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National Electrical Code Articles and Information

National Electrical Code Top Ten Tips: Article 394 through Article 398 -- Wiring, Miscellaneous

Based on the 2017 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 394 through NEC Article 398 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. NEC Articles 394 through 398 contain the requirements for various types of wiring, including concealed knob-and-tube wiring, messenger supported wiring, and open wiring on insulators. Remember that, and your life will be much easier.
  2. Note that each of these wiring types is a subcategory of wiring in general. These are very specific wiring methods. The general wiring methods also apply--but now you have additional requirements if you use any of these three methods.
  3. Each Article in this series provides the uses permitted and the uses not permitted.
  4. NEC Article 394 provides the requirements for concealed knob-and-tube wiring. While this method is largely disappearing, there's a huge installed base of this type of wiring. You can install this kind of wiring only to extend or repair an existing installation.
  5. Taps on concealed knob-and-tube wiring must be soldered.
  6. NEC Article 396 provides the requirements for messenger supported wiring. You must use one of the cable types listed in Table 396.10(A) and follow the appropriate Article for that cable type.
  7. An exception to the rule just stated applies for industrial installations [396.10(B)]. This exception seems almost pointless, since industrial establishments are much better served with modern wiring methods than with something they should have replaced decades ago.
  8. NEC Articles 398 provides the requirements for open wiring on insulators. You won't find open "insulators" defined in Article 100. So, what does this mean? Look no further than 398.2--this "open wiring on insulators" is a wiring method. It is not an approach to wiring that involves generic insulators.
  9. If you use the open wiring on insulators method, you must use bushings to pass the open conductors through framing members [398.17].
  10. Observe the clearances provided in 398.19.


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