The ampacity of Type NM cable shall be in accordance with which conductor temperature rating?

In the context of ampacity for Type NM (non-metallic sheath) cable, the correct conductor temperature rating is 60 C (140 F). This rating is significant because it establishes the maximum temperature that the conductors can safely handle, directly impacting their overall capacity to carry electrical current without overheating.

Type NM cable is typically used in residential and commercial buildings, and its design includes a combination of insulation and conductors that are rated for these temperature limits. Using this rating ensures safe operation under expected loads and contributes to the overall safety and reliability of electrical installations.

Using a higher temperature rating, such as 75 C or 90 C, would not be appropriate for Type NM cable, as the cable's materials and construction are not designed to handle those higher thermal limits. Therefore, referencing the 60 C rating is essential for determining the proper ampacity and ensuring compliance with electrical codes.