Hitachi RAS-10HRNM, Service Manual, Page: 208 / 482

Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Insufficient cooling
process
Indoor cool load is greater 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 field-
supplied pipes
Use the correct pipes
Incorrect activation of
the check valve of the
outdoor unit
Check whether or not the temp.
difference exists before/after the
check valve
Replace the check valve for 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 temp. 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 temp. difference Remove the clogging
Insufficient air flow to the
indoor unit heat
exchanger
Check for clogged air filter Clean the air filter
Check for an obstacle at the inlet
or the outlet
Remove the obstacles
Excessively low air
temp. to the indoor unit
heat exchanger
Insufficient speed of the indoor
unit fan motor?
Replace the fan motor
Short-circuited indoor unit air?
Remove the cause of the short-
circuited air
8 Troubleshooting
200
SMGB0060 rev. 1- 12/2010