NFPA Journal

BY DEREK VIGSTOL

Throughout its long and storied history, NFPA 70®, National Electrical Code® (NEC), has contained requirements that protect buildings from the hazards that come from installing electrical systems in buildings. One of the ways this safeguarding has been accomplished has been to limit the amount of electricity or current that can be supplied by a given size of a conductor. This was such a cornerstone of how we protect buildings that it warranted the creation of a new word—ampacity—to describe the current (amps) carrying capacity of a conductor without damaging its insulation. It is safe to say that overcurrent protection is big in the NEC world.

But current isn’t the only electrical force at work in our systems. There’s also voltage—but have there been requirements to protect our electrical systems from overvoltage like we have for overcurrent? Surge protection has been a part of the NEC for as long as I have been alive, and prior to that lived as part of grounding and bonding, as it was listed in the NEC as a lightning arrester. The requirements back then and all the way up through the 2017 NEC focused on how to install these devices—though there was really nothing that required one to be installed.

Excessive voltage imposed on electrical conductors and equipment can be just as damaging—and in some cases more damaging—than overcurrent. An example is what can happen inside a house when lightning finds its way onto the premises wiring system. Often there are burn marks throughout the home. Equipment stops working or, if it remains operational, the integrity of the internal components has usually been severely compromised. This type of event often requires a comprehensive inspection of the electrical system by somebody who knows what they are doing before this system is used again. There is often no way of knowing what the extent of the damage is to the internal workings of the system without doing a little digging first.

For this reason, a requirement for surge protection at the service level is being added for all dwelling unit services installed under the 2020 NEC, including replacement or upgraded service installations. Substantiation submitted for this revision pointed out that product standards for life saving devices such as GFCIs and fire detection and notification equipment have adjusted to account for damage caused internally by transients. It was recognized in the product standard development process that transient voltages can often damage the sensitive electronics in devices like GFCI receptacles and could render the devices inoperable. However, the device might still function as a receptacle, only without the ability to interrupt the circuit when needed. Without regular inspections by the building occupants or homeowner, this condition could go unnoticed until it’s too late.

Section 230.67 was created to prevent a situation where this could happen. In addition to the requirement that all services supplying dwellings be protected from overvoltage by a surge protective device (SPD), this section also requires this device to be installed either at the service equipment or immediately adjacent to it. There is an exception to the location requirement, provided the SPD is located at the next distribution equipment downstream. For example, a multifamily dwelling might have the service equipment installed in a central location for ease of maintenance and supervision. The individual SPD for each unit would then be able to be installed at the dwelling unit panelboard itself, even though this is not service equipment.

This device, whether installed at a single-family dwelling service or at a sub-panel feeding an apartment in a high-rise downtown, must be either a Type 1 or Type 2 SPD. This means that it must be permanently connected to the system. While point-of-use SPDs are still recommended for protection of equipment like TVs, computers, and anything else utilizing sensitive electronic components, it can’t be used to satisfy this new requirement as it can easily be removed by an occupant.

Additionally, there is another revision that combines the “over 1000V” and “under 1000V” requirement into a single new Article 242 and deletes Articles 280 and 285. Article 242 is where the installation requirements for SPDs will be found. Requirements for SPDs to be listed, how to be connected within the panelboard, and short-circuit current ratings can be found in Article 242.

While the revision process is still underway for the 2020 NEC, there were no certified amending motions submitted to challenge this new requirement. Therefore, the requirement most likely will remain as it is in the second draft when you get your copy of the 2020 edition. How individual jurisdictions apply this new requirement will be the next item to watch. 

Derek Vigstol is an NFPA technical lead, Electrical Tech Services.