NBR 5410 ampacity tables (current-carrying capacity)

What these tables give

Ampacity (Iz) is the continuous current a cable can carry without its conductor exceeding the insulation temperature limit — 70 °C for PVC, 90 °C for EPR/XLPE. The values below reproduce the NBR 5410 series (Tables 36 to 39, aligned with IEC 60364-5-52) for 3 loaded conductors, ambient 30 °C in air and 20 °C in the ground, sections 2.5 to 630 mm².

The installation methods (columns A1 to F)

• A1 — insulated conductors in conduit inside a thermally insulating wall;
• A2 — multicore cable in conduit inside a thermally insulating wall;
• B1 — insulated conductors in conduit on a wall (apparent);
• B2 — multicore cable in conduit on a wall;
• C — cables on a wall or non-perforated tray;
• D — cables in buried ducts;
• E — multicore cable on perforated tray or ladder;
• F — single-core cables in trefoil on perforated tray or ladder.

The same section can differ by 40% or more between methods: a 95 mm² XLPE copper cable carries 216 A embedded (A1) and 328 A in trefoil on a ladder (F). Getting the method right is worth more than one section step.

What still needs to be applied on top

The table Iz assumes the reference ambient and a single circuit. Real capacity is:

Iz' = Iz × Ft × Fa (× Fs × Fp for buried lines)

where Ft corrects for ambient temperature, Fa for grouping of circuits, Fs for soil thermal resistivity and Fp for burial depth. All factor tables are on the NBR 5410 correction factors page of this reference section. Cable sizing must also check voltage drop and short-circuit withstand independently — the LOGOS cable engine runs all criteria at once.