Systems with hermetic compressors seldom requires charging with oil. When a leak occurs, oil escapes with the refrigerant and must be replaced for proper lubrication. Loud compressor noises can sometimes be remedied by adding a small amount of oil (usually no more than one-half cup) to the hermetic system. Use oil compatible with the system and of proper viscosity.
1. Install two access valves on the refrigerator, one on the suction line, and one on the liquid line (see figs. 45f, 45k, 21, 79).
2. Connect the manifold gauges to the valves. Compound gauge to the valve on the suction line, and high pressure gauge to the liquid line. By opening the valves on the manifold, freon can be released through the middle hose on the manifold. By law, the middle hose must be connected to a recovery machine (p. 139) to recover the freon into an empty cylinder to be used again. Details about this can be obtained from any refrigeration supply house where these tools are sold.
3. As shown in fig. 84, connect a vacuum pump to the unit, and pull a vacuum to 29″ of mercury, close the valves on the manifold, and turn off the vacuum pump.
4. As shown in fig.45i, submerge the manifold middle hose in the compressor oil.
5. Open the manifold low pressure valve and allow oil to be drawn into the compressor.
CAUTION: Shut off the low-side manifold valve while the end of the hos is still submerged in oil to prevent air from entering the system.
Access valves come in a variety of sizes and styles.