The first four chapters of the NEC apply to all installations, except as modified by Chapters 5, 6, 7, and 8. The requirements for “equipment for general use” are in Chapter 4.
This equipment is in contrast to the “special equipment” covered in Chapter 6. The difference can seem somewhat arbitrary. It makes sense that motors, so ubiquitous, would be considered ”for general use” . But why is fixed outdoor electric de-icing and space-heating equipment covered in Chapter 4  while elevators, which have a much wider range of application (at least geographically) are covered in Chapter 6 ?
The best solution to this question is to simply realize that equipment is covered in either Chapter 4 or Chapter 6, with the former being dedicated to general use equipment and the latter to special use equipment, but there may be crossover. In other words, if you don’t find your equipment in one of these chapters, try the other.
Most types of equipment covered by Chapter 4 clearly belong there, without question. These include:
- Flexible cords and cables
- Fixture wires
- And, of course, motors