fixed a refrigerant leak on a walk-in today. it had a copeland KAGA-0150-TAC-211 semi hermetic (r22). I noticed the oil sight glass was foamy with no noticeable oil level and didnt see any oil safety switch.The compressor is in the basement and walk-in is on first floor. Is there any way the oil could have migrated to the evap? How would I be able to check it without worry of over filling it?