Frost Protection For The Boiler; Protective Boiler Startup - Siemens RVP360 Basic Documentation

52/106
Siemens
Building Technologies
SD
Switching differential
w
Boiler temperature setpoint
x
Actual value of boiler temperature
T
Kx
T + 0,5 SD
*
Kw
T - 0,5 SD
*
Kw
Y
B1
1
0
INT
max.
FGI
0
FG
B2
1
0
Y
B2
1
0
FG Release for burner stage 2
B2
FGI Release integral
INT
Integral
RSI Reset integral
SD
Switching differential

12.4.3 Frost protection for the boiler

Frost protection for the boiler operates with fixed values:
Switch-on point: 5 °C boiler temperature
Switch-off point: Minimum limit of boiler temperature plus switching differential
If the boiler temperature falls below 5 °C, the burner is always switched on and
keeps running until the boiler temperature exceeds its minimum limit by the amount
of the switching differential.

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 temperature differential (minimum limit value minus
actual value) is integrated. From this, a critical locking signal is generated and
forwarded to the connected consumers. This causes the loads to reduce their
setpoints, aimed at consuming less energy. If the critical locking signal exceeds
a defined value, the boiler pump is deactivated as well.
If the boiler temperature returns to a level above the minimum limit, the integral is
reduced, resulting in a reduction of the critical locking signal.
If the integral falls below a defined level, the boiler pump is activated again. The
connected consumers increase their setpoints again.
Basic Documentation RVP360
12 Function block: Boiler
max.
RSI
t Time
T Boiler temperature setpoint
Kw
T
Actual value of boiler temperature
Kx
Y Control signal for burner stage 1
B1
Y
Control signal for burner stage 2
B2
t
t
RSI
t
t
t
CE1P2546en
2017-07-24