Originally Posted By: jtedesco
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|Project Hanford Lessons Learned
Title: Ground Fault Circuit Interrupter Testing
Date: January 20, 2000
Lessons Learned Statement:
A ground fault circuit interrupter (GFCI) can fail in a way that permits the device to be reset and pass current without providing ground-fault protection. Many people do not understand how a GFCI works and hence may believe that protection is being provided when, in fact, the device has failed.
Discussion of Activities:
A recent article in IAEI News (International Association of Electrical Inspectors) reported a high failure rate of GFCIs. The Hanford Workplace Electrical Safety Board (HWESB) determined that there is a need to inform workers about proper GFCI test procedures.
The protective circuitry in a GFCI is vulnerable to voltage spikes such as those caused by lightning and high-voltage switching. It is possible for the device to eventually fail to provide ground-fault protection while still providing power for tools and appliances. A proper test sequence can help assure that the GFCI is still providing ground fault protection.
Permanently installed GFCIs (receptacles and circuit breakers) are required to be tested at least monthly, or within 30-days of use for devices located in hazardous areas, remote locations, etc. Portable GFCI "pigtails" must be tested before use. The user may be allowed to test a permanently installed GFCI before use if doubt exists as to the last time it was tested. Some GFCI installations protect additional outlets "downstream" from the GFCI itself so testing the GFCI will interrupt power to any such outlets and may be unsafe or undesirable. If you are unsure whether the GFCI supplies additional outlets, DO NOT TEST IT. Contact your manager, building administrator, or electrical maintenance department.
The HWESB recommends these steps for testing GFCI's:
Visually inspect the device for obvious defects and broken parts (do not continue if the device is broken!).
Press the reset button (or check for voltage at the device) to determine if it is tripped.
If device was found in a tripped state (no voltage, or you hear or feel a "click" when you press the reset button), be suspicious - ground fault protection may be inoperative when voltage is present after the device is reset - DO NOT USE until you complete the following test sequence!
Press the test button and observe that the device trips (hear or feel a "click").
Verify no voltage at the outlet (a voltage meter, load device, or trouble light will work).
Press the reset button and verify that power is restored.
If the device fails to respond in the expected manner at any stage of the test, then it should not be used. Report the failed test to your manager, building administrator, or electrical maintenance department so that appropriate troubleshooting and corrective action can be taken.
Joe Tedesco, NEC Consultant