gauge manifold valves are opened, and the hoses are purged of atmospheric air. The center (yellow) hose serves as the suction line for withdrawing vapor from the system. A recovery unit includes an evaporator, compressor, condenser, various safety devices, and a separate refillable cylinder for liquid storage. As mentioned earlier, most recovery units are able to remove refrigerant in the liquid or vapor state, though liquid removal is much faster. However, some recovery units are rated according to pounds of liquid recovered per minute, even when the unit only removes vapor. Older recovery systems contain compressors that use oil, so the recovery unit requires oil separators because some oil is removed from the system along with the refrigerant. Oil separators are not totally effi- cient. Consequently, some contaminated oil appears in the recovery cylinder. The contaminated oil, in turn, contaminates the recovery compressor oil. The contamination should be removed by replacing the oil in the compressor crankcase. Oil replacement can only be performed when the compressor has an oil sight glass and drain plug. Before using a recovery unit to process a different refrigerant than the one last processed, the unit’s oil may need to be drained and replaced. Most recovery units manufactured today contain oil-less compressors and have eliminated the need to change oil. See Figure 15-12. The EPA requires the use of low-loss fittings on recovery units and manifold hose ends. These fittings prevent loss of refrigerant to the atmo- sphere when connecting or disconnecting hoses from the recovery unit to a refrigeration system. The trapped refrigerant inside the recovery unit acts as a “holding charge” and prevents contami- nation by air. This is not a problem if the recovery unit is used for just one type of refrigerant. However, if it is used for different refrigerants, the recovery unit must be evacuated with a vacuum pump before use. Evacuation prevents contamination in the cylinder by two refrigerants. 15.10 Recovery Procedures It is important to recover only one type of refrigerant into a recovery cylinder. Each recovery cylinder should be designated and properly marked for a specific refrigerant type. Do not mix refrigerants in a recovery cylinder. A mixture may be impossible to reclaim. If a reclaim facility receives making repairs to a refrigeration system. Recovery equipment is essentially a refrigeration system designed to remove and store refrigerant in a refillable cylinder. See Figure 15-11. After recovery, refrigerant may be returned to the system from which it was removed or added to another system owned by the same person or company, without the refrigerant being recycled or reclaimed. While recovered refrigerant can simply be returned to the system from which it was originally withdrawn, it should be cleaned of any contamination before use in another system owned by the same person. Many types of recovery and recycling systems are available, and an operator’s manual is supplied with each unit for proper connection and operation of the unit. Some recovery machines are capable of removing liquid or vapor, while others remove vapor only. Removal of refrigerant in the liquid state is less time-consuming than removal of vapor. However, after removing all liquid from a system, the remaining vapor must also be recovered. For instance, an average 350-ton R-123 chiller at 0 psig (0 kPa) pressure (with all the liquid removed) still contains 100 pounds of refrigerant in the vapor state. Refrigerant recovery is accomplished by connecting a gauge manifold to the suction and discharge service valves, then connecting the center (yellow) hose from the manifold to the recovery unit. The system service valves are opened, the Refrigerant Recovery System Compressor off (not running) Scale for automatic shut-off Goodheart-Willcox Publisher Figure 15-11. Recovery equipment is a refrigeration system designed to remove and store liquid refrigerant in a refillable cylinder. Chapter 15 Refrigerant Recovery and Recycling 269 Copyright Goodheart-Willcox Co., Inc.