When the temp. of the panels is superior to that of the water in the boiler, the thermostat starts the pump the allows for temp exchange between the panels and the boiler. With clock visability of temp.of collector and boiler.Collector 0°-200°C Feed 230V exit conn. for pump to boiler 5A Dimensions 131x88x(H)27.2 Probes connectabile upto 100mt.