As problem of title, I have received the problem report from quality assurance department.

I would like to inform about problem report detail.

  • Problem detail

Product : ASTG18/22/24KMCA
Number of accident : 8 ( 18;4 units, 22,;1unit, 24;3units)

Problem contents :

Refrigerant noise was occurred when heating operation starts. (it was not occurred when cooling operation starts)

It was easy to occur when outdoor temp is low.
This problem was not fixed even if IU/OU have changed.

  • Analysis result
    Carried out the replication test at FGL by sample unit from FG AUST, and FGL units.
    Then, this problem was reproduced at both unit.
    <Occurrence condition>
    * When heating operation will start up.(after 3 hours from compressor was stopped.)
    EEV pulse control are different between within 3 hours and 3 hours or more.
    *When outside temperature is 20 degree or more.
  • *When outside temperature is less than 12 degree, this problem does not occur.
    *compressor stopping time is approximately 1 night(8 hours).
  • Speculation of this result’s cause.

Cause of this issue is from influence from R32 refrigerant’s flow speed.

When refrigerant condition which is mixture(liquid and gas) keeps long time, because, liquid conditions refrigerant was left at indoor unit.

and, refrigerant speed is high(when compressor frequency is 66rps or higher).

Flow speed different between liquid and gas will become large.

Then, turbulence of refrigerant occur at before EEV.
As the result, turbulence make the noise when refrigerant come in EEV, and noise travels to inside.

If EEV is more closed when heating operation starts the refrigerant noise does not occur.
(because, the possibility that turbulence will be occurred become low by refrigerant condition easy to change from mixture to liquid only.)

  • As to R410A model, same control was used. However, this problem did not occur.
  • Measure
    Software(EEV control at heating operation starts) was changed.
  • Measure to product

Already installed product; ; measures by each location if problem is occur.

Stock product; no measures.

Manufacture product ; About each units it will measure by below schedule at factory.
24KMCA ; 4th August
22KMCA ; 8th September
18KMCA ; 28th July

If you have any question, please let me know,