Hitachi UTOPIA RAS-4HVRP2E Service Manual page 231

10 Troubleshooting
Initial troubleshooting
Phenomenon
Insufficient Heating
Operation
229 SMGB0136 rev.0 - 07/2021
Cause
Indoor Heat Load is greater than
Heating capacity
Gas leakage
or insufficient
refrigerant
charge
Excessively
small diameter
tube or long
piping
Failure or
malfunction
of electronic
expansion valve
Clogging of
Indoor unit/
Excessively
Outdoor unit
low suction
Strainer
pressure
Clogging of
suction piping
Insufficient air
flow through
Outdoor Unit
Heat Exchanger
Excessively low
air temperature
through Outdoor
Unit Heat
Exchanger
Defrosting is
insufficiently
completed
Check Item
Calculate heat load
Measure superheat
Measure field-supplied pipes
Check for clogging
Check for connection cord
and connector
Is there operation sound
from coil?
Is thermistor on compressor
normal?
Is thermistor installed
correctly on compressor?
Check temperature
difference between inlet and
outlet of strainer
Check temperature difference
of each part
Is outdoor unit heat
exchanger clogged?
Is there any obstacles at inlet
or outlet of outdoor unit?
Is service space for outdoor
unit sufficient?
Check for speed of outdoor
unit fan
Check for any short-circuited
air to outdoor unit
Check thermistor for
defrosting
Action (Turn OFF
Main Switch)
Use a bigger unit
Correctly charge refrigerant
after repairing gas leakage
Use correct pipes
Remove clogging
Replace connector
Replace coil
Replace thermistor
Correctly install it
Replace strainer for outdoor
unit or indoor unit
Remove clogging
Remove clogging
Remove obstacles
Secure sufficient service
space
Replace fan motor
Remove cause of short-
circuited air
Replace thermistor for
defrosting
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