FB_BA_AC_ErcPl_01

The template represents the open-loop and closed-loop control of an energy recovery system with plate heat exchanger.

The main tasks of the template are:

Control of the supply air temperature
Minimum limitation of exhaust air temperature
Anti-icing of the heat exchanger by means of a differential pressure sensor above the heat exchanger
Control of a bypass damper system
Collecting and evaluating safety-relevant faults using the PlantLock
To be part of the step sequence control of an air conditioning system, see Aggregates

The exhaust air minimum limiter TExhACtrl and the frost protection program IcePrtcDiffPrssCtrl limit the control value of the temperature sequence controller TSuACtrl of the energy recovery system via a minimum selection to prevent the heat exchanger from icing up.

Principle diagram 01

The diagram shows the intended use of the template with the plant elements involved.

Principle diagram 02

The diagram shows the integration of the template within a plant.

	The initialization of the template takes place within the method FB_Init.

Block diagram

Syntax

FUNCTION_BLOCK FB_BA_AC_ErcPl_01 EXTENDS FB_BA_View
VAR_INPUT
  fSpTSuA                 : REAL;
  fTSuA                   : REAL;
  bSyncTSuACtrl           : BOOL;
  fSyncTSuACtrl           : REAL;
  bDehumf                 : BOOL;
  fTExhA                  : REAL;
  fTExtA                  : REAL;
  fTWth                   : REAL;
END_VAR
VAR_OUTPUT
  fPresentValue           : REAL;
  eAction                 : E_BA_Action;
  bActiveSeqCtrl          : BOOL;    
END_VAR
VAR_IN_OUT
  stTSeqLink              : ST_BA_SeqLink;
  stAggregate             : ST_BA_Aggregate;
END_VAR
VAR_INPUT CONSTANT    
  TSuACtrl                : FB_BA_AC_PreHtrTSuACtrl;
  TExhACtrl               : FB_BA_PID_Sp;
  Dmp                     : FB_BA_ActuatorAnalog;
  DiffPrssSensor          : FB_BA_SensorAnalog;
  Damping                 : FB_BA_FilterPT1;
  IcePrtcDiffPrssCtrl     : FB_BA_PID_Sp;
  PlantLock               : FB_BA_PlantLock;
  Aggregate               : FB_BA_Aggregate;
END_VAR
VAR
  bPrioSfty               : BOOL;
  bPrioCrit               : BOOL;
  PrioSwiVal              : FB_BA_PrioSwi_B04;
END_VAR

Inputs

Name	Type	Description
fSpTSuA	REAL	Setpoint of the supply air temperature
fTSuA	REAL	Measured value of the supply air temperature
bSyncTSuACtrl	BOOL	Pulse for synchronization of the sequence controller TSuACtrl.
fSyncTSuACtrl	REAL	Value for the synchronization of the supply air sequence controller TSuACtrl.
bDehumf	BOOL	Input dehumidification mode active. This state has an effect on the sequence control in the supply air temperature control TSuACtrl template.
fTExhA	REAL	Measured value exhaust air temperature
fTExtA	REAL	Measured value extract air temperature
fTWth	REAL	Measured value weather temperature

Outputs

Name	Type	Description
fPresentValue	REAL	Current value of the bypass damper system
eAction	E_BA_Action	The output of the control direction of the supply air controller TSuACtrl is required within an air conditioning system for the setpoint strategy.
bActiveSeqCtrl	BOOL	The sequence controller TSuACtrl is the active one in the sequence control.

Inputs/outputs

Name	Type	Description
stSeqLink	ST_BA_SeqLink	The data and command structure is the link between the supply air temperature sequence controller Ctrl and the supply air temperature sequence controller TSeqLink of an air conditioning system.
stAggregate	ST_BA_Aggregate	Bidirectional aggregate structure via which the enables and switching values are transmitted to the evaluation function block of the step sequence control Aggregate. The aggregate structure transmits the recorded feedback signals up and down to the central plant control.

Inputs CONSTANT

Name	Type	Description
TSuACtrl	FB_BA_AC_PreHtrTSuACtrl	The function block represents the supply air temperature control of energy recovery and is part of the temperature sequence control of an air conditioning system. The control signal is forwarded to the analog control of damper Dmp via a minimum selection.
TExhACtrl	FB_BA_PID_Sp	The function block represents the exhaust air temperature control for the anti-icing of the plate heat exchanger.
Dmp	FB_BA_ActuatorAnalog	The function block is used to control the analog damper of the plate heat exchanger.
DiffPrssSensor	FB_BA_SensorAnalog	The analog input object represents a differential pressure sensor above the heat exchanger. This is the control variable for the differential pressure control IcePrtcDiffPrssCtrl.
Damping	FB_BA_FilterPT1	The function block is used to damp the differential pressure sensor DiffPrssSensor.
IcePrtcDiffPrssCtrl	FB_BA_PID_Sp	The function block represents the differential pressure control for the anti-icing of the heat exchanger.
PlantLock	FB_BA_PlantLock	When the function block is called, the relevant faults of the event-enabled objects are collected and output at this and lower levels of the template. These relevant faults cause specific switching actions via the variables bPrioSfty and bPrioCrit in the template. The parameterization of the lock priority of the event-enabled objects can be found in the FB_init of this template.
Aggregates	FB_BA_Aggregate	The aggregate function block represents a receive block of a step sequence controller. Within the function block, the aggregate structure stAggregate is evaluated and integrated into the template using the inputs and outputs.

Variables

Name	Type	Description
bPrioSfty	BOOL	The variable is an evaluation of the Safety lock priority of the event-enabled objects in the project structure and causes targeted switching actions in the template when a relevant fault is triggered.
bPrioCrit	BOOL	The variable is an evaluation of the Critical lock priority of the event-enabled objects in the project structure and causes targeted switching actions in the template when a relevant fault is triggered.
PrioSwiVal	FB_BA_PrioSwi_B04	The priority switch PrioSwiVal determines the switching conditions and enables for the supply air temperature control TSuACtrl and the differential pressure control for anti-icing IcePrtcDiffPrssCtrl using the aggregate function block Aggregate and the global variable list Priority.

Requirements

Development environment	Necessary function
TwinCAT from v3.1.4024.35	TF8040 \| TwinCAT Building Automation from V5.0.0.0