Question by  karebeer (429)

What is the correct wire size for 40 amp breaker?


Answer by  LeheckaG (1826)

Contact your-local-building/zoning-department for your-local-regulations, and whether you require a license/permit. Refer to the NEC/National-Eletrical-Code for proper insulation/wire-size/type selection; 40-Amp circuits require AT LEAST #8 AWG Copper wire, at ambient room temperatures. There are circumstances, like high-ambient-temperatures, where your-wire-capacities are required to be "de-rated" and you need to use larger-gauge-wire, refer to the appropriate tables in NEC Article 310.

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