Protective Boiler Startup - Siemens RVL481 Basic Documentation

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Siemens
Building Technologies

12.4.4 Protective boiler startup

If the boiler temperature falls below the minimum limit of the boiler temperature while
the burner is running, the differential (minimum limit value minus actual value) will be
integrated. From this, a critical locking signal will be generated and transmitted to the
connected loads. This causes the loads to reduce their setpoints, thus consuming less
energy. If the critical locking signal exceeds a defined value, the boiler pump will be
deactivated also.
If the boiler temperature returns to a level above the minimum limit, the integral will be
reduced, resulting in a reduction of the critical locking signal. If the integral falls below a
defined level, the circulating pump will be activated again if it had been switched off.
The connected loads rise their setpoint values.
When the integral reaches the value of zero, protective boiler startup will be deacti-
vated, in which case the critical locking signal is zero.
Protective boiler startup can be interrupted to ensure that, in the event of a burner fault,
for instance, frost protection for the plant will be provided.
In the case of protective boiler startup and simultaneous frost protection for the plant,
the boiler temperature gradient must turn positive within 15 minutes. Otherwise, the
locking signal will become invalid for at least 15 minutes. On completion of the 15 min-
utes, protective boiler startup will become active again as soon as the boiler tempera-
ture gradient turns positive.
If the boiler carries out protective boiler startup, the boiler temperature controller's dis-
.
play shows
Protective boiler startup cannot be deactivated.
Section "25.4.7 Gain of locking signal" provides information on who receives the boiler
temperature controller's critical locking signal and how the consumers respond to it.
Individual unit:
Controller 1 generates a critical locking
Controller 1
signal which deactivates the heating circuit
Plant type 2-1
pump and the d.h.w. charging pump
Interconnected plant:
Controller 1
Plant type 5-0
Controller 1 switches
boiler pump off
Critical locking signal
Heating and D.h.w. Controller RVL481
12 Function block "Boiler"
Critical locking signal
LPB
Controller 2
Controller 3
CE1P2541en
20.05.2008