There is a generally recognised method of approaching fault-finding , which is referred to as the 5-Point FaultFinding approach… the most important factor in this method concerns attaining as much ‘information’ as possible regarding the ‘cause & effect’ of the fault, as follows….
It is understood that sometimes it is not easy to get this information, as you may be the only person on site & no one is there to explain ‘what happened’, but you need to go the extra half mile to find out, as it will make your job much easier…
The following is a concise list of typical faults that are the most common causes of a circuit ceasing to operate correctly. Once you learn the symptoms of each it should become straightforward to resolve the issues you will encounter…
Loss of Supply
Why (Loose Connection – Tripped CB – Blown Fuse – Internal Fuse)
Tripping Circuit Breaker/RCD – device will not re-engage (or will for a short while – then possibly a switched circuit contains the fault)
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
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’)
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)