Code Change Summary: The rules on surge protection for services have been expanded.

The 2020 NEC^® introduced a new requirement in Section 230.67 to have a Type 1 or Type 2 surge protective device (SPD) for dwelling unit services. Additionally, an SPD is required when an existing service is replaced.

In the 2023 NEC^®, surge protection is now required for services supplying the following specific dwelling types:

• Dwelling units
• Dormitory units
• Guest rooms and guest suites of hotels and motels
• Areas of nursing homes and limited-care facilities used exclusively as patient sleeping rooms

Similar code language was added in Section 215.18 for feeders, and Section 225.42 which covers outside branch circuits and feeders.

A surge is a transient wave of voltage or current. The duration is not consistent but is usually less than a few milliseconds. Transients and Surges can have peak values in excess of 10kA or 10kV. During a surge, the waveform has a very rapid rise to the peak and then falls off at a much slower rate. Transients and Surges can be caused by external sources such as lightning or short circuits, or from internal sources such as variable speed drives, contactor or capacitor switching.

A surge protective device protects the sensitive electronics in most modern appliances as well as devices installed for the safety of the occupants such as AFCI, GFCI and smoke/carbon monoxide detection, and other equipment commonly found in dwellings.

SPD’s are most effective when they are closest to the branch circuits being protected. Simply having surge protection at the electrical service will not afford the same protection as having a SPD at the dwelling unit panelboard supplied by the load end of a long run of feeder conductors. This is why the requirement for surge protection at the service equipment from Section 230.67(B) has an exception to permit the SPD to be located at each next level distribution equipment downstream toward the load instead of at the service.

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.