Navigating Chapter 3, Wiring Methods and Materials

Mark W. Earley 

The National Electrical Code^® Committee started a usability initiative in the 1999 cycle to improve the ease of use of the Code. The improvements have been taking place over time. One of the most significant changes has been the reorganization of Chapter 3. Initially, the reorganization focused on combining all of the cable articles and combining all of the conduit and tubing articles. The initial result generated complex tables that did not improve usability. The Committee then decided that the best approach would be to improve the ease of navigation through the chapter.

• Since Chapter 3 deals with wiring and protection, equipment articles were relocated to Chapter 4. (These now appear as Articles 404, 406, and 408.)
• Temporary wiring was moved to Chapter 5. (This now appears as Article 590.)
• The remaining articles were rearranged so that similar subjects are grouped together.
• The articles were renumbered with gaps in numbering to allow for insertion of new articles in the future.

The resulting chapter layout is as follows:

General Articles

300 Wiring Methods

310 Conductors for General Wiring

312 Cabinets, Cutout Boxes, and Meter Socket Enclosures

314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures

Cables

320 Armored Cable: Type AC

322 Flat Cable Assemblies: Type FC

324 Flat Conductor Cable: Type FCC

326 Integrated Gas Spacer Cable: Type IGS

328 Medium Voltage Cable: Type MV

330 Metal-Clad Cable: Type MC

332 Mineral-Insulated, Metal-Sheathed Cable: Type MI

334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS

336 Power and Control Tray Cable: Type TC

338 Service-Entrance Cable: Types SE and USE

340 Underground Feeder and Branch-Circuit Cable: Type UF

Circular Raceways

342 Intermediate Metal Conduit: Type IMC

344 Rigid Metal Conduit: Type RMC

348 Flexible Metal Conduit: Type FMC

350 Liquidtight Flexible Metal Conduit: Type LFMC

352 Rigid Polyvinyl Chloride Conduit: Type PVC

353 High Density Polyethylene Conduit: Type HDPE Conduit

354 Nonmetallic Underground Conduit with Conductors: Type NUCC

355 Reinforced Thermosetting Resin Conduit: Type RTRC

356 Liquidtight Flexible Nonmetallic Conduit: Type LFNC

358 Electrical Metallic Tubing: Type EMT

360 Flexible Metallic Tubing: Type FMT

362 Electrical Nonmetallic Tubing: Type ENT

366 Auxiliary Gutters

Other Raceways and Cable Assemblies

368 Busways

370 Cablebus

372 Cellular Concrete Floor Raceways

374 Cellular Metal Floor Raceways

376 Metal Wireways

378 Nonmetallic Wireways

380 Multioutlet Assembly

382 Nonmetallic Extensions

384 Strut-Type Channel Raceway

386 Surface Metal Raceways

388 Surface Nonmetallic Raceways

390 Underfloor Raceways

392 Cable Trays

394 Concealed Knob-and-Tube Wiring

396 Messenger-Supported Wiring

398 Open Wiring on Insulators

The next step was to create a common numbering system within the articles to improve navigation within each article. The general layout of the cable and raceway articles follows the following format:

I                       General

3xx.1                Scope

3xx.2                Definitions

3xx.3                Other Articles

3xx.4                Listing Requirements

II                     Installation

3xx.10              Uses Permitted

3xx.12              Uses Not Permitted

3xx.14              Dissimilar Metals

3xx.16              Temperature Limits

3xx.20              Size

3xx.22              Number of Conductors

3xx.24              Bends-How Made

3xx.26              Bends-Number in One Run

3xx.28              Trimming

3ss.30              Securing and Supporting

3xx.40              Boxes and Fittings

3xx.42              Couplings and Connectors

3xx.44              Expansion Fittings

3xx.46              Bushings

3xx.48              Joints

3xx.50              Conductor Terminations

3xx.60              Grounding

III                    Construction Specifications

3xx.100            Construction

3xx.110            Corrosion Protection

3xx.120            Marking

3xx.130            Standard Length

3xx.140            Conductors and Cables

3xx.150            Conductor Fill

If there are no requirements of a specific type, the section number is not used. For example, there are no requirements for reaming and threading of nonmetallic sheathed cable, so there is no Section 334.28. However there are requirement for reaming and threading of rigid metal conduit, so there is a Section 344.28. Some wiring methods have unique requirements that do not fit into this number template. For those articles, other sections have been added to that one article, while preserving the overall template. Examples include Sections 334.15, Exposed Work; 324.56, Splices and Taps; and 330.31, Single Conductors.

This template is also designed with numbering gaps to allow future expansion within the articles. This should make the template useful for some time to come.

Mark W. Earley, P.E., is Assistant Vice President of Electrical Engineering at NFPA, serves as secretary of the NEC^® Committee, and is the chief editor of the National Electrical Code Handbook. He joined NFPA in 1986, is co-author of  Electrical Installations in Hazardous Locations, and has published numerous technical articles on the fire protection of electrical equipment.