*****INTERNAL*****30 R_D proof- 26.10.2022 / 09:15:46- VaillantGroup\DOC-agt\Brand\VIH_QW_190_6\ENG\OI-II_GB_0020291525
60 Installation and maintenance instructions 0020291525_04
Code Meaning Cause
Remedy
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
F.821 Sensor fault: Immers. heater flow
temp.
– The sensor is not connected or the
sensor input has short-circuited
– Both of the flow temperature sensors
in the heat pump are defective
– Check and, if required, replace the
sensor
– Replace the wiring harness
F.823 Hot gas temperature switch open – The hot gas thermostat shuts down
the heat pump if the temperature
in the refrigerant circuit is too high.
Following a waiting period, the heat
pump attempts to start once more.
After three failed start attempts
in succession, a fault message is
displayed.
– Max. refrigerant circuit temperature:
110 °C
– Waiting period: 5 mins (after it first
occurs)
– Waiting period: 30 mins (after it
occurs a second time and any other
time after that)
– The fault counter is reset if both of
the following conditions are met:
– Heat requirement without switch-
ing off prematurely
– 60 mins uninterrupted operation
– Check the EEV
– Replace the dirt filter in the refrigera-
tion circuit, if required
F.824 Building circuit : Brinepressure
too low
Note
Can only occur in conjunction with
an installed and activated intermedi-
ate heat exchanger set.
Fault refers to the outdoor unit's
brine pressure sensor.
– Pressure loss in the building circuit
due to leakages or air pockets
– Building circuit pressure sensor
defective
– Check the building circuit for leaks
– Top up with water, purge
– Check the quality of the plug contact
on the PCB and on the wiring har-
ness
– Check that the pressure sensor is
working correctly
– Replace the pressure sensor
F.825 Sensor fault: Capac. inlet temp. – Refrigerant circuit temperature
sensor (vapour-forming) not con-
nected or the sensor input has short-
circuited
– Check and, if required, replace the
sensor and cable
F.1100 Immersion heater: Safety cut-out
open
The safety cut-out on the electric back-
up heater is open due to:
– Insufficient volume flow or air in the
building circuit
– The immersion heater is operated
when the building circuit is not filled
– Immersion heater operation at flow
temperatures above 89 °C trips the
safety fuse of the safety cut-out and
requires that the fuse be replaced
– Feed-in of external heat into the
building circuit
– Check the circulation in the building
circuit pump
–
If required, open the stopcocks
– Replace the safety cut-out
– Reduce or stop the external heat
that is entering
– Check that the dirt filter that is in
place is permeable
F.1117 Compressor: Phase failure – Defective fuse
– Incorrect electrical connections
– Mains voltage too low
– Compressor/low tariff power supply
not connected
– Energy supply company lockout for
over three hours
– Check the fuse
– Checking the electrical connections
– Check the voltage at the heat pump
electrical connection
– Set the max. duration of the ESCO
anti-cycling time to at least three or
more hours
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