Which temperature rating does the ampacity in NEC comply with?

Ampacity, or the current-carrying capacity of a conductor, in the National Electrical Code (NEC) is primarily related to the temperature ratings of the conductors and their insulation. The NEC specifies that the ampacity ratings for wires or cables are based on insulation that can operate safely at higher temperatures, specifically at ratings of 75 degrees Celsius and 90 degrees Celsius.

The significant reason for considering 75 degree C and 90 degree C is that these temperature ratings allow for safe and efficient operation of electrical systems under typical conditions. Conductors rated at 90 degree C can carry more current than those rated at lower temperatures, which may be crucial in applications where space is limited, or where more power is needed.

This focus on the higher temperature ratings ensures that electrical installations remain safe, efficient, and reliable across various applications and conditions. The NEC incorporates these standards to help prevent overheating and related hazards, which can result from overloading conductors.