BAC_AC_ErcPl_02

Application

The template BAC_AC_ErcPl_02 is used for control and anti-icing of an energy recovery unit with plate heat exchanger.

Within the call template the following subtemplates are called and linked with each other:

ErcSuA_PID: supply air temperature control
ErcExhA_PID: minimum limitation of exhaust air temperature
ErcIcPrt: anti-icing of the heat exchanger by means of a differential pressure switch
ErcDmp: control of a damper
ErcByDmp: control of a bypass damper system

The exhaust air minimum limiter ErcExhA_PID and the frost protection program ErcIcPrt limit the control value of the supply air temperature controller ErcSuA_PID of the energy recovery unit via the minimum value option, in order to prevent icing up of the heat exchanger.

Interface

BAC_AC_ErcPl_02 1:

Plant diagram 01

Plant diagram 02

The output of the control signal for controlling the performance of the energy recovery refers to the damper Dmp (see diagram). The control signal for the bypass damper ByDmp is inverted.
When commissioning the VAC system, care must be taken that both dampers are operated with a direct direction of action.

Block diagram

VAR_INPUT

rSuAT      : REAL;
rSpErc     : REAL;
udiPltStp  : UDINT;
udiOpMod   : UDINT;
bDeHum     : BOOL;
rExhAT     : REAL;
rExtAT     : REAL;

rSuAT: Measured value inlet air temperature

rSpErc: Set value inlet air temperature

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

udiOpMod: Plant operation mode. The plant operation mode is determined in the mode selection program BAC_AC_OpMod_01.

bDeHum: Status message dehumidification mode. Disabling of energy recovery in heating mode (outside temperature > outlet air temperature) .

rExhAT: Measured value exhaust air temperature

rExtAT: Measured value outlet air temperature

VAR_OUTPUT

bActn      : BOOL;

bActn: control direction of the supply air temperature control SuA_PID. The control direction of the energy recovery is required by various setpoint programs or cascade controllers for determining setpoint for the supply air temperature of the energy recovery unit, e.g. BAC_AC_SpSuAT_02, BAC_AC_CasCtrlT_02.

Program description

Instance	Type	Task
SuA_PID	BAC_AC_ErcT_PID_01	Sub template inlet air temperature control. The temperature control is analog via PID sequence controller
ExhA_PID	BAC_PID_02	Sub template exhaust air temperature control. The control is used for anti-icing and serves as prevention, before the ramp function IcPrt becomes active.
IcPrt	BAC_ErcIcPrt_01	Sub template anti-icing via differential pressure switch
Dmp	BAC_Uni_Dmp_01_05	Sub template for controlling an analog damper
Inv	FB_BA_Chrct02	Inversion of the control signal of the analog damper for controlling the bypass damper.
ByDmp	BAC_Uni_Dmp_01_05	Sub template for controlling an analog bypass damper
	MIN, MIN	MIN selection of the control signals for inlet air temperature control SuA_PID,exhaust air temperature control ExhA_PID and the frost protection ramp function

Version history

Version number	Comments
1.0.0.1	First release