Type Of Lead Boiler Operation - Siemens RVA47.320 User Manual

General
Autonomous:
Example:
linked:
Example:
Note
128/166
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HVAC Products
6.4.1

Type of lead boiler operation

The type of lead boiler operation describes the way the individual boilers in the cascade
are controlled.
The RVA47.320 delivers a boiler temperature setpoint to the BMUs.
The released BMUs then control their output autonomously between 0 and 100 % in
order to reach the preset boiler temperature setpoint.
w = 70°C w = 70°C
t t
1
P = 50 %
P = 51 %
w = Boiler temperature setpoint
t
It is thus possible that individual boilers will be operated outside their output range. The
average actual output is within the defined output range, however (for exceptions, refer
to lines 51 and 52).
A differentiation is made between lead boiler and lag boilers. The RVA47.320 delivers a
temperature setpoint to the lead boiler, which translates it into output. The lag boilers
take this output as maximum limitation of output, thus following the lead boiler.
w = 70°C
t
1
T = 69°C
P = 50 % w = 50 %
p
w = Boiler temperature setpoint for lead boiler
t
w = Nominal output setpoint for BMUs 1 - 4
p
P = Actual output
T = Actual temperature
This means that all boilers will be operated within the defined output range (for
exceptions, refer to pages 14 and 132).
In the case of linked lead boiler operation, the controller considers the ratio of the
nominal BMU outputs and matches the speed of lag boiler operation accordingly.
Basic Documentation RVA47.320
Description of the OEM settings
w = 70°C w = 70°C
t t
2
3
P = 53 %
=
2
3
T = 68°C
w = 50 %
p
4
P = 48 %
Actual output
4
T = 73°C
w = 50 %
p
CE1P2379E
15.07.2002