Viessmann VITODENS 300 Service Instructions Manual page 101

Control functions
The operating mode changeover
remains active for as long as the con-
tact remains closed, however at least
as long as the duration selected in
coding address "F2".
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
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 s respec-
tively over a period of 20 min.
(cont.)
In coding address "32" you can select
the influence the "Ext. blocking" sig-
nal 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.
For a certain period, the changeover
valve is alternately set towards heat-
ing mode and DHW heating. The
burner is switched OFF during the
venting program.
The venting program is activated via
coding address "2F:1". The program
is automatically disabled after
20 minutes, and the coding address is
set to "0".
Function description
101