75☌/167☏: 1 gauge wire (AWG 1) features an Ampacity of 130A, 60☌/140☏: 0 gauge wire (AWG 0) features an Ampacity of 125A, Thus, for 100 Amp service, the required wire thickness is: Hence, we should not look for wires being able to carry 100 Amps, but 125 Amps: The 80% Safety RuleĨ0% Rule states that actual wire current should be at most 80% of its default Ampacity. 90☌/194☏: 3 gauge wire (AWG 3) features an Ampacity of 115A.īut, these wire thicknesses are not recommended for actual use since wires should never carry current that equals their default values for safety reasons - hence the 80% Rule. 75☌/167☏: 3 gauge wire (AWG 3) features an Ampacity of 100A, 60☌/140☏: 1 gauge wire (AWG 1) features an Ampacity of 115A, Note: Ampacities are given for enclosed wires ambient temperatures.Īs one can see, the Ampacity of wires is given at three different temperatures (60☌/140☏, 75☌/167☏, and 90☌/194☏), but for most residential installations, 60☌/140☏ is the maximum allowed wire surface temperature.Īlso, if the value is not given for a required current, one has to look for a wire with a larger Ampacity.įor example, if we are going to look for 100 Amp wire size using default Ampacities for solid copper wire, then:

100 amp wire size copper