93
When cascade connection is programmed correctly, the boiler display will show the following.
Explanation "Cascade communication indicator"
NO CASCADE COMMUNICATION
> > >
no.1
Always showing the fixed ">>>"
CORRECT CASCADE COMMUNICATION
>
>
no.1
no.2
>
Showing alternating no.1 & no.2 with 1 second interval.
11.4.2
M
ONITOR SCREENS
To obtain cascade information, see chapter 10.4.
11.4.3
O
UTPUT CONTROL AND BURNER SEQUENCE
The total cascade set-up will act as one single big boiler, switching on- and off burners, depending on the total load
necessary to adjust and keep the flow temperature at the calculated value.
When the heat demand rises, more burners are switched on, and when heat demand falls, one or more burners will
be switched off. The burner that was switched on last, will be switched off first, see table below.
To distribute operating hours equally over all burners, the working sequence of the burners will change every two
hours.
Hour
Switching ON sequence
Switching OFF sequence
X
Master
– Slave 1 – Slave 2 – Slave 3 –
Slave 4
– Slave 5 – Slave 6 – Slave 7
Slave 7
– Slave 6 – Slave 5 – Slave 4 –
Slave 3
– Slave 2 – Slave 1 – Master
X+2
Slave 7
– Master – Slave 1 – Slave 2 –
Slave 3
– Slave 4 – Slave 5 – Slave 6
Slave 6
– Slave 5 – Slave 4 – Slave 3 –
Slave 2
– Slave 1 – Master – Slave 7
X+4
Slave 6
– Slave 7 – Master – Slave 1 –
Slave 2
– Slave 3 – Slave 4 – Slave 5
Slave 5
– Slave 4 – Slave 3 – Slave 2 –
Slave 1
– Master – Slave 7 – Slave 6
X+6
Slave 5
– Slave 6 – Slave 7 – Master –
Slave 1
– Slave 2 – Slave 3 – Slave 4
Slave 4
– Slave 3 – Slave 2 – Slave 1 –
Master
– Slave 7 – Slave 6 – Slave 5
………..
………………………………………………… …………………………………………………
Table
: Burner sequence example of a four boiler cascade (four S-CB
+
400 & 550 boilers = eight burners).
In this table a total of four boilers (one master burner, seven slaves) is mentioned as an example, in practice the
maximum number in a cascade, without extra (external) control, is six boilers (= twelve burners).
