If the temperature is greater than 86℉, the ampacity from the table must be corrected based on the values found in NEC Table 310.15(B)(2)(a). NEC® Table 310.15(B)(16) ampacities are based on an ambient temperature of 86℉. The environment surrounding a wiring method can affect the ampacity of the conductors. NM-B is permitted to be manufactured with conductors as large as 2 AWG, but multiconductor UF-B is limited to conductors no larger than 6 AWG by the UL standard. Note: The calculator will permit choosing NM-B and UF-B up to 2 AWG. The app limits the final ampacity of the wire to the most conservative of: the corrected and adjusted ampacity the equipment temperature limitation default values as described in NEC® 110.14(C)(1) or the cable type temperature limitation. This app assumes installation in conduit or direct burial when individual insulated wire types are chosen. For example, Type NM-B is limited to the ampacity values in the 60℃ column, even though the insulation on the conductors is required to be rated at 90℃. The installed equipment may have different temperature limitations, so be sure to check the actual ratings.Ĭertain cable types may also have a specified maximum temperature limit. Based on NEC 110.14(C)(1), conductors sized 14 AWG to 1 AWG are assumed to be connected to equipment limited to 60℃, and conductors 1/0 AWG and larger are assumed to be connected to equipment limited to 75℃. As an example, 600-volt panelboards have a maximum temperature limit of 75℃. However, electrical equipment (such as panelboards or circuit breakers) typically has an additional limiting temperature rating that must be considered when determining the ampacity of the wire that connects to the equipment. The resulting value is the ampacity of the wire installed throughout the building or other installation. Insulated wire types like THHN/THWN-2, XHHW-2 and USE-2/RHH/RHW-2 have an insulation temperature rating of 90℃, and any temperature correction factors or ampacity adjustment factors can be applied to the insulation temperature rating. For example, 3/0 AWG copper has an ampacity of 200 amps at 75℃, while 3/0 AWG aluminum has an ampacity of 155 amps at 75℃.

Each has a different ampacity for a specified gauge size, and these ampacities are found in NEC® Table 310.15(B)(16) for the calculations in this app. The primary two metals used for electrical conductors are copper and aluminum. For more information on ampacity calculations, please consult our technical resources. All calculations assume a voltage of no more than 2000 volts and that the appropriate NEC® requirements are followed by the installer, engineer or other responsible party. Insulated single conductors are assumed to be installed in conduit or direct buried. Certain installations (such as cable trays and medium-voltage conductors) are not included in this app. This calculator also complies with the 2020 NEC requirements. This app uses the calculation requirements found in the 2017 National Electrical Code® to determine the ampacity of insulated conductors and certain cable-type wiring methods. Ampacity Calculator Information & Instructions:

Amp wire gauge chart