FB_BA_AC_SeqT

The template represents the start and control of the supply air temperature sequence control of an air conditioning (HVAC) system.

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

Start behavior of the sequence

On startup of the air-conditioning plant the system determines whether to start with the heating, cooling or heat recovery sequence. The start sequence is selected depending on the plant operation mode eOpMode and the outside temperature fTWth. The result of the network at the input nNumStartCtrl of the function block SeqLink determines the start controller of the control sequence.

If the sequence controller specified at nNumStartCtrl is not ready for operation, the parameter enum eNoStartCtrlFound of the function block SeqLink is used to define the procedure for finding a new start controller. This ensures that the sequence always starts.

Control of the sequence control

Only one element of the sequence can be controlling. If a regulating sequence controller reaches its maximum or minimum value (Ymax,Ymin), the next controller in the sequence is switched to depending on the control direction.

Switching to another sequence controller can be delayed by specifying the time nSwiOverTi of the function block SeqLink.

The order of the temperature control sequences is specified by the globally defined enumeration variable E_BA_SeqNumber_T.

Block diagram

Principle diagram plant

Syntax

FUNCTION_BLOCK FB_BA_AC_SeqT EXTENDS FB_BA_View
VAR_INPUT
  bEn                 : BOOL;
  eOpMode             : E_BA_AC_OpMod01;
  fTWth               : REAL;
END_VAR
VAR_OUTPUT
  bSumLmt             : BOOL;
  bWinLmt             : BOOL;
  nActvSeqCtrl        : UDINT;
END_VAR
VAR_IN_OUT
  stTSeqLink          : ST_BA_SeqLink;
END_VAR
VAR_INPUT CONSTANT
  WthTLmtSum          : FB_BA_AV_Op;
  WthTLmtWin          : FB_BA_AV_Op;
  SeqLink             : FB_BA_SequenceLinkBase;
  ActvSeqCtrl         : FB_BA_MV_Op;
END_VAR
VAR
  WthTLmtWinHys       : FB_BA_Swi2P;
  WthTLmtSumHys       : FB_BA_Swi2P;
  StartSeq            : FB_BA_PrioSwi_UDI08;
END_VAR

Inputs

Name	Type	Description
bEn	BOOL	Activation of the supply air temperature sequence control.
eOpMode	E_BA_AC_OpMod01	The plant operation mode is used for the selection of the start sequence controller.
fTWth	REAL	Input for the weather temperature.

Outputs

Name	Type	Description
bSumLmt	BOOL	The output variable indicates that the ventilation system starts with the cooling sequence.
bWinLmt	BOOL	The output variable indicates that the ventilation system starts with the heating sequence.
nActvSeqCtrl	UDINT	The output variable shows the number of the active sequence controller.

Inputs/outputs

Name	Type	Description
stTSeqLink	ST_BA_SeqLink	Data and command structure between the individual sequence controllers FB_BA_SeqCtrl of the temperature control sequence (preheater, energy recovery, cooler) and the control block SeqLink.

Inputs CONSTANT

Name	Type	Description
WthTLmtSum	FB_BA_AV_Op	AV object for input of an outside temperature limit value from which the air-conditioning plant starts in the heating sequence.
WthTLmtWin	FB_BA_AV_Op	AV object for input of an outside temperature limit value from which the air-conditioning plant starts in the cooling sequence
SeqLink	FB_BA_SequenceLinkBase	The function block SeqLinkH is the core of the template FB_BA_AC_SeqT. The sequence linker is connected to the supply air controllers of the sequence via the data structure stTSeqLink. It is the central control element, and responsible for switching between the sequence controllers and starting of the control sequence.
ActvSeqCtrl	FB_BA_MV_Op	The MV object indicates the currently active sequence controller.

Variables

Name	Type	Description
WthTLmtWinHys	FB_BA_Swi2P	Two-position switch which generates the binary switching signal for bWinLmt based on the weather temperature fTWth and the winter weather temperature limit value WthTLmtWin.
WthTLmtSumHys	FB_BA_Swi2P	Two-position switch which generates the binary switching signal for bWinLmt based on the weather temperature fTWth and the limit value weather temperature summer WthTLmtSum.
StartSeq	FB_BA_PrioSwi_UDI08	The priority switch is used to select the start sequence. Prio 1: bEN01 In the overheating protection E_BA_AC_OpMod01.eOverHeatingProtection, the cooling sequence (E_BA_AC_SeqNumber.eCooler) is always started. Prio 2: bEN02 In the cool-down protection mode E_BA_AC_OpMod01.eCoolDownProtection, the heating sequence (E_BA_AC_SeqNumber.ePreHeater) is always started. Prio 4: bEN04 The upstream function block WthTLmtWinHys checks whether the actual outside temperature is below the critical value of AV object WthTLmtSum. If this is the case, the air-conditioning system starts with the sequence controller of the preheater (E_BA_AC_SeqNumber.ePreHeater). Prio 5: bEN05 The upstream function block WthTLmtSumHys checks whether the actual outside temperature is above the value of AV object WthTLmtSum. If this is the case, the air conditioning system starts with the sequence controller of the cooler (E_BA_AC_SeqNumber.eCooler). Prio 8: bEN08 In the transitional periods between winter and summer, the inputs of StartSeq.bEn04 and StartSeq.bEn05 are FALSE on account of the weather. In this case, priority 8 applies to the priority switch, meaning that the air-conditioning system is started in the energy recovery sequence (E_BA_AC_SeqNumber.eEnergyRecovery).

Name

Type

Description

WthTLmtWinHys

FB_BA_Swi2P

Two-position switch which generates the binary switching signal for bWinLmt based on the weather temperature fTWth and the winter weather temperature limit value WthTLmtWin.

WthTLmtSumHys

FB_BA_Swi2P

Two-position switch which generates the binary switching signal for bWinLmt based on the weather temperature fTWth and the limit value weather temperature summer WthTLmtSum.

StartSeq

FB_BA_PrioSwi_UDI08

The priority switch is used to select the start sequence.

Prio 1: bEN01

In the overheating protection E_BA_AC_OpMod01.eOverHeatingProtection, the cooling sequence (E_BA_AC_SeqNumber.eCooler) is always started.

Prio 2: bEN02

In the cool-down protection mode E_BA_AC_OpMod01.eCoolDownProtection, the heating sequence (E_BA_AC_SeqNumber.ePreHeater) is always started.

Prio 4: bEN04

The upstream function block WthTLmtWinHys checks whether the actual outside temperature is below the critical value of AV object WthTLmtSum. If this is the case, the air-conditioning system starts with the sequence controller of the preheater (E_BA_AC_SeqNumber.ePreHeater).

Prio 5: bEN05

The upstream function block WthTLmtSumHys checks whether the actual outside temperature is above the value of AV object WthTLmtSum. If this is the case, the air conditioning system starts with the sequence controller of the cooler (E_BA_AC_SeqNumber.eCooler).

Prio 8: bEN08

In the transitional periods between winter and summer, the inputs of StartSeq.bEn04 and StartSeq.bEn05 are FALSE on account of the weather. In this case, priority 8 applies to the priority switch, meaning that the air-conditioning system is started in the energy recovery sequence (E_BA_AC_SeqNumber.eEnergyRecovery).

Requirements

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