Viessmann VITOTRONIC 200 Installation And Service Instructions Manual page 78

Function Description, Vitotronic 300-K
Cascade Control
Conventional boiler strategy 1 (code "3C:1")
H With conventional boiler strategy 1, an additional
boiler will only be started if the maximum output
of all currently active burners is insufficient to achieve
the set supply temperature.
H A boiler will be shut down when the remaining boiler(s)
can achieve the required output independently.
Benefit:
H As few boilers as possible are active.
Starting criterion
H The boilers are started via a starting integral.
H The start criterion is met when the start integral
exceeds a limit set via coding address "45" and the
next boiler in the sequence will start (see page 52).
Shutdown criterion:
H Boilers are shut down via an output statement
(code "3D:1").
H A boiler is shut down when the currently required
output can be achieved without the boiler that was
started last.
Starting
Shutdown
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Vitotronic 200 and 300-K Installation and Service
Conventional boiler strategy 2 (code "3C:2")
H With conventional boiler strategy 2, an additional
boiler will only be started if the maximum output
of all currently active burners is insufficient to achieve
the set supply temperature.
H A boiler will be shut down if the burners were returned
to their minimum output because of a large negative
control deviation and the output is still too high.
Benefit:
H Long burner runtimes
Starting criterion
H The boilers are started via a starting integral.
H The start criterion is met when the start integral
exceeds a limit set via coding address "45" and the
next boiler in the sequence will start (see page 52).
Shutdown criterion:
H The boilers are shut down via a shutdown integral.
H The shutdown criterion is met when the shutdown
integral exceeds a limit set via coding address "46"
and the boiler started last will be shut down.
Starting
Shutdown