Viessmann B2TF - Fault Messages

79
Note
For diagnosis and troubleshooting, see chapter
"Repairs".
Fault messages dependent on appliance equipment
level
Displayed fault
code
System characteristics Cause Measures
F.5 Flow rate not being moni-
tored. System continues op-
erating in normal mode with
replacement value.
Lead break or short cir-
cuit, flow sensor
Check plug 33/X6 and cable be-
tween BCU burner control unit and
flow sensor:
■
Check voltage level, to see if 5 V
present at plug 33, pin 1 and 2.
■
Turn the gas condensing boiler
ON/OFF switch off and back on
again.
F.7 No DHW heating Lead break, cylinder tem-
perature sensor
■
Check DHW setting in the com-
missioning assistant and correct
if required.
■
Check cylinder temperature sen-
sor (plug 5, wires 3 and 4).
■
Measure voltage at sensor input
on electronics module. Set value:
3.3 V– with sensor disconnected.
Replace faulty component if re-
quired.
F.8 No DHW heating Short circuit, cylinder tem-
perature sensor
Check cylinder temperature sensor
(plug 5, wires 3 and 4).
Replace faulty component if re-
quired.
F.11 No solar DHW heating or
central heating backup
Lead break, collector tem-
perature sensor
■
Check collector temperature sen-
sor.
■
Measure voltage at sensor input
on electronics module. Set value:
3.3 V– with sensor disconnected
F.12 No solar DHW heating Short circuit, collector
temperature sensor
■
Check collector temperature sen-
sor.
■
Measure voltage at sensor input
on electronics module. Set value:
3.3 V– with sensor disconnected
F.13 Regulates as if the outside
temperature were 0 °C.
Lead break, outside tem-
perature sensor
■
Check operating mode setting in
commissioning assistant and
remedy if required.
■
Check outside temperature sen-
sor and connection to sensor
(external plug, contacts 1 and 2).
■
Measure voltage at sensor input
on electronics module. Set value:
3.3 V– with sensor disconnected.
Replace faulty component if re-
quired.
F.14 Regulates as if the outside
temperature were 0 °C.
Short circuit, outside tem-
perature sensor
Check outside temperature sensor
and connection to sensor (external
plug, and contacts 1 and 2). Re-
place faulty components if neces-
sary.
Troubleshooting
Fault messages
6151778
Service