Fault Finding

Fault Finding

The 5-Point Fault Finding approach

There is a generally recognised method of approaching fault-finding , which is referred to as the 5-Point Fault Finding approach.  The most important factor in this method concerns attaining as much ‘information’ as possible regarding the ‘cause & effect’ of the fault, as follows:

  1. Gather Information – Ask as many people as possible who were there, when & how the fault occurred
  2. Analyse Information – decide the probable cause based on past experience & training
  3. Investigate – now attempt to find the fault from your analysis
  4. Rectify – once found, safely repair the fault
  5. Test – when the fault is put right & restored, test your work before re-energising
Standard/Fundamental Faults

Fault Finding Process

To be able to fully trace and identify the fault, there is a list of “typical faults” that are the most common causes of a circuit ceasing to operate corectly.  Therefore we work through this list to resolve the issue:

    Loss of Supply
     Why (Loose Connection – Tripped CB – Blown Fuse – Internal Fuse)

    Earth Fault
     Tripping Circuit Breaker/RCD – device will not re-engage (or will for a short while – then possibly a switched circuit contains the fault)

    Dead Short
     Phase to Neutral/Phase to Phase – has the main fuse at origin blown

    Correct Protective Device in place
     Type B – Type C – Type D Circuit Breakers / S’Type RCD’s

    Defective Components
     Switches – Relays –Contactors, etc, not functioning correctly (brings about the decision as to replace or repair)

    Breakdown of Control Circuits
     Internal Wiring/PCB’s & Electronics (How far to go for an ‘electircian’)

    Reversed Polarity
    At supply Origin – at a single outlet (Phase Neutral reversed or neutral earth reversed) or at a single fitting (Phase – Neutral) – Live Test Vs Dead Test.

    Mostly seen in Industry
    Control Circuits (Internal Fuses) – Contactors (Breakdown of Parts)  – 3PH motors (Loss of  Phases &/Or burnt out coils) – Single Phase Motors – (Carbon Brushes)

    Initial Faults on newly Installed work
    Reversed Polarity – Discrimination – loose connections – Protective Devices –Faulty Portable equipment – (NB: Cannot be ‘ware and tear’)

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