... Control thermal system; 3.Temperature differential mechanism; 4.RS485/232. Temperature Differential Solar Water System ControllerKTD-Pro ... loop and closed loop. Main functions are: temperature differential control, conventional energy control, thermostat, recirculation, frost ... underneath the displayTemperature range: 0°C-99°CTemperature differential: adjustable within3°C-15°CWater volume: 1-6 ...