The AJ series of air-conditioning compressors ranges in size from 1100 to 19,500 Btu (see Fig. 9-23). An oil charge of 26 or 30 oz is standard, depending upon the model. They are mounted on three or four points (see Fig. 9-24). A snap-on terminal cover allows quick access to the connections under the cover (see Fig. 9-25). This particular model has an antislug feature that is standard on all AJM 12 and larger models (see Fig. 9-26). (An anti-slug feature keeps the liquid refrigerant moving.)
This type of compressor relies upon the permanent split-capacitor motor. In this instance, the need for both start and run capacitor is not presented. The start relay and the start capacitor are eliminated in this arrangement (see Fig. 9-27). With the PSC motor, the run capacitor acts as both a start and run capacitor. It is never disconnected. Both motor windings are always engaged while the compressor is starting and running.
PSC motors provide good running performance and adequate starting torque for low line voltage conditions. They reduce potential motor trouble since the electrical circuit is simplified (see Fig. 9-28).
The figure shows a run capacitor designed for continuous duty. It increases the motor efficiency while improving power and reducing current drain from the line. Do not operate the compressor without the designated run capacitor. Otherwise, an overload results in the loss of start and run performance. Adequate motor overload protection is not available either. Arun capacitor in the circuit causes the motor to have some rather unique characteristics. Such motors have better pullout characteristics when a sudden load is applied.
Figure 9-29 shows how this particular series of compressors is wired for using the capacitor in the run and start circuit. Note the overload is an external line breaker. This motor overload device is firmly attached to the compressor housing. It quickly senses any unusual temperature rise or excess current draw. The bimetal disk reacts to either excess temperature or excess current draw. It flexes downward, thereby disconnecting the compressor from the power source (see Fig. 9-30).
