Ground Fault Circuit Interrupters : NS Labour and Advanced Education, Hazard Alerts

Date of Issue: September 09, 2002

Hazard Summary

Portable electric power tools often require the use of extension cords and are at times used in wet locations. When cords, cord receptacles or connected equipment are improperly used, poorly maintained or wet a hazardous electrical leakage can occur. Employees who are in contact with the equipment at the time of leakage may get an electric shock.

What is a Ground Fault?

If you have experienced an electric shock it probably happened because your hand or some other part of your body contacted a source of electrical current and your body provided a path for the electrical current to go to the ground.

An unintentional electric path between a source of current and a grounded surface is referred to as a “ground fault.” Ground faults occur when a current is leaking somewhere, in effect it is escaping to the ground.

The severity and effects of an electrical shock depend on a number of factors such as whether the skin is wet or dry, the pathway through the body, the amount of current, and the length of time of the exposure. Remember water, from most sources, is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin.

What is a Ground Fault Circuit Interrupter?

A Ground Fault Circuit Interrupter (GFCI) is a device that detects any leakage current in an electrical circuit and turns off (trips) the circuit whenever the leakage current is greater than 5/1000 of an ampere. For comparison two 60 Watt light bulbs draw a total of 1 ampere of current.

There are three types of GFCIs that may be used at a worksite:

  • A GFCI receptacle can be used in place of a standard receptacle.
  • A portable GFCI which plugs into a standard receptacle (Note: this provides protection only to the outlet the GFCI is plugged into, not the whole receptacle).
  • A GFCI circuit breaker combines leakage current detection with the function of a circuit breaker.

Whenever working in a wet area or outdoors the employer should use 1 of these types of GFCI.

To prevent nuisance tripping of GFCIs the following work practices are recommended:

  • Mount GFCI receptacles and GFCI circuit breakers in dry locations; if this isn't possible, use portable GFCIs rated as rain proof.
  • Connect only one power tool to each GFCI, unless the manufacturer's specifications allows more than one tool to be connected.
  • When not in use, cover power tools to protect them from rain or moisture.
  • Store power tools and extension cords in a dry place.
  • Maintain extension cords and power tools in good condition.
  • Use extension cords intended for industrial / heavy duty usage or better.
  • Do not use extension cords longer than 45 metres (150 feet).
  • Test and maintain the GFCI as per the manufacturer's instructions/specifications.