Troubleshooting Electric Motor Issues

When an electric motor fails, replacement might not always be necessary. With some skilled troubleshooting, motors can often be repaired, sparing owners the sometimes-great expense of replacing it. Even if a failed motor is not repairable and requires replacement, it is important to determine the cause of failure to ensure that the new motor doesn’t succumb to the same issues. Motor issues can occur in fans, chilled water pumps, reheat hot water pumps, domestic water booster pumps, etc.

Here are some common electric motor problems, symptoms and causes:

  • Failure to start can sometimes be traced to something as simple as a tripped fuse or breaker, or to a failed power supply. Once these easily-fixable issues have been ruled out, the problem may be caused by a blown stator, motor overload, failed starting switch, or, if a single-phase motor, a bad capacitor.

  • Overheating can be due to bad current values, high-temperature environments, inadequate ventilation, or poor cooling air supply. Excessive dust and dirt accumulation can damage motors and block cooling fans.

  • Slow motor acceleration is often a sign of a defective capacitor, a faulty stationary switch, bad bearings, or low voltage.

  • If a motor runs but dies down, check to see if the load has increased or the equipment gotten tighter. Fan motors can be affected in this way if there has been a change in airflow.

  • A frequently-tripped overload protector is often a sign that the load is too high, but can also signify that the ambient temperature is too high, the stator is shorted or grounded, or the protector itself is defective.

  • Motor vibration can be a symptom of bad motor bearings, or bearings may be in need of lubrication. If the bearings are good, the rotor may be out of balance. Other causes are load misalignment, bent motor shaft, excessive play in the shaft, or defective winding.

  • Repeated bearing failure can indicate excessive or unbalanced load to motor, or incorrect belt tension. Bearings also fail when operated in high ambient temperatures, so make sure the correct type of bearing grease is being used.

  • Noise at startup can mean that the rotor is striking the stator. This is often due to physical damage that may not be repairable, but sometimes can be eliminated by disassembling and reassembling the motor.

  • If starting capacitors frequently fail, the motor may be undersized and can require replacement. If the motor is being cycled too frequently, this can sometimes be fixed by installing a capacitor with a higher voltage rating or by adding a bleed resistor. Capacitor failure can also be caused by low voltage or a bad starting switch.

  • Run capacitor failure is often due to high ambient temperatures or a power surge.

As with all mechanical systems and equipment, preventive maintenance is imperative to avoid costly problems and keep motors running smoothly and efficiently. If you are experiencing problems with an electric motor, please call PJM Service Department at 609-921-1394.

About PJM

PJM Mechanical Contractors, Inc. is a multi-faceted mechanical contractor providing construction and installation, service and maintenance, and design/build services in a comprehensive range of mechanical disciplines that include HVAC, plumbing, controls, refrigeration, custom metal fabrication, piping, fire protection, and backflow preventer testing. PJM primarily serves clients in pharmaceuticals, manufacturing, healthcare, institutional, and other various commercial and industrial sectors.

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 1688 5th Street | Ewing, NJ  08638 | Tel: 609.921.1394 | Fax: 609.530.1437

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