43
Multiple-boiler control unit
The modulating cascade control communicates with the boilers via the KM-BUS interface. It calculates the
required supply temperature using an outdoor reset control unit.
Start-up and shutdown of individual boilers
Depending on the heat demand, individual boilers are started or shut down.
A boiler is started up if:
H the required heat load is higher than the total output of all boilers which are currently operating.
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 boilers which are currently operating.
H the shutdown delay of a boiler has expired.
Boilers are operated in modulating mode within the modulation range
(see Fig. below) and in accordance
with current load demands.
In the ” Operating data” menu the output of individual boilers can be scanned in %.
The boiler output is controlled by the control unit of the gas-fired wall-mounted boiler 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 data” menu (displayed as ”Set flow-
temp” for each individual boiler).
Start-up delay
A delay before start-up of individual boilers can be selected, for example to prevent boilers from cycling.
Boiler base load 1
Mod. to boiler 1
Lag boiler base load
Mod. to lag boiler
Boiler modulation range
Lag boiler base load
Boiler base load 1
FK Lag boiler
K 1 Boiler 1
P System output
(two-boiler system)
t
RV
Control delay
t
Wa
Shutdown delay
t
We
Start-up delay
Nominal value (multiple-boiler control unit)
Start-up delay.
5285 565 v1.35285 565 v1.3
0
t
P
t
RV
K1
t
RV
FK
t
We
FK
t
Wa
Delaytime boiler
sequence 7 min
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