Constant pressure pumps are a much better set up. The Grundfos SQE is a
great example. Your well driller is right on target.
However, expecting 10 gpm from a 600 ft deep well off grid is overkill.
I would compromise on that flow rate. 5 gpm will be plenty of water in
most cases, outside of watering the garden.
Once you have a system with constant 50 psi output, you will never want
to go back to the old down to 30psi, up to 50 psi pressure variation.
Also, you can save money and space by using a smaller pressure tank, if
at all.
The Franklin drives work as well, but they are also constant pressure.
I didn't notice the high idle current on the VFD, we might have had
that only turn on via a pressure switch.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 10/5/2016 5:15 PM, James Jefferson Jarvis wrote:
Wrenches,
I have a project that needs a deep well submersible pump. I want to
find a pump that will be compatible with an off grid system, probably
using a single or two in parallel Magnum MS4024PAE or MS4048PAE
inverters. I usually using Grundfos SQ pumps for these applications.
The soft starting SQ work wonderfully with the inverters with no
brownouts during startup.
But, in this case, the well is too deep for the SQ pumps. Well company
is specifying 2HP, 4" diameter. Well is likely ending up 600ft deep,
probably 400 to 500' deep pump, and needing to supply 10 GPM when
running.
Customer and I are most familiar with a standard pressure tank type
system with pump turning on at low pressure and off at high pressure.
Well driller, in an effort to provide system with a soft start, are
encouraging a constant pressure system. I am not thrilled with the
thought of the pump starting up constantly for somebody to brush their
teeth or wash their. Or am I mis-understanding how constant pressure
systems?
Any recommendations for a 2 HP pump system that will have minimal
starting surge (ie run happily on inverter power)? My brief searching
shows I can do a capacitor start system (three wire, with control box
on the surface) and do somewhat better than across the line starting.
Or I can do a 3 phase pump and then manufacturer / pump specific VFD
on the surface ... at the penalty of huge $ cost and high idle power
on the VFD control (65 watts in the case of a Franklin drive!). Or I
can use an off-the-shelf 3 phase pump, and an off the shelf line
reactor and VFD combination.
Thanks,
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