Viessmann VITOCAL 151-A Installation And Service Instructions Manual page 109

Fault messages
(cont.)
Message code System characteristics
F.847 Refrigerant circuit off: Inverter
and compressor cannot be
switched on.
F.848 Refrigerant circuit off: Inverter
and compressor cannot be
switched on.
F.864 No defrost
■
Compressor cannot be
■
switched on.
F.865 Refrigerant circuit off
F.866 Refrigerant circuit off
Cause
Voltage error on inverter
Voltage error on inverter
Outdoor unit defrost at-
tempt unsuccessful
High pressure fault:
Air in the secondary cir-
■
cuit
Secondary circuit/heat-
■
ing circuit shut off
Secondary pump or
■
heating circuit pumps
blocked or faulty
Condenser contamina-
■
ted
High pressure sensor
■
faulty
Set flow temperatures
■
for central heating/DHW
heating too high
Low pressure fault:
Too little refrigerant
■
Evaporator contamina-
■
ted
Fans blocked or faulty
■
Troubleshooting
Measures
Isolate the system from the power
supply. Restart the system.
If the fault persists, replace the in-
verter.
Isolate the system from the power
supply. Restart the system.
If the fault persists, replace the in-
verter.
Check outdoor unit for icing up.
De-ice if necessary.
Vent the secondary circuit.
■
Check the system pressure.
■
Check secondary pump and
■
heating circuit pumps.
Flush heating circuits.
■
Measure voltage at connec-
■
tion X14.1/X14.2 of the
VCMU refrigerant circuit control-
ler. Replace sensor if required.
Adjust set temperatures of con-
■
sumers.
Check outdoor unit for icing up.
■
De-ice if necessary.
Check amount of refrigerant. Top
■
up refrigerant if required.
Clean the evaporator.
■
Check fans. Remove blockages.
■
Replace fans if required.
109