Viessmann Vitocrossal 300 CA3 2.5 Installation And Service Instructions Manual page 125

Vitocrossal 300 CA3 Series 2.5 to 6.0 Installation/Service
Cascade Control Unit
Shutdown
(continued)
Starting
Control strategies
Condensing strategy
Benefit:
Optimal utilization of the condensing effect and long
burner run-times.
Set coding "3C:0" in the "Cascade" group. It is the aim
of the condensing strategy to operate as many boilers as
possible at the lowest output level.
Starting criterion:
An output statement causes the boilers to start
(Coding "3d:1" in the "Cascade" group).
An additional boiler will start if the current heat demand
can be covered by the currently active boilers plus the
next boiler in the boiler sequence.
Shutdown criterion:
The boilers are shut down via a shutdown integral.
When the shutdown integral exceeds a limit set at
coding "46" in the "Cascade" group, the shutdown
criterion is met and the boiler started last will be shut
down.
Example (coding "3C:0" in the "Cascade" group)
Two-boiler system with modulating burners:
Boiler 1: 100% rated heating output
(base load set to 33%)
Boiler 2: 100% rated heating output
(base load set to 33%)
Function Description
125