Hitachi RAS-(3-6)HVNC1(E) Service Manual page 226

8 Troubleshooting
Phenomenon
Indoor cool load is greater than the cooling
capacity
Insufficient cooling
process
Excessively low
suction pressure
212
SMGB0087 rev.0 - 12/2013
Cause
Calculate the cool load
Gas leakage or
shortage of Measure superheat
refrigerant
Excessively small
Measure and check the
diameter tube or long
field-supplied pipes
piping
Incorrect activation Check whether or not the
of the check valve of temperature difference exists
the outdoor unit before/after the check valve
Check for clogging
Check the connection cord
and the connector
Failure or malfunc- Is there an operation sound
tion of the expansion from the coil?
valve
Is the thermistor on the
compressor normal?
Is the thermistor installed
correctly on compressor?
Clogged strainer in
Check the temperature
the indoor unit; clog-
difference at the inlet and the
ging at the low pres-
outlet of the strainer
sure piping
Clogging at the low Check the temperature
pressure piping difference
Check for clogged air filter
Insufficient air flow to
the indoor unit heat
Check for an obstacle at the
exchanger
inlet or the outlet
Insufficient speed of the
Excessively low air
indoor unit fan motor?
temperature to the
indoor unit heat
Short-circuited indoor unit
exchanger
air?
Check item
(Turn OFF the main switch)
Use a bigger unit
Correctly charge the
refrigerant after repairing the
gas leakage
Use the correct pipes
Replace the check valve for
the outdoor unit
Remove the clogging
Replace the connector
Replace the coil
Replace the thermistor
Correctly install the
thermistor
Replace the strainer in the
indoor unit
Remove the clogging
Clean the air filter
Remove the obstacles
Replace the fan motor
Remove the cause of the
short-circuited air
Action