121
Displayed fault
code
System characteristics
Cause
Measures
49
No reheating suppression via
Vitosolic 100/200 possible
Lead break to
Vitosolic 100/200 (KM-
BUS)
Check KM-BUS connection to
Vitosolic
51
No control mode at heating
circuit 1
Short circuit, flow temper-
ature sensor, heating cir-
cuit 1
Check flow temperature sensor,
heating circuit 1
52
No control mode at heating
circuit 2
Short circuit, flow temper-
ature sensor, heating cir-
cuit 2
Check flow temperature sensor,
heating circuit 2
53
No control mode at heating
circuit 3
Short circuit, flow temper-
ature sensor, heating cir-
cuit 3
Check flow temperature sensor,
heating circuit 3
54
No DHW heating
Short circuit, cylinder tem-
perature sensor
Check cylinder temperature sensor
55
No flow control
Short circuit, return tem-
perature sensor
Check return temperature sensor
56
No solar yield
Short circuit, collector
temperature sensor
Check collector temperature sen-
sor
57
No solar yield
Short circuit, solar refer-
ence sensor
Check solar reference sensor
58
No control mode at heating
circuit 4
Short circuit, flow temper-
ature sensor, heating cir-
cuit 4
Check flow temperature sensor,
heating circuit 4
61
No control mode at heating
circuit 1
Lead break, flow tempera-
ture sensor, heating cir-
cuit 1
Check flow temperature sensor,
heating circuit 1
62
No control mode at heating
circuit 2
Lead break, flow tempera-
ture sensor, heating circuit
2
Check flow temperature sensor,
heating circuit 2
63
No control mode at heating
circuit 3
Lead break, flow tempera-
ture sensor, heating cir-
cuit 3
Check flow temperature sensor,
heating circuit 3
64
No DHW heating
Lead break, cylinder tem-
perature sensor
Check cylinder temperature sensor
65
No flow control
Lead break, return tem-
perature sensor
Check return temperature sensor
66
No solar yield
Lead break, collector tem-
perature sensor
Check collector temperature sen-
sor
67
No solar yield
Lead break, solar refer-
ence sensor
Check solar reference sensor
68
No control mode at heating
circuit 4
Lead break, flow tempera-
ture sensor
Check flow temperature sensor
8A
Burner locked out
Flue gas temperature in
load operation too low
■
Check position of ash box and fit
correctly if necessary
■
Check flue gas temperature sen-
sor
■
Check air dampers
8B
Burner locked out
Flue gas temperature too
high
■
Clean the boiler
■
Check flue gas temperature sen-
sor
■
Check air dampers
Troubleshooting
Fault codes
(cont.)
5679249
Diagnosis