In my experience as an electrical trainer and instructor, the easiest and most effective way to learn National Electrical Code (NEC) navigation is to associate each chapter title with a specific objective. The natural arrangement of the codebook, its chapters and titles can be confusing for first-time trainees as well as some experienced electricians in the field. It’s safe to say that if you can remember the main focus of each chapter, you can navigate the Code with confidence and precision.
Let’s take the example of Chapter 4, dedicated to the things you see every day. This general-purpose piece of equipment requires no one-time installation or niche-forming guidelines – these are essential items you see as you move around throughout the day, typically found in a dwelling unit (homes and residential apartments), a place of business (special occupancies), warehouses, or a manufacturing plant (hazardous areas). The general purpose equipment contained in these items encompasses the following areas:
- Use electrical energy
Here are some chapter 4 items for equipment/materials that distribute electrical energy.
Item 400 — Flexible Wires and Cables
This handy article covers specific uses for cords and cables that can prevent the transmission of noise and vibration to general purpose electrical appliances and equipment. When tools or equipment need to be secured in place (and allow quick removal for maintenance and repair of mechanical connections and moving parts), use the convenient cords and cables listed in this article. Additionally, these cables are used to distribute power to lamps, elevators, vacuum cleaners, electric heaters, portable power tools, stage lighting and power, electric stoves and dryers, cords used for heavy duty, and electric vehicle charging stations. .
Art. 400 also provides the following information for cables and cords in table 400.4:
- Cable tension limits;
- Description of the exterior coating(s);
- Conductor sizes and gauges available;
- Approved applications and uses for each cord and cable;
- The number of conductors available in a flexible cord or cable; and
- Commercial names of cables and cords with their abbreviations or designation letters.
Dos and Don’ts for Flexible Cables
Keep a few things in mind when selecting cables found in Art. 400. First, flexible cords and cables should not be used as a substitute for fixed wiring in a building or construction. These materials are covered in Chapter 3, Wiring Methods, which covers the construction phase of construction projects.
Do not run these cables through holes in the walls; above structural, suspended or suspended ceilings; or floors. They cannot be concealed by walls, floors or ceilings nor pass through doors or windows. Be careful not to place them where they will suffer physical damage. If you must attach any of these cables to the surface of a building, follow the provisions of Sec. 368.56(B) Exception 1 to 4.
Article 408 — Switchboards, equipment and distribution panels
This article covers equipment that houses overcurrent protective devices (fuses and circuit breakers), busses (single and three-phase), switches, and various auxiliary power control instruments. This equipment, found in a large or small panel or frame, can be mounted on the front, back or both, accessible from the back as well as the front. Not intended for installation in cabinets, this also includes equipment which is completely enclosed on all sides (including the top and excluding openings for ventilation and inspection).
This equipment contains doors, removable covers and is made of sheet metal. Be prepared to browse this article for license and journeyman exams. These are important provisions of the NEC against which you can be tested.
Art. 408 covers the following information:
- 4 wire high delta leg identification requirements;
- Support and arrangement of busbars and conductors;
- Additional code references for grounding and bonding; and
- Minimum spacing requirements between busbars and the bottom of an enclosure.
Here are some basic guidelines for installing panelboards, switchgear, and switchboards.
Panels must have a circuit directory (Sec. 408.4), so put a label on it! Each new circuit or circuit modification made in a panel or switchboard should be legibly identified for its specific purpose or use. To avoid confusion, mark, label or identify all unused overcurrent devices, switches or spare positions in the panel. Locate the circuit directory on the front or inside of the panel door.
Panelboards, switchgear, or switchboards must not be protected on the “supply side” by a fuse, circuit breaker, or overcurrent protective device that exceeds or is rated higher than the distribution panel. Cabinets, boxes, fittings, nipples, fittings, brackets and supporting hardware “in direct earth contact” must be suitable for installation in concrete or in direct contact with earth or in areas subject to severe corrosive influences. If the material is approved for this condition, a corrosion protection approved for the condition must be used (Sec. 300.6).
Enclosures installed in damp locations must be listed as weather resistant and adhere to the following guidelines: If surface mounted, they must be located or installed in such a way as to prevent moisture or water from entering and escaping. accumulating in the closet. Mount it so that there is at least 1⁄4″ of air space between the speaker and the wall or other supporting surface. For all enclosures located in damp locations, raceways or cables entering the panelboard or switchboard must use fittings listed for damp locations above uninsulated live parts. (Second. 312.2). Non-metallic enclosures should be permitted to be installed without the air space on a concrete, masonry, tile or similar surface.
Remember that these are minimum guidelines to follow. Your local jurisdiction may have stricter requirements depending on where you work.
Follow my column for how-to articles and more practical tips for applying basic electrical concepts in the field: Daily Instructions for Electricians, Introduction to Commercial Service Calculations, Introduction to Home Service Calculations, The Learner’s Guide to Non-Metallic Sheathed Cables, NEC Learner’s Guide Chapter 4, Apprentice’s Guide to Art. 300and the Apprentice’s Guide to Art. 640. For more information on why a structured approach is so important to navigating the NEC and how to put its requirements into practice in real-world contexts, read The NEC for beginners.
Harold De Loach, master electrician and electrical trainer/instructor, is the founder of the Academy of Industrial Arts (www.taia-school.com) in Philadelphia. With over 30 years of experience in the field, he regularly writes exclusive content for the E-Train and can be reached at [email protected].