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Siemens Heating and D.h.w. Controller RVL481 CE1P2541en
Building Technologies 9 Function block "Cascade slave" 20.05.2008
9 Function block "Cascade slave"
This function block facilitates integration of the controller as a cascade slave into a heat
source cascade. A heat source cascade is the combined operation of several oil- / gas-
fired boilers.
9.1 Operating lines
Line Function, parameter Factory setting (range) Unit
59 Release integral for boiler sequence 200 (0…500) °C×min
60 Reset integral of boiler sequence 50 (0…500) °C×min
9.2 Mode of operation
The surplus heat or heat deficit of the boiler is ascertained with the help of the boiler
sequence integral and communicated to the cascade master via LPB.
9.2.1 Boiler sequence release integral (KFI)
The boiler sequence release integral is a variable generated from the progression of
the cascade flow temperature and time (t). If the variable falls below the setpoint, the
difference will be communicated to the cascade master as the heat deficit.
KFI =
∆Tdt
t
0
∫
where: ∆T = ( T
VKw
− 0,5 × SD − T
VKx
) > 0
T
VKw
Flow temperature setpoint of the cascade
T
VKx
Actual value of cascade flow temperature
SD Switching differential of the boiler
t Time
9.2.2 Boiler sequence reset integral (KRI)
The boiler sequence reset integral is a variable generated from the progression of the
cascade flow temperature and time (t). If the variable exceeds the setpoint, the differ-
ence will be communicated to the cascade controller as surplus heat.
KRI =
∆Tdt
t
0
∫
where: ∆T = ( T
VKx
− T
VKw
+ 0.5 × SD ) > 0
Automatic boiler sequence changeover according to the number of burner operating
hours is not possible with the RVL481 since this controller does not acquire the number
of burner operating hours. Boiler management functions must be provided in the cas-
cade master.
Note
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