Viessmann Vitocrossal 200 CM2 400 Service Instructions Manual page 56

Troubleshooting
Fault Codes
(continued)
Displayed System Characteristics
Fault Code
F EE Burner control unit in a fault
state
F EF Burner control unit in a fault
state
F F0 Emergency operation
according to internal
default
F F1 Burner control unit in a fault
state; system cools down
F F2 Burner control unit in
a fault state; system
cools down
F F3 Ionization flame monitor reports
faulty flame signal during start-
up or after the post-purge
F F4 No flame formation during
safety time; ionization flame
monitor reports no flame signal
F F4 No flame formation during
safety time; ionization flame
monitor reports no flame signal
F F4 No flame formation during
safety time; ionization flame
monitor reports no flame signal
F F4 Poor start-up characteristics,
rotary damper does not close,
solenoid valve does not switch
F F4 No flame builds during safety
time; ionization flame monitor
reports no signal
F F4 No flame builds during safety
time; ionization flame monitor
reports no signal
56
Vitocrossal 200, CM2 400, 500, 620 and 620 TX Service
Cause
Internal error in feedback from
gas safety valves; output relay
does not respond
Internal error in feedback from
gas safety valves; output relay
does not respond
Communication error KM BUS
burner control unit
Flue gas excess temperature;
excessive gas throughput
Excessive boiler
water temperature
Gas valve leaking (flame
present); incorrect coding card
Ionization electrode incorrectly
adjusted; ionization electrode
not plugged in. Ground fault
of electrode or cable
Ignition electrode not set
correctly; earth leakage of
electrodes; ignition unit faulty;
burner control unit faulty
Insulation body of ignition or
ionization electrode cracked
Servomotor faulty, servomotor
connecting cable faulty,
solenoid valve faulty, burner
control unit output relay faulty
Incorrect gas type selected
Gas valve does not open
Measures
Reset burner control unit; replace
burner control unit
Reset burner control unit; replace
burner control unit
Check the KM BUS cable
plug for firm seating;
check all KM BUS cables
Wait until temperature falls below
the permissable flue gas temperature.
Reset burner control unit. Check water
level; check heat exchanger surfaces
for contamination; check CO
set gas throughput according to rated
boiler heating output (see connection
values page 18).
Wait until temperature falls below the
permissable boiler water temperature;
reset burner control unit
Check ionization path; replace coding
card; replace gas valve
Insert plug of ionization electrode;
check cables; adjust ionization
electrode (see page 24)
Adjust ignition electrodes (see page 24);
replace ignition unit; replace burner
control unit
Replace ignition or ionization electrode
Replace connecting cable; replace
servomotor; replace solenoid valve;
replace burner control unit
Adjust gas type (see page 12)
Check the connecting cable; check
the gas valve and replace
if required
setting;
2