small well pump system (for a property that I will be building a house on)

[JohnMH]

Location: South Florida

I'm looking at installing a well on a property I am closing on shortly. I have been looking at installing a grundfos SQflex pump (operates 30-300 VDC or 90-240 VAC).

I'm looking at 3x 300 watt panels in series attached to a classic 250 (oversized, but that is what I would want) charging a 48 volt battery bank.

Should I use a relay controlled by the classic 250 to turn off power to the pump so that it doesn't have a way of discharging the batteries too much (voltage in batteries bellow a certain point will not allow poweer to pump)?

Should I use any electrical panel mounted next to the classic 250? This will be DC only... no inverter.

Where would you attach the surge suppression device/devices in this system?

Just information: The pump water would connect to a large pressure tank which also has a pressure switch controlling power to the pump.

[mike90045]

The pressure switch is likely only rated for AC voltage, DC would fry it.  So either use an inverter and all AC, or if you want to go DC only, rig the pressure switch to a SSR or contactor for the pump

Lightning in Florida ?

Surge protection, I'd put SPD's at the PV, + & - and then another one + & - at the Input of the controller,  and another at any point in the system with more that 10' of wire, so one right at the pump wires before it goes underground.   I'd have at least 2 ground rods by the pump, you don't want the surge to follow the wires 40' down and go through the pump to the water.
I'd have another rod at the PV array, and one at the controller.    Do you bond all the rods together ?  I don't know.

Are you going to have any night time usage ? 

[JohnMH]

Evidently square D makes DC rated pressure switches. Also, the pressure switch can be used in place of the float switch connection on the Grunfos controller for the pump.

I do plan on using it at night, hence the 48v battery bank. But I do want to stop it from draining the batteries too low... that was why the solid state relay controlled from the charge controller AUX 1 port.

I didn't want to use an inverter... adds too much cost for now. The Grunfos can run on 48v power with no starting surge... sounded like the best option to me.