Multi-Boiler Control Unit - Viessmann Cascade control unit Installation, Operating And Service Instructions

Functions

Multi-boiler control unit

The modulating cascade control communicates with the boilers via the
KM BUS interface. It calculates the required flow temperature using a
weather-compensated control unit.
Starting up and shutting down individual boilers
Depending on heat demand, individual boilers are started up or shut down.
A boiler will be started up if:
H the required heat load is higher than the total output of all currently
operational boilers
H the start-up delay of a boiler has expired.
A boiler will be shut down if:
H the required heat load is lower than the total output of all currently
operational boilers
H the shutdown delay of a boiler has expired.
Boilers are operated in modulating mode in accordance with the current load
within modulating range E (see fig. on page 27).
In the "Operating details" menu (see page 15), the output of individual boilers
can be scanned in %.
The boiler output is controlled by the gas fired wall-mounted boiler control unit
in accordance with the set default value of the cascade control and the current
boiler water temperature. The current boiler water temperature is transferred
to the cascade control and can be displayed in the "Operating details" menu
(see page 15) (displayed as "Set flow temp." for each individual boiler).
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