133
3. Isolate the system from the power supply. Wait at
least 2 min. Switch on the system.
4. Replace inverter.
F.847 Inverter current sensor recognises unchanging compressor current
F.847
System characteristics
Refrigerant circuit off: Inverter and compressor cannot
be switched on.
Cause
Inverter current sensor detects unchanging compres-
sor current.
Measures
1. Isolate the system from the power supply. Wait at
least 2 min. Switch on the system.
2. Replace inverter.
F.848 Inverter current sensor recognises fluctuating compressor current
F.848
System characteristics
Refrigerant circuit off: Inverter and compressor cannot
be switched on.
Cause
Inverter current sensor detects fluctuating compressor
current.
Measures
1. Isolate the system from the power supply. Wait at
least 2 min. Switch on the system.
2. Replace inverter.
F.864 Defrost not terminated successfully
F.864
System characteristics
■
No defrost
■
Compressor cannot be switched on.
Cause
Defrost process aborted 9 times
Measures
1. Check the evaporator for dirt. Clean if necessary. If
necessary, carefully de-ice mechanically.
2. Check that the condensate can drain freely. Clean
if necessary. Check the electric ribbon heaters if
necessary.
3. Check refrigerant circuit for damage.
4. Check the temperature sensors of the outdoor unit.
If necessary, perform measures as described in
F.123, F.124, F.770, F.771, F.866.
5. Check minimum flow rate of secondary circuit.
6. Check whether the electric ribbon heater is work-
ing. Replace if necessary.
7. Check instantaneous heating water heater.
Replace if necessary.
8. Check the external heat generator (if installed).
9. Inform Viessmann Technical Service.
10. Unlock refrigerant circuit via ViGuide.
Messages
Fault messages (cont.)
6218234
Diagnosis
To Next Page