The proper application of circuit protective devices is crucial in the design and construction of a safe and reliable power distribution system. On the one hand, we use fuses and circuit breakers to protect electrical equipment. But when it comes to safeguarding persons from injury, ground-fault circuit interrupters (GFCIs) are the item of choice. But are these devices really providing the full-time protection everyone thinks they are? The answer may surprise you.
Pass & Seymour/Legrand first introduced the GFCI to the electrical market more than 30 years ago. Initially, the NEC only required you to install a GFCI for temporary wiring at construction sites, underwater swimming pool lights, and in dwelling unit bathrooms. But in recent years, Code requirements have expanded to include many other areas, including commercial occupancies, fountains, and swimming pools. According to the National Electrical Safety Foundation, an estimated 400 million GFCIs have since been installed in homes and most private residences, apartments, hotels, motels, and public facilities.
But recent research and testing by the National Electrical Manufacturers Association and Underwriters Laboratories (UL) indicates approximately 10% of installed GFCIs in their sample group continued to supply power without providing ground-fault protection. Another study, conducted by the American Society of Home Inspectors, revealed 19% of GFCI receptacles inspected didn't provide protection. The number of people depending on these devices makes these numbers particularly alarming.
In many cases, damage to the internal transient voltage surge suppressors that protect the GFCI sensing circuit is responsible for failure of the device. This is especially true in areas of high lightning activity, such as Florida. Installing GFCI receptacles in wet or damp locations can also expose the devices' internal circuitry to corrosion. Miswiring the device — mistakenly reversing the line and load connections — is another problem. And exposure to radio frequencies has also caused devices to fail. And the real kicker is hardly anyone ever properly tests these devices before using them.
That's why UL has revised its standard for GFCIs, UL 943. The testing organization issued a press release on July 24, setting forth the following six revisions to the standard that will become effective Jan. 1, 2003:
A more stringent voltage surge test to ensure the device can handle a higher surge current.
A new corrosion test to demonstrate greater immunity to moist conditions.
An operating test to verify that proper operation of the GFCI cannot be prevented by manipulation of its controls.
A reverse line-load miswire test that requires the device to trip when miswired.
An abnormal overvoltage test that requires the GFCI not become a fire or shock hazard during extreme overvoltage conditions.
An increased requirement for GFCIs to operate properly after exposure to conducted radio frequencies.
Although these devices have served homeowners well for the past 30 years, UL's new requirements are meant to raise the bar and make them more robust and resistant to actual field conditions. But let's not lose sight of the most important issue of all — safety. Protecting human life, like the baby shown on the cover, is what it's really all about. For an in-depth report on this topic, be sure and turn to page 24 for this month's cover story, “Leaving a Mark,” written by Senior Associate Editor Matthew Halverson.