After Unit Start/Stop (parameter) is ON, the program immediately opens Circulating Pump (DO, OFF -> ON) if Secondary Return Water Pressure Setpoint (AI) is at least 0.5 bar higher than Circulating Water Pump Shut-down Return Water Pressure Setpoint. Since Secondary Supply Water Temperature (AI) defaults to 0 °C, which is lower than Secondary Supply Water Temperature Setpoint (parameter, 50 °C), the primary valve (AO) opens gradually from 0 to 10 V (fully open). Since Secondary Return Water Pressure (AI) defaults to 0 bar, which is lower than Secondary Return Water Pressure Setpoint (parameter, 2.5 bar), the makeup pump (DO) turns on.
Secondary Supply Water Temperature is adjustable. If the temperature is higher than 50 °C, the primary valve (AO) gradually closes from 10 to 0 V.
Secondary Return Water Pressure is also adjustable. If the pressure is 4 bar higher than Secondary Return Water Pressure Setpoint, the makeup pump (DO) closes.
Circulation Pump Fault Alarm: Occurs at any time a circulating pump fault (DI) is closed. Once it occurs, the circulating pump output (DO) switches off and the primary valve output (AO) closes to 0 V.
Makeup Pump Fault Alarm: Occurs at any time a makeup pump fault (DI) is closed. Once it occurs, the makeup pump output (DO) switches off.
Secondary Supply Water Pressure High Alarm: Occurs when Secondary Supply Water Pressure (AI) is higher than Circulating Water Pump Shut-down Supply Water Pressure Setpoint after Unit Start/Stop is ON. Once it occurs, the circulating pump output (DO) switches off and the primary valve output (AO) closes to 0 V.
Secondary Return Water Pressure Low Alarm: Occurs when Secondary Return Water Pressure (AI) is lower than Circulating Water Pump Shut-down Supply Water Pressure Setpoint after Unit Start/Stop is ON. Once it occurs, the circulating pump output (DO) switches off and the primary valve output (AO) closes to 0 V.