*****INTERNAL*****30 R_D proof- 26.10.2022 / 09:15:46- VaillantGroup\DOC-agt\Brand\VIH_QW_190_6\ENG\OI-II_GB_0020291525
0020291525_04 Installation and maintenance instructions 57
Code Meaning Cause
Remedy
F.517 Sensor fault: Compr. outlet temp. – The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.519 Sensor fault: Building circuit re-
turn temp.
– The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.520 Sensor fault: Building circuit flow
temp.
– The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.526 Sensor fault: EEV outlet temp. – The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.546 Sensor fault: High pressure – The sensor is not connected or the
sensor input has short-circuited
– Check the sensor (e.g. using an in-
stallation aid), and replace if neces-
sary
– Replace the wiring harness
F.582 Fault: EEV – EEV is not connected correctly or
there is a cable break to the coil
– Check the plug connections and, if
required, replace the coil from the
EEV
F.585 Sensor fault: Capac. outlet temp. – The sensor is not connected or the
sensor input has short-circuited
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.703 Sensor fault: Low pressure – The sensor is not connected or the
sensor input has short-circuited
– Checking the sensor (e.g. using an
installation aid), and replacing it if
necessary
– Replace the wiring harness
F.718 Fan unit 1: 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.729 Compressor outlet temperature
too low
– The compressor outlet temperature
is lower than 0 °C for more than 10
minutes or the compressor outlet
temperature is lower than -10 °C
even though the heat pump is in the
operating characteristics.
– Checking the high-pressure sensor
– Checking that the EEV is working
correctly
– Check the condenser outlet temper-
ature sensor (supercooling)
– Check whether the 4-port diverter
valve is in the intermediate position
– Checking the refrigerant volume for
overfilling
F.731 High-pressure switch open – Refrigerant pressure too high. The
integrated high-pressure switch
in the outdoor unit has tripped at
31.5 bar (g) or 32.5 bar (abs)
– Insufficient energy output via the
condenser
– Purging the building circuit
– Too low a volume flow as a result
of closing single room controls in an
underfloor heating system
– Check that the dirt filter that is in
place is permeable
– Refrigerant flow rate too low (e.g.
electronic expansion valve defective,
4-port diverter valve is mechanically
blocked, filter is blocked). Inform
customer service.
– Cooling mode: Check the fan unit for
dirt
– Check the high-pressure switch and
high-pressure sensor
– Reset the high-pressure switch and
carry out a manual reset on the
product.
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