Viessmann VITOCROSSAL CRU 800 kW Service Instructions Manual page 39

Fault codes
(cont.)
Displayed fault System characteristics
code
F B7 Burner control unit in a fault
state; system cooling down;
burner control unit locked out.
F B7 Type of coding card
F E4 Burner shuts down.
F E5 Burner control unit in a fault
state
F EE Burner control unit in a fault
state
F EF Burner control unit in a fault
state
F F3 Ionisation flame monitor re-
ports faulty flame signal dur-
ing start-up or after the post-
purge.
Ionisation electrode or burner
gauze assembly damaged.
F F4 No flame formation during
safety time; ionisation flame
monitor reports no flame sig-
nal.
F F4 No flame formation during
safety time; ionisation flame
monitor reports no flame sig-
nal.
F F4 No flame formation during
safety time; ionisation flame
monitor reports no flame sig-
nal.
F F4 Poor start-up characteristics
(start enrichment). Solenoid
valve not switching.
Cause
Coding card not inserted
in the burner control unit;
incorrect or faulty coding
card
Coding card does not
match burner control unit.
Multiple detection of un-
dervoltage with recurrence
and renewed undervolt-
age
Internal fault of the burner
control unit and during test
of ionisation input
Internal error in feedback
from gas safety valves.
The output relay does not
respond.
Internal error in feedback
from gas safety valves.
The output relay does not
respond.
Gas train leaks (gas is es-
caping and burning). In-
correct coding card.
Ionisation electrode incor-
rectly adjusted, ionisation
electrode not plugged in.
Earth fault of electrode or
cable
Ignition electrodes incor-
rectly adjusted, electrode
earth fault, ignition unit
faulty, burner control unit
faulty
Insulation body of ignition
or ionisation electrode
cracked
Compensation lines not
connected, solenoid valve
faulty, output relay of
burner control unit faulty
Troubleshooting
Measures
Insert coding card. Check coding
card. Replace if necessary.
Replace coding card or burner
control unit.
Danger
Plug-in terminals on the
burner control unit are live.
Only replace the coding card
when the burner control unit
has been isolated from the
power supply.
Check the power supply.
Replace burner control unit.
Reset or replace burner control
unit.
Reset or replace burner control
unit.
Check ionisation path. Check ioni-
sation electrode for earth fault.
Check burner gauze assembly for
deformation.
Replace coding card. Replace gas
train.
Insert plug of ionisation electrode;
check cable; adjust ionisation elec-
trode (see page 24).
Adjust ignition electrodes (see
page 24); replace ignition unit. Re-
place burner control unit.
Replace ignition or ionisation elec-
trode.
Check compensation lines and
connections, replace compensa-
tion lines. Replace the solenoid
valve. Replace burner control unit.
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