BAC_AC_CasCtrlT_02

Application

The template is a cascade controller for the supply air temperature, consisting of two master controllers for set value calculation for heating, cooling and energy recovery.

Interface

BAC_AC_CasCtrlT_02 1:

Plant diagram 01

Plant diagram 02

Block diagram

VAR_INPUT

rRmT         : REAL; 
rSpRmHtg     : REAL;
rSpRmCol     : REAL;
udiPltStp    : UDINT; 
udiOpMod     : UDINT;

rRmT: Input variable to which the room temperature is applied. The room temperature is the control value of the PID master controllers. If no room temperature is available, the outlet air temperature of a ventilation system can be used as control value.

rSpRmHtg: Input variable for the room temperature set value for heating, see template BAC_AC_SpRmT_02.

rSpRmCol: Input variable for the room temperature set value for cooling, see template BAC_AC_SpRmT_02.

bErcActn: Input variable to which the direction of action for the energy recovery is applied. The set value for the energy recovery is determined depending on the direction of action.
TRUE = direct = cooling; FALSE = reverse = heating

udiPltStp: Steps during startup of the air-conditioning plant. See also BAC_AC_Start_01

udiOpMod: Plant operation mode. See also BAC_AC_OpMod_01

VAR_OUTPUT

rSpHtg     : REAL; 
rSpErc     : REAL; 
rSpCol     : REAL; 
rYMax      : REAL;
rYMin      : REAL;

rSpHtg: Calculated set value of the supply air temperature for heating

rSpErc: Calculated set value of the supply air temperature for energy recovery

rSpCol: Calculated set value of the supply air temperature for cooling

rYMax: Upper value of the controller output limitation

rYMin: Lower value of the controller output limitation

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
X	FB_BACnetAVDisplay	The input variable rRmT is connected to the AV object. It is referenced to the actual value inputs of the BACnet loop objects PID_Htg and PID_Col.
W_Htg	FB_BACnetAVDisplay	The input variable rSpRmHtg is connected to the AV object. It is referenced to the setpoint input of the BACnet loop object PID_Htg.
W_Col	FB_BACnetAVDisplay	The input variable rSpRmCol is connected to the AV object. It is referenced to the setpoint input of the BACnet loop object PID_Col.
OpModPrio	FB_BA_MMUX_B08	The multiplexer defines the enable conditions of the two PID master controllers depending on the plant operation mode udiOpMod.
		udiOpMod			Enable cascade control
		OPMOD_AC_SMEXTTPRG	Smoke extraction program		TRUE
		OPMOD_AC_SMEXTTSUA	Smoke extraction supply air		TRUE
		OPMOD_AC_SMEXTTEXHA	Smoke extraction exhaust air		TRUE
		OPMOD_AC_FORCVENT	Forced ventilation		TRUE
		OPMOD_AC_MANON	Manual on		TRUE
		OPMOD_AC_ON	On		TRUE
En	FB_BACnetBV1204	The BV object is used to display the controller enable in the MCL or in a local operator display.
	>=, AND	The result of this network is the enable of the two PID master controllers. The enable depends on the plant operation mode udiOpMod and the plant steps udiPltStp during startup of the ventilation system.
PID_Htg	FB_BACnetLoop1201	Master controller for a room temperature control via room supply air cascade. It provides the supply air temperature setpoint for heating.
PID_Col	FB_BACnetLoop1201	Master controller for a room temperature control via room supply air cascade. It provides the supply air temperature setpoint for cooling.
rtrigSync	R_TRIG	Upon receipt of the controller enable En, rtrigSync triggers synchronization of the two master controllers PID_Htg / PID_Col with the input value lrSync.
Y_Htg	FB_BACnetAVSetpoint	The AV object is referenced to the control value output of the BACnet loop object PID_Htg. It shows the supply air temperature setpoint for heating.
TLogY_Htg	FB_BACnetTLog1201	Trend logging of the supply air temperature setpoint for heating Y_Htg.
Y_Col	FB_BACnetAVSetpoint	The AV object is referenced to the control value output of the BACnet loop object PID_Col. It shows the supply air temperature setpoint for cooling.
TLogY_Col	FB_BACnetTLog1201	Trend logging of the supply air temperature setpoint for cooling Y_Col.
PID_Sync	FB_BA_PISync1201	The function block synchronizes the parameters for the two master controllers PID_HTG / PID_COL.
tonDlySp	TON SEL	Upon receipt of the controller enable En, this network forwards the supply air temperature setpoints to the downstream multiplexers with a delay.
OpModSpHtg	FB_BA_MMUX_R04	The multiplexer defines the heating setpoint rSpHtg depending on the plant operation mode udiOpMod in certain cases.
		udiOpMod			Setpoint
		OPMOD_AC_COLDWNPRTC	Support operation, cooling protection		rYMax, upper setpoint of the controller output limitation
OpModSpCol	FB_BA_MMUX_R04	The multiplexer defines the cooling setpoint rSpCol depending on the plant operation mode udiOpMod in certain cases.
		udiOpMod			Setpoint
		OPMOD_AC_OVRHTGPRTC	Overheating protection		rYMin, lower setpoint of the controller output limitation
SelSpErc	FB_BACnetBV1204	Selection strategy setpoint energy recovery. TRUE: average of rSpHtg and rSpCol; FALSE: depends on the control direction, defined by input bErcActn
	SEL, ADD, DIV, SEL	The result of this network supplies two setpoints for energy recovery. Which value is used depends on the energy recovery setpoint strategy, see SelSpErc
OpModSpErc	FB_BA_MMUX_R04	The multiplexer defines the energy recovery setpoint rSpErc depending on the plant operation mode udiOpMod in certain cases.
		udiOpMod				Setpoint
		OPMOD_AC_COLDWNPRTC		Support operation, cooling protection		rYMax, upper setpoint of the controller output limitation
		OPMOD_AC_OVRHTGPRTC		Overheating protection		rYMin, lower setpoint of the controller output limitation

Version history

Version number	Comments
1.0.1	First release