Revisions to UL Standard 943 Ground-Fault Circuit Interrupter (GFCI) Standard

Revisions to UL Standard 943 Ground-Fault Circuit Interrupter (GFCI) Standard The National Electrical Manufacturers Association (NEMA) with UL has announced major revisions to UL 943 that require improvements in GFCI performance that will provide better protection from serious injury and electrocution from electrical shock.

These revisions were developed by a NEMA-led group in response to the Consumer Product Safety Commission requesting auto-monitoring requirements on GFCIs. While GFCIs have reduced the number of electrocutions since their introduction in the 1970s, many consumers did not perform periodic testing.

As a result, they could have mistakenly assumed that the GFCI was functioning correctly and providing protection from electrocution. Furthermore, even if consumers did perform the tests, it was possible for an undetected failure or malfunction to occur between tests without an auto-monitoring system.

As a result, the following improvements will be made to GFCIs in order for them to meet the new UL Standard 943:

  1. Auto-Monitoring or Self-Test Function: This function allows for periodic, automatic testing of the ability of the GFCI to respond to a ground fault. If the Self-Test function detects a problem, the GFCI must deny power or provide visual and/or audible indication.
  2. Reverse Line-load Misfire Function - Repeated: If the line cable is wired to the load terminals of a receptacle GFCI, power to the receptacle face will be denied. This requirement applies to the initial installation and any subsequent re-installations.


In order for a GFCI to be certified by UL, it must meet many demanding requirements, such as:

  • Detecting ground fault and interrupting circuit
  • Corrosion resistance
  • Grounding
  • Drop and impact


To maintain UL certification, all manufacturers must meet these revisions with GFCIs produced after June 28, 2015. The current GFCIs bearing the UL Certification Mark can no longer be produced after June 28, 2015, but can be sold by manufacturers, retailers, and distributors, and can be used by installers until their inventories are depleted.

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  • After installation
  • At least once a month
  • After a power failure1
  • According to the manufacturer’s instructions



  • Plug a lamp into the outlet and turn the lamp on
  • Press the GFCI’s test button. Did the light go out? If not, the GFCI is no working or has not been correctly installed. Contact a qualified electrician to correct the wiring and/or replace the defective GFCI.
  • Press the reset button. Did the light come back on? If not, replace the GFCI.


Source: U.S. Consumer Product Safety Commission Fact Sheet