Appendix
0020257319_02 Hydraulic station Installation and maintenance instructions
55
Code
Meaning
Cause
Remedy
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
F.741
Building circuit: Return temp. too
low
–
During the de-icing, the return tem-
perature falls below 13 °C
–
Ensure the minimum installation
volume is maintained; if required,
install a series return cylinder
–
The fault message is displayed until
the return temperature increases to
above 20 °C.
–
Activate the electric back-up heater
in the product's control panel and
in the system control in order to
increase the return temperature. The
compressor is blocked while the fault
message is present.
F.752
Fault: Frequency converter
–
Internal electronics fault on the in-
verter PCB
–
Mains voltage outside of 70 V
–
282 V
–
Check the integrity of the power sup-
ply cables and compressor connec-
tion cables
The plugs must audibly click into
place.
–
Check the cable
–
Check the mains voltage
The mains voltage must be between
195 V and 253 V.
–
Check the phases
–
Replace the frequency converter, if
required
F.753
Connection fault: Freq. conv.
n.recogn.
–
Missing communication between the
frequency converter and the outdoor
unit's control PCB
–
Check the integrity of the cable
harness and plug connection and,
if required, replace them
–
Check the frequency converter by
actuating the compressor safety
relay
–
Read the assigned parameters for
the frequency converter and check
whether values are displayed
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
