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Switch 4: Heating/Cooling Control Mode

The FCU application is designed to cooperate with two types of heating/cooling devices (analog or digital). The type of control is selected with the S3 CFG DIP switch number 4, where the off position corresponds to the digital control and on position corresponds to the analog control.

Analog Control Mode

In this mode, the algorithm is controlled by the PI regulator, which calculates the output value in the range from -100% to 100%, basing on the Effective_Setpoint and CV (room temperature) values. The range from -100% to 0 is for cooling control, and the range from 0 to 100% is for heating control. Basing on this output, the FCU controller controls actuators in binary or analog control. The PI regulator can be adjusted with Kp and Ti network parameters. In order to prevent the algorithm from activating heating and cooling in rapid succession, the Valves_dead_band value can be adjusted. It defines temperature deviation from setpoint, if the PI regulator does not activate neither heating or cooling mode.

Valve dead band operation chart

Digital Control Mode

In this mode, the control algorithm works as a typical thermostat, basing on the Effective Setpoint and Control Value with heating/cooling Diff parameters.

Note: This mode affects also outputs enabled/disabled in the 1st stage. In the first stage, outputs O4 and O5 can work only in binary control mode. If the user wants to run the binary control mode without operating these outputs, the outputs can be disabled by setting corresponding to network parameter in false state (O4: HTG_Relays_Enable, O5: CLG_Relays_Enable).

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