How the 2017 NEC is expanding ground-fault protection
BY JEFFREY SARGENT
Ground-fault protection required by NFPA 70®, National Electrical Code® (NEC®), is intended to provide shock or fire protection when something goes wrong within electrical equipment, whether it’s a faulty consumer appliance or damaged electrical infrastructure. A number of changes related to ground-fault protection were proposed for the 2017 NEC and have been accepted by the code-making panels, changes that expand the protection offered by the NEC across a range of uses and occupancies. These proposals await final approval by the NFPA Standards Council when it meets in August. Among the highlights:
» Ground-fault circuit interrupter (GFCI) protection in commercial, institutional, industrial, and all other nondwelling occupancies has been expanded to include single-phase receptacles rated 150 volts to ground or less with current ratings up to 50 amperes. Also included in this expansion are three-phase receptacles rated 150 volts to ground or less with current ratings up to 100 amperes.
» Areas where GFCI protection is required have been expanded to include unfinished portions of basement and crawl spaces in commercial, institutional, industrial, and all other nondwelling occupancies.
» Special-purpose ground-fault circuit interrupters (SPGFCI) have been recognized as an option for providing protection for personnel using receptacles rated more than 30 amperes at 125 volts for temporary power applications covered in Article 590. SPGFCI protection while operating at higher current differentials than the normal (Class A) GFCI is considered to be shock protection for personnel in accordance with the applicable product certification standards.
» The maximum level of ground-fault protection of equipment in marinas and boatyards has been reduced from 100 mA to 30 mA.
According to the Electrical Safety Foundation International, home electrocutions have been cut by half since GFCIs were first introduced into residential wiring systems in the early 1970s. It is an unfortunate reality that a number of the NEC requirements for GFCI protection were substantiated by deaths or injuries that occurred in homes and workplaces as a result of electrocutions caused by ground faults.
Not all of the ground-fault protection rules in the NEC are about protection against electric shock. Rules requiring enhanced levels of ground- fault protection to respond to dangerous arcing ground faults within electrical equipment have been in the NEC since the 1971 edition. This level of protection, referred to in the NEC as ground protection of equipment, has also been successful at preventing catastrophic electrical equipment burndowns that start with an arcing ground fault. Other requirements for higher levels of ground-fault protection have been supported by fire data, such as structure fires originating from arcing at joints of grounded metal roofing components with the current leaking from deteriorating cables used for melting snow.
A recent expansion of ground-fault protection has been in the marine environment. The 2011 NEC contained new requirements for enhanced levels of ground-fault protection for the electrical infrastructure at marinas, boatyards, and floating buildings. Persons in the water at these locations can experience disabling levels of electrical current, and drownings at marinas resulting from electric shock have made headlines across the country. Sources of this electrical current vary, including the electrical infrastructure used to support marina operation. Properly maintained wiring systems generally do not pose a threat, but maintenance is often the missing factor in the electrical safety equation.
Like the ground-fault protection requirements that were included in previous editions of the NEC, it is a foregone conclusion that the changes proposed for the 2017 edition will provide a greater measure of protection against unplanned or unintended events that pose shock or fire hazards.