> settings are 30/40. This way not  much water is lost before the pump
> cuts on again.
> 
> Advantages of a single pump (even where there already exists a
> storage tank) are simplicity, less cost, less to go wrong, and not
> least, a much better assurance of sanitary water. IF they decide in
> the future that they need full-flow pressurizing, they can utilize
> the same well pump to fill the storage tank, and then add a
> pressurizing pump.
> 
> So Kelly, now you have a number of options, including an option for
> later expansion. Hope this helps.
> 
> Windy
> 
>> From: Todd Cory <toddcory at finestplanet.com>
>> 
>> I think the ground level storage tank was because they wanted to pump
>> the well very slowly to reduce salt infiltration.
>> 
>> Todd
> 


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