*****INTERNAL*****30 R_D proof- 26.10.2022 / 09:15:46- VaillantGroup\DOC-agt\Brand\VIH_QW_190_6\ENG\OI-II_GB_0020291525
58 Installation and maintenance instructions 0020291525_04
Code Meaning Cause
Remedy
F.732 Compressor outlet temperature
too high
The compressor outlet temperature is
above 110 °C:
– Application limits exceeded
– EEV does not work or does not open
correctly
– Refrigerant volume too low (frequent
defrosting due to extremely low
evaporation temperatures)
– Check the compressor inlet sensor
and outlet sensor
– Check the compressor outlet temper-
ature sensor (TT135)
– Check the EEV (does the EEV
move to the limit stop? Use the
sensor/actuator test)
– Check the refrigerant volume (see
Technical data)
– Carry out a leak-tightness test
– Check whether the service valves on
the outdoor unit are open.
F.733 Evaporation temperature too low – Insufficient air volume flow through
the outdoor unit's heat exchanger
(heating mode) leads to an insuffi-
cient energy input in the environment
circuit (heating mode) or building cir-
cuit (cooling mode)
– Refrigerant volume too low
– If the building circuit contains ther-
mostatic valves, check that they are
suitable for cooling mode (check
volume flow in cooling mode)
– Check the fan unit for dirt
– Check the EEV (does the EEV
move to the limit stop? Use the
sensor/actuator test)
– Check the compressor inlet sensor
– Check the refrigerant volume
F.734 Condensation temperature too low – The temperature in the heating
circuit is too low, outside of the
operating characteristics
– Refrigerant volume too low
– Check the EEV (does the EEV
move to the limit stop? Use the
sensor/actuator test)
– Check the compressor inlet sensor
– Check the refrigerant filling volume
(see technical data)
– Check whether the 4-port diverter
valve is in an intermediate position
and is not correctly switched
– Checking the high-pressure sensor
– Check the pressure sensor in the
heating circuit
F.735 Evaporation temperature too high – Temperature in the environment
circuit (heating mode) or building
circuit (cooling mode) too high for
compressor operation
– Feed-in of external heat into the
environment circuit too high due to
increased fan speed
– Check the system temperatures
– Check the refrigerant filling volume
for overfilling
– Check the EEV (does the EEV
move to the limit stop? Use
sensor/actuator test)
– Check the sensor for the evaporation
temperature (depending on the
position of the 4-port diverter valve)
– Check the volume flow in cooling
mode
– Check the air volume flow in heating
mode
F.737 Condensation temperature too
high
– Temperature in the environment
circuit (cooling mode) or building
circuit (heating mode) too high for
compressor operation
– Feed-in of external heat into the
building circuit
– Refrigerant circuit overfilled
– Insufficient flow rate in the building
circuit
– Reduce or stop the external heat
that is entering
– Check the back-up heater (heats
up even though it is off in the
sensor/actuator test?)
– Check the EEV (does the EEV
move to the limit stop? Use the
sensor/actuator test)
– Check the compressor outlet sensor,
compressor outlet temperature
sensor (TT135) and high-pressure
sensor
– Check the refrigerant filling volume
for overfilling
– Check whether the service valves on
the outdoor unit are open.
– Check the air volume flow in cooling
mode for sufficient flow rate
– Checking the heating pump
– Check the building circuit flow rate
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