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Building Technologies
Boiler Sequence Controller RMK770
CE1P3132en
HVAC Products
6 Boiler sequence management
01.03.2005
100
200
300
400
100
200
300
30
400
240
180
95
10
5
120
16
0
1K
1K
1K
1K
1K
1K
1K
1K
1K
1K
60
K+
kW
70
50
150
250
350
60
60
60
60
60
60
47.
5
47
.5
80
80
80
90
90
95
3132D
07
The diagram above shows an example with 4 modulating boilers that are sequentially
switched on and off.
The basic stage of the first boiler be 30 % of the rated capacity.
As heat consumption increases, each boiler modulates up to 100 kW (100 %) before
the next boiler is switched on. Hence, 4 boilers can modulate delivering a total output of
400 kW.
The downward sequence output limit will be set to 60 %.
To enable the fourth boiler to be switched off, all 4 boilers must have modulated below
240 kW (60 % of 400 kW) for 20 minutes, that is, below 60 kW on average. After
switching off, the operating point of the remaining 3 boilers is at 80 kW.
To enable the third boiler to be switched off, all 3 boilers must have modulated below
180 kW (60 % of 300 kW) for the duration of the switch-off delay, that is, below 60 kW
on average. After switching off, the operating point of the remaining 2 boilers is at
90 kW.
To enable the second boiler to be switched off, both boilers must have modulated be-
low 95 kW for the duration of the switch-off delay, that is, below 47.5 kW on average. If
switching off took place at 60 kW as above, the second boiler would switch on again
after a short period of time due to insufficient heat supply. Hence, the operating point of
the remaining boiler after switching off is at 95 kW.
Example
Switching boiler 4 off
Switching boiler 3 off
Switching boiler 2 off