FB_HVACHeatingCurveEx

The heating curve serves to determine the setpoint for the flow temperature of a heating circuit, depending on the outside temperature. Compared with the FB_HVACHeatingCurve, the heating curve is shown as a function.

FB_HVACHeatingCurveEx 2:

z = 20 - rDesignTemp;

u = 20 - rOutsideTemp;

VAR_INPUT

eDataSecurityType    : E_HVACDataSecurityType;
bSetDefault          : BOOL;
rOutsideTempDamped   : REAL;
bDayOperation        : BOOL;
bReset               : BOOL;

eDataSecurityType: If eDataSecurityType:= eHVACDataSecurityType_Persistent, the persistent VAR_IN_OUT variables of the function block are stored in the flash of the computer if a value changes. For this to work, the function block FB_HVACPersistentDataHandling must be instanced once in the main program, which is called cyclically. Otherwise the instanced FB is not released internally.

A change of value can be initiated by the building management system, a local operating device or via a write access from TwinCAT. When the computer is restarted the saved data are automatically read back from the flash into the RAM.

Application example: example_persistent.zip

If eDataSecurityType:= eHVACDataSecurityType_Idle the persistently declared variables are not saved in a fail-safe manner.

Notice
A cyclically changing variable must never be linked with the IN_OUT variable of a function block, if eDataSecurityType:= eHVACDataSecurityType_Persistent. It would lead to early wear of the flash memory.

bSetDefault: If the variable is TRUE, the default values of the VAR_IN_OUT variables are adopted.

rOutsideTempDamped: This input variable transfers the current damped outside temperature to the function block.

bReset: Acknowledge input in the event of a fault.

VAR_OUTPUT

rTempSetpoint     : REAL;
bInvalidParameter : BOOL;

rTempSetpoint: The calculated setpoint [°C] for the flow temperature.

bInvalidParameter: Indicates that there is an incorrect input parameter. bInvalidParameter must be acknowledged with bReset.

VAR_IN_OUT

rMinTempSetpoint  : REAL;
rMaxTempSetpoint  : REAL;
rDesignTemp       : REAL;
rSlope            : REAL;
rCurve            : REAL;

rMinTempSetpoint: The minimum value for the setpoint of the flow temperature [°C] is defined by this variable. The variable is saved persistently. Preset to 20.

rMaxTempSetpoint: The maximum value for the setpoint of the flow temperature [°C] is defined by this variable. The variable is saved persistently. Preset to 90.

rDesignTemp: Design temperature [°C] for the dimensioning of a heating system. Typical values for Germany lie between -12 ° C and -16 ° C. The variable is saved persistently. Preset to -16.

rSlope: Factor for the slope. The variable is saved persistently. Preset to 1.

rCurve: Factor for the curve. The variable is saved persistently. Preset to 0.5.

Course of the heating characteristic curves

FB_HVACHeatingCurveEx 3:

Flow temperature of 50 °C at approx. -9.2 °C

Flow temperature of 50 °C at approx. -9.4 °C

Flow temperature of 50 °C at approx. -7.8 °C

Flow temperature of 50 °C at approx. -8.3 °C

FB_HVACHeatingCurveEx 5:

Flow temperature of 60 °C at approx. -0.2 °C

Flow temperature of 60 °C at approx. -3.0 °C

Requirements

Development environment	required library	required function
TwinCAT 3.1 build 4022.16 or higher	Tc2_HVAC V3.3.1.0	TF8000 \| TC3 HVAC V1.0.0.0