Viessmann VITODENS 300 Service Instructions Manual page 105

Control functions
External blocking
The function "External blocking" is
connected via input aVD of the exter-
nal extension.
External demand
The function "External demand" is
connected via input aVD of the exter-
nal extension.
In coding address 34 you can select
the influence the signal "Ext. demand"
should have on the connected circula-
tion pumps.
Venting program
Note
Close the gas shut-off valve when
operating the venting program.
During the venting program, the circu-
lation pump will be alternately
switched ON and OFF for 30 seconds
respectively over a period of
20 minutes.
Filling program
Note
Close the gas shut-off valve when
operating the filling program.
(cont.)
In coding address 32 you can select
the influence the signal "Ext. block-
ing" should have on the connected cir-
culation pumps.
In coding address 9b, you can select
the minimum set boiler water tem-
perature in case of external demand.
The diverter valve is alternately
switched for a certain period towards
heating and DHW operation. The bur-
ner is switched OFF during the vent-
ing program.
The venting program is activated via
coding address 2F:1. The program is
automatically deactivated after
20 minutes, and the coding address is
set to 0.
In the delivered condition, the diverter
valve is set to its central position,
enabling the system to be filled com-
pletely. After starting the control unit,
the diverter valve no longer goes into
its central position.
Function description
105