open loop solar water heater that wont freeze
I have a plan for an open loop system that will latch on to an existing tank and supplement the heat but wont freeze. What i need is a circuit that will shut off the pump when the sun is down and a water thermostat i can stick in the existing tank that will also shut the pump off. I think they should be one circuit somehow and should be 12v DC so the pump can be solar powered. They should also be as cheap as possible.
I'm not good with circuits so i could use some help. Perhaps there is some way to reverse a dusk-to-dawn switch. Please help.