LG ARNU Series, Service Manual

Page: 136 / 226

Troubleshooting Guide
136 Outdoor Unit
Protection of
Inverter compres-
sor from over cur-
rent (Detection of
over 80A per
1.8ms IPM )
Error
Code
Error Contents Meaning Main Causes
Error display
position
21
Defective inverter com-
pressor, Inverter element
(IPM) defect
Concerned
Remote controller
Panel Display
Outdoor unit
1. Over current detection at the invert-
er compressor (U,V,W)
2. IPM Overheating .
3. Insulation damage of the compres-
sor / motor damage
5. Low input voltage at the outdoor
6. Inverter compressor terminal dis-
connected or loose .
7. Inverter PCB/IPM PCB defect
■
Defect inspection method :
1) Check whether the insulation of the compressor, motor coil resistance is normal ? Otherwise, replace the com-
pressor .
- Motor Coil resistance normalcy : Resistance between each terminal of Inverter compressor =1.33
Ω
±7% ,
Resistance between the each terminal of the constant speed compressor =1.83
Ω
±7% (The 3 measured value
must be similar)
- Insulation normalcy : Resistance between the compressor terminal and the product body = Above 2M
Ω
(Measured within specified time after the compressor stop )
2) Check whether the IPM/3 phase rectification Diode is normal ? Otherwise, replace the IPM/ Diode .
- Tester : After setting the Diode mode , test with the tester probe in + ,- sequence.
- IPM:'U-P/V-P/W-P' measurement : 0.3~0.6 V, Reverse polarity measurement :Above 2.6 V
'N-U/N-V/N-W' measurement : 0.3~0.6 V, Reverse polarity measurement : Above 2.6 V
- 3 phase rectification diode : ~ & + / ~ & + / ~ & +' sequential measurement : 0.3~0.6 V,
Reverse polarity measurement : Above 2.6V
3) Check whether the input voltage is 360V~410V(AC).
4) Check the balance between each phase at the main breaker of the building (phase distribution ) (Below 5~10V).
5) Check whether the terminal connection is normal ?
(Comp connecting terminal, IPM connecting terminal, diode connecting terminal, capacitor connecting terminal)
6) Check whether the IPM Pin connecting to PCB soldering is normal ?
(Dismantle the PCB and check the soldering at the back side of the PCB .)
In case if any abnormality please replace the IPM PCB.
7) Check whether the Outdoor Unit fan is working ? In case of any abnormality please check the outdoor fan
(Refer to CH105~CH108)
8) Check whether the supplied power is normal or insufficient.
9) After the inspection, check whether the input power to the IPM during the trial run is 450V~560V(DC).
(Set the tester at the DC mode)
Check the IPM terminal connecting condition.
(Comp connecting terminal, IPM connecting terminal, diode connecting terminal, capacitor connecting terminal )
10) Measure the current at each phase (U,V,W) of the inverter compressor during the trial run after the completion
of the inspection.
In case the deviation between the current in each phase is above 1.5A then replace the PCB .