Viessmann VITOCAL 300 Installation And Service Instructions Manual page 60

Troubleshooting
Control unit diagnostics
Fault messages
48 Flow sensor
HC 2
4C Flow sensor NC
4D Room tempera-
ture sensor NC
50 DHW sensor top
52 DHW sensor bot-
tom
58 DHW sensor top
5A DHW sensor bot-
tom
60 Buffer cylinder
sensor
61 Secondary return
sensor
62 Buffer cylinder,
bottom
63 Ext. heat source
64 Mixer ext. heat
source
68 Buffer cylinder
sensor
69 Secondary return
sensor
6A Buffer cylinder,
bottom
6B Ext. heat source
6C Mixer ext. heat
source
A8 Pump HC 1
60
(cont.)
Cause
Lead broken
Short circuit
Lead broken
Short circuit
Lead broken
No DHW circulation
Measures
Check the terminals; replace
the sensor, if required
Check the sensor; replace if
required
Check the terminals; replace
the sensor, if required
Check the sensor; replace if
required
Check the terminals; replace
the sensor, if required
Check the external heating
circuit pump (see page 49);
replace the pump, if required