Support
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• Identification of the parameters to be evaluated What can be measured ? What test equipment is needed ? Is there access for testing ? What are the expected values ? Could other factors have any effects on the readings ?
• Identify the source of the problem Isolate components and measure values ; identify visually damaged components ; confirm identifications .
• Correct / repair the fault Replace faulty component or repair faulty component ( s ); make corrective adjustments .
• Verify the repair Retest all parameters , confirm adjustments , confirm correct operation .
• Perform root cause analysis
Troubleshooting Chart Failure Fault Probable cause ( symptom ) Corrective measures
No voltage supply
Low voltage supply
Check control system and from this to motor . Check power circuit . Check fuses and circuit breakers . Check system safety devices . Check conductors .
Check voltage supply and ascertain that voltage remains within 10 % of the rated voltage shown on the motor nameplate ( Some manufacturers may stipulate 5 %)
Motor fails to start
Excessive noise
Overheating of Motor
Wrong wiring connections
Heat damage / poor connections at terminals .
Compare connections with the wiring diagram and on the motor nameplate
Loose connections , tighten all connections
Overload tripping Try to start motor under no load conditions . Check overload setting . Brushes ( single phase ) Brushes may be worn , dirty or incorrectly fitted . Motor start relay
Test relay Measure winding resistance Winding / s damaged Capacitor
Capacitor damaged , test / replace Mechanically seized Obstruction or bearing failure .
Excessive axial or radial load on belt / s
Deformed shaft Damaged bearings
Loose or poorly-fitted motor end shields , feet or fan .
Lack of lubrication Obstructed cooling system Overload
Incorrect voltages and frequencies
Unbalanced windings
Rotor dragging on stator / bearings damaged .
V belts are over-tensioned Damaged loose fan
Align pulleys and correctly tension
Replace Replace
Repair
Corrective action Clean and dry motor ; inspect air vents and windings Correct
Compare values on motor nameplate with those of mains supply . Also , check voltage at motor terminals under full load . Check for excessive volt drop .
Re-wind
Replace
Corrective action Corrective action / replace
www . hvacronline . co . za RACA Journal I November 2020 39