FB_HVACHeatingCurveEx

FB_HVACHeatingCurveEx 1:

Application

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: FB_HVACHeatingCurveEx 3: 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:= eDataSecurityType_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;           ° C
bInvalidParameter   : BOOL;

rTempSetpoint: the calculated setpoint for the flow temperature.

bInvalidParameter: indicates that an incorrect input parameter is present. 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.