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National Electrical Code Top Ten Tips: Article 315 through Article 340 -- Cables

Based on the 2023 NEC

by Mark Lamendola

Please note, we do quote from copyrighted material. While the NFPA does allow such quotes, it does so only for the purposes of education regarding the National Electrical Code. This article is not a substitute for the NEC.

These are the 10 NEC Article 320 through NEC Article 340 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. Article 315 through 340 contain the requirements for various types of cable. Remember that, and your life will be much easier. What is a cable? If you look in Article 100, you will find over 40 entries that begin with "cable". This is a generic term, but in these articles of the NEC it refers to an assembly that is made of individual conductors that are bundled inside some kind of jacket. In a more generic sense, a cable may contain a single optical conductor or a single electrical conductor or it may contain a mix of these. It can be a signal cable, power cable, or cable for control wiring. It helps to think of individual conductors as not cables and anything else that is in a sheath as a cable (you will be right almost every time). You can think of the cable sheath as taking the place of a raceway for what's inside the cable.
  2. Each Article in this series provides the uses permitted and the uses not permitted. At one time, you had to hunt for where each article listed these. Since the 2020 revision, you will find them in subsection 10 and 12, respectively.
  3. Until the 2023 revision, Article 328 provided the requirements for Medium Voltage Cable (Type MV). Now that is Article 315 and there is no Article 328. You cannot use Type MV Cable on systems above 35 kV (35,000 volts).
  4. Article 320 presents requirements for type AC: Armored Cable. This kind of cable has a metallic jacket. While many people assume it's the most durable of all cables and can be used anywhere, this is not true.
  5. Article 322 and Article 324 address two types of flat cable assembly. Only one of them is designed for use under carpet squares.
  6. Article 326: You cannot use Integrated Gas Spacer Cable (Type IGS) inside buildings. This makes sense when you think about it. What happens if it leaks?
  7. Article 330 provides the requirements for Metal-Clad Cable (Type MC). Note, this differs from armored cable. Article 332 provides the requirements for Mineral Insulated, Metal-Sheathed Cable, Type MI.
  8. Article 334 provides the requirements for various kinds of Non-Metallic Sheathed Cable (Types NM and NMC). Article 336 provides the requirements for Power and Control Tray Cable, Type TC.
  9. Article 337 covers Type P Cable. Article 338 provides the requirements for Service Entrance Cable (Type SE and Type USE).
  10. Article 340 provides the requirements for Underground Feeder and Branch-Circuit Cable (Type UF).

The other NEC Articles from this point forward to the end of NEC Chapter 3 are short, and each is specific to a type of raceway. Do not confuse raceway with conduit; conduit is just one type of raceway.