UST500 CONTROL BOARD40 06MC0074@00B010014/04/2010Automatic changeoverThe automatic changeover function can be enabled in parameter St01.Heat or cool mode are activated via two different differentials that can be set in the relative parameter (Pa St03 for the heat mode and Pa St04for the cool mode); in the neutral zone (between the two setpoints), the mode can be set from a key as well (if enabled) See the graph below formore details; in the example, the differentials are both positive but can also be set with a negative value.Example of automatic changeover based on external air temperatureMODE Operating modeEXT TEMP. External temperatureCOOLSETPOINTtr04 - Temperature controller setpoint in CoolHEATSETPOINTtr05 - Temperature controller setpoint in HeatSt03 Differential for automatic mode change in HeatSt04 Differential for automatic mode change in CoolN.B.: St04 is added to COOL setpoint; St03 is added to HEAT setpoint.N.B.: St03+St04 < HEAT setpoint - COOL setpoint, or the sum of differentials must never be more than HEAT setpoint - COOL setpointCOOLHEATONSt04 St03Set COOL Set HEATExt Temp.MODE
