Viessmann PLC VITOCAL 350-HT PRO Service Instructions For Contractors page 34

Troubleshooting
Overview of fault messages
ID Fault message
67 "Fault, oil sump heater 2"
68 "Fault, oil sump heater 3"
69 Pre-alarm, evaporation temp
too low
70 Pre-alarm, condensatn temp
too high
71 "Sensor fault, buff. t, HWBC
top"
72 "Sens. fault, buff. t, HWBC
bottom"
73 "Ext. set value, HW buffer cyl" Cylinder charging of the heating
74 "Sensor fault, temp, resid.
heat"
75 "Sensor fault, coolant temp."
76 "Sensor fault, buffer t, CBC
top"
77 "Sensor fault, buffer t, CBC
bottom"
78 "Sensor fault, flow temp,
DHW"
79 "Sensor fault, cylinder t,
DHW"
80 "Modbus RS485"
81 "Modbus IP"
82 "M2 flash not installed"
83 "Modbus server TCP"
84 "Failed to save conf. and set
values"
85 "Failed to load conf. and set
values"
86 "Risk of frost"
34
(cont.)
Effects
Compressor 2 switches on auto-
matically as soon as the fault is
no longer current
Compressor 3 switches on auto-
matically as soon as the fault is
no longer current
A compressor switches off to al-
low the evaporation temperature
to rise. It switches on again as
soon as the restart block time
has elapsed
A compressor switches off to al-
low the condensation tempera-
ture to drop. It switches on again
as soon as the restart block time
has elapsed
Cylinder charging of the heating
water buffer cylinder is no longer
activated
Cylinder charging of the heating
water buffer cylinder is no longer
activated
water buffer cylinder is no longer
activated
The residual heat function is not
activated
The coolant buffer cylinder is not
being cooled
The coolant buffer cylinder is not
being cooled
The coolant buffer cylinder is not
being cooled
The domestic hot water is not
being heated
The domestic hot water is not
being heated
Communication via ModBus
RS484 may not be possible
Communication via ModBus IP
may not be possible
It may not be possible to save
the configuration and log data
Communication via ModBus IP
may not be possible
Set values cannot be saved
Set values cannot be loaded
The heat pump output is re-
duced
Possible cause
The oil sump heater of compres-
sor 2 was switched off for too
long
The oil sump heater of compres-
sor 3 was switched off for too
long
At least one compressor has had
to switch off due to the evapora-
tion temperature being too low
At least one compressor has had
to switch off due to the conden-
sation temperature being too
high
Heating water buffer cylinder
temperature sensor, top is faulty
Heating water buffer cylinder
temperature sensor, bottom is
faulty
External set value from higher
ranking system is outside the
range
Flow temperature sensor, residu-
al heat is faulty
Coolant flow temperature sensor
is faulty
Coolant buffer cylinder tempera-
ture sensor, top is faulty
Coolant buffer cylinder tempera-
ture sensor, bottom is faulty
Flow temperature sensor, DHW
heating is faulty
DHW cylinder temperature sen-
sor is faulty
Faulty configuration
Faulty configuration
SD card fault
Faulty configuration
Write access to the SD card de-
nied or not possible
Read access to the SD card has
not been granted
The evaporation temperature has
undershot the frost protection
value