solar direct and grid backup system

[jmcg]

I am in the process of designing a domestic water system. My current system has been developed over the last 20 years with grid power. My well produces 3 gpm. I am currently using a 1/3 hp groundfos pump to fill a holding tank. The holding tank as a float switch in it. The submerisble pump has a pump tech that shuts the pump off when the well goes dry (activated on sudden current drop - no load and then comes back on via a timer). I need to pump between 2500 to 3000 gallons a day from May to Sept. The remainder of the year water usage is much less.

I want to have a water system that runs a dc submersible pump directly off PV as much as possible but when either low sunlight or no sunlight the system would switch automatically over to a backup system (24V from batteries). I need to know if anyone knows of a controller or a switching circuit available to switch from PV directly when the current from the panel drops to a certain level? I can see how a simple relay would do the switching but need a circuit to do the sensing and the activation of the relay. Also, there seems likely there needs to be delay or timer in the circuit to keep it from switching back and forth when they are scattered clouds intermittently blocking the sun. At first, I will use my existing AC pressure pump to pressure the system the holding tank. The DC pump will fill the holding tank.

I would appreciate any help that anyone can give me. Thank you.


When I talk to people in the industry they steer me towards solutions they have already and seem not to hear what I am asking for. Which makes sense, they are use to what they normally sell and know their products. I don't have a lot of experience with electronics but a good working knowledge.

[inetdog]

The submerisble pump has a pump tech that shuts the pump off when the well goes dry (activated on sudden current drop - no load and then comes back on via a timer). I need to pump between 2500 to 3000 gallons a day from May to Sept. The remainder of the year water usage is much less.

Using the PumpTech will cost you total output because the timeout may be a lot longer than the recharge time of the well. Have you considered using a throttle valve on the pump output to limit it to the recharge rate of the well? Or else using a timer to limit the on-time of the pump with an off-time matched to the recharge rate?

How many gallons storage do you have in the well itself between the standing water level and the pump?
(I have given this a lot of thought since I have a house on 5 acres with a 350 foot well that produces only 1.6 GPM.)