57
Fan pressure monitoring function (LDW1)
The switching threshold of air pressure switch 1 (plug
aCA
) is monitored in all fan ramp-up phases and
checked during modulating burner operation. This
ensures a minimum pre-purge.
Air pressure switch 1 triggers a fault shutdown of the
burner control unit under the following circumstances:
■
The static pressure check was unsuccessful after
approx. 5 minutes.
■
The air pressure is outside the permissible range
during the pre-purge phase. Tolerance time approx.
5 min.
■
The air pressure switch fails in control mode or the
air pressure lies outside the permissible range.
The fault shutdown is indicated by fault codes "F F5"
and "F F7" on the burner control unit display (see
page 39).
Fault resetting: Hold down reset button
R
for longer
than 0.5 s.
LDW1 setting
:
■
Rated heating output 800 kW: 2 mbar (0.2 kPa)
■
Rated heating output 1000 kW: 4 mbar (0.4 kPa)
Combustion chamber pressure monitoring function (LDW2)
To monitor the combustion chamber pressure, the
switching threshold of air pressure switch 2 (plug
aCA
A) is monitored in all operating phases (except dur-
ing safety and stabilising time).
If the combustion chamber pressure lies outside the
permissible range, air pressure switch 2 triggers a fault
shutdown on the burner control unit.
The combustion chamber pressure lies outside the
permissible range in the following operating phases:
■
In the pre-purge phase
■
In control mode
■
In the post-purge phase after 2 attempts
The fault shutdown is indicated by fault code "F FB" on
the burner control unit display (see page 39).
Fault resetting: Hold down reset button
R
for longer
than 0.5 s.
LDW2 setting
: 10 mbar (1 kPa)
Boiler water temperature sensors and flue gas temperature sensors
The temperature sensors are of a dual sensor design.
Connection to burner control unit:
§
A/
§
B Boiler water temperature sensors
aG
A/
aG
B Flue gas temperature sensors
NTC 10 k
Ω
10
1
10
30
50
70
90
110
Temperature in °C
0.4
0.6
0.8
2
4
6
8
20
Resistance
in kΩ
Fig. 30
Function description
Air pressure switch
5833296
Functions
