FB_BC9191FctSelection
Application
This function block is for enabling room heating or room cooling. It can be used for 2-wire pipe systems (changeover) or 4-wire pipe systems.
In the case of a 4-wire pipe system the changeover from heating to cooling operation takes place automatically on the basis of a comparison of the setpoint for the room temperature with the actual value for the room temperature.
Sketch:
In the case of a 2-wire pipe system the heating operation or cooling operation may only be enabled when heating or cooling medium is present. The room temperature controller gets this information from the primary units.
In both 2-wire and 4-wire pipe systems the changeover between heating operation and cooling operation can be delayed by a timer. The input variable udiChangeOverDelay must be greater than zero for this.
The following tables describe the interrelationship between the inputs and the eCtrlFct output of the FB_BC9191FctSelection function block.
In the 2-wire pipe system
bEnable | bPipeSystem | bFeedbHeatMedium | bFeedbCoolMedium | interim result | bDewPoint | eCtrlFct |
|---|---|---|---|---|---|---|
0 | 0 | 0 | 0 | OFF | TRUE / FALSE | OFF |
1 | 0 | 0 | 0 | Heating | TRUE / FALSE | Heating |
1 | 0 | 0 | 1 | Cooling | TRUE | OFF |
|
|
|
|
| FALSE | Cooling |
1 | 0 | 1 | 0 | Heating | TRUE / FALSE | Heating |
1 | 0 | 1 | 1 | Heating | TRUE / FALSE | Heating |
In the 4-wire pipe system
bEnable | bPipeSystem | T_Room ≤ Tsetpoint | T_Room > Tsetpoint | interim result | bDewPoint | eCtrlFct |
|---|---|---|---|---|---|---|
0 | 1 | 0 | 0 | OFF | TRUE / FALSE | OFF |
1 | 1 | 0 | 1 | Cooling | TRUE | OFF |
|
|
|
|
| FALSE | Cooling |
1 | 1 | 1 | 0 | Heating | TRUE / FALSE | Heating |
1 | 1 | 1 | 1 | Heating | TRUE / FALSE | Heating |
VAR_INPUT
Name : Type
bSetDefault : BOOL;
bEnable : BOOL;
bPipeSystem : BOOL;
bFeedbHeatMedium : BOOL;
bFeedbCoolMedium : BOOL;
bDewPoint : BOOL;
rRoomTemp : REAL;
stSetpoint : ST_BC9191SetpointRoom;
bSetDefault: If the variable is TRUE, the default values of the VAR_IN_OUT variables are adopted.
bEnable: TRUE enables the function block. If FALSE the function block is disabled and eCtrlFct := eCtrlFct_Off.
bPipeSystem: FALSE means that a 2-wire pipe system is present. TRUE means that a 4-wire pipe system is present.
bFeedbHeatMedium: Signal from the power generation or distribution that heating medium is available.
bFeedbCoolMedium: Signal from the power generation or distribution that cooling medium is available.
bDewPoint: The dew point sensor is connected to this input. If this is triggered the cooling control function is deactivated and eCtrlFct:= eCtrlFct_Off is set.
rRoomTemp: This input variable transfers the current room temperature to the function block.
stSetpoint: STRUCTURE containing the setpoints for the individual energy levels.
VAR_OUTPUT
Name : Type
eCtrlFct : E_BC9191CtrlFct;
uiReqHeating : UINT;
uiReqCooling : UINT;
udiRT_ChangeOverDelay : UDINT;
eCtrlFct: This output contains the current control function.
uiReqHeating: Is 1 if the room/zone requests heating energy. It is 0 if there is no heating requirement.
uiReqCooling: Is 1 if the room/zone requests cooling energy. It is 0 if there is no cooling requirement.
udiRT_ChangeOverDelay: Indicates the time remaining until the active control function is changed over.
VAR_IN_OUT
Name : Type Persistent Default
udiChangeOverDelay : UDINT; x 0
udiChangeOverDelay: Changeover time between the control functions. Must be specified in seconds. If the input is greater than 0 it will always be observed. The variable must be 0 if there is to be no changeover time between the control functions.