Hitachi RAS-(4-12)HNP(1)(E) - Decrease of Discharge Gas Superheat

8 Troubleshooting
237
SMGB0087 rev.0 - 12/2013
8
Alarm code
07
Decrease of Discharge Gas Superheat
• This alarm code is indicated as follows:
- When the temperature at the top of the compressor is lower than condensing temperature and indoor expansion
valve opening is lower than 300 pulse for 30 minutes in cooling operation, retry operation will be performed once.
When outdoor expansion valve opening is lower than 70 pulse for 30 minutes in heating operation, retry operation
will be performed once. If these occurs again within 120 minutes after the retry, the alarm code will be indicated.
No
Faulty thermistor
Yes
Yes
Heating
No
Is the thermistor
on top of compressor
normal?
Install it correctly
Heating operation
Cooling
Cooling operation
Check the IU expansion valve opening and
the temperature on the top of the
compressor by the outdoor unit PCB.
Plug the
connectors
properly
No
Replace fan motor
Charge correct
refrigerant volume
No
No
Repair leaks of gas.
Correctly charge refrigerant.
Check the expansion
valve or remove the
cause of discharge air
short-circuit at indoor
and outdoor units.
Is the thermistor
installed correctly on the
compressor?
Is it at cooling or
heating mode when the
alarm has occurred?
IU expansion valve
opening lower than 300
pulse?
Yes
Check the OU expansion valve opening and
the temperature on the top of the
compressor by the outdoor unit PCB.
OU expansion
valve opening lower than
70 pulse?
Yes
No
No
Yes
Yes
No
No
Is the temperature
on the top of compres-
sor less than estimated conden-
sation temperature?
Is the temperature
on the top of compres-
sor less than estimated conden-
sation temperature?
Are the connectors for the
indoor expansion valve
connected properly?
- Connector on IU PCB for expansion valve
- Junction connector for expansion
valve
No
Yes
Is the outdoor fan
normal?
Yes
Is the refrigerant
correctly charged?
Yes
Is gas leaking?
Yes