The ampacity of types NM and NMC cable shall be that of ___ degree C conductors.

The ampacity of NM (non-metallic) and NMC (non-metallic clad) cable is dictated by the insulation type and conductor ratings established in the National Electrical Code (NEC). Specifically, NM and NMC cables are typically built with conductors that are rated for 60 degrees Celsius.

This means that when determining the ampacity of NM and NMC cables, electricians and contractors should refer to the 60°C rating for conductor sizing and load calculations. It is crucial to adhere to these ratings to ensure that the conductor does not overheat, leading to potential fire hazards or insulation breakdown. The importance of knowing the correct temperature rating is paramount in ensuring safety and compliance with electrical standards.

While there are higher temperature ratings like 75°C and 90°C, they apply to different types of conductors (such as THW, THHN, or THWN) used in other types of wiring methods or applications, and not for NM and NMC cables. Therefore, the correct ampacity is indeed based on the 60 degrees Celsius standard for the specified cable types.