Patent ID: 8075283

Claim:
A compressor system comprising: a first compressor in a first casing, said first compressor having a first low side lubricant sump; a second compressor in a second casing, said second compressor having a second low side lubricant sump; said first and second compressors being connected in series; a lubricant transfer conduit connected between said first low side sump of said first compressor and said second low side sump of said second compressor; a normally open check valve in said lubricant transfer conduit; said normally open check valve permitting lubricant flow between both of said lubricant sumps when both of said compressors are off; said normally open check valve permitting lubricant flow from said first lubricant sump to said second lubricant sump when said first compressor is off and said second compressor is on said normally open check valve being closed when both of said compressors are on; and a bypass associated with said check valve to permit lubricant flow from said second compressor casing to said first compressor casing when said normally open check valve is closed.