NEC and CEC are not two labels on one calculation

It is tempting to treat the NEC and the CEC as the same calculation with different table numbers. For a conductor at 30 C, three current-carrying conductors in a raceway, they do agree. That corner proves nothing, because it is the one place the two codes were harmonised.

Where they actually diverge

• More than three current-carrying conductors. NEC Table 310.15(C)(1) steps 80/70/50/45/40/35 percent. CEC Table 5C steps 80/70/60/50. At twelve conductors that is 0.50 against 0.70, which is not a rounding difference.
• Termination temperature. NEC 110.14(C)(1) derates the insulation column and caps at the uncorrected termination column. CEC 4-006(1) derates the termination column itself, so a 90 C conductor gets no 90 C benefit at a 75 C lug.
• Small conductors. NEC 240.4(D) sets hard overcurrent caps. The CEC has no equivalent rule.
• Medium voltage in air. The NEC tabulates it. The CEC does not.

The practical test

If a tool gives the same answer under both codes, confirm it is because the codes agree there and not because the two paths quietly merged into one. Test at more than three conductors, at elevated ambient, with parallel sets, and outside a raceway. Any of those will separate genuinely different code paths from a shared one wearing two labels.