Bitzer 8FC-70.2Y-40P operation problem

[matijaZGB]

Dear forum members,


I need your technical support for Bitzer piston compressor type 8FC-70.2Y-40P.
Our client has 4 of these piston compressors and one of them has a problem when
changing capacity from 100% to 50%.
Compressor is electrically connected to work only at 50% or 100% (both solenoid valves on the top two cylinder heads get current at the same time).
Problem starts when compressor is working at 100% capacity and switches to 50%,
it makes rough (dull) sound.
That sound is sometime there all the time before the compressor stops or change back
to 100% capacity.
Sometimes the sound stops just after few seconds like on the video we taken, which is attached below.
Also sometimes there is no sound when compressors capacity is changed from 100% to 50%.

What can be the cause of this?

Video link: http://www.youtube.com/watch?v=MEg2aAuh8Dc


Regards.
Matija

[Magoo]

Hi does not sound good what ever it is, do you have correct cylinder banks unloading for crank shaft load balance.
.

[CJG]

I always have used the two side cylinder banks for capacity control as per Bitzer documentation, maybe swap them over & see if it helps

[Chillermaster]

Hello matijaZGB,

Try to replace both coils of solenoids.
I already had an identical issue and the problem was inside the coil.