The popular Resol DeltaSol BS solar thermal controller series offers many possibilities - drainback option, cooling functions and pump speed control in all versions, thermal disinfection, thermostat function and evacuated tube collector function in the two-relay versions BS/4 and BS Plus. With the BS Plus, you can choose from 10 basic system layouts, including one for heat dissipation. An extended priority logic controls the distribution of solar heat between two heat sinks - be it two tanks or a tank and a swimming