posted 1 year ago
It is not so easy to add a second siphon if you intend to include a hand pump. Larger AC well-pumps almost always have what's called "torque arrestors" incrementally positioned down the well. They are rubber bulbs that wrap around the well-pipe, to cause friction against the sides of the well-casing, so that the pipe doesn't spin in the opposite direction the pump is spinning. That means you can't just slip a second pipe down the well.
That being said, solar alone can do it, especially if your pump is only 3/4hp. Looking at my pump chart, a 3/4hp pump at 240VAC needs 8.4A to run, and 31.4A to start. Starting is the big deal. The starting current, called the "inrush" is typically 4-5X higher than what it takes to run the pump. For my 1hp Grunfos, the running amps is 9.5A and starting is 38A. My Schneider XW+ 6848 inverter handles that starting surge just fine.
You might not need an inverter as large as my 6848. Schneider does though make a smaller 48V model, the Conext SW4048, which is documented to surge to 7000W for 5 seconds, with a peak current rating of 41A. Since your pump only draws 31A at startup, I'd think it would work. The 4048 is nice in that it is a native 120/240VAC inverter, and also has a built-in generator charging circuit. That means you just plug the inverter into a generator, and it accepts generator power to charge the batteries in rainy/snowy weather.
A good rule of thumb I recommend is to have 2X the watts of panels for the watts of your single biggest load. If your pump draws 8.4A X 240V = 2016W, I'd recommend having about 4000W of solar. High-voltage residential panels in the 250W range are running 40-50$ these days, so you are likely to get the 16 panels needed for ~800$. Look at some of my other posts. I built a rotating array frame that can hold six 250W panels. If you made two of those carrying 1500W each, when rotated towards the sun, you most certainly will make enough power to run your pump, as long as the panels are oriented towards the sun. When they are, my 2X rule only needs to be a 1.5X rule.
With 3000W of solar, charging at 50+V, you'll need a charge controller that can handle at least 60A. Epever makes a Tracer6415AN that is running ~250$ I think.
Be careful though evaluating cheaper imported inverters. A lot of them will claim they can surge to 200% their rated wattage. What they don't tell you is that their inverters can only surge that high for 8-16 milliseconds (not seconds). You need a quality low-frequency transformer-based inverter that can handle a well-pump with a starting surge in the 500-1000 millisecond range.
So, a Conext 4048 inverter, 6415AN controller, 16 250W panels, and eight Trojan L-16 batteries, and you will have a working system that will start your pump. Throw in some extra for breakers, copper wire, and sweat.
3
