Viessmann VITODENS 333 Service Instructions Manual page 102

Function description
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
102
(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 function External
changeover of operating mode is
selected via coding address 91.