Ground Fault Circuit Interrupters (GFCI)
A GFCI is a ground fault circuit interrupter designed to protect people from severe and sometimes fatal electrical shock. A GFCI detects ground faults and interrupts the flow of electric current and is designed to protect the worker by limiting the duration of an electrical shock.
Example: How a GFCI Works
A homeowner is using an old drill with a loose bare wire inside it touching the outer metal housing.
How GFCIs Work
With the drill plugged in, the housing is charged with electricity. If it is used outside in the rain and the worker is standing on the ground, there is a path from the hot wire inside the drill through the worker to the ground. If electricity flows from hot to ground through the worker, it could be fatal. GFCIs monitor the current-to-the load for leakage to ground. When this leakage exceeds 5 mA + 1 mA, the GFCI interrupts the current, trips the circuit, and cuts off the electricity.
Description of Accident
One employee was climbing a metal ladder to hand an electric drill to the journeyman installer on a scaffold about five feet above him.
When the victim reached the third rung from the bottom of the ladder, he received an electric shock that killed him. The investigation revealed that the extension cord had a missing grounding prong and that a conductor on the green grounding wire was making intermittent contact with the energizing black wire thereby energizing the entire length of the grounding wire and the drill's frame. The drill was not double insulated.
Inspection Results
As a result of its investigation, OSHA issued citations for violations of construction standards.
What would you recommend?
Recommendations
- Use approved ground fault circuit interrupters (GFCI) or an assured equipment grounding conductor program to protect employees on construction sites [1926.404(b)(1)].
- Use equipment that provides a permanent and continuous path from circuits, equipment, structures, conduit or enclosures to ground [1926.404(d)(6)].
- Inspect electrical tools and equipment daily and remove damaged or defective equipment from use until it is repaired [1926.404(b)(iii)(c)].
Knowledge Check Choose the best answer for the question.
2-4. A GFCI protects the worker by _____.
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