Installation and operating instruction
Gas condensing unit WTC-GB 15-B Compact and WTC-GB 25-B Compact
10 Troubleshooting
83309302 1/2018-05 La
136-196
The following faults must only be rectified by qualified personnel:
Fault
Cause
Rectification
F 20
Burner control:
Flame failure in safety time
Check gas connection pressure [ch. 7.1.2]
(flow operated safety device).
Check the ionisation electrode, replace if
necessary [ch. 9.1.4].
Clean burner surface, if necessary replace
[ch. 9.1.3].
Check combustion air for contamination.
With room-air-independent operation, check
soundness of flue gas system [ch. 7.3].
Time until flame formation too long, increase para-
meter
2.3.5 Correction gas surge at
start
step by step, whilst observing CO
content [ch. 6.6.2.3].
Time until flame formation too long, increase para-
meter
2.3.1 Correction gas quantity
at start
step by step, whilst observing CO
content [ch. 6.6.2.3].
Ensure that the flue gas ducts are unimpeded.
Flue gas resistance too high, check condensate
drain.
Check flue gas shut off device, if necessary re-
place.
Check gas combi valve, if necessary replace.
F 21
Burner control:
No flame formation at burner start
Check gas connection pressure [ch. 7.1.2]
(flow operated safety device).
Check the ionisation electrode, replace if
necessary [ch. 9.1.4].
Clean burner surface if necessary replace
[ch. 9.1.3].
Check combustion air for contamination.
Check the ignition unit and replace if necessary
Time until flame formation too long, increase para-
meter
2.3.1 Correction gas quantity
at start
step by step, whilst observing CO
content [ch. 6.6.2.3].
With room-air-independent operation, check
soundness of flue gas system [ch. 7.3].
Ensure that the flue gas ducts are unimpeded.
Flue gas resistance too high, check condensate
drain.
Check flue gas shut off device, if necessary re-
place.
Check gas combi valve and cable, replace if ne-
cessary.
F 23
Flame simulation
Check phase position and earth.
Optimise EMC measures.
Reset appliance, replace appliance electronics
WEM-FA-G if occurring repeatedly.
F 24
Burner lockout function activated
Check components connected to input H1 and/
or H2 of WTC.
F 29
DHW outlet sensor defective
Check the sensor and cable and replace if neces-
sary
F 30
Flow sensor (eSTB) defective
Check the sensor and cable and replace if neces-
sary
F 31
Flue gas sensor defective
Check the sensor and cable and replace if neces-
sary