It is the job of the GFCI to detect irregularities in current flowing between the two conductors and respond by interrupting power (tripping) instantaneously to prevent injury. The “tripping” process is achieved when the solid-state circuitry detects a potentially hazardous condition and causes the switching contacts to open and de-energize the circuit. This is done in a split second; in time to prevent injury to a person who may be in the path of the current flowing in the unwanted path.
Studies were conducted to derive the correct amount of ground fault current that should cause a GFCI to trip. The findings also indicated the minimum amount of current that would be perceptible, the minimum amount of current that would cause a startle reaction, and the minimum amount of current that would cause an individual to be unable to let go of a hot wire. This is outlined below:
Perceptible Current
0.2mA minimum for women
0.3mA minimum for men
Startle Current
0.5mA minimum
Let-Go Current
6.0mA (for almost all people)
GFCI Trip Current
4.0 – 6.0mA minimum
Product standards and performance requirements are based on this information and engineers use this information when designing GFCIs in order to make them as effective as possible when in use.
Once installed, the best way to verify that a GFCI is providing protection is to test it on a monthly basis. All GFCI outlets have clearly marked “TEST” and “RESET” buttons on the face of the device, providing a simple, distinct means to conduct this testing. And now, there is a technology that can supplement manual testing and regularly conduct an automatic test of the circuit. This technology has been incorporated into a UL standard requiring all GFCI receptacles to have a self-test function; which improves safety for end users by confirming that the GFCI can respond to a ground-fault. And, if not, the GFCI either takes itself out of service or the user is given an indication that the device needs to be replaced.
Leviton offers a wide variety of GFCI devices, including hospital grade and cord sets, for protection in the home, industry, outdoor work site, or wherever electrical products are used in damp or wet locations. Remember, these devices are designed to reduce the occurrences of serious injury or death associated with electrical accidents and therefore are a must for optimal personal protection and safety.