Cascade Control Of The Vitotronic 300-K - Viessmann Vitotronic 300-K Installation And Service Instructions Manual

Function Description

Cascade Control of the Vitotronic 300-K

Brief description
The supply temperature is regulated by starting or
stopping the burners or by starting/stopping individual
burner stages.
H Stand-alone control
H Sequential control
H Subject to the system version, we differentiate between
condensing strategy and two conventional strategies.
Set supply temperature
The set supply temperature is determined from the
following parameters:
H Set supply temperature of system circuit A1 (heating
circuit 1) and heating circuits with mixing valve M2
(heating circuit 2) and M3 (heating circuit 3).
H Set supply temperature of further consumers.
H Set DHW temperature.
H External demands.
Upper control range limits:
Maximum limit of the system supply temperature
(coding address "37" in the "Cascade" group).
Lower control range limits:
Minimum limit of the system supply temperature
(coding address "36" in the "Cascade" group).
110
Vitotronic 100, GC1B / Vitotronic 300-K, MW1B Installation and Service
Cascading Layouts
Boilers connected in parallel
H Without and with supply temperature sensor.
H Set code "3B:0" or "3B:1" in the "Cascade" group.
H The cascade control specifies the set boiler water
temperature for all currently active boilers. Every boiler
control unit regulates to the specified set value.
The following control strategies are available:
H Condensing strategy (see page 111)
H Conventional strategy 1 (see page 111)
H Conventional strategy 2 (see page 112)
Boilers connected in series
H Without and with supply temperature sensor.
H Set code "3B:2" or "3B:3" in the "Cascade" group.
H The control strategy is set automatically to conventional
strategy 2, code "3C:2" (see page 112).
H The cascade control specifies the set boiler water
temperature for all currently active boilers. Every
boiler control unit regulates to the specified set value.
If the lead boiler (condensing boiler) does not achieve
the specified set value, it will only act to control
the return temperature of the conventional boiler
downstream. The conventional boiler is started late and
is also shut down late.
H With supply temperature sensor:
Set code "3B:1" or "3B:3" in the "Cascade" group.
The control deviation is calculated from the set supply
temperature and the actual supply temperature to
determine the start and shutdown criteria.
H Without supply temperature sensor:
Set code "3B:0" or "3B:2" in the "Cascade" group.
To determine the start and stop criteria, the control
deviation is calculated from the set boiler water
temperature and the estimated average actual boiler
water temperature of the currently active boilers.
Only boilers with open isolation valves are taken into
consideration.
Sequential control
H With supply temperature sensor.
H Set code "3B:4" in the "Cascade" group.
H The control strategy is set automatically to conventional
strategy 2, code "3C:2" (see page 112).
H The cascade control unit regulates to the specified set
supply temperature by stipulating the output for each
individual boiler. The lead boiler can be operated in
modulating mode. All other boilers are operated in two
stages via a specified output (incl. modulating burners).