Hitachi RAS-(3-6)HVNC1(E) - Page 226

8 Troubleshooting
212
SMGB0087 rev.0 - 12/2013
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Insufcient 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
eld-supplied pipes
Use the correct pipes
Incorrect activation
of the check valve of
the outdoor unit
Check whether or not the
temperature difference exists
before/after the check valve
Replace the check valve for
the outdoor unit
Failure or malfunc-
tion 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; clog-
ging at the low pres-
sure piping
Check the temperature
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 temperature
difference
Remove the clogging
Insufcient air ow to
the indoor unit heat
exchanger
Check for clogged air lter Clean the air lter
Check for an obstacle at the
inlet or the outlet
Remove the obstacles
Excessively low air
temperature to the
indoor unit heat
exchanger
Insufcient speed of the
indoor unit fan motor?
Replace the fan motor
Short-circuited indoor unit
air?
Remove the cause of the
short-circuited air