to eliminate the oil level issue on hermetic compressors in paralell; you simply drill a hole in the bottom of the shell, and drill a hole at the upper part of the compressor, or use the service pipes to equalise the gass pressure. By doing so the oil flows freely from one compressor to the other. If one compressor is not running, ther wil be no problem since the compressor high pressure valves are shut due to the pressure difference.