well pump

MichaelK said:

What kind of instrumentation did you use to come up with your pump numbers?  I would suspect they are wrong.  I'm powering a 1hp 240VAC Grunfos pump, so I have very good data on what a 1hp pump needs.  The 9.5 amps running number looks about right, but I very much question the 13amps startup number.  Was this with a regular clamp meter?  Did it blink at 13 for one second before dropping down to 9.5A?  A regular meter does not respond fast enough to capture the real starting amperage.  You need a meter that has "inrush current" capability.  I would predict your real startup amperage to be 37 to 40 amps.

In any case, there are both AC and DC solutions to your problem.  One way is to build an AC system capable of running that pump.  With AC, about 3000W of panels might run your pump from about 9am till about 3pm.  I have 4500W of panels on rotating mounts, so I can pump from about 8am till 4pm.

The DC method is to replace the pump with a DC version and attach it to a solar pump controller,  The controller starts the pump sloooowly in the morning, reaches full power at noon, and then slowly tapers off in the afternoon.  The pump manufacturer will have charts telling you how many watts are needed for so many gallons at such and such depth.

The DC version will let you set it up and walk away.  You just need to check every couple of days to see if output is what you expected.  The AC version will need monitoring in real-time, unless you have an automatic timing system.

The inrush occurs when the rotor is at stall, usually for less than 10 miliseconds, gradually dropping for around 70 miliseconds until the run current settles to its rated value, which will be influenced by load, the greater the total head the higher the run current. 

These are the values taken from a 230V 1hp single phase submersible pump with a total head of ~24 feet, inrush 42A, run 4.6A, maximum rated current is 8.9A. The biggest problem using an AC single phase pump with solar is the inrush, since an inverter would be required a battery would also be required along with a charge controller. The battery would have to be sufficiently sized to not only support the running when a cloud passes for example, but also the inrush demands during start up. In the above example the 42A inrush at 230V would mean ~420A at 24V which is what I was using, if the battery is too small in capacity the voltage will drop causing the inverter to fault, needless to say the inverter itself needs to be capable of supporting the required current demands

The DC pump is one option usually with a DC - DC controller to restrict low voltage starting attempts, this  eliminates the need for the battery, and inverter. The other is a solar MPPT / VFD driving a 3 phase AC pump, the benefit of this method is the pump will operate at lower speeds outside the solar peak allowing better overall pumping performance.