Written by Pat Hansen, Southeast Iowa Electrical Inspector Supervisor, Iowa Department of Public Safety
Ground Fault Circuit Interrupters (GFCIs) are required as a safety measure in the National Electrical Code (section 210.8). You will most often see them in the bathroom, kitchen, and garage, although they may also be found on electric panels as a circuit breaker. You’ll recognize them as the receptacles that have the “test” and “reset” buttons on them.
GFCI protected circuits are designed to protect you and your family from accidental electrocution. They do this with high-tech internal electronics (similar to the electronics in your TV, computer, and range) that monitor current flow within the conductors connected to the device. If there is more than a 5 milliamp variance between the conductors, the GFCI trips off to prevent a shock.
A mystery and a shocking discovery
In the past 10 to 15 years, experts have made a “SHOCKING” discovery (pardon the pun): Many defective GFCI protected receptacles have been discovered, usually as the result of an electrocution. The first tragedy occurred in Texas, when, ironically, the daughter of a major stakeholder of a GFCI manufacturer was electrocuted. This sparked an investigation in Texas, where high numbers of defective GFCIs were detected. The devices seemed to be functioning because there was power and the devices appeared to be energized. However when tested, they did not perform to the minimum standards set forth by Underwriter’s Laboratory (UL).
The conclusion was … lightning strikes caused a vast majority of the failures. A lightning strike can deliver approximately 30,000 volts, while the receptacle and its high tech electronics are rated at 120 volts. Consequently, the electronics are no match for the lightning.
While through the years, manufacturers have designed the GFCIs to avoid nuisance tripping and to offer fail-safe installation, no one can contain and control Mother Nature.
• Self-test your home’s GFCI receptacles once a month. The units come with a chart to keep records of your monthly testing.
• Periodically have all GFCI receptacles tested by a qualified electrician to be sure they are functioning properly.
• If after an electrical storm, you find a GFCI receptacle tripped, DO NOT just reset it and use it. Rather, have it tested and then replace it if need be. (In this situation, I would replace the GFCI if it has been affected by lightning, rather than testing it.)
Source: Patrick Hansen, Iowa Electrical Inspector Supervisor, Iowa Department of Public Safety, State Fire Marshal’s Office, Electrical Bureau. Contact: firstname.lastname@example.org