Safety Earthing
An undersized earth conductor typically shows no symptom at all — until the exact moment it matters most.
Most electrical undersizing mistakes eventually announce themselves — a dimming light under load, a nuisance-tripping breaker, a warm cable to the touch. An undersized earth/ground conductor is different: it typically shows no symptom whatsoever under normal operation, right up until the exact moment an actual fault occurs.
The earth/protective conductor carries essentially no current during normal, fault-free operation — its entire job exists for the specific moment something goes wrong. An undersized one performs identically to a correctly sized one on every single day the installation operates normally, which is exactly why the mistake can persist undetected for years.
When an actual fault does occur, an undersized earth conductor may add enough resistance to the fault loop that the protective device doesn't trip fast enough — or at all — leaving a hazardous touch voltage present on equipment for longer than the design intended, exactly when someone might be in contact with it.
Never estimate an earth/ground conductor size "by eye" or by a rough ratio to the active conductor — always look it up from the applicable code's actual table, precisely because there's no ongoing feedback loop that would otherwise catch the mistake before it matters.
Check the correct minimum size for your installation in the applicable Earthing/Grounding calculator.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks