Viessmann Vitodens 300 Service Instructions Manual page 101

Extensions for external connections (accessory)
External extension H2
The external extension is connected
to the boiler control unit via the KM
BUS. The following functions can be
controlled or processed via this exten-
sion:
sK
DHW circulation pump
fÖ
Power supply
Function description
(cont.)
aVD
&
External blocking
(terminals 2 - 3)
&
External demand
(terminals 1 - 2)
&
External operating mode chan-
geover (terminals 1 - 2)
aVG KM BUS
The allocation of the "External chan-
geover of operating mode" function is
selected via coding address 91.
101