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Siemens
Basic Documentation RVP360
CE1P2546en
Building Technologies
12 Function block: Boiler
2017-07-24
When the integral reaches the value of zero, protective boiler startup becomes
inactive, in which case the critical locking signal is zero.
If protective boiler startup is active, the boiler temperature controller's display
shows
.
Protective boiler startup cannot be deactivated.
Chapter 17.4.5 "Locking signal gain" provides information on who receives the
boiler temperature controller's critical locking signal and how the consumers re-
spond to it.
Controller 1
Plant type 5-1
2
4
7
7
B
0
2
e
Controller 1 generates
a critical locking signal
internally
Controller 1
Plant type 5-1
Controller 2
Critical locking signal
LPB
2
4
7
7
B
0
3
e
Critical locking signal
Controller 3
Controller 1 generates
internally a critical
locking signal
12.4.5 Protection against boiler overtemperatures
To prevent heat from building up in the boilers (protection against
overtemperatures), the controller provides a protective function.
When the first burner stage is shut down, the controller allows pump M1 to run
for the set overrun time (operating line 174 on the boiler temperature controller),
forwarding at the same time a forced signal to all loads (inside the controller and
on the data bus). If the boiler temperature controller is located in segment 0, the
forced signal is sent to all consumers in all segments. By contrast, if the boiler
temperature controller is located in segment 1...14, the signal is only sent to the
consumers in the same segment.
All consumers (heating and d.h.w. circuits) and heat exchangers that abruptly
reduce their request for heat monitor the data bus during the set pump overrun
time to see if a forced signal is being sent by the boiler.
If no forced signal is received, the consumers and heat exchangers only perform
pump overrun (refer to chapter 17.4.2 "Pump overrun").
If, in this time window, a forced signal is received, the consumers continue to
draw heat from the boiler in the following manner:
Plant types with heating circuits using a mixing valve/2-port valve maintain
the previous setpoint
Plant types with pump heating circuits allow the pumps to run
Autonomous unit
Interconnected plant
