Drinking water heating process
The drinking water outlet temperature of the heat exchanger is controlled according to the set
point in the parameter Drinking water temperature. The setting of the control parameters con-
cerning the achievable control quality is decisive for this.
Should the capacity available for a parallel operation of both circuits heating circuit and
drinking water circuit be too low when the maximum capacity is required, the function block
FB 8 can be activated.
With the setting FB 8 = ON and the option "Ab" selected Drinking water priority through set-
back operation the heating circuit is set to reduced operation for 20 minutes when there is a
system deviation of more than 5 K in the drinking water circuit: its capacity requirement is
moved back by reducing the current flow temperature by the value set in Set-back of flow tem-
perature for reduced operation.
With the setting FB 8 = ON and the option "In" selected Drinking water priority through
reverse control the capacity requirement of the heating circuit is reduced when there is a sys-
tem deviation of more than 5 K in the drinking water circuit. This is achieved by the three-point
stepping output of the drinking water circuit having an effect on the heating circuits control
valve in the opposite direction. The time span before the priority mode responds can be set in
FB 8.
The circulation pump ZP always runs according to its time schedule.
Observe the following for devices to be used in the drinking water control loop regarding the
drinking water temperature sensor VFTW and the control valve:
You must use a temperature sensor with fast response (we recommend a Pt100 sensor with z 09
= 2.3 seconds Type 5209) for measuring the drinking water outlet temperature. This is necess-
ary in order to keep the duration of temperature peaks as well as the temperature peaks them-
selves as small as possible. In addition, an actuator with a transit time of max. 40 seconds is re-
quired.
We strongly recommend that the circulation pump be operated during times-of-use of the drink-
ing water circuit!
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