Ampacity
Definition
The maximum current a conductor can carry continuously without exceeding its temperature rating. Ampacity depends on conductor size, insulation type, installation method, and ambient conditions. Defined in NEC Table 310.16.
Practical Note
A #12 AWG copper THHN wire has 25A ampacity at 75°C. Ampacity must be derated for high ambient temperatures and multiple conductors in a raceway. Always size for 125% of continuous loads.
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