A Look Ahead: Surge Protection for Dwelling Units

The 2020 National Electrical Code (NEC) is well into its development process with issuance anticipated in 2019. During the first-draft stage, there were a few changes related to rules for surge arresters and surge-protective devices (SPDs). This article provides a review of the revisions made regarding these protective devices. Information in this article is derived from the NFPA 70 2020 First Draft report, which is available for public viewing at nfpa.org/70next.

The first revision to discuss is how and where the rules for surge arresters and SPDs will appear in the 2020 NEC . During the first-draft stage, a new Article 242, Overvoltage Protection, was introduced by Code -Making Panel 10. This article is a result of First Revision 8221 and is logically arranged into three parts. Part I covers general requirements, installation requirements and connection requirements for overvoltage protection and overvoltage protective devices. Part II covers SPDs permanently installed on premises wiring systems of not more than 1,000 volts (V), nominal. Part III covers surge arresters permanently installed on premises wiring systems over 1,000V, nominal. Article 242 resulted from coordinated work between Code Panel 5 and Code Panel 10 along with initial development work by an assigned NEC Correlating Committee task group.

The new article combines the requirements contained in 2017 NEC Article 280, which covered surge arresters, and 285, which covered SPDs. These two articles were deleted while new Article 242 was developed and acted upon by Code -Making Panel 10, simultaneously. The other thing that happened was a change in responsibility for these Code rules. Code Panel 5 has responsibility for electrical grounding and bonding rules in articles 200 and 250 and had technical responsibility for articles 280 and 285 prior to the 2020 NEC revision process. Since the relocated rules in proposed Article 242 are mainly related to “overvoltage protection” and deal with protection of equipment, it is a logical shift in responsibility to Code Panel 10, since they cover overcurrent protection in Article 240.

Now that we’ve reviewed the relocation of existing requirements, let’s move on to new requirements for SPDs proposed for the 2020 NEC . Code Panel 10 acted favorably to Public Inputs 4118 and 2696 and, as a result, developed First Revision 8546. This is a new Section 230.67 in Article 230 titled “Surge Protection.” The new rule requires all services for dwelling units be provided with a Type 1 or Type 2 SPD. SPDs are defined in Article 100, where the Types of SPDs are differentiated. The SPD can be located within the service equipment, or it can be installed immediately adjacent to it.

The substantiation for adding the requirements for SPDs indicated a recognized and growing need for surge protection to protect sensitive electronic circuitry and insulation systems found in most electronics, appliances and other equipment used in dwellings and buildings. Additionally, the expanding use of distributed energy resources within electrical systems often results in more opportunity or greater exposure for the introduction of surges into the building electrical system. Surge protection also is needed to lessen the impact of high system harmonic content from inverter-based sources and the resulting potential for damaging transients.

SPDs installed in or at dwelling unit service equipment and used in conjunction with SPDs at the point of use within the dwelling unit, offer a significant degree of protection against damaging surge events. Type 3 SPDs are typical point of utilization types and commonly found in portable power taps (plug strips) or SPDs that connect directly to receptacle outlets within the home.

At this stage of the 2020 NEC development process, existing requirements for surge arresters and SPDs (former articles 280 and 285) have been relocated to new Article 242, Overvoltage Protection. A new requirement for SPDs at dwelling unit services has been added in proposed new Section 230.67.

About the Author

Michael Johnston

Executive Director of Standards and Safety, NECA

Michael Johnston is NECA’s executive director of standards and safety. He is chair of the NEC Correlating Committee; chair of the NFPA Electrical Section; and a member of the IBEW, NFPA Education Section and the UL Electrical Council. Reach him at mj...

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