Which conductors can be grouped together in ferrous metal raceways to avoid heating?

The concept behind grouping conductors in ferrous metal raceways revolves around the proper management of heat buildup that can occur from electrical currents. When conductors are placed together, they can generate heat due to the electrical resistance of the materials they are composed of. In ferrous metal raceways, which can provide electromagnetic shielding and potential heat dissipation, it is essential to consider which types of conductors can safely be grouped without leading to overheating.

Grouping all conductors—whether they are power conductors, grounding conductors, or insulated conductors—is permissible in ferrous metal raceways as long as the installation adheres to the guidelines specified in the National Electrical Code (NEC). These guidelines allow for more flexibility since ferrous metal raceways offer effective heat dissipation and have properties that can mitigate the risks of overheating due to the magnetic fields produced by the conductors.

Insulated conductors can be grouped, but the term "insulated conductors" alone excludes potentially safer groupings with uninsulated or other types of conductors. Thus, while it's true that only insulated conductors might seem adequate based on their thermal characteristics, the flexibility to group all conductors together offers a more comprehensive solution, allowing for efficiency and safety in electrical installations.