Viessmann Vitocal 350-A Installation And Service Instructions Manual page 145

Control unit diagnostics
Message
System characteristics Cause
«BE HC3 R/C KM BUS
«BF Communication module
«C2 Power supply monitor
¸C5 Power-OFF
(cont.)
Communication error -
KM BUS remote control;
heating circuit with mixer
M3
LON communication
error; incorrect LON
communication module
Compressor power sup-
ply fault or phase monitor
faulty
Power-OFF enabled
(triggered by power sup-
ply utility)
Troubleshooting
Measures
Check remote control
connections and coding.
Check connections and
type of LON communica-
tion module.
If required, replace in the
following order: PCB 3,
ribbon cables between
PCB 3 and 2, PCB 2
Check phase connection
and power supply; check
phase monitor.
The switching signal can
be tested at terminals
1X5.4 and 1X5.3.
No measures required.
If message persists:
Check connections 1X3.6
and 1X3.7.
145