Ampacity is defined as:

• A. The maximum voltage rating of a conductor.
• B. The maximum current a conductor can carry continuously under installation conditions.
• C. The maximum number of loads on a circuit.
• D. The minimum breaker size required.

Answer: (C)

Ampacity is the maximum current a conductor can carry continuously under installation conditions. This reflects how much heat the conductor can safely generate without the insulation or surroundings exceeding their temperature rating, given the specific installation environment. It’s not about the voltage a conductor can carry, nor about how many loads are on a circuit, and it doesn’t specify the minimum breaker size. In practice, you size the conductor so its ampacity meets or exceeds the expected continuous current, and you select a protective device that will limit current to protect the conductor from overheating. Factors that influence ampacity include the conductor material, the insulation’s temperature rating, ambient temperature, and derating for multiple conductors in a raceway or bundle. So ampacity is all about safe current-carrying capacity driven by heat, not voltage rating or the count of loads.