BAC_AC_ErcRot_01

Application

The template BAC_AC_ErcRot_01 is used for control and anti-icing of an energy recovery unit with rotary heat exchanger.

The template BAC_AC_ErcRot_01 is a call template.
Within the call template, the following subtemplates are called and linked together:

ErcSuA_PID: control of the supply air temperature
ErcExhA_PID: minimum limitation of exhaust air temperature
ErcMot: control of WRG control unit
ErcIcPrt: anti-icing of the heat exchanger by means of a differential pressure switch
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.

The supply air controller is enabled in the subtemplate BAC_AC_ErcT_PID_01, depending on the plant operation mode. In operation modes such as summer night cooling, for example, the supply air controller is disabled. The hysteresis module HysByDmp is used to open the bypass damper when energy recovery is disabled. In this way, unnecessarily high flow resistances are avoided, and the energy consumption of the fans is reduced.

Interface

BAC_AC_ErcRot_01 1:

Plant diagram 01

Plant diagram 02

Block diagram

VAR_INPUT

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

rSuAT: Measured value supply air temperature

rSpErc: Set value supply air temperature

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 program BAC_AC_OpMod_01.

bDeHum: Status message dehumidification mode. If dehumidification is active, energy recovery is disabled in heating mode. If the heat recovery unit recovers ‘coolth’ from the outlet air, it is switched to 100% in dehumidification mode.

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 supply air temperature control. The temperature control is analog via PID sequence controller
ExhA_PID	BAC_PID_02	Sub template exhaust air temperature control for anti-icing
IcPrt	BAC_ErcIcPrt_01	Sub template for anti-icing of an energy recovery unit via differential pressure switch
Mot	BAC_Uni_FC_01_223	Sub template for controlling a frequency converter, which then controls the motor of the rotary heat exchanger.
HysByDmp	FB_BA_Swi2P	The function block HysByDmp is a two-point switch, which opens or closes the bypass damper as a function of a hysteresis. The control value for the motor of the rotary heat exchanger serves as input variable for the two-point switch.
ByDmp	BAC_Uni_Dmp2P_01_08	Sub template for controlling the bypass damper.
	MIN, MIN	MIN selection of the control signals for supply air temperature control SuA_PID,exhaust air temperature control ExhA_PID and the frost protection ramp function

Version history

Version number	Comments
1.0.1	First release