Viessmann VITODENS 200-W Service Instructions Manual page 94

Function description
Extensions for external connections...
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 simultaneously via the
extension:
A ON/OFF switch (on site)
sK DHW circulation pump (only for
weather-compensated operation)
fÖ Power supply
94
(cont.)
aVD ■ External blocking
(terminals 2 - 3)
■ External demand
(terminals 1 - 2)
■ External heating program
changeover (terminals 1 - 2)
(only for weather-compensated
operation)
The allocation of the function
"External heating program
changeover" is set via coding
address "91".
aVG KM BUS