DIY solar pump

I just checked the manual for my cheap VFD which controls my 3 phase pump and it has an analog input which can directly control the speed of the pump. This can be set to either voltage or current mode, where it will expect an input of either 0-10V DC or 4-20mA. So I can vary the speed (and therefore the power) of the pump directly using this input.

Both the outback and midnite classic have a diversion controller output which can be used to divert excess power....... so, how easy would it be to convert the output of those controllers into a signal the VFD could understand? If it was simple, easy and cheap, we could effectively build a direct solar pump controller using off the shelf components:
- MPPT charge controller
- car battery (won't be cycle at all, just used because the controller needs something to connect to)
- Electronics to convert controller diversion output into either 0-10Vdc or 4-20mA.
- Any 3-phase pump

And grundfos can eat my shorts.


  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: DIY solar pump

    Oops, just realised that my pie in the sky is missing an inverter... which will make this way too expensive. Carry on, nothing to see here.... :blush:
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: DIY solar pump

    were you first thinking about running an AC pump off DC? or is it an AC/DC pump? If the latter, don't see why something along your line wouldn't work.
    ps IF AC don't you need the inverter anyway?
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  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: DIY solar pump

    I wasn't thinking ;) It could work, but would require quite a bit of hacking with the VFD. Internally, I think the VFD first rectifies the incoming single phase 230V to DC, and then it creates its own wave form based on that. So in theory if you could hook into the circuitry just after the rectifier and provide whatever DC it's expecting there from solar, then you'd have a pretty cheap pump controller- albeit without variable speed. But all that is waaay beyond my electric ability.

    But if the VFD is rectifying the incoming AC anyway, perhaps you could just supply it with a cheap MSW inverter and then hook the MPPT charge controller up as originally posted- giving you variable speed pump based on available solar power.
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