Hitachi RAS-(3-6)HVRNM2E Service Manual page 272

8 Troubleshooting
Phenomenon
Activation of High Pressure Switch
due to Excessively High Discharge
Pressure during Heating Operation
Activation of High Pressure Switch
due to Excessively High Discharge
Pressure during Heating Operation
N O T E
This alarm code is indicated when the outdoor unit protective device is activated by high discharge pressure dur-
ing 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.
262
SMGB0064 rev.0 - 08/2011
Cause
Insufficient Air Flow to Heat
Exchanger of Indoor Unit
Excessively High Temp. Air to
Indoor Unit Heat Exchanger
Faulty Pressure
Switch
Faulty High
Insufficient
Pressure Switch
Contacting
Incorrect
Connection
Faulty of Outdoor Fan Control
Faulty of Pressure Switch for
Control
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
Check item
Clogging of Heat Exchanger
Check for dust on air filter
Check for any obstacle at inlet or
outlet of heat exchanger
Check the service space
Check for fan speed.
(Cooling: Outdoor Fan Heating:
Indoor Fan)
Calculate heat load.
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 decreasing air flow volume
at pressure switch for control
activative
Check activated pressure and
connecting wire
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
Action
(Turn OFF Main Switch)
Remove it
Secure service space
Replace fan motor if faulty
Reduce heat load or use a bigger
unit
Make good circulation
Remove short-circuited air
Remove heat source
Replace it if faulty
Repair looseness.
Replace connector
Repair connections
Replace thermistor for evaporating
temp. if faulty
Replace it if pressure switch for
control is faulty
Charge refrigerant correctly
Recharge refrigerant after vacuum
pumping
Remove clogging
Remove clogging
Replace connector
Replace coil
Replace thermistor
Reattach thermistor
Fully open stop valve