closed system is opened and, unless precautions are taken, refrigerant is lost to the atmosphere. The best way to contain the refrigerant (gas and liquid) is to trap it in the condenser and receiver by pumping down the system.
To pump down the system, proceed as follows:
1. Secure electric power to the unit and connect the refrigerant manifold test set, as shown in figure 6-55.
2. Close the receiver stop (king) valve (by turning the valve stem inwards as far as it will go), and close both gauges on the gauge manifold (LO and HI valves).
3. Start the compressor and mid-seat the discharge and suction service valves.
4. Operate the compressor until the pressure on the suction (LO) gauge on the manifold shows a vacuum at 0 to 1 psi.
5. Stop the compressor. If the pressure rebuilds appreciably, operate the unit again until pressure registers between 0 to 1 psi. Repeat this step until the pressure no longer rebuilds appreciably.
6. When suction pressure remains at about 0 to 1 pound as read on the compound gauge, then front-seat the suction and discharge service valves (fig. 6-56). This procedure traps practically all the refrigerant in the condenser and receiver.
Laws governing the release of chlorofluorocarbon refrigerants (CFCs) into the atmosphere have resulted in the development of procedures to recover, recycle, and reuse these refrigerants. Many companies have developed equipment necessary to prevent the release of CFCs into the atmosphere. Refrigerant recovery management equipment can be divided into three categories - recovery, recycle, and reclaiming equipment.
Removing refrigerant from a system in any condition and storing it in an external container is called "recovery." Removal of refrigerant from the system is necessary, in some instances, when repair of a system is needed. To accomplish this, you can use special recovery equipment, which is now a requirement when removing refrigerant from a system. This equipment ensures complete removal of the refrigerant in the system.
Recovery is similar to evacuating a system with the vacuum pump and is accomplished by either the vapor recovery or liquid recovery method. In the vapor
Figure 6-55. - Connections for pumping down a system.Continue Reading