refrigerants respond to a pressure-temperature relationship. Cold ambients result in low pressure, which results in a thin vapor and slow recovery rate. At low pressure, one pound of refrigerant vapor occupies several cubic feet of space. Likewise, high temperature results in high pres- sure, which results in a thicker vapor and faster recovery rate. At high pressure, one pound of refrigerant vapor occupies a much smaller volume. With these interdependent pressure-temperature principles in mind, use short hoses with large diam- eters when recovering refrigerant. Also, to prevent high pressure from slowing recovery in the recovery cylinder, consider placing the recovery cylinder in a large bucket of ice and water. The low temperature of the cold water will cause lower pressure in the cylinder. This will allow liquid refrigerant to flow in more quickly and prevent excessive high pressure from building up inside the cylinder, Figure 15‑13. The two most common methods of recovering refrigerant from mechanical refrigeration systems are using passive recovery and active recovery. 15.10.1 Passive Recovery Method The passive recovery method is used on a refrigeration system that has a working compressor. The compressor of the refrigeration system is used to push the refrigerant into a recovery cylinder. See Figure 15‑14. 1. Connect the low-side gauge manifold hose to the suction service valve of the system. This will be for monitoring low-side pressure during recovery. 2. Connect the high-side gauge manifold hose to the liquid line service valve in the liquid line or on the receiver. This will be for recovering liquid refrigerant. 3. Place the recovery cylinder on a refrigerant scale and perform any scale operations necessary for monitoring the refrigerant being recovered. Safety Note Monitoring Refrigerant Recovery Always use a refrigerant scale to measure the weight of the recovery cylinder, regardless of the type of recovery being used. Never overfill a recovery cylinder. See Figure 15‑15. Ritchie Engineering – YELLOW JACKET Products Division Figure 15‑13. Recovery cylinder in an ice bucket for faster recovery time. Sight glass Goodheart-Willcox Publisher Figure 15‑14. Passive recovery method using a refrig- eration system’s compressor to push the refrigerant into the recovery cylinder. Chapter 15 Refrigerant Recovery and Recycling 271 Copyright Goodheart-Willcox Co., Inc.