Safety Practical
Past success is not the same as correctness — a reflection on why an unverified habit can persist for years before failing.
"I've always sized it this way and never had a problem" is a genuinely common and genuinely risky argument in electrical work — worth examining honestly, because the underlying logic doesn't hold up as well as it feels like it should.
Many undersizing and shortcut mistakes — undersized earth conductors, skipped voltage drop checks, generic "close enough" cable sizing — don't produce an immediate, obvious failure. As covered in the dedicated slow-failure and undersized-earth-conductor articles, some consequences take years to surface, or only surface under a specific fault condition that simply hasn't happened yet. Absence of a visible failure isn't the same as evidence the practice was correct.
A habit that's been repeated across many jobs without visible consequence feels validated by that repetition — but if the underlying risk is genuinely rare (a specific fault condition, a specific extreme-load scenario), many repetitions without incident don't meaningfully reduce the risk on the next job; they just mean it hasn't happened yet.
Run the actual calculation for the actual project's actual conditions, every time — not because past experience is worthless, but because the specific combination of load, length, ambient conditions, and governing code changes from job to job in ways that "it's always worked" simply doesn't account for.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks