Tool Box Talk

Ground-Fault Circuit Interrupters (GFCI)                                              BACK




A ground-fault occurs when there is a break in the low-resistance grounding path from a tool or electrical system. The electrical current may then take an alternative path to the ground through the user, resulting in serious injuries or death. 

The ground-fault circuit interrupter, or GFCI, is a fast-acting circuit breaker designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second. It works by comparing the amount of current going to and returning from equipment along the circuit conductors. When the amount going differs from the amount returning by approximately 5 milliamperes, the GFCI interrupts the current.

 The GFCI is rated to trip quickly enough to prevent an electrical incident. If it is properly installed and maintained, this will happen as soon as the faulty tool is plugged in. If the grounding conductor is not intact or of low-impedance, the GFCI may not trip until a person provides a path. In this case, the person will receive a shock, but the GFCI should trip so quickly that the shock will not be harmful.

The GFCI will not protect you from line contact hazards (i.e. a person holding two "hot" wires, a hot and a neutral wire in each hand, or contacting an overhead power line). However, it protects against the most common form of electrical shock hazard, the ground-fault. It also protects against fires, overheating, and destruction of wire insulation.

For construction applications, there are several types of GFCIs available, with some variations:

Receptacle Type

The Receptacle Type incorporates a GFCI device within one or more receptacle outlets. Such devices are becoming popular because of their low cost.

 Portable Type

Portable Type GFCIs come in several styles, all designed for easy transport. Some are designed to plug into existing non-GFCI outlets, or connect with a cord and plug arrangement. The portable type also incorporates a no-voltage release device that will disconnect power to the outlets if any supply conductor is open. Units approved for outdoor use will be in enclosures suitable for the environment. If exposed to rain, they must be listed as waterproof.

Cord-Connected Type

The Cord-Connected Type of GFCI is an attachment plug incorporating the GFCI module. It protects the cord and any equipment attached to the cord. The attachment plug has a non-standard appearance with test and reset buttons. Like the portable type, it incorporates a no-voltage release device that will disconnect power to the load if any supply conductor is open.


All GFCIs have a built-in test circuit, with test and reset buttons, that triggers an artificial ground-fault to verify protection.

 Test portable-type GFCIs before each use.

Test every permanently wired GFCI:

  • After installation
  • At least once a month
  • After power failure2

Test according to the manufacturer’s instructions.

1. If you do not have the instructions follow this procedure:

2. Plug a lamp into the outlet and turn the lamp on.

3. Press the GFCI’s test button. Did the light go out? If not, the GFCI is not working or has not been correctly installed. Contact a qualified electrician to correct the wiring and/or replace the defective GFCI.

4. Press the reset button. Did the light come back on? If not, replace the GFCI

Ground-fault protection, such as GFCIs provide, is required by OSHA in addition to (not as a substitute for) general grounding requirements.

GFCI Program

The following is the section of GFCI pulled directly form Abc company’s Safety Program.


Competent person: A person who it capable of identifying existing and predictable hazards in the surrounds or working conditions which are unsanitary, hazardous or dangerous to employees and who has the authorization to take prompt corrective measure to eliminate them.

Ground- Fault Circuit Interrupter:  a device for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.

1. One or more competent person(s) on-site shall implement this GFCI program.

2. This procedure applies to all construction sites covering all cord sets, receptacles that are not a part of the building or structure and equipment connected by cord and plug, which are available for use or used by employees.

3. Each cord set, attachment cap, plug and receptacle or cord set and any equipment connected by cord and plug, except cord sets and receptacles which are fixed and not exposed to damage will be visually inspected before each day’s use for external defects, such as deformed or missing pins or insulation damage and for indication of possible


5. Only heavy –duty extension cords shall be used and be tagged as UL Approved by a testing laboratory.

6. All 120-volt, single phase, 15 and 20 ampere receptacle outlets on construction sites that are not a part of the permanent wiring of the building or structure and that are used by employees shall have approved ground-fault circuit interrupters for personnel protection.Receptacles on a two-wire, single-phase portable or vehicle mounted generator rated not more than 5kW, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, do not need to be protected with ground0fault circuit interrupters.