An exception to the rule where two different temperatures are encountered for the same conductors permits the application of the higher ampacity (lower temperature) if the length of the conductors that enter a higher temperature is not more than 10 ft (3.0 m) or not more than 10% of the total circuit length.

ampacity derating.

Explanation:

Conduction involves the transfer of electric charge or thermal energy due to the movement of particles. When the conduction relates to electric charge, it is known as electrical conduction while when it relates to thermal energy, it is known as heat conduction.

In the process of heat conduction, thermal energy is usually transferred from fast moving particles to slow moving particles during the collision of these particles. Also, thermal energy is typically transferred between objects that has different degrees of temperature and materials (particles) that are directly in contact with each other but differ in their ability to accept or give up electrons.

Any material or object that allow the conduction (transfer) of electric charge or thermal energy is generally referred to as a conductor. Conductors include metal, steel, aluminum, copper, frying pan, pot, spoon etc.

An exception to the ampacity derating rule where two different temperatures are encountered for the same conductors permits the application of the higher ampacity (lower temperature) if the length of the conductors that enter a higher temperature is not more than 10 ft (3.0 m) or not more than 10% of the total circuit length.