BAC_DHW_Ctrl_01

Application

The template controls the charging of a hot water tank.
The template is enabled via the input variable bEn. In the template the temperature at the top of the tank rTTop is compared with the value of the difference Sp - Hys. If the temperature at the top of the tank falls below the value, charging of the hot water tank is enabled.
If the temperature at the bottom of the tank rTBot exceeds the set value Sp, charging of the hot water tank is disabled.

Interface

BAC_DHW_Ctrl_01 1:

System diagram

Block diagram

VAR_INPUT

bEn        : BOOL;
rTTop      : REAL;
rTBot      : REAL;

bEn: Template enable input. If this input is FALSE, the value 0 is output at rSp, and bQ becomes FALSE.

rTTop: Input for temperature at the top of the tank

rTBot: Input for temperature at the bottom of the tank

VAR_OUTPUT

bQ     : BOOL;
rSp    : REAL;

bQ: Hot water tank charging output.

rSp: Hot water temperature set value output.
If enable En of the template is FALSE, the value 0 is output at rSp.

VAR CONSTANT

PLT_NUM    : BYTE := 1;

PLT_NUM: all alarms and events of all plant components within a controller are included in a global alarm and event list. The assignment of events and alarms to a plant is defined by the assignment of a PLT_NUM plant number.
The recording and processing of an alarm from an aggregate or a device takes place within the templates by means of the alarm function block FB_BA_Alarm.
The evaluation of the alarms of a plant, e.g. for the generation of a collective message or for plant shutdown in case of relevant faults, takes place within the template BAC_PltAlm_01 by means of the function block FB_BA_AlarmPlt.
The evaluation of different plant events within the templates of a plant, takes place within the template BAC_PltComnMsg_01 by means of the function block FB_BA_ComnMsg.

Important! The assignment and evaluation of the alarms and events of a plant can only be done correctly if all templates of a plant have the same plant number!

The plant number can be assigned in the Project Builder in the parameter menu for the templates or via a column in the Excel import.

Program description

Instance	Type	Task
En	FB_BACnetBV1204	BV object for displaying the hot water tank charging template enable.
Sp	FB_BACnetAVSetpoint	AV object for entering the set value for the hot water temperature. If the temperature at the bottom of the tank rTBot exceeds this value, charging of the hot water tank is disabled. The hot water tank has reached the required temperature.
Hys	FB_BACnetAVSetpoint	AV object for entering the set value hysteresis. If the temperature at the top of the tank rTTop falls below the value of the difference Sp - Hys, charging of the hot water tank is enabled. This is indicated with BACnet object Q.
MultiCalc	FB_BA_MultiCalc_R04	The function block determines the maximum and minimum of the inputs r01-r04 and outputs the values at rMax and rMin.
DHW2P	FB_BA_DHW2P	The function block is the main control feature for charging the hot water tank. Charging of the hot water tank is controlled by means of an on-off controller. Tank heating is activated at input bEn. If tank heating is active the output bLd is TRUE. The variables rSp is used to transfer the set value for the hot water temperature to the function block. At input rTMin a minimum selection of all temperature sensors for the hot water tank is connected, at input rTMax a maximum selection of all temperature sensors. Due to the thermal stratification in the hot water tank, the sensor at the top is generally the one showing the highest temperature, the one at the bottom the lowest.
Q	FB_BACnetBVDisplay	BV object for indicating whether charging of the hot water tank is enabled.

Version history

Version number	Comments
1.0.0.1	First release