Hitachi RAS-10HRNM, Service Manual, Page: 270 / 482

Phenomenon Cause Check item
Action
(Turn OFF Main Switch)
Activation of High Pressure Switch
due to Excessively High Discharge
Pressure during Heating Operation
Insufficient Air Flow to Heat
Exchanger of Indoor Unit
Clogging of Heat Exchanger
Remove it
Check for dust on air filter
Check for any obstacle at inlet or
outlet of heat exchanger
Check the service space Secure service space
Check for fan speed.
(Cooling: Outdoor Fan Heating:
Indoor Fan)
Replace fan motor if faulty
Activation of High Pressure Switch
due to Excessively High Discharge
Pressure during Heating Operation
Excessively High Temp. Air to
Indoor Unit Heat Exchanger
Calculate heat load.
Reduce heat load or use a bigger
unit
Check for hot air near the ceiling Make good circulation
Check for short circuited air Remove short-circuited air
Check for other heat source Remove heat source
Faulty High
Pressure Switch
Faulty Pressure
Switch
Measure discharge pressure.
Check continuity after decreasing
of pressure
Replace it if faulty
Insufficient
Contacting
Measure resistance by tester
Repair looseness.
Replace connector
Incorrect
Connection
Check connections Repair connections
Faulty of Outdoor Fan Control
Check decreasing air flow volume
at pressure switch for control
activative
Replace thermistor for evaporating
temp. if faulty
Faulty of Pressure Switch for
Control
Check activated pressure and
connecting wire
Replace it if pressure switch for
control is faulty
Overcharged Refrigerant Check cycle operating temp. Charge refrigerant correctly
Mixture of Non-Condensable Gas in
Refrigerant Cycle
Check ambient temp. and pressure
Recharge refrigerant after vacuum
pumping
Clogging of Discharge Piping Check for clogging Remove clogging
Faulty or Malfunction of Expansion
Valve
Check for clogging Remove clogging
Check connecting wiring and
connectors
Replace connector
Check operating sound from coil Replace coil
Check discharge gas thermistor Replace thermistor
Check attaching state of discharge
gas thermistor
Reattach thermistor
Liquid Line Stop Valve or Gas Line
Stop Valve are not in Operation
Check stop valves Fully open stop valve
N O T E
This alarm code is indicated when the outdoor unit protective device is activated by high discharge pressure during
heating 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.
8 Troubleshooting
262
SMGB0060 rev. 1- 12/2010