Code Comparison

Why Cable Sizing Tables Aren’t Interchangeable Between Codes

A deeper look at why the same load and length produce genuinely different results under different codes.

It's a natural assumption: physics is physics, so a cable correctly sized under one code should be roughly right under another. In practice, PEC, AS/NZS, and NEC tables are independently derived datasets, built from different reference conditions, different testing methodologies, and different historical safety margins.

Where the Divergence Actually Comes From

• Different reference ambient temperatures baked into each table's baseline
• Different assumed installation practices common to each region
• Independently conducted thermal testing and modeling, not a shared underlying dataset
• Different historical safety margin conventions embedded in each code's drafting process

The Practical Consequence

Two engineers, each correctly following their own code's process, can legitimately arrive at different final cable sizes for what looks like an identical load and length — and both can be completely correct, each within their own governing code.

See the full breakdown of what's genuinely universal vs. genuinely code-specific in the dedicated "Three Philosophies, One Physics" article.

Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks

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