BAC_AI_Enthalpy_01

Functional description

The template logs the two analog input values temperature and relative humidity of a Bus Terminal (see IO linking) and converts them to real process values.
The function block HX is used to calculate the dew point temperature, the specific enthalpy, the wet bulb temperature and the absolute humidity.

Interface

BAC_AI_Enthalpy_01 1:

Block diagram

VAR_OUTPUT

rH       : REAL;
rT       : REAL;
rX       : REAL;
rE       : REAL;
H_bHiLmt : BOOL;
H_bLoLmt : BOOL;
T_bHiLmt : BOOL;
T_bLoLmt : BOOL;

rH: current value of the analog input object H - relative humidity [%]

rT: current value of the analog input object T - temperature [°C]

rX: current value of the analog value object X - absolute humidity g water in kg of dry air [g/kg]

rE: calculated value enthalpy [kJ/kg]

H_bHiLmt: relative humidity High Limit

H_bLoLmt: relative humidity Low Limit

T_bHiLmt: temperature High Limit

T_bLoLmt: temperature Low Limit

VAR CONSTANT

PLT_NUM    : BYTE := 1;

PLT_NUM: all alarms and events of all plant components within a controller are included in a global alarm and event list. The assignment of events and alarms to a plant is defined by the assignment of a PLT_NUM plant number.
The recording and processing of an alarm from an aggregate or a device takes place within the templates by means of the alarm function block FB_BA_Alarm.
The evaluation of the alarms of a plant, e.g. for the generation of a collective message or for plant shutdown in case of relevant faults, takes place within the template BAC_PltAlm_01 by means of the function block FB_BA_AlarmPlt.
The evaluation of different plant events within the templates of a plant, takes place within the template BAC_PltComnMsg_01 by means of the function block FB_BA_ComnMsg.

Important! The assignment and evaluation of the alarms and events of a plant can only be done correctly if all templates of a plant have the same plant number!

The plant number can be assigned in the Project Builder in the parameter menu for the templates or via a column in the Excel import.

Program description

Instance	Type	Task
T	FB_BACnetAI1203	Analog input object for temperature display
AlmT	FB_BA_Alarm	Logging and further processing of the status flag Fault of the temperature Actions to be taken after the input Fault status flag was triggered can be parameterized in the template at function block AlmT.
T_TLog	FB_BACnetTLog1201	Trend logging of the measured value of the AI object T
H	FB_BACnetAI1203	Analog input object for relative humidity display
AlmH	FB_BA_Alarm	Logging and further processing of the status flag Fault of the relative humidity Actions to be taken after the input Fault status flag was triggered can be parameterized in the template at function block AlmH.
H_TLog	FB_BACnetTLog1201	Trend logging of the measured value of the AI object H
HX	FB_BA_HX	This function block is used to calculate the dew point temperature, the specific enthalpy and the absolute humidity. The temperature, the relative humidity and the barometric air pressure are required for the calculation of these parameters. Enthalpy is a measure of the energy of a thermodynamic system.
X	FB_BACnetAVDisplay	Analog value object for absolute humidity display
X_TLog	FB_BACnetTLog1201	Trend logging of the measured value of the AV object X

IO linking

Variables for linking with the terminals

Parameter	Type	optional	Process image
AI_Temperature	INT		Input	Analog input - temperature
AI_Relative_Humidity	INT		Input	Analog input - relative humidity

Version history

Version number	Comments
1.0.1	First release