SOLAR CONTROLLERS and TEMPERATURE SENSORS
The Solar Controller is the brain of our solar system.
The controller monitors the temperature in the solar collector located on the roof and also the temperature in the water cylinder or in the swimming pool.

During the night the collector will not collect any energy so the controller will switch the circulation pump off. As the sun rises the collector will warm, as soon as the controller senses that the collector is 6 degrees higher in temperature than the water in the hot water cylinder, the solar controller will start the solar circulation pump, which transfers the heat to the hot water cylinder.

The differential controller tells the pump when to turn on and off. The controller, via sensors connected to the flat plate collector (on the roof) and the storage tank, determines whether the flat plate collector outlet is sufficiently warmer than the bottom of the tank to turn the circulating pump on.

The sensors are located at the collector outlet, and at the bottom of the solar storage tank. These sensors are thermistors that change their resistance with temperature. The differential control compares the resistances of the two sensors. It turns the pump on when the collectors are warmer (usually 20°F) than the bottom of the solar storage tank to collect useful heat. The controller usually shuts the pump down when the temperature difference is 3 to 50F.

Our solar controllers can also store and output data to a computer or digital display. They also have a freeze prevention feature which pulses the pump if at regular intervals when the collector temperature drops below 10c.

Our domestic systems use a 12 volt solar powered controller and 12 volt pump which is powered by a photovoltaic panel, a backup battery is also incorporated in the 12 volt system.