Hitachi RAS-2-HVNP Service Manual page 204

8. Troubleshooting
Phenomenon
Indoor heat load is greater than the heating ca-
Excessively low suction
pressure
Insufficient heating
process
Excessively high dis-
charge pressure
Malfunction or internal leakage of the 4-way valve
Malfunction of the check valve of the outdoor unit
Excessively high suction
pressure
Discharge temp. of the indoor unit is unstable
190
SMGB0079 rev.0 - 01/2013
Cause
pacity
Gas leakage or insuffi-
cient refrigerant charge
Excessively small di-
ameter or long piping
Check the connection cord and
Is there an operation sound
Failure or malfunction
of the expansion valve
Is the thermistor on the com-
Is the thermistor installed cor-
Clogging of I.U./O.U.
between the inlet and the outlet
strainer
Clogging of suction Check the temp. difference of
piping
Are there any obstacles at the
inlet or the outlet of outdoor
Insufficient air flow
through the outdoor
unit heat exchanger
Is the service area for the out-
Check the speed of the outdoor
Excessively low air
temp. through the Check for any short-circuited
outdoor unit heat ex-
changer
Defrosting is insuffi- Check the thermistor for the
ciently completed
Check the filter for a clogging
Insufficient air flow to Check for any obstacles at the
the indoor unit heat inlet or the outlet of the indoor
exchanger
Check the indoor fan speed
Excessively high air
Check whether or not the short-
temp. to the indoor unit
heat exchanger
Excessively charged Check the refrigerant quantity
refrigerant
Non-condensate gas in Check the refrigerant quantity
ref. cycle
Clogging of the dis-
charge pr. piping
Check the temp. difference at
the inlet and the outlet of the
Check the temp. difference at
the inlet and the outlet of the
Check the temp. difference at
Malfunction or internal
the inlet and the outlet of the
leakage of 4-way valve
of the indoor unit in the same
Check item
Calculate the heat load
Correctly charge the refrigerant
Measure superheat after the gas leakage check and
Measure the field supplied
piping
Check for clogging
the connector
from the coil?
pressor normal?
rectly on compressor?
Check the temp. difference
Replace the strainer for the out-
of strainer
each part
Is the outdoor unit heat ex-
changer clogged?
unit?
Secure a sufficient service area
door unit sufficient?
unit fan
Remove the cause of the short-
air to the outdoor unit
defrost operation
unit
Remove the cause of the short-
circuited air exists
Correctly charge the refrigerant
*4)
Recharge the refrigerant after
*4)
Check for clogging
4-way valve
check valve
4-way valve
Check the expansion valve
system
Action
(Turn OFF the main switch)
Replace the unit with a bigger
unit
repairing
Use the specified pipes
Remove the clogging
Replace the connector
Replace the coil
Replace the thermistor
Correctly install the thermistor
door unit or the indoor unit
Remove the clogging
Remove the clogging
Remove the obstacles
Replace the fan motor
circuited air
Replace the thermistor for the
defrost operation
Remove the clogging
Remove the obstacles
Replace the fan motor
circuited air
the vacuum pumping
Remove the clogging
Replace the 4-way valve
Replace the check valve
Replace the 4-way valve
Replace the failed expansion
valve of the indoor unit