Editing National Electrical Code (section)

===Temperature rating===
The temperature rating of a wire or cable is generally the maximum safe ambient temperature that the wire can carry full-load power without the cable insulation melting, oxidizing, or self-igniting. A full-load wire does heat up slightly due to the metallic resistance of the wire, but this wire heating is factored into the cable's temperature rating. (NEC 310.10)<ref name="table 310 reference and details">{{cite web |title=Temperature Limitations of Connections Must Not Be Exceeded |url=https://www.ecmag.com/section/codes-standards/temperature-limitations-connections-must-not-be-exceeded |website=Electrical Contractor Magazine |language=en}}</ref>

The NEC specifies acceptable numbers of conductors in crowded areas such as inside conduit, referred to as the ''fill rating''. If the accepted fill rating is exceeded, then all the cables in the conduit are ''derated'', lowering their acceptable maximum ambient [[operating temperature]]. Derating is necessary because multiple conductors carrying full-load power generate heat that may exceed the normal insulation temperature rating. (NEC 310.16)

The NEC also specifies adjustments of the ampacity for wires in circular raceways exposed to sunlight on rooftops, due to the heating effects of solar radiation. Electrical Construction and Maintenance Magazine, Conductors for General Use,  Chapter 3 Articles in NEC, starting with Article 342 This section is expected to be modified to include cables in future editions.

In certain situations, temperature rating can be higher than normal, such as for [[knob-and-tube wiring]] where two or more load-carrying wires are never likely to be in close proximity. A knob-and-tube installation uses wires suspended in air. This gives them a greater heat dissipation rating than standard three-wire [[Thermoplastic-sheathed_cable#North_America|NM-2 cable]], which includes two tightly bundled load and return wires.<ref name="nm cable specifications">{{cite web |title=334.30 Securing and Supporting. |url=https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=891.0 |website=ElectricalLicenseRenewal.com}}</ref>