Digital controller SR81 needed to set the desired temperature and keep it constant.
When solar collector temperature reaches a predetermined value, the digital controller automatically switches ON the circulation pump. The circulation pump automatically circulates the liquid, which transfers heat to the water through the heat exchanger. The digital controller regulates not only for heating of the water in the tank but also protects the tank from overheating, including the so-called, night mode. In this case, the controller sends a signal to switch the pump, the operation of which circulates the working fluid from the heat exchanger back to the collector tank. The controller has the ability to connect an additional temperature sensor and the second circulator.