Hitachi UTOPIA RAS-4HVRP2E - Abnormal Operation of the Devices

10 Troubleshooting
Initial troubleshooting
SMGB0136 rev.0 - 07/2021
214
10.1.1.3 Abnormal operation of the devices
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
No defrost operation
mode is available
during the heating
process or the defrost
operation continues
Failure of
thermistor
for outdoor
evaporating
temperature during
heating
Failure of thermistor
Replace or correctly connect when it is abnormal
Disconnected wire of
thermistor
Failure of 4-way
valve
Disconnected 4-way
valve coil
Measure the resistance of coil
Replace the 4-way valve
Incorrect activation of
4-way valve
Enforced power supply
Disconnected control wires between indoor
unit and outdoor unit
Check the connectors Correctly connect the wiring
Failure of the PCB
of the indoor unit
Disconnected wiring
to PCB
Check the connectors Correctly connect the wiring
Failure of PCB
Check PCB by means of the
self-check mode
Replace PCB when the
check mode is not available
Failure of the PCB
of the indoor unit
Disconnected wiring
to PCB
Check the connectors Correctly connect the wiring
Failure of the PCB
Check PCB by means of the
self-check mode
Replace if PCB fails
Insufcientcooling
process
Indoor cool load is higher than the cooling
capacity
Calculate the cool load Use a bigger unit
Excessively low
suction pressure
Gas leakage or
shortage of refrigerant
Measure superheat
Correctly charge the
refrigerant after repairing the
gas leakage
Excessively small
diameter tube or long
piping
Measureandchecktheeld-
supplied pipes
Use the correct pipes
Incorrect activation of
the check valve of the
outdoor unit
Check whether or not the
temperature difference before/
after the check valve
Replace the check valve of
the outdoor unit
Failure or malfunction
of the expansion valve
Check for clogging Remove the clogging
Check the connection cord
and the connector
Replace the connector
Is there an operation sound
from the coil?
Replace the coil
Is the thermistor on the
compressor normal?
Replace the thermistor
Is the thermistor installed
correctly on compressor?
Correctly install the
thermistor
Clogged strainer in the
indoor unit; clogging
at the low pressure
piping
Check the temperature
difference at the inlet and the
outlet of the strainer
Replace the strainer in the
indoor unit
Clogging at the low
pressure piping
Check the temperature
difference
Remove the clogging