BAC_AC_PreHtr_01

Application

The call template BAC_AC_PreHtr_01 is used to control a hot-water air heater.

The main tasks of the template are:

Control of the supply air temperature
Control of the return temperature
Frost monitoring air side with frost protection thermostat FrstThermostat
Frost monitoring air side with analog frost protection sensor FrstT
Frost monitoring water side with return temperature sensor RetWtrT
Enable the heater pump
Control and monitoring of the heater valve

Interface

BAC_AC_PreHtr_01 1:

Plant diagram 01

Plant diagram 02

Block diagram

VAR_INPUT

rSuAT          : REAL;
rSpHtg         : REAL;
bDeHum         : BOOL;
udiPltStp      : UDINT;
udiOpMod       : UDINT;
bWthTLmttCrit  : BOOL;
bRst           : BOOL;

rSuAT: Measured value of the supply air temperature

rSpHtg: Set value for the supply air temperature

bDeHum: Status message dehumidification mode

If dehumidification is active, the supply air temperature controller SuA_PID is disabled and therefore removed from the sequence control.

udiPltStp: Plant start sequence steps. The plant steps are generated in the system start program BAC_AC_StartT_01.

udiOpMod: Plant operation mode. The plant operation mode is determined in the mode selection programBAC_AC_OpMod_01.

bWthTLmtCrit: Status message weather temperature critical. This information is generated in the system start program BAC_AC_StartT_01.

The following actions are triggered when the outside temperature falls below a critical value:

Heater pump activation, forced pump operation
Return temperature control enable BAC_AC_RetWtrCtrl_01
During plant startup prerinsing mode is active, see BAC_AC_RetWtrCtrl_01

bRst: Acknowledge frost protection message.

VAR_OUTPUT

bFrst      : BOOL;
bPreriRdy  : BOOL;

bFrst: Frost protection program output active.

bPreriRdy: Pre-rinsing process output complete.

Program description

Instance	Type	Task
RetWtrT	BAC_AI_02	Subtemplate AI object return temperature sensor
FrstT	BAC_AI_02	Subtemplate AI object frost protection sensor air side
FrstThermostat	BAC_BI_02	Subtemplate BI object frost protection thermostat
SuA_PID	BAC_AC_PreHtr_PID_01	Subtemplate loop object supply air temperature control
RetWtrCtrl	BAC_AC_RetWtrCtrl_01	Subtemplate return temperature control of the hot water air heater
FrstPrt	BAC_FrstPrt_01	Subtemplate frost protection program
Vlv	BAC_Uni_Vlv_01_13	Subtemplate control valve
Pu	BAC_Uni_Pu1st_01_189	Subtemplate pump
	MAX	MAX selection of the control signals for supply air temperature control SuA_PID and return temperature control RetWtrCtrl
	OR	Collects frost events and passes them to the frost protection program. The frost event occurs in the following conditions The frost protection thermostat is triggered The air temperature after the heating coil falls below the LowLimit The return temperature falls below the LowLimit (RetWtr.bLoLmt = TRUE)

Version history

Version number	Comments
1.0.1	First release