Viessmann VITODENS 343-F WS4A Installation And Service Instructions Manual page 121

Control functions
External blocking
The "External blocking" function is
connected via the external extension
input "aVD".
External demand
The "External demand" function is
connected via the external extension
input "aVD".
In coding address "34" you can select
the influence the "Ext. demand" signal
should have on the connected circula-
tion pumps.
Venting program
During the venting program, the circu-
lation pump will be alternately
switched ON and OFF for 30 s respec-
tively over a period of 20 min.
For a certain period, the diverter valve
is alternately set towards heating and
DHW heating. The burner is switched
OFF during the venting program.
Filling program
In the delivered condition, the diverter
valve is set to its central position,
enabling the system to be filled com-
pletely. After switching ON the control
unit, the diverter valve no longer goes
into its central position.
(cont.)
In coding address "32" you can select
the influence the "Ext. blocking" sig-
nal should have on the connected cir-
culation pumps.
The minimum set boiler water tem-
perature in case of external demand
is selected in coding address "9b".
The venting program is activated via
code "2F:1". The program is automati-
cally disabled after 20 min, and cod-
ing address "2F" is set to "0".
Afterwards, the diverter valve can be
moved via code "2F:2" into the central
position. In this position, the control
unit can be switched OFF, and the
system can be filled completely.
Function description
121