I am new here and already looking for some help. I hope this is in the right place.

I'm working on a 30gb200-600 Serial X396113 Carrier liquid chiller, air cooled. It's an 83 model. Each of the two circuits is made up of four 275 compressors. Each side has one liquid line and two suction lines branching into four suction lines going to the compressors. This unit does not have the big oil equalizer lines out of the sight glass holes. It does have the 1/4" pressure equalizing lines out of the bottom of the compressor motor barrel connecting all four compressors together.

Circuit 2 only has compressor 2 & 4 running at this time. Before I started the unit up I adjusted the oil levels to the recommended bottom of sight glass to 3/8 of sight glass as usual for the 06E short stroke compressors. After several hours of running the oil in the non running #6 & #8 compressor has migrated down to the running #2 & #4 compressors. The oil level reached the point that I need to drain some out to avoid valve damage I think.

Can someone please help me out with what's going on? I thought the small 1/4" pressure equalizing lines were supposed to keep the suction pressure equal between the operating and the non operating compressors to keep the oil from migrating. What's happening? What can I do to stop it?

I don't have any manuals on this old machine. I'm not a Carrier dealer and have to rely on Mingledorff, my local carrier distributor for literature and they can't seem to find anything this old. Does anyone have a link to a control and operation manual?