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Running a 240v submersible well pump on solar energy??

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  • Running a 240v submersible well pump on solar energy??

    We have a 1100 watt solar array, hooked into a midnight charge controller then to a total of 6 total 12v batteries then to a magna truesign inverter then to a electrical box were we have a 240v submersible pump hooked in to two 15 amp breakers then it runs in the house to the pressure pump switch then out to the pump. The pump will work if we kick the gas generator (9000 watt peak gen) that we use to charge batteries if we don't have enough sun, but even if our batteries are fully charged and we shut off the generator and use water in tank, as soon as tank gets to 30 psi and clicks the solar batteries power being inverted will not kick the well pump on. Any ideas why? Or what we need to add? Our well is only 63 ft deep. Pump is two wire plus a ground. Help if you can????

  • #2
    Centrifugal well pumps draw a lot of starting inrush current. They are not good match with PV system unless they are equipped with VF drives. The bummer is 2 wire pump is not readily converted to VF drive, Three wire pumps with an external capacitor box can be converted with a Franklin monodrive conversion but its pricey. Centrifugal pumps are generally not very efficient. Best approach is switch to DC positive displacement pump in the well pumping to gravity tank in an elevated location. .


    • #3
      Large 2 volt batteries would be better than small 12 volt batteries...never skimp on copper either.

      Like any chain, batteries are only as strong as it's weakest link...
      Last edited by neweclipse; 05-07-2019, 08:37 AM.


      • #4
        What voltage are your batteries wired for ?

        What is the size/power of the 240V pump ?

        My 240V 1/2hp 3 wire pump consumes a solid 1,000 w when running. On my 48v system, that's 20A of load, and starting surge is close to 200A for 2 seconds

        This chart may help you figure it out:
        Well Pump Motor Specs.jpg
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A



        • #5
          Likely your system is far too small. Which MagnaSine inverter are you using? The 12V MS2812 has a 5 second peak of 3900 watts. Even their 24V MS4024 only has a 5 second peak of only 5800watts. I myself run my pump solely on solar now, but I know exactly what my numbers are. My 240VAC Grunfos pump uses 38amps at startup, and 9.5 amps running. At 240VAC that corresponds to 9100 and 2300 watts. My numbers track closely to the chart that Mike above posted. I have a Schneider XW+6848, which is designed to handle that surge current. It's fueled by 4500 watts of solar. Is your system voltage 12V? Six 12V batteries wired in parallel is a very poor configuration. You are drawing a lot of amps through a lot of wire to get the power you need, but it isn't enough. You'd be better off using lower voltage batteries wired in series to get a system voltage higher than 12V. If you give us more information, we can help you design a system that would run your pump. We need from you 1) pump size/amp draw; 2)system voltage; and 3) which inverter you have. A good rule of thumb is you need about twice the amount of solar that your load requires. So, if your pump draws about 1500watts, then about 3000 watts of panels would successfully power it. A smaller pump might be run on a 24V system, but I would run a large pump from a 48V system.
          Last edited by MichaelK!; 05-22-2019, 01:53 PM.