BAC_AC_CasCtrlT_01

Application

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

Interface

BAC_AC_CasCtrlT_01 1:

Plant diagram 01

Plant diagram 02

Block diagram

VAR_INPUT

rRmT         : REAL; 
rSpRm        : 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 controller. If no room temperature is available, the outlet air temperature of a ventilation system can be used as control value.

rSpRm: Input variable for the room temperature set value, see template BAC_AC_SpRmT_01.

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	BACnetAVDisplay	The input variable rRmT is connected to the AV object. It is referenced to the actual value input of the BACnet loop object PID.
W	BACnetAVDisplay	The input variable rSpRm is connected to the AV object. It is referenced to the setpoint input of the BACnet loop object PID.
OpModPrio	FB_BA_MMUX_B08	The multiplexer defines the enable conditions of the PID master controller 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
En	>=, AND	The result of this network is the PID master controller enable. The enable depends on the plant operation mode and the plant steps udiPltStp during startup of the ventilation system.
PID	FB_BACnetLoop1201	Master controller for a room temperature control via room supply air cascade. Supplies a simple supply air temperature setpoint.
rtrigSync	R_TRIG	Upon receipt of the controller enable En, rtrigSync triggers synchronization of the master controller PID with its input value lrSync.
Y	FB_BACnetAVSetpoint	The AV object is referenced to the control value output of the BACnet loop object PID. It shows the supply air temperature setpoint.
TLogY	FB_BACnetTLog1201	Trend logging of the supply air temperature setpoint Y
tonDlySp	TON SEL	Upon receipt of the controller enable En, this network forwards the supply air temperature setpoint 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		udiOpMod
		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
OpModSpErc	FB_BA_MMUX_R04	The multiplexer defines the energy recovery setpoint rSpErc depending on the plant operation mode udiOpMod in certain cases. see "Extracted nested table 121"
		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