General testing
Control voltage, single-phasing, and method.
No control voltage in the panel
Nothing in the control circuit will operate — contactors won't pull in, indicators are dead, the PLC may be off. The control voltage that should be there simply isn't.
Three-phase equipment single-phasing (lost a phase)
Three-phase equipment is misbehaving — motors humming, struggling, overheating, or tripping — because one phase has been lost somewhere between the supply and the load.
E-stop circuit won't reset / machine won't start
The machine won't start because the emergency-stop circuit won't reset — the safety relay stays dropped out, holding everything off, even with all e-stops apparently released.
MCB (circuit breaker) keeps tripping
A circuit breaker trips repeatedly — instantly on reset, or after a load runs for a while — and you need to tell a short from an overload from a faulty breaker.
Intermittent fault that's hard to reproduce
Something fails occasionally — random trips, dropouts, or stoppages — but works fine when you go to look at it. The classic 'can't fault it on the bench' problem.
Voltage drop on a long cable run
Equipment at the end of a long run misbehaves — dim lights, a contactor that won't hold, a motor struggling — because volt-drop along the cable leaves too little voltage at the load.
Loose connection overheating (discolouration / smell)
A terminal or connection is overheating — discoloured insulation, a burning smell, or heat you can feel — a common cause of nuisance faults and a real fire risk.
Lost or high-resistance neutral
Strange symptoms across a circuit or installation — voltages going high and low on different loads, flickering, equipment damage — pointing to a lost or high-resistance neutral.
Whole circuit / board nuisance tripping
A whole circuit or board protective device trips intermittently with no obvious single cause — affecting several loads — and you need a systematic way to corner it.
No supply at a socket-outlet or point
A socket-outlet or point is dead — nothing plugged in works — while other points may be fine. A bread-and-butter 'trace it back' fault.
Equipment tripping the supply on startup surge
Switching on a piece of equipment trips an upstream breaker or causes a momentary dip — the inrush/startup surge is exceeding what the protection or supply can ride through.
Three-phase equipment running hot from supply imbalance
Three-phase equipment (motors, heaters, large gear) runs hotter than expected or nuisance-trips, traced to a voltage/current imbalance between phases rather than the equipment itself.
High earth-fault loop impedance / earthing concern
Testing shows a high earth-fault loop impedance (or an earthing concern) on a circuit — meaning protection might not operate fast enough on a fault, which is a safety issue to resolve.