Article 100 Definitions. Stranding.
Code Change Summary: New definitions were added to Article 100 covering the different types of conductor stranding.
In the past, the terms in the NEC® related to conductor stranding were all over the book but not properly defined in Article 100.
NEC Tables 312.6(A) and (B) specify the minimum wire-bending space required at terminals and the minimum width of wiring gutters. These tables have only two columns describing the conductor type; “Compact Stranded Aluminum”, and “All Other Conductors”.
How would one know which column to use for an installation into a cabinet using stranded aluminum wire without an Article 100 definition for the three different types of stranding configurations? If it’s not “compact stranded” aluminum wire, then Tables 312.6(A) and (B) would consider it “all other conductors” and require a greater wire-bending space for the installation.
Most code readers had no idea that the definition of “compact stranding” has been at the bottom of Tables C.1(A) through C.13(A) in Annex C for many years.
The term “compressed” was mentioned (but not defined) in footnote 3 under Chapter 9, Table 8; and the term “concentric” was mentioned (but not defined) in Chapter 9, Table 1, foot note (10), and Annex C.
Now there are definitions that will help the code reader know exactly which type of stranding applies.
Compact Stranding is a stranding method where each layer of strands is pressed together, minimizing gaps between the strands so the overall diameter of the finished conductor is less than a concentric stranded conductor and also less than a compressed stranded conductor.
Compressed Stranding is a stranding method where the outer layer of conductor strands is pressed together which results in the overall diameter of the finished conductor being smaller than a concentric stranded conductor but larger than a compact stranded conductor.
Concentric Stranded conductors have a straight central strand surrounded by one or more layers of strands, helically laid in a geometric pattern.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.
2020 Code Language:
These definitions did not exist.
2023 Code Language:
N Stranding, Compact. (Compact Stranding). A conductor stranding method in which each layer of strands is pressed together to minimize the gaps between the strands so the overall diameter of the finished conductor is less than a concentric stranded conductor and less than a compressed stranded conductor.
N Stranding, Compressed. (Compressed Stranding). A conductor stranding method in which the outer layer of strands is pressed together so the overall diameter of the finished conductor is less than a concentric stranded conductor but greater than a compact stranded conductor.
N Stranding, Concentric. (Concentric Stranding). A conductor consisting of a straight central strand surrounded by one or more layers of strands, helically laid in a geometric pattern.