Hitachi RAS-(3-6)HVNC1(E) Service Manual page 271

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 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.
257
SMGB0087 rev.0 - 12/2013
Cause
Insufficient Air Flow to Heat
Exchanger of Indoor Unit
Excessively High Temperature
Air to Indoor Unit Heat Ex-
changer
Faulty
pressure
switch
Faulty high
pressure
Insufficient
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 indoor fan speed
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 decreas-
ing 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
temperature
Check ambient temperature
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 big-
ger 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 temperature 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
8