Viessmann Vitodens 200 Service Manual page 103

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 simulta-
neously via the extension:
sK
DHW circulation pump
fÖ
Power supply
Function description
(cont.)
aVD
&
External blocking
(terminals 2 - 3)
&
External demand
(terminals 1 - 2)
&
External changeover of operat-
ing mode (terminals 1 - 2)
The allocation of the "External
changeover of operating
mode" function is selected via
coding address 91.
aVG KM BUS
103