FB_BA_SpSupvis

FB_BA_SpSupvis 1:

Function block for processing and checking the lower and upper setpoint of an inlet air humidity or temperature control.

Checking and limitation of the setpoints

The function block limits the setpoints. The following two tables show which parameters are checked and what the response is in the event of an error.

Checking

Action

rSpLo > rSpHi

last valid values of rSpLo and rSpHi are used

rSpMin >= rSpMax

last valid values of rSpMin and rSpMax are used

rSpHi > rSpMax

rPrSpHi = rSpMax

rSpLo < rSpMin

rPrSpLo = rSpMin

Checking

bErr

Action

rSpMin >= rSpMax

TRUE

rSpErr = ((rSpMin + rSpMax) / 2)

rPrSpHi = rPrSpLo = rPrRcv = rSpErr

rSpHi < rSpMin

rSpLo > rSpMax

The difference between the setpoints describes an energy-neutral zone. With inlet air control, no heating or cooling would take place within the neutral zone.

FB_BA_SpSupvis 2:

The checked and, if necessary, limited setpoints are output at the function block output as rPrSpHi and rPrSpLo (Present Setpoint).

Setpoint for heat recovery

For heat recovery, the setpoint rSpRcv is optionally calculated from the mean value of the upper and lower setpoint, rSpHi and rSpLo, or depending on the control direction of the heat recovery system.
The method is defined through the input variable bSlcnSpRcv:

b SlcnSpRcv

rSpRcv

TRUE

Mean value of rSpLo and rSpHi

FALSE

Depends on direction of action, defined through input bActRcv


If the setpoint is defined depending on the direction of action, the following applies:

bActRcv

Control direction

rSpRcv

TRUE

direct (cooling)

rSpHi

FALSE

indirect (heating)

rSpLo

Heat recovery

FB_BA_SpSupvis 3:

VAR_INPUT

bEn        : BOOL;
rSpHi      : REAL;
rSpLo      : REAL;
rSpMax     : REAL;
rSpMin     : REAL;
bActnRcv   : BOOL;
bSlcnSpRcv : BOOL;

bEn: function block enable. If bEn = FALSE, all output parameters are 0.0.

rSpHi: Upper setpoint input value to be checked.

rSpLo: Lower setpoint input value to be checked.

rSpMax: Maximum setpoint.

rSpMin: Minimum setpoint.

bActnRcv: Direction of action of the downstream heat recovery.

bSlcnSpRcv: Setpoint selection of the downstream heat recovery system.

VAR_OUTPUT

rPrSpHi   : REAL;
rPrSpLo   : REAL;
rSpRcv    : REAL;
bErr      : BOOL;
sErrDescr : T_MAXSTRING;

rPrSpHi: Output value for the upper setpoint.

rPrSpLo: Output value for the lower setpoint.

rSpRcv: Output value for the resulting heat recovery setpoint.

bErr: This output is switched to TRUE if the parameters entered are erroneous.

sErrDescr: Contains the error description.

Error description

01: Warning: The setpoints are not in a logical order: Either (rSpMin >= rSpMax) OR (rSpHi < rSpMin) OR (rSpLo > rSpMax)

Requirements

Development environment

Required PLC library

TwinCAT from v3.1.4024.7

Tc3_BA from v1.1.6.0