Ampacity is the maximum current, in amps, that a wire can carry continuously without overheating. It depends on wire size, conductor material, and insulation temperature rating, and is set by CEC Table 2 for copper or Table 4 for aluminum under normal conditions.

Which insulation temperature column should I use?

When unsure, use the 75°C column only when the breaker lugs and other terminals are marked 75°C. Unmarked equipment counts as 60°C under CEC Rule 4-006. The terminal temperature rating, not NMD90 insulation alone, sets the usable column.

🔥 Ampacity Check

Ampacity = the most current a wire can carry safely without overheating. Enter your wire and load, get a clear yes/no.

What this checks (and what it doesn't)

We look up your wire in the Canadian ampacity tables (CEC Table 2 for copper and Table 4 for aluminum; the sealed values are harmonized with NEC Table 310.16). For small wires we also apply CEC Rule 14-104: 14 AWG copper tops out at a 15 A breaker, 12 AWG at 20 A, and 10 AWG at 30 A.

Not included: hot attics/engine rooms, bundles of more than three current-carrying wires, and continuous loads (running 3+ hours straight needs 25% headroom). Those all reduce what the wire can carry — when in doubt, go up a size or ask an electrician.

Ampacity and voltage drop are separate checks — a wire must pass both.