120
Control unit
message
System characteristics
Cause
Measures
F.303/C2F0
No power generation
Fault, stack voltage 1 (fuel
cell)
■
Check balanced flue system for:
–
Flue gas recirculation
–
Leaks
■
Check ventilation air supply for:
–
Ingress of flue gas due to non-
compliance with chimney clear-
ances, e.g. by a solid fuel boil-
er
–
Outgassing/contamination in
the air supply system (e.g. sili-
cones, oils, paints, detergents,
deposits, etc.)
If faults recur, contact Viessmann
Technical Service.
Note
Fault message can
only
be reset
on the programming unit of the fuel
cell module.
F.304/C2F1
No power generation
Fault, stack voltage 2 (fuel
cell)
■
Check balanced flue system for:
–
Flue gas recirculation
–
Leaks
■
Check ventilation air supply for:
–
Ingress of flue gas due to non-
compliance with chimney clear-
ances, e.g. by a solid fuel boil-
er
–
Outgassing/contamination in
the air supply system (e.g. sili-
cones, oils, paints, detergents,
deposits, etc.)
If faults recur, contact Viessmann
Technical Service.
Note
Fault message can
only
be reset
on the programming unit of the fuel
cell module.
Troubleshooting
Fault messages on the gas condensing…
(cont.)
5853335
Diagnosis