As an assistance to those attempting to navigate the NEC® with consistency and accuracy, JCR is posting the “Paralleled Numbering System” used within the articles of 320 through 392. (Articles 372, 374, & 390 do not use the numbering system as of the 2014 NEC®)
The system uses a constant section suffix along with a constant name for the suffix to consistently identify a specific function of a section within the article used. There are some article omissions from the system, but overall, with a little practice it can eliminate the need and usage of the index for obtaining most cable and raceway information.
The numbers (suffixes) and names within most articles and sections are as follows:
- .1 = SCOPE (ex: 320.1, 330.1, 342.1 all concern scope)
- .2 = DEFINITIONS
- .6 = LISTING REQUIREMENTS
- .10 = USES PERMITTED
- .12 = USES NOT PERMITTED
- .14 = DISSIMILAR METALS
- .15 = EXPOSED WORK
- .17 = THROUGH OR PARALLEL TO FRAMING MEMBERS
- .18 = CROSSINGS
- .20 = SIZE (CONDUIT & TUBING)
- .21 = SIZE OF CONDUCTORS (STRUT TYPE RACEWAY)
- .22 = NUMBER OF CONDUCTORS PERMITTED IN RACEWAY
- .24 = BENDING RADIUS (CABLES) / BENDS HOW MADE (CONDUIT)
- .26 = BENDS; NUMBER IN ONE RUN (360 RULE)
- .28 = TRIMMING / REAMING
- .30 = SECURING AND SUPPORTING
- .31 = SINGLE CONDUCTORS
- .40 = BOXES & FITTINGS
- .41 = FLOOR COVERINGS
- .42 = DEVICES / COUPLINGS AND CONNECTORS
- .44 = EXPANSION FITTINGS
- .46 = BUSHINGS
- .48 = JOINTS
- .50 = CONDUCTOR TERMINATIONS
- .56 = SPLICES AND TAPS OR BRANCHES FROM BUSWAYS
- .58 = INSULATED CONDUCTORS OR DEAD ENDS
- .60 = GROUNDING
- .70 = EXTENSIONS FROM WIREWAYS / COMBINATION RACEWAYS
- .100 = CONSTRUCTION
- .104 = FLAT CONDUCTORS
- .120 = MARKING
While these relative constants above of suffix/name are used within the applied article(s) listed above, this paralleled numbering system is not normally intuitive to the average NEC® student or user. This is because not every suffix/name combination is located in each article using the system. Hence the question; “How can this be a paralleled numbering system if some articles have the suffix/name combination but some do not”? As an example, .22 (Number of conductors permitted in) is not seen in any of the cable articles of 320 through 340, but it is seen in all of the conduit and tubing articles of 342 through 362. I can best answer the question by using this explanation…… If the suffix/name combination is not found in an article, it is not applicable to that article and don’t waste the ink to print it! There you have it. It is an applicability concept. The number of conductors permitted in a cable is not applicable to an appropriate installation of a given cable type, while the number of conductors permitted in a given conduit or tubing type and trade size is applicable to a conduit or tubing installation. Now that the issue of applicability is exposed you know why the “paralleled numbering system” does offer constant suffix/name combinations but does not place each one in every article.
This posting by JCR Productions Inc. is the beginning of many postings to follow intended to break the NEC® down into it’s groupings and basics so that it can be navigated quickly and professionally. The NEC® should not overwhelm you when you are looking for an article or specific section. Your search can be completed in seconds instead of minutes or even hours, and our upcoming postings will uncover many additional concepts that if followed will make your code searches SIMPLE! Hence our motto of “Code Made Simple”!
Respectfully yours,
Jeff Rodriquez / Code Consultant
JCR Productions, Inc.