Operation

Relay #1 enables the boilers to operate if the outdoor air temperature is below the low setpoint and the schedule is occupied. Each boiler is enabled to operate if the previous boiler is currently active and has been on for at least 5 minutes. All four boilers monitor the same analog input sensor for the Water Temperature reading. The #1 Enable Relay can monitor a global broadcast from another controller on the RS-485 communications loop for the outdoor air temperature but, in this case, we are reading the Outdoor Air Temperature on Analog Input #2. Notice on the Analog Output #2 configuration screen that it was also configured to broadcast on Global Analog Channel #2. That is because the GPC Plus doesn’t have any other way of knowing that it is the one reading the outdoor air temperature.

The voltage output is not used so no control source is selected, and no other related setpoints require modification.

Shown below is a sample Status Screen for this sample application. Notice that the boilers are not enabled even though the schedule is active because the outdoor air temperature is too high.