Return Temperature Controller for Boiler Blocks (v2.0)

Lib.Mervis.v2_0.ReturnTempController

Description

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 Type	Retain	Mandatory to Connect	Meaning
Demand	Lib.Mervis.v2_0.StageControlType	No	Yes
State	Lib.Mervis.v2_0.StageInfoType	No	Yes
ReturnTemperature	real	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

Name	Data 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
ShortCircuitPumpDemand	bool	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.