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4.12.4 Procedure
P4/P5
The power supply is abnormal
Excess refrigerant
System contains air or nitrogen
The condenser heat exchange is poor
1
The high pressure side is blocked, caused
by crushed or bent pipe or blocked EXV
2
Inverter module has short-circuited
3
Compressor has malfunctioned
4
Replace outdoor main PCB
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
Check the power supply equipment
Discharge part of the refrigerant. Add
oil if it leaks during discharge process
Inspect the system and fix the error
Inspect the system and fix the error
Replace the inverter module
Replace the compressor
Flush all refrigerant then vacuum the
system and recharge refrigerant. Add
oil to the system if it leaks
Notes:
1. In heating mode check water side heat exchanger, water piping, circulator pumps and water flow switch for dirt/blockages. In cooling mode check air side
heat exchanger, fan(s) and air outlets for dirt/blockages.
2. High pressure side blockage causes discharge temperature to be higher than normal, discharge pressure to be higher than normal and suction pressure to be
lower than normal.
3. Set a multi-meter to buzzer mode and test any two terminals of P N and U V W of the inverter module. If the buzzer sounds, the inverter module has short-
circuited.
4. The normal resistances of the inverter compressor are 0.7-1.5Ω among U V W and infinite between each of U V W and ground. If any of the resistances differ
from these specifications, the compressor has malfunctioned.
