What is wire ampacity?

Ampacity is the maximum current a wire can carry continuously without exceeding its temperature rating, per NEC Table 310.16.

How does temperature affect ampacity?

Higher ambient temperature reduces ampacity. Correction factors apply above 30°C. For example, 40°C ambient = 0.82 factor for 75°C rated wire.

When more than 3 current-carrying conductors share a raceway, ampacity is reduced: 4-6 wires = 80%, 7-9 = 70%, 10-20 = 50%.

Base ampacity from NEC Table 310.16, then apply correction factors: Corrected = Base × Temp Factor × Bundling Factor.

Temperature correction applies when ambient exceeds 30°C. Bundling derating when more than 3 current-carrying conductors share a raceway.

Max current without exceeding temperature rating.

Higher temp = lower ampacity. Correction factors apply.

4-6 wires: 80%, 7-9: 70%, 10-20: 50%.