Bosch Condens 7000 F Installation And Maintenance Instructions For The Contractor page 50

Operating and fault displays
1)
Type Error 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 gas supply
pressure.
Flue gas pressure
limiter has tripped
Differential
pressure switch
has tripped.
Differential
pressure switch
defective.
B 8L 579 No gas supply
pressure.
V 8P 580 Solenoid valve 1
leaking.
V 8U 581 Solenoid valve 2
leaking.
B 8U 584 No diverter
module feedback
50
Description Test procedure/Cause
The mains voltage is The mains voltage must not fall
too low. below 195 V.
There has been a brief Check the mains cable for loose
interruption in the mains contacts.
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 limiter,
Check whether there is gas pressure.
differential pressure
Check whether the flue gas pressure
switch, valve testing
limiter has responded.
system) is open;
If the flue gas pressure limiter has
Fig. 74, page 61
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 whether the differential
pressure switch has responded.
Check whether the valve testing
system has responded.
Although the solenoid Check that the gas isolator is open.
valve 1 must have opened,
Measure the gas supply pressure.
there is no gas supply
Where required, Replace air/gas
pressure. The burner
ratio control valve.
makes three successive
attempts at starting, then
waits for one hour before
making three more start
attempts.
The valve test system has Check the air/gas ratio control valve
detected an unacceptably for contamination.
high leakage rate on
Gas filter fitted.
solenoid valve 1.
The valve test system has Check the air/gas ratio control valve
detected an unacceptably for contamination.
high leakage rate on
Gas filter fitted.
solenoid valve 2.
Diverter module does not No feedback from external
receive feedback within components.
the specified time.
Power cable damaged or faulty.
Faulty external component.
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.
▶ 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 54).
▶ Replace the gas filter if necessary.
▶ Replace the air/gas ratio control
valve if necessary.
▶ If necessary, replace the air/gas ratio
control valve.
▶ Check whether there is any gas
supply pressure.
▶ Replace air/gas ratio control valve.
▶ Replace air/gas ratio control valve.
▶ Check flue gas damper or other
connected component.
▶ Check diverter module.
▶ Check the plug-in connection.
▶ Replace power cable if necessary.
▶ Replace external component if
necessary.
Condens 7000 F – 6720871560 (2019/11)