Which of the following best describes the NEC® requirement for box fill volume?

The requirement that boxes must not exceed allowable fill volume is grounded in the principles defined by the National Electrical Code (NEC). These regulations are designed to ensure safety and prevent overheating or potential hazards associated with overcrowded electrical boxes.

The NEC specifies that a box's fill volume must be calculated based on various factors, including the number and type of conductors, devices, and fittings contained within the box. This regulation ensures that there is adequate space for each component to operate safely, thereby reducing the risk of damage from heat accumulation or electrical failure.

By adhering to the allowable fill volume, electricians maintain a safe environment within the electrical installation. Overloading a box can lead to serious issues, and the NEC's guidelines are established to promote safe practices in wiring and electrical connectivity. Hence, option B accurately reflects the requirement needed to maintain compliance and safety standards in electrical installations.