FB_BA_SpSupVis

FB_BA_SpSupVis 1:

Function block FB_BA_SpSupVisdient for processing and checking the lower and upper setpoint of a supply air humidity or temperature control.

Checks and limits for 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

fSpLo > fSpHi

Last valid values of fSpLo and fSpHi are used.

fSpMin >= fSpMax

Last valid values of fSpMin and fSpMax are used.

fSpHi > fSpMax

fPrSpHi = fSpMax

fSpLo < fSpMin

fPrSpLo = fSpMin

Checking

bErr

Action

fSpMin >= fSpMax

TRUE

fSpErr = ((fSpMin + fSpMax) / 2)

fPrSpHi = fPrSpLo = fPrRcv = fSpErr

fSpHi < fSpMin

fSpLo > fSpMax

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

FB_BA_SpSupVis 2:

The checked and possibly limited setpoints are output at the function block output as fPrSpHi und fPrSpLo (Present Setpoint).

Setpoint for heat recovery

For a heat recovery system, the setpoint fSpRcv is calculated either from the average of the upper and lower setpoints, fSpHi and fSpLo or as a function of the control direction of the heat recovery system.
The method is defined by the input variable bSlcnSpRcv:

b SlcnSpRcv

fSpRcv

TRUE

Average of fSpLo and fSpHi

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

fSpRcv

TRUE

direct (cooling)

fSpHi

FALSE

indirect (heating)

fSpLo

Heat recovery

FB_BA_SpSupVis 3:

FB_BA_SpSupVis 4: Inputs

VAR_INPUT
  bEn         : BOOL;
  fSpHi       : REAL;
  fSpLo       : REAL;
  fSpMax      : REAL;
  fSpMin      : REAL;
  bActnRcv    : BOOL;
  bSlcnSpRcv  : BOOL;
END_VAR

Name

Type

Description

bEn

BOOL

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

fSpHi

REAL

Upper setpoint input value to be checked.

fSpLo

REAL

Lower setpoint input value to be checked.

fSpMax

REAL

Maximum setpoint

fSpMin

REAL

Minimum setpoint.

bActnRcv

BOOL

Direction of action of the downstream heat recovery.

bSlcnSpRcv

BOOL

Setpoint selection of the downstream heat recovery system.

FB_BA_SpSupVis 5: Outputs

VAR_OUTPUT
  fPrSpHi    : REAL;
  fPrSpLo    : REAL;
  fSpRcv     : REAL;
  bErr       : BOOL;
  sErrDescr  : T_MAXSTRING;
END_VAR

Name

Type

Description

fPrSpHi

REAL

Output value for the upper setpoint.

fPrSpLo

REAL

Output value for the lower setpoint.

fSpRcv

REAL

Output value for the resulting heat recovery setpoint.

bErr

BOOL

In case of a fault, e.g. if warning stages are active, this output is set to TRUE.

sErrDescr

T_MAXSTRING

Contains the error description.

Error description

01: Warning: The setpoints are not in a logical order: Either (fSpMin >= fSpMax) OR (fSpHi < fSpMin) OR (fSpLo > fSpMax)

Requirements

Development environment

Required PLC library

TwinCAT from v3.1.4024.22

Tc3_BA2 from v5.2.5.0