Dry run protection for DC Solar Pump sourcing water from a borehole

[Dream_Renewables]

We are installing solar power irrigation systems for smallholding farmers in Rural Ghana,

We have 12V DC 0.18kW (max 20A) pumps, there only power source will be a voltage varying from 15-20V coming from solar panels.

The boreholes are narrow, therefore is not much room for a float switch,

The max flow is 20 Litres per minute but more typical flows would be 5-10 liters a minute

Can anyone advise on flow or pressure switch solutions (I have done a google but I don't have experience in this area and am not confident myself)

Ideally, there would be no second power source or battery needed, and the solution should be as low-cost as possible. something under £20 per unit for 20 units would be ideal.

(It's a charity project replicating 20 units - so cost is important)

let me know if i missed out any key info

 

[frontporch]

No experience here either, but I do know that pumps use more energy when pumping fluid. Would there be a "simple" way to shut off the pumps based on current flow? Electronics are always cheaper than mechanical switches I would think. Issue would be how to start those pumps up again when there is water to pump, but is that a manual process?

 

[Dream_Renewables]

yes someone on an electronics forum has just recommended wiring the windings and main contactors ina relay in series to achieve essentially what you just said.

thing is although electronic switches are cheaper they often need a separate voltage regulated power supply which can be expensive

 

[Valveman]

If the irrigation system is being supplied with any pressure, a simple low pressure cut off switch may work. You would have to hold the little lever on the side of the switch to start the pump each time. But if the pressure dropped a certain amount the switch would cut the circuit.