Vaillant VWZ AI User Manual

Appendix
0020291573_00 Heat pump control interface module Installation instructions 33
Code Meaning Cause
Remedy
F.755 Fault: 4-port valve position not
correct
– Incorrect position of the 4-port di-
verter valve. If, in heating mode, the
flow temperature is lower than the
return temperature in the building cir-
cuit.
– The temperature sensor in the elec-
tronic expansion valve environment
circuit displays an incorrect temper-
ature.
– Check the 4-port diverter valve (is an
audible switching available? Use the
sensor/actuator test)
– Check that the coil is positioned
correctly on the 4-port valve
– Check the cable harness and plug
connections
– Check the temperature sensor in the
electronic expansion valve environ-
ment circuit
F.774 Sensor fault: Air inlet temp. – The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the cable harness
F.785 Fan unit 2: Fan blocked – There is no confirmation signal stat-
ing that the fan is rotating
– Check the air route and, if required,
remove any blockages
F.788 Building circuit: Pump fault – The electronics system of the high-
efficiency pump has detected a
fault (e.g. dry running, blockage,
overvoltage, undervoltage) and has
switched off and locked the pump.
– Switch the heat pump off for at least
30 seconds (no current)
– Check the quality of the plug contact
on the PCB
– Check that the pump functions cor-
rectly
– Purging the building circuit
– Check that the dirt filter that is in
place is permeable
F.817 Freq. converter fault: Compressor – Defect in the compressor (e.g. short
circuit)
– Defect in the frequency converter
– Connection cable to the compressor
is defective or loose
– Measure the winding resistance in
the compressor
– Measure the frequency converter
output between the three phases, (it
must be > 1 kΩ)
– Check the cable harness and plug
connections
F.818 Freq. converter fault: Mains
voltage
– Incorrect mains voltage for operating
the frequency converter
– Shutdown via the energy supply
company
– Measure and, if required, correct the
mains voltage
The mains voltage must be between
195 V and 253 V.
F.819 Freq. converter fault: Overheating – Internal overheating of the frequency
converter
– Allow the frequency converter to cool
and restart the product
– Check the frequency converter's air
route
– Check that the fan is working cor-
rectly
– The maximum environmental tem-
perature of the outdoor unit (46 °C)
has been exceeded.
F.820 Connection fault: Building circuit
pump
– Pump does not report any signal
back to the heat pump
– Check the cable to the pump for
defects and, if required, replace it
– Replace the pump

Vaillant VWZ AI Specifications

General

Brand	Vaillant
Model	VWZ AI
Category	Control Unit
Language	English