[RE-wrenches] Deep well submersible pump query

[Ray Walters]

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,
>
>