What is the available power percentage per NEC per amperage in a circuit?

The correct answer of 80% pertains to the National Electrical Code (NEC) guidelines, which indicate that for continuous loads, the maximum demand on a circuit should not exceed 80% of its capacity. This means that when determining the available power for a circuit, particularly when planning for equipment that will be running continuously, it is prudent to use 80% of the circuit's rated amperage to ensure safety and compliance.

The rationale behind this guideline is to allow for a margin of safety and to prevent overheating or overloading of the circuit, which could lead to electrical failures or hazards. Continuous loads are defined as loads that run for three hours or more, so taking only 80% of the circuit's capacity allows for proper management of the electrical system and helps prevent potential interruptions or damage.

Using the remaining options, while they suggest other percentages, these do not align with the NEC regulations for continuous loads. Thus, the adherence to 80% enables professionals in fields involving electrical and structural work to follow best practices and ensure safer installations.