Hitachi UTOPIA RAS-4HVRP2E - Page 218

10 Troubleshooting
Initial troubleshooting
SMGB0136 rev.0 - 07/2021
216
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Insufcientheating
process
Indoor heat load is greater than the heating
capacity
Calculate the heat load
Replace the unit with a
bigger unit
Excessively low
suction pressure
Gas leakage or
insufcientrefrigerant
charge
Measure superheat
Correctly charge the
refrigerant after the gas
leakage check and repairing
Excessively small
diameter or long piping
Measuretheeldsupplied
piping
Usethespeciedpipes
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
Clogging of IU/OU
strainer
Check the temperature
difference between the inlet
and the outlet of strainer
Replace the strainer for the
outdoor unit or the indoor unit
Clogging of suction
piping
Check the temperature
difference of each part
Remove the clogging
Insufcientairow
through the outdoor
unit heat exchanger
Is the outdoor unit heat
exchanger clogged?
Remove the clogging
Are there any obstacles at the
inlet or the outlet of outdoor
unit?
Remove the obstacles
Is the service area for the
outdoorunitsufcient?
Secureasufcientservice
area
Check the speed of the
outdoor unit fan
Replace the fan motor
Excessively low air
temperature through
the outdoor unit heat
exchanger
Check for any short-circuited
air to the outdoor unit
Remove the cause of the
short-circuited air
Defrosting is
insufciently
completed
Check the thermistor for the
defrost operation
Replace the thermistor for
the defrost operation
Excessively high
discharge pressure
Excessively charged
refrigerant
Check the refrigerant quantity Correctly charge the refrigerant
Non-condensate gas
in refrigerant cycle
Check the refrigerant quantity
Recharge the refrigerant after
the vacuum pumping
Clogging of the
discharge pressure
piping
Check for clogging Remove the clogging
Malfunction or internal leakage of the 4-way
valve
Check the temperature
difference at the inlet and the
outlet of the 4-way valve
Replace the 4-way valve
Malfunction of the check valve of the
outdoor unit
Check the temperature
difference at the inlet and the
outlet of the check valve
Replace the check valve
Excessively high
suction pressure
Malfunction or internal
leakage of 4-way valve
Check the temperature
difference at the inlet and the
outlet of the 4-way valve
Replace the 4-way valve
Discharge temperature of the indoor unit is
unstable
Check the expansion valve
of the indoor unit in the same
system
Replace the failed expansion
valve of the indoor unit