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