BAC_AC_RetWtrCtrl_01

Application

The call template BAC_AC_RetWtrCtrl_01 is used for controlling the return temperature of the hot-water air heater.

The main tasks of the template are:

Control of the return temperature during the pre-rinsing process on plant startup.
Control of the return temperature to a frost protection set value during plant operation and standstill.

Interface

BAC_AC_RetWtrCtrl_01 1:

Diagram

Block diagram

VAR_INPUT

bEn        : BOOL;
rX         : REAL;
rSync      : BOOL;
bSync      : UDINT;
udiPltStp  : UDINT;

bEn: Return temperature control enable.

rX: Measured value of the return temperature

rSync: Synchronization value for the controller PID

bSync: Input for synchronization of the controller PID

udiPltStp: Steps during startup of the air-conditioning plant. See also BAC_AC_StartT_01

AR_OUTPUT

rY         : REAL;
bPreriRdy  : BOOL;

rY: Control value output

bPreriRdy: Pre-rinsing process message complete

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
SpPreriScaleX1	FB_BACnetAVSetpoint	AV object for input of the setpoint for prerinsing scaling point X1
SpPreriScaleX2	FB_BACnetAVSetpoint	AV object for input of the setpoint for prerinsing scaling point X2
SpPreriScaleY1	FB_BACnetAVSetpoint	AV object for input of the setpoint for prerinsing scaling point Y1
SpPreriScaleY2	FB_BACnetAVSetpoint	AV object for input of the setpoint for prerinsing scaling point Y2
SpRetWtrT	FB_BACnetAVSetpoint	AV object for input of the setpoint for the return temperature water
SpPreriScale	FB_BA_Chrct02	Function block for calculating the prerinsing temperature depending on the outside temperature for return temperature control during plant startup.
HysPreri	FB_BA_Swi2P	When the air-conditioning plant starts up at low outside temperatures, the heating coil is pre-rinsed with warm water. Only then are the dampers opened and the fans switched on. When the prerinsing temperature SpPreriScale_lrY has been reached, the function block HysPreri switches the variable bPreriRdy to TRUE. This tells the plant start program BAC_AC_StartT_01 that the prerinsing process is complete. If the input variable bEn is not set to TRUE during the plant startup, bPreriRdy is set immediately, without waiting for the prerinsing process to complete. This means that at higher outside temperatures the air-conditioning plant starts without prerinsing of the heating coil.
	SUB	The value of the subtraction is the lower switching point of the two-point switch HysPreri.
	OR	Outputs the prerinsing status through HysPreri or bEn.
X	FB_BACnetAVDisplay	AV object for displaying the return temperature of the hot water air heater. The AV object is referenced to the actual value input of the BACnet loop object PID.
W	FB_BACnetAVDisplay	AV object for displaying the setpoint of the return temperature controller. The AV object is referenced to the setpoint input of the BACnet loop object PID.
	>=, <=, AND, SEL	The value of this networks determines the setpoint for the return temperature control of the hot water air heater PID.
En	FB_BACnetBV1204	The BV object is used to display and activate the controller enable in the MCL or in a local operator display. The controller is enabled via the input variable bEn.
PID	FB_BACnetLoop1201	Loop object Return temperature control of the hot water air heater. It is responsible for the prerinsing of the heating coil during the plant start of the ventilation system and the control of the return temperature to the setpoint SpRetWtrT. The return temperature control is enabled at low outside temperatures by the input variable bEn. The enable takes place in the call template BAC_AC_PreHtr_01.
Y	FB_BACnetAVSetpoint	AV object for displaying the control value of the return temperature control. The AV object is referenced to the control value output of the BACnet loop object PID.

Version history

Version number	Comments
1.0.1	First release