Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 143

Messages
(cont.)
Message
System characteristics Cause
CA Primary source
CB Primary temperature
Heat pump stops.
CC Coding card
CD KM BUS Vitocom
Primary circuit fault:
■ Primary circuit pres-
sure switch/frost pro-
tection monitoring has
responded
■ Primary pump thermal
circuit breaker (heat
pump stage 1,
type BW or common
primary pump)
Min. primary flow tem-
perature (brine inlet) not
achieved
The coding card cannot
be read
Communication error -
KM BUS Vitocom 100
Troubleshooting
Measures
■ Check safety equip-
ment on cross connect
PCB, terminals X3.9
and X3.8; in systems
without safety equip-
ment, check jumper
between X3.9/X3.8.
■ Reset thermal relay,
check primary pump
and replace if required
The switching signal can
be tested at connection
215.3.
Check primary circuit for
flow rate.
■ Check coding card and
replace if required.
■ Check controller and
sensor PCB and
replace, if required.
Check Vitocom 100 con-
nections and connecting
cables.
Check connections at the
controller and sensor
PCB, plug aVG KM BUS.
A fluctuating DC voltage
between approx. 20 V and
30 V can be measured at
the terminals.
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