Parameters
WE
Parameter level / Range of values
DHW demand ON
40 °C
PA4 / 20 to 90 °C
Hysteresis
5 °C
PA4 / 0 to 30 °C
Charging temperature
55 °C
PA4 / 20 to 90 °C
Storage tank charging pump
deactivation limit
50 °C
PA4 / 20 to 90 °C
6.3 Priority operation
In many district heating systems with primary DHW heating, the allotted amount of water is only
intended to supply the heating system. As a result, the capacity required for DHW heating
needs to be taken from the heating system when great heating loads occur; and this, until DHW
heating has been concluded.
Nevertheless, heating operation is not to be simply interrupted. Only the amount of energy re-
quired for DHW heating is to be deducted. This can be achieved by using the priority functions
Reverse control
and
Set-back operation
.
6.3.1 Reverse control
In all systems with DHW heating and at least one heating circuit with a control valve, the DHW
heating can be given priority by applying a reverse control. With the setting Co4 -> Fb06 =
ON, the charging temperature can be monitored. If the temperature also falls below the charg-
ing temperature after the time period set in function block Fb07 has elapsed, the heating circuit
is closed and the set point remains the same.
Which circuit is closed depends on how the system (Anl) is configured:
4
Anl 2: Heating circuit with the highest flow set point
4
Anl 4: Heating circuit
4
Anl 5: Heating circuit 1;
Switching off the pump heating circuit with Co4 -> Fb05 possible.
4
Anl 7: Pre-control circuit of heating
4
Anl 8: Pre-control circuit of heating
4
Anl 9: Heating circuit 1
4
Anl 10: Both heating circuits
Functions
WE
Configuration
Reverse control
ON
Co4 -> Fb06 = ON
Time until reverse control
ON
Co4 -> Fb07*
* Co4 -> Fb07 = ON: 2 minutes
Co4 -> Fb07 = OFF: 10 minutes
56
EB 5179 EN
Appendix
