Improving GFCI Safety Through UL 943

Since its first requirement 50 years ago, the Ground Fault Circuit Interrupter (GFCI) has undergone numerous design improvements to increase personnel protection. These changes were catalyzed by input from organizations such as the Consumer Products Safety Commission (CPSC), the National Electrical Manufacturers Association (NEMA), and Underwriters Laboratories.

One of these standards, UL 943, provides specific requirements for ground-fault circuit-interrupters that adhere to the electrical installation codes of Canada, Mexico, and the United States. In June 2015, UL amended their 943 criteria to require that all permanently installed units (such as receptacles) include an auto-monitoring function. Manufacturers were able to sell existing stock to their customer base, with the intent being that as older units were phased out, their replacements would incorporate this additional safety measure.

Auto-monitoring, also known as self-testing, refers to a process that ensures a unit is working properly by automatically verifying the sensing and trip ability is functional. This self-testing ensures the GFCIs are tested regularly, which is something users infrequently do. If the self-test fails, many GFCI’s also feature an end-of-life indicator to alert the end user when the unit needs replacing.

The second aspect of the updated UL 943 mandates repeated Reverse Line-load Mis-wire Protection. Line-Load reversal obstructs power to the unit and prevents resetting it when there is an issue with the wiring. Whether the unit is being utilized for the first time or is being re-installed, any incorrect wiring to the self-testing GFCI will result in power loss and/or the inability to reset the equipment. 

As of May 5^th, 2021, UL 943 requires that products used in portable applications (In-line GFCI cordsets and Portable Distribution Units, for example) incorporate auto testing technology to further elevate worker and worksite safety. Ericson Manufacturing is the first to comply with this requirement.