Hitachi RASC-4HNPE Service Manual page 214

10 Troubleshooting
Troubleshooting procedure
Phenomenon
Excessively high temperature air to
the indoor unit during heating mode
Activation of the
high-pressure
switch due to the
excessively high
discharge pressure

(PSH)
Mixture of the non-condensate gas in
Liquid or gas line stop valve does not
Faulty magnetic
contactor switch
No power at the magnetic contactor
Variable frequency
driver failure Over temperature of the VFD device
(VFD)

(LED ALM on VFD:
ON (*) )
?
N O T E
(*): Once the VFD contactor is open, the LED ALM on VFD is turned OFF after few seconds. Therefore, pay attention when revising the
VFD, since the LED ALM may be OFF even though the alarm 02 has been caused due to VFD failure.
204 SMGB0091 rev.2 - 11/2015
Cause
Faulty pressure
switch
Faulty high-
pressure switch
Insufficient
contacting
Incorrect
connection
Faulty or malfunction of the
expansion valve
Faulty gas bypass solenoid valve
Overcharged refrigerant
the refrigerant cycle
Clogging of the discharge piping
operate correctly
Clogging of the check valve
No power is supplied to the coil
Faulty variable frequency driver
Check item
Calculate the heat load
Check for hot air near the
ceiling (heating)
Check for short-circuited air
(heating)
Check if there is any heat
source near the unit
Measure the discharge
pressure. Check the continuity
after the decrease of the
pressure
Measure the resistance using
the tester
Check the connections
Check for clogging
Check the connect wiring and
the connectors
Check the operation sound
from the coil
Check the discharge gas
thermistor
Check the attaching state of
the discharge gas thermistor
Disconnected of the connector
or coil not well assembled
Fully closed and locked
Check for clogging
Check the cycle operation
temperature
Check the air temperature and
the pressure
Check for clogging
Check the stop valves
Check for clogging
Check connections
Measure the resistance using
a tester
Check the temperature in the
installation area
-
Action
(Turn OFF the main switch)
Reduce the heat load or use a
bigger unit if possible
Provide good circulation
Remove the short-circuited air
Remove the heat source
Replace the pressure switch
if faulty
Fix the looseness.
Replace the connector
Repair the connections
Remove the clogging
Replace the connector
Replace the coil
Replace the thermistor
Reattach the thermistor
Fix the looseness or reconnect
the connector
Replace the expansion valve
Replace the gas bypass
solenoid valve
Charge the refrigerant correctly
Recharge the refrigerant after
the vacuum pumping
Remove the clogging
Fully open the stop valves
Replace the check valve
Set the connections properly.
Replace the magnetic switch if
it is broken
Ensure that the installation
area has a proper ventilation
so that ambient temperature
around the unit does never
exceed 46ºC
Replace the variable frequency
driver