Generator Output Conductor at 115% (NEC 445.13)

The conductor rule from a generator to its first overcurrent device, which estimators routinely get wrong.

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NEC 445.13(A) sets the ampacity at not less than 115% of the generator NAMEPLATE current -- not 125% of a computed load, not the connected running load. A 150 kW, 480 V three-phase generator at 0.8 pf draws 225.6 A nameplate, so the conductor must carry 1.15 x 225.6 = 259.4 A. Where the design prevents output above nameplate (overload-limited), the basis drops to 100% and it is just 225.6 A. Enter the nameplate current directly or derive it from kW, voltage, phase, and pf. The 110.14(C) termination limit and 310.15 adjustments still apply. A design aid; the AHJ governs.

nameplate = given, or kW x 1000 / (sqrt(3) x V x pf) three-phase, or kW x 1000 / (V x pf) single-phase; basis = overload_limited ? 1.00 : 1.15; required_ampacity = basis x nameplate.

The generator output-conductor ampacity rule of NEC 2023 445.13(A) -- not less than 115% of the generator nameplate current, or 100% where the design prevents output above the nameplate -- by name. A computational aid; the AHJ-adopted NEC edition governs.

NEC is free to read at nfpa.org/freeaccess. The 115% basis is on the nameplate current, not 125% of a computed load; the 110.14(C) termination limit and 310.15 ambient/fill adjustment are stated as out of scope, not modeled.

Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.

Field names used by the API: gen_kw, voltage_v, phase, power_factor, overload_limited, nameplate_a, basis, required_ampacity_a

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