Dual DR's [RE-wrenches]

[allan]

John (and wrenches),
    We are caught up in a related problem with a DR1524.  We almost never
sell them, preferring to recommend the "20 amp circuit" capacity of the 2424
for this application niche, but last year we did an unusual water
pumping/Y2K system for a woman in town, that has become an ongoing headache,
still not resolved.  The situation:
    Her primary need was for water supply, so we designed a SunRise/Booster
Pump system for her.  She drilled a 350' well and put in a 1200gal buried
cistern tank and a pit for the pumps and power system.  She also wanted
minimal lights and to run a small refrigerator.  So we used a DR1524 to feed
a subpanel near her back door, with switchable grid backup charging to
supplement the 450W of PV.
    All worked well for awhile on a clean, affordable, tightly designed
system.  The 1524 could backup charge from grid, so the low (35A) charge
rate wasn't a problem on the 8 golf carts.  Then she reported that the water
stopped coming out of the two hydrants we installed.
    As it turns out, the well has continued to produce an extremely fine
silt that is pumped up with the water.  The cistern is 70' away from the
well pit.  The SunRise pumps OK, but at its slow rate, the silt settles out
inside the 1 1/4" lateral line from pit to tank.  When the pressure switch
turns on the Booster Pump, the higher flow of the pump draw disturbs the
silt and flushes it into the filter.  It either caused the filter to clog up
and the pump to cavitate, wearing out the head, or it was so fine that it
passed through the 10-micron filter cartridge and wore out the head.  Note
that this inability to tolerate any sediment, thus requiring complete
filtration on the suction side, is a major design weakness of the Flowlight
Booster Pump.
    Anyway, to shorten an already long story, we put in a 1/3HP AC Monarch
shallow-well jet pump to replace the Booster Pump (special-ordered, as 1/2
hp is the smallest normally carried by our AC pump supply distributor).  The
1524 wouldn't start it under load, and at this point we think we have
toasted the AC motor trying.
    We are going to see if the motor starts on grid, and fix it if it is
fried.  The customer has been patient, but is ready to pull everything out
and just put in a 220V pump running off of grid power.  She can't afford a
Solar Force (which will pump silty water OK); she may accept trading in the
DR1524 on a DR2424; and we may just try to use this 1/3HP AC pump on grid,
now that Y2K didn't happen.
    This got pretty long-winded, because it's really two issues: 1) John,
I'd be careful about using the 1524.  It's just too weak; maybe not now, but
down the road.  The 2424 is much more capable, and has twice the
(theoretical) charge rate from an AC source; and 2) wrenches, help! I'm
stuck with a system we designed carefully, but for one unforseen
complication (silty water) we can't make the system do what the customer
wants.  Ideas?

Thanks, Allan @ Positive E

-----Original Message-----
From: John Blittersdorf, Cent. VT Solar & Wind

>Hi Wrenches,
>    As I sit on my rain and wind swept mountainside listening to Prairie
Home
>Companion, I am thinking of ways to provide budget systems for the poorer
>folks in the area who need to run well pumps (fairly common in this area).
I
>have been testing the DR1524 running my house for the last two weeks and so
>far I am quite impressed with the results.  I have run all house lights,
>stereo and TV, computer and propane furnace(450 watts-manually switching
>blower on as the mod square will not work the controller) and my wife asked
>me if she could turn on the microwave.  I guess I like living on the edge
so
>I said OK and continued the test of an inverter that is already sold... to
be
>installed next week.  So far, no problems.  It does seem to be sluggish at
>charge rate from a 2200 watt generator which according to the documentation
>for the DR is normal.  It will be running off a 3600 watt Honda in its
>permanent home and should charge somewhat better.
>
>Since this is the least expensive DR inverter, and Trace says it will
handle
>3500 watts for 1 minute,  what do you think about using dual stacked
DR1524's
>to run a well pump.  Has anyone done this or with the bigger DR's.  This
>would be cheaper than a PS2512 and theoretically could deliver more power.


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