LG LFXS28566S - Compressor Check D: System Diagnosis

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12-4 Check D
D1. Activate Protection logic
- We have to check Condenser fan and Freezer fan before performing Check D
- Locked Piston, Current trip and stroke trip can be activated by other problems then the driver or compressor.
Cycle check with protection logic
High Pressure
Side
Restricted
→ When process line on compressor is opened, and refrigerant is not expelled
because it has accumulated in condenser.
→ If fault is corrected after refrigerant is recaptured from sealed system, change
dryer.
→ Low side restriction can cause a stroke trip.
→ If fault is corrected after refrigerant is recaptured, perform a sealed
system evacuation and dryer replacement.
→ Check Suction line
→ If refrigerant is overcharged and suction line temperature is lower
than ambient temperature (about 5~10 degrees) or frost is present
150mm from where the suction line enters the compressor..
→ Customer complains of longer run times and poor cooling performance.
→ Lack of refrigerant can, in some incidents, cause piston over travel.
→ Pressure of refrigerant cycle is usually higher than ambient pressure,
therefore oil will flow out with the refrigerant at leak point.
→ Temp. of compressor and discharge line is normal to slightly higher.
High side pressure is normal to slightly higher than normal
conditions. This is because condenser cannot condense the air
that is trapped in the condenser. The high side pressure and
temperature will not mimic the low side pressures and
temperatures.
Over charging
Refrigerant
Low side
Refrigeration
leak
Locked piston
Current trip
Refrigerant leak
Low
Side
Restriction
Stroke trip
D2. sealed system diagnosis
- Check as follows;
Sealed system
No
No
Check for oil
Remaining in drip tray
Check for Oil leaks
In machine compartment
Comp,Cond T >
Ambient temp+5deg
Check Temp of
Discharge line
and Condenser
Check frost status
Of Evaporator
Is frost pattern
uniform?
Heat Inlet tubing
using heat gun.
Is frost patern
Uniform?
OK
Yes
Yes
No
Frost only
Evaporator inlet
Yes
No
Sealed System
is OK
Sealed System
is OK
Repair leak
at point where
Oil is present.
Yes
Yes
A
In/Out Leakage
Evaporator
Leakage
A
Replace
Evaporator
A
A
Check for Oil leakage
at each joint
of the Evaporator
Is there frost
on Suction Line?
Yes
A
No
No
A
Heavy repair
Welding point
1. Comp process stub,
2. Comp discharge
3. Hot Line inlet
4. Drier inlet
5. Drier outlet
6. Evaporator inlet
7. Evaporator outlet
8. suction pipe