Return Temperature Controller for Boiler Blocks (v2.0)

Lib.Mervis.v2_0.ReturnTempController

  • Lib.Mervis

Auxiliary block for boilers used for controlling the return water temperature.

program test
    var
        returntempctrl: lib.mervis.v2_0.ReturnTempController;
    end_var

    returntempctrl();
end_program
Name Data TypeRetainMandatory to Connect Meaning
Demand Lib.Mervis.v2_0.StageControlTypeNo Yes
State Lib.Mervis.v2_0.StageInfoType No Yes
ReturnTemperaturereal No No Return water temperature
SetPoint real No No Desired return water temperature
Xp real No No PI controller - proportional band width
Ti real No No PI controller - integral time constant
Hysteresis real No No Hysteresis used for switching the short-circuit pump
ControlMethod ReturnControlMethodType No No Method used for controlling the return water temperature
NameData Type Meaning
MinimalSetpoint real Calculated minimum desired output temperature
SetPointIncrease real Calculated increase in desired output temperature
ValveDemand real Request to open the three-way valve
ShortCircuitPumpDemandbool Request to activate the short-circuit pump

The block implements control of the return water temperature using the following methods:

  • Increasing Desired Temperature - The increase is controlled by a simple PI controller, which adjusts the desired temperature from the cascade controller.
  • Three-way Valve in the Return Line - Here, hot water from the boiler output is mixed with cooler water from the heating system, thereby increasing the return water temperature to the boiler.
  • Short-circuit Pump - Used to increase the desired temperature, and simultaneously, when the difference between the output and return water temperatures is less than the set hysteresis, it activates the command for the short-circuit pump/valve connected between the boiler output and return lines.
  • © Energocentrum Plus, s.r.o. 2017 - 2024