Bosch Condens 7000 FP Installation And Service Instructions Manual page 60

Operating and fault displays
1)
Type Fault Sub Cause
code code
B 7A 550 Voltage too low.
B 7A 551 Power failure.
B 7P 549 The safety chain
has opened.
V or B 8L 534 No sufficient gas
supply pressure.
Flue gas pressure
limiter has tripped
Differential
pressure switch
has tripped.
Differential
pressure switch
defective.
60
Description Test procedure/Cause
The mains voltage is too The mains voltage must not fall
low. below 195 V.
There has been a brief Check the mains cable for loose
interruption in the contacts.
mains voltage.
Check the wiring and correct
contacts of the mains plug at the
control unit and burner control unit.
The continuity of the Check the continuity of the
external components components.
integrated into the
safety chain has been
interrupted.
The internal safety chain Check that the gas isolator is open.
(flue gas pressure
Check whether there is gas pressure.
limiter, differential
Check whether the flue gas pressure
pressure switch, valve
limiter has responded.
testing system) is open;
If the flue gas pressure limiter has
Fig. 92, page 71
responded, check connections and
tightness of the flue system!
Check flue and combustion air pipe
for soiling (possible soiling of filter, if
installed) or blockage.
Check gas filter for contamination.
Check if the differential pressure
sensor has switched(Fig. 86,
page 66).
Check whether the valve testing
system has responded.
Action
▶ Connect the correct power
supply.
▶ Remedy any contact problems if
required.
▶ If required, replace faulty
components.
▶ Measure gas pressure.
▶ After resetting the flue gas
pressure limiter, find the cause
of the trigger, check the burner
rod, check the position of the
ignition electrode, check the
condition of the ignition
electrode, check ignition spark,
check ignition cable contact.
▶ After triggering, check the boiler
flue gas pressure limiter for leaks
and damage.
▶ Check the following
components:
– Air intake worm
– Burner rod
– Cleaning cover at the
condensation catch pan
– Coupling piece from
condensation catch pan to
flue elbow (inside the casing)
– Flue gas system, in particular
in the installation room
– Motorised flue gas damper (if
fitted)
▶ Blow out burner rod against the
flow direction.
▶ When using the "air filter"
accessory set, check the filter for
contamination. To do so, pull off
the PWM plug on the fan and
when the fan is running, check
whether the yellow warning is
visible at the fill level indicator.
If it is, replace the filter.
▶ Test the differential pressure
switch (Chapter 16,
page 65).
▶ Replace the gas filter if
necessary.
▶ Replace the air/gas ratio control
valve if necessary.
Condens 7000 FP – 6721846699 (2022/12)