Hitachi RAS-5HVRNM1E Service Manual page 208

8 Troubleshooting
Phenomenon
Indoor cool load is greater than the cooling capacity
Insufficient cooling
Excessively low suction
process
pressure
200
SMGB0060 rev. 1- 12/2010
Cause
Gas leakage or shortage
of refrigerant
Excessively small
Measure and check the field-
diameter tube or long
piping
Incorrect activation of Check whether or not the temp.
the check valve of the difference exists before/after the
outdoor unit
Check the connection cord and
Is there an operation sound from
Failure or malfunction of
the expansion valve
Clogged strainer in the
Check the temp. difference at the
indoor unit; clogging at
inlet and the outlet of the strainer
the low pressure piping
Clogging at the low
pressure piping
Insufficient air flow to the
indoor unit heat
Check for an obstacle at the inlet
exchanger
Insufficient speed of the indoor
Excessively low air
temp. to the indoor unit
heat exchanger
Short-circuited indoor unit air?
Check item
Calculate the cool load
Correctly charge the refrigerant
Measure superheat
after repairing the gas leakage
supplied pipes
Replace the check valve for the
check valve
Check for clogging
the connector
the coil?
Is the thermistor on the
compressor normal?
Is the thermistor installed
Correctly install the thermistor
correctly on compressor?
Replace the strainer in the indoor
Check the temp. difference
Check for clogged air filter
or the outlet
unit fan motor?
Remove the cause of the short-
Action
(Turn OFF the main switch)
Use a bigger unit
Use the correct pipes
outdoor unit
Remove the clogging
Replace the connector
Replace the coil
Replace the thermistor
unit
Remove the clogging
Clean the air filter
Remove the obstacles
Replace the fan motor
circuited air