FB_BA_SpSupvis
Function block for processing and checking the lower and upper setpoint of a supply air humidity or temperature control.
Functional description
Checks and limits for the setpoints
The function block checks and 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) | |
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.
The checked and possibly 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 calculated either from the average of the upper and lower setpoints, rSoHi and rSpLo, or as a function of the control direction of the heat recovery system.
The method is defined by the input variable bSlcnSpRcv:
b SlcnSpRcv | rSpRcv |
|---|---|
TRUE | Average of rSpLo and rSpHi |
FALSE | Depends on control direction, defined through input bActRcv |
If the setpoint is defined depending on the control direction, the following applies:
bActRcv | Control direction | rSpRcv |
|---|---|---|
TRUE | direct (cooling) | lrSpHi |
FALSE | indirect (heating) | lrSpLo |
Heat recovery
Inputs/outputs
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: input value of the upper setpoint to be checked
rSpLo: input value of the lower setpoint to be checked
rSpMax: maximum setpoint
rSpMin: minimum setpoint
bActnRcv: control direction of the downstream heat recovery
bSlcnSpRcv: setpoint selection of the downstream heat recovery
VAR_OUTPUT
rPrSpHi : REAL;
rPrSpLo : REAL;
rSpRcv : REAL;
bErr : BOOL;
udiErrId : UDINT;
udiErrArg : UDINT;
rPrSpHi: output value of the upper setpoint
rPrSpLo: output value of 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.
udiErrId / udiErrArg: contains the error number and the error argument. See error codes.
Requirements
Development environment | Target system | required library | required supplement |
|---|---|---|---|
TwinCAT 2.11 R3/x64 | PC/CX | TcBA library from V1.0.0 | TS8040 | TwinCAT Building Automation from V1.0.0 |