Faults Without Fault Display - Viessmann VITOCROSSAL CRU 800 kW Service Instructions Manual

Fault codes
(cont.)
Detailed er- Component/signal Cause of fault
ror code
35 Plug 41 demand T2 High switching se-
36 Plug 90 T8
37 Plug 90 T7 SK
38 Fuel valve 1 feed-
back
3A Ignition feedback
3B Air pressure switch
2
60 Hall signal fan feed-
back (RM-N)

Faults without fault display

Fault
Combustion faults due to
pulsation
Thermo-acoustics/combus-
tion noise
CO content too low
2
CO formation or burner is
very sooty.
Flame tears off during oper-
ation
Flue gas temperature too
high
quence, switch flutters
External voltage
High switching se-
quence, switch flutters
External voltage
High switching se-
quence, switch flutters
External voltage
Incorrect return voltage
(e.g. DC voltage)
Actuator faulty
Incorrect return voltage
(e.g. DC voltage)
Actuator faulty
For type CM3C only:
High switching se-
quence, switch flutters
External voltage
Fan speed too high. In-
correct fan or incorrect
coding card
Cause of fault
Excessive gas throughput
Insufficient or excessive air
Condensate backed up in flue
system
Flue outlet not installed cor-
rectly
Incorrect CO settings; insuffi-
2
cient or excessive air
Incorrect setting
Insufficient or excessive air
Insufficient draught in flue
system
Intake strainer of gas train
soiled
Excessive gas throughput
Measure
Check whether external voltage present.
Check on-site connection.
Check whether external voltage present.
Check on-site connection.
Check whether external voltage present.
Check on-site connection.
Remove plug from fuel valve 1, reset burner con-
trol unit and check error messages. If F Fd recurs,
replace burner control unit. Otherwise, replace
fuel valve 1.
Disconnect cable from ignition module, reset
burner control unit and check error messages. If
F Fd recurs, replace burner control unit. Other-
wise, replace ignition module.
Check flue gas path and reheating surfaces.
Check air pressure switch 2 setting.
Check the fan. Check coding card.
Measure
Adjust gas throughput in accordance with the rated
boiler heating output.
Check condensate drain.
Check flue outlet and flue system.
Adjust burner in accordance with the details on
page 16 onwards.
Check whether the burner has been adjusted to the
correct gas type; change gas restrictor if required
(see page 10 onwards).
Adjust burner in accordance with the details on
page 16 onwards.
Correct the settings. Check ventilation in installation
room.
Check flue system.
Remove flange and clean strainer. See page 28.
Adjust gas throughput in accordance with the rated
boiler heating output. Check condition of heating
surfaces. Clean if required.
Troubleshooting
43