Part I of any NEC Article provides the general requirements for that Article. But if Art. 110 provides the general requirements that apply to all electrical installations (except where amended elsewhere in the Code), why does Art. 110 also have a Part I with general requirements?
The answer becomes evident when you see that Part II provides general requirements that apply specifically to installations with a nominal voltage of 1,000V or less and Part III provides general requirements to installations over 1,000V. Common sense tells us these would likely have different requirements, and a comparison of the Part I requirements to the Part II requirements shows this is the case.
But that’s not all. Article 110 also contains Part IV for tunnel installations over 1,000V nominal and Part V for manholes and other electrical enclosures intended for personnel entry.
Something clearly missing from Art. 110 is a section that provides the grounding and bonding requirements. Aren’t these general requirements? Yes, they are. But as with some other general requirements, they are found in one of the three subsequent chapters. Specifically, these requirements are in Art. 250.
To answer the question of why this is, we refer to the statement of scope for Art. 110. The statement of scope for a given article is always at X.1, with X being the Article number. Turning to Sec. 110.1, we see that it isn’t written to provide all requirements that are general in nature. Instead, its purpose is to provide the general requirements for the following in relation to electrical conductors and equipment:
- Examination and approval.
- Installation and use.
- Access to and spaces about.
That’s the first part of the scope, and it’s addressed in Part I, Part II, and Part III. Separated from it by semicolons are the fourth and fifth parts of the scope. If you haven’t already guessed by now, those are enclosures intended for personnel entry (Part IV) and tunnel installations (Part V).
One concept that will help you understand the Code arrangement is to understand that the first four chapters are intended for typical electrical work. They are, in that sense, general requirements. That’s why you see (for example) requirements for services in Art. 230, requirements for general wiring in Art. 310, and requirements for motors in Art. 430. These first four chapters are followed by three that start with the word "special." Then Chapter 8 provides requirements for communications systems, and Chapter 9 provides tables.
