National Electrical Code Top Ten Tips: Article 242 -- Overvoltage Protection

Based on the 2026 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 242 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

1. Article 242 is entirely new with the 2020 NEC. With the 2020 revision, Articles 280 and 285 were deleted and replaced by Article 242. Other than the fact that the definitions were (as with all Articles in the Code) moved to Article 100, only 242.22 (surge arrester rating requirements) had any significant change with the 2023 revision. Article 242 consists of three Parts: General, Surge-Protective Devices (SPDs) 1000V or less, and SPDs over 1,000V.
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2. The General requirements are thin, to say the least. In the 2023 revision, there was just ae statement of scope (summed up in the second sentence above) and a requirement to refer to Table 242.3. With the 2026 revision, there's still the statement of scope but the table reference is gone. Added are a requirement that SPDs not over 1000Vac or 1500Vdc be listed and that reconditioned SPDs and surge protectors are not permitted.
   
3. In the 2023 revision, Table 242.3 listed 15 other Articles that may apply. That table is now gone.
   
   SPDS rated 1000V or less [Part II]:
   
4. SPDs may be Type 1, Type 2, Type 3, or Type 4. The definitions are in Article 100, under "Surge-Protective Device (SPD". Types 1 - 3 are differentiated by where they are installed. Type 4 are component SPDs and assemblies. See UL 1449 for more information about these Types. Uses not permitted are enumerated in 242.12, which in the 2023 revision provided the requirements for Type 1 (those are now in 242.13).
   
5. Each type of SPD, as you may have guessed, has its particular requirements. See 242.13, 14, 16, and 18.
   
6. SPDs must be inaccessible to unqualified people unless listed for installations in accessible locations [242.22].
   
   Surge Arrestors rated for over 1000V [Part III]:
   
7. Surge arrestors cannot be installed where the surge arrestor rating is less than the maximum continuous phase-to-ground voltage at the power frequency available at the point of application [242.40].
   
8. Where used at a point on a circuit, there must be a surge arrestor for each ungrounded conductor [242.44].
   
9. You must connect the surge arrestor to a grounded service conductor, grounding electrode conductor, grounding electrode for the service, or equipment grounding terminal in the service equipment [242.50]. Do you see what's missing here? That's right, you can't just drive a ground rod and connect to that. Why? Because electricity seeks to get back to the source (thus, grounding electrode for the service). Simply driving a ground rod creates a dangerous multi-path of varying impedances to the source.
   
10. You make different kinds of interconnections based on the various conditions listed in 242.54. For example, if you have a multi-grounded neutral primary system there has to be at least one other ground one the ground conductor of the secondary (among other requirements) [242.54(B)(2)].

Check out this grounding case history!