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NORA Oilheat Technicians Manual

PSC Motor Troubleshooting Condition Cause Recommended Action Motor does not start No power to motor Check wiring and power from primary Chapter 10 Motors control lead. If necessary, replace control, limit controller or fuses (time-delay type). Insufficient voltage supply Check power from primary control. Thermal protector has Determine and repair cause of thermal overtripped load and reset (if manual re-settable). Pump shaft will Disconnect motor from pump. Turn coupling not turn to ensure free rotation of pump shaft. Capacitor or windings Check capacitor and windings. have failed Motor bearings have failed Turn the motor shaft, which should turn easily. Motor starts, but does not Motor is overloaded Disconnect pump from motor. Turn pump reach full speed shaft to ensure free rotation. Insufficient voltage supply Check power from primary control. Voltage should be 110V - 120V. Capacitor or windings Check capacitor and windings. have failed. Motor vibrates or Bearings are worn, damaged Replace motor. is noisy or fouled with dirt or rust Motor and pump are mis- Check pump to motor, motor to housing, aligned with each other and pump to housing alignment. or housing Blower wheel or wheel Check blower wheel and balancing weight balancing weight (if ap- (if applicable) for location and tightness. plicable) is loose Motor draws excessive Motor and pump misaligned Check pump to motor, motor to housing, with each other or housing and pump to housing alignment. Motor is undersized for Increase motor size if needed. the application Motor windings are damaged Check windings. If damaged, replace motor. Checking the PSC Motor windings: 1. Remove power from the burner, and detach the motor power leads from the burner. 2. Disconnect the two leads from the capacitor terminals. 3. Connect one Ohmmeter lead to the L1 motor power lead and the other meter lead to each of the capacitor leads, one at a time. See Figure 10-15. 4. Record the two resistance values. 5. Repeat by measuring the other motor power lead (L2) and each of the capacitor leads one at a time. Chapter 10—Motors 10-17


NORA Oilheat Technicians Manual
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