What is the adjustment factor for 12 current-carrying conductors according to the NEC?

The adjustment factor for 12 current-carrying conductors according to the National Electrical Code (NEC) is indeed 0.5. This adjustment factor is derived from the NEC tables that provide corrective measures for the ampacity of conductors when multiple conductors are installed together.

When there are more than three conductors in a raceway or cable, the ability of the conductors to dissipate heat is impaired due to the proximity of the conductors to one another. This results in a need to reduce the current-carrying capacity, which is commonly known as ampacity. For 12 current-carrying conductors, the NEC specifies that the ampacity should be multiplied by an adjustment factor of 0.5.

This means that if you were to calculate the allowable ampacity for each conductor based on its size, you would then apply this 0.5 factor to ensure the conductors operate safely without overheating. Utilizing this adjustment is critical to comply with the NEC guidelines and ensure the safety and reliability of electrical installations.