Hitachi RAS-2-HVNP Service Manual page 242

8. Troubleshooting
Phenomenon
Activation of High Pressure
Switch due to Excessively High
Discharge Pressure during
Cooling Operation
N O T E
This alarm code is indicated when the outdoor unit protective device is activated by high discharge pressure du-
ring cooling operation. Accordingly, when this alarm code is indicated, there is high possibility of high pressure
switch actuation and the above troubleshooting actions are based on such cases.
228
SMGB0079 rev.0 - 01/2013
Cause
Insufficient Air Flow to Heat
Exchanger of Outdoor Unit
Excessively High Temp. Air to
Outdoor Unit Heat Exchanger
Faulty Pressure
Switch
Faulty High
Insufficient
Pressure Switch
Contacting
Incorrect
Connection
Overcharged Refrigerant
Mixture of Non-Condensable Gas in
Refrigerant Cycle
Clogging of Discharge Piping
Faulty or Malfunction of Expansion
Valve
Liquid Line Stop Valve or Gas Line
Stop Valve are not in Operation
Locking up Outdoor Unit Expansion
Valve Closure
Check item
Clogging of Heat Exchanger?
Check for dust on air filter
Check the service space
Check for outdoor fan speed
Check for hot air near the ceiling
Check for short circuited air
Check for other heat source
Measure discharge pressure.
Check continuity after decreasing
of pressure
Measure resistance by tester
Check connections
Check cycle operating temp.
Check ambient temp. and
pressure
Check for clogging
Check for clogging
Check connecting wiring and
connectors
Check operating sound from coil
Check discharge gas thermistor
Check attaching state of discharge
gas thermistor
Check stop valves
Check expansion valve actuation
Action
(Turn OFF main switch)
Remover clogging
Remove dust
Secure service space
Replace fan motor if faulty
Make good circulation
Remove short-circuited air
Remove heat source
Replace it if faulty
Repair looseness.
Replace connector
Repair connections
Charge refrigerant correctly
Recharge refrigerant after vacuum
pumping
Remove clogging
Remove clogging
Replace connector
Replace coil
Replace thermistor
Reattach thermistor
Fully open stop valve
Replace outdoor
expansion valve