noise inverter compressor

[Airclima]

Hi all
I have a problem with a VRF Hitachi RAS-10 FS2 R-22. The compressor Inverter after 5 years operation without problems, began to do a hard noise. The cooling capacity was as good as the first time. I supplemented oil without however exists no improvement, therefore i replaced with a new.
Τhe oil was clean in the old compressor without scrap of iron in.
But after 3 months and the new one began again to make the same noise. A very hard noise. The total length of pipings is roughly 100 m, the outdoor unit is in same level and only 2 indoors units are more highly at 4 metres. The number of indoors are 10 capacity 0.8 Hp, 8.000 btu/h. Compressor amper, high presure, Hz, are normal.
Does anybody know what is that bring on the problem?

Thanks
Stelios

[kerrcell]

Stelios,
Same happened to me on a Mitsubishi heavy industries vrv.replaced the inverter compressor due to noise problem.After 3 weeks,it went to earth!! Found also to make things worst the sealed pcb on the back panel and also a high wattage resistor of 8 ohms.I cannot understand this.This type of vrv houses an inverter comp and a normal one.