Viessmann VITOTRONIC 100 Installation And Service Instructions Manual page 116

Troubleshooting
Faults which are displayed at the programming unit
Fault
System
code
characteristics
Control mode
aa
Controlled
ab
operation, perhaps
DHW cylinder cold
Control mode
ac
ad
bC 0
116
Cause
Therm Control
configuration error
Plug aJA of
Therm Control
temperature sensor
not inserted
Cylinder storage
system
configuration error:
Code "55:3" has
been set, but
plug aJB is not
plugged in
and/or
Code "4C:1" and
"4E:1" have not
been set
Return temperature
raising
configuration error:
Code "0C:1" has
been set, but
plug aJA is not
plugged in
and/or
Code "4E:0" is not
set
Butterfly valve
configuration error:
Code "0C:2",
"0C:3" or "0C:4" is
set
and
Code "4E:1" is set
Short circuit
Flue gas
temperature sensor
(cont.)
Remedy
Insert plug aJA
Code "0d:0" must
be set for
Vitocrossal
Insert plug aJB
and check code
Insert plug aJA
and check code
With butterfly valve:
Code "4E:0" is set
Without butterfly
valve: Set code
"0C:0" or "0C:1"
Check flue gas
temperature sensor
(see page 132)