Nobu NBL4-18IDU32 Service Manual page 58

(6) Malfunction of IPM Protection (H5)
Main check point:
Whether input voltage is within the normal range?
Whether wires of compressor are connected reliably, tightly or correctly?
Whether the resistance of compressor coil is normal? Whether the insulation between compressor coil and copper
pipe is in good condition?
Whether the unit is overloading? Whether the radiation for the unit is in good condition?
Whether the volume of charged refrigerant is proper?
Malfunction diagnosis process:
1.Whether the heat exchangers for indoor unit and
outdoor unit are dirty? Whether the heater exchangers
2.Whether indoor fan and outdoor fan operate normally?
3.Whether system pressure is too high?
4.Whether voltage is too high due to superfluous
Yes
72 54
Energize and
turn on the unit
Please check:
are covered by other objects?
refrigerant?
Whether compressor wires
are connected correctly?
Yes
Measure the resistance
beween two phases of three
phases of compressor
Is resistance value normal?
Yes
Measure the resistance
between three-phase of
compressor and copper pipe
Is resistance value more than
500MΩ?
No
Replace compressor
Is malfunction eliminated?
No
Replace main board of
outdoor unit
End
Whether therere above
No
Connect compressor wires
according to correct wiring
method
No
Yes
Yes
circumstances?
No
Modify it according to Service
Manual and then energize
and turn on the unit
Installation and Maintenance
Installation and Maintenance
Service Manual
Service Manual