Why can more wires be installed in non-metallic boxes compared to metal boxes of the same size?

Non-metallic boxes can accommodate more wires because they typically have thinner walls compared to metal boxes. The thinner walls of non-metallic boxes allow for a larger internal volume for the same external dimensions, which can increase the available space for multiple wires or conductors. This is particularly beneficial when wiring a project that requires several circuits or connections.

The advantage of increased space is crucial for ensuring compliance with electrical code requirements that dictate the number of conductors allowed in a given box size based on its fill capacity. By maximizing the available volume, non-metallic boxes can be easier to work with when managing wire placement and minimizing potential overcrowding that can lead to overheating or other electrical issues.