Faults Without Fault Display - Viessmann Vitocrossal CRU 800 Service Instructions For Contractors

Fault codes with display on burner control unit
Detailed er- Component/signal Cause of fault
ror code
34 Gas pressure
switch 1
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.
High switching se-
quence, switch flutters
External voltage
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; insuf-
2
ficient or excessive air
Incorrect setting
Insufficient or excessive air
Insufficient draught in flue
system
(cont.)
Measure
Check the gas supply. Check setting GDW1 and
gas train intake screen.
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 11 onwards).
Adjust burner in accordance with the details on
page 16 onwards.
Correct the settings. Check ventilation in installation
room.
Check flue system.
Troubleshooting
43