I have a York model YT 500 Ton chiller in my facility. It has been retrofitted to r-123 refrigerant. I have recently noticed that the refrigerant sight glass is brown and a our oil is missing from the oil sump sight glass. The Johnson Controls techs and I added refrigerant since it was low on charge. The chiller has been running with a load for about a week and a half and little oil has returned to sight glass. I isolated system and removed the eductor and found it to be a little ubstructed. Cleaned it and the piping connected to it and noticed little oil recovery, but that was two days ago. Is there a certain amount of time it needs to recover the oil or is there something else we can check? Thanks.