Lightning, Surge Protection, and the 2020 NEC
By Nick Mahoney, P.E., CFEI
S-E-A
In recent years, lightning has accounted for tens of thousands of homeowner’s insurance claims across the United States according to the Insurance Information Institute [1]. Florida has typically led the U.S. in number of claims per year with Georgia and other southeastern states making the top ten. Lightning has been a known hazard to life and property since before Benjamin Franklin studied it. Until recently, residential structures were not required to have protection against lightning. With the release of the 2020 edition of National Fire Protection Association (NFPA) 70, the National Electrical Code (NEC), that trend may change [2].
Lightning can damage structures from a direct or indirect strike, and damage sensitive electronic equipment due to the surge generated in conductive power or communications lines. It can generate enough heat to ignite combustible materials and damage windows or structures from the resultant pressure wave caused by the rapid expansion of air near the strike. Several methods can be used to protect against these various types of lightning damage.
Many have likely had the experience of taking clothing out of a clothes dryer and feeling the effect of static electricity, or static discharge. In a similar way, lightning begins with the separation of static electric charge in clouds that is eventually discharged between the cloud and earth. Lightning protection systems for structures, like those defined in NFPA 780, the Standard for the Installation of Lightning Protection Systems, are used to protect against direct lightning strikes by providing a path for the static electric charge to flow to or from earth, limiting damage to nearby structures [3]. Lightning protection systems utilize a series of air terminals, also known as lightning rods, installed along rooflines and other elevated locations. These systems are not designed to prevent the occurrence of lightning but have been shown in several studies to be effective at reducing or preventing damage from direct strikes [4].
Protection against the surge from an indirect lightning strike can be accomplished as part of an overall lightning protection system or separately. Devices known as surge protectors or surge protective devices (SPDs) are used to protect against a surge caused by an indirect lightning strike. SPDs for home use are divided into three main categories which determine where they can be installed [2]. Many are familiar with Type 3 surge protectors, often used with computer or home entertainment systems, and commonly have several plug points. The other two main categories, Type 1 and Type 2, are perhaps not as familiar. Typically, these two types are permitted to be installed where the electric utility service enters the home (Type 1 SPDs) or in the panel where the main circuit breaker is installed (Type 1 or Type 2 SPDs). Often, Type 1 and Type 2 SPDs are referred to as whole-home surge protectors. These devices are designed to protect the entire electrical system in a home rather than an individual appliance or circuit. Type 4 and Type 5 SPDs exist as well but are only found inside appliances or electronics and installed by the manufacturer.
SPDs are likely to mitigate lightning damage in many cases, but an SPD does not prevent damage in all cases. Several factors can impact whether an SPD will prevent damage and to what extent. Factors such as the rating of the SPD, the age of the SPD, the proximity of the strike, the intensity of the strike, and whether the SPD was installed properly impact the effectiveness of SPDs. The age and design of electronic equipment connected to an SPD will also influence whether damage could occur. SPDs are tested against the industry standard Underwriters Laboratories (UL) 1449, Standard for Surge Protective Devices, which requires SPDs to be tested under conditions similar to lightning strikes; however, empirical data on the effectiveness of SPDs to protect from actual lightning strikes is limited [5], [6].
Historically, SPDs were not required in residential systems, but the release of the 2020 edition of the NEC may change this trend. The SPD was first introduced in the 2002 edition of the NEC, but at that time, only the allowable use and installation of SPDs was outlined. Article 230.67 of the 2020 edition of the code now requires a Type 1 or Type 2 SPD be installed for all new and updated dwelling units, such as single-family homes, condominiums, and apartments. The new edition also requires that a Type 1 or Type 2 SPD is installed when electrical service equipment, like circuit breaker panels, are replaced.
As with any new edition of the NEC, it will take time for each state and municipality to decide whether to adopt the 2020 edition as its local code. As of the writing of this article, the state of Massachusetts has already adopted the 2020 edition and sixteen other states including Georgia have begun the process of adoption [7]. As adoption of the 2020 edition of the National Electrical Code increases, so will the prevalence of Type 1 and Type 2 surge protectors and the need for claims professionals to consider their impact on a claim.
References:
[1] Insurance Information Institute, Inc., “Facts + Statistics: Lightning,” [Online]. Available: https://www.iii.org/fact-statistic/facts-statistics-lightning. [Accessed 24 March 2020].
[2] NFPA, 70, National Electrical Code, 2020.
[3] NFPA, 780, Standard for the Installation of Lightning Protection Systems, 2020.
[4] The Committee on Atmospheric and Space Electricity of The American Geophysical Union, “The Scientific Basis for Traditional Lightning Protection Systems,” 2001.
[5] UL, 1449, Standard for Surge Protective Devices, 2014.
[6] E. Davis, N. Kooiman and K. Viswanathan, “Data Assessment for Electrical Surge Protection Devices,” Fire Protection Research Foundation, 2014.
[7] “NEC Enforcement,” NFPA, [Online]. Available: https://www.nfpa.org/NEC/NEC-adoptionand-use/NEC-adoption-maps. [Accessed 24 March 2020].
If you would like more information regarding this subject, please contact Mr. Nick Mahoney, P.E., CFEI at (770) 638-8300 or email him directly at nmahoney@SEAlimited.com