What is Ground-fault Circuit Interrupters?

Time:2017-10-26 Source:KEYGMA--GFCIs


This category covers ground-fault circuit interrupters (GFCI) for use in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).

A GFCI is a device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the circuit.

GFCIs are intended to be used only in circuits where one of the conductors is solidly grounded.

Class A GFCIs trip when the current to ground has a value in the range of 4 through 6 mA. Class A GFCIs are suitable for use in branch and feeder circuits, including swimming pool circuits. However, swimming pool circuits installed before local adoption of the 1965 NEC may include sufficient leakage current to cause a Class A GFCI to trip.

GFCIs of the enclosed type that have not been found suitable for use where they will be exposed to rain are so marked.

The "TEST" and "RESET" buttons on the GFCIs are only intended to check for the proper functioning of the GFCI. They are not intended to be used as "ON/OFF" controls of motors or other loads unless the buttons are specifically marked "ON" and "OFF." Products with "ON" and "OFF" markings have been additionally covered under Motor Controllers, Mechanically Operated and Solid-state.


Receptacle GFCIs

Some GFCIs include flush receptacles and are intended to be installed in an outlet box for fixed installation on a branch circuit similar to a conventional receptacle.

Receptacle-type GFCIs for use in wet and damp locations in accordance with Articles 406 of the NEC are identified by the words "Weather Resistant" or the letters "WR" where they will be visible after installation with the cover plate secured as intended.

Weather-resistant receptacle-type GFCIs installed in wet locations are intended to be installed within an enclosure that is weatherproof, whether or not the attachment plug cap is inserted.

Receptacle-type GFCIs intended for use where tamper-resistant receptacles are required by the NEC are identified by the words "Tamper Resistant" or the letters "TR" located where they will be visible after installation with the cover plate removed.

Receptacle-type GFCIs that have additionally been found to meet appropriate receptacle requirements are marked "Hospital Grade" (or "Hosp. Grade" or "HG") and a green dot and/or "CO/ALR" on the device.

Receptacle-type GFCIs with receptacles rated 15 or 20 A that are provided with more than one set of terminals for the connection of line and neutral conductors are suitable for through wiring on 20 A branch circuits.

The standard horsepower ratings for specific general-use receptacle configurations are also applicable to the receptacle portion of a GFCI employing the same receptacle configuration.

See Receptacles for Plugs and Attachment Plugs for further information.


Portable GFCIs

This category also covers portable GFCIs. These are plug-in type ground-fault circuit interrupters provided with male blades or an integral power-supply cord for connection to a receptacle outlet. Portable GFCIs are also provided with one or more receptacle outlets located on the GFCI or on a cord-connector body at the end of a length of flexible cord.

Only devices identified as "Portable GFCIs" are constructed so that either:

1. GFCI protection is also provided, or
2. the device interrupts power to the load,

when any single supply conductor, including the neutral conductor, is opened. This feature maintains protection to the user in the event that continuity of a supply conductor is lost as a result of wear in the receptacle to which the device is connected, or if the integral power-supply cord to the GFCI is damaged.


Self-contained GFCIs

Self-contained GFCIs are provided with a complete enclosure intended to be permanently attached to the mounting surface, and a means of permanent connection to the supply conductors. They may be provided with one or more receptacle outlets or a means for permanent connection of the load conductors.

All self-contained GFCIs intended for installation in a counter are suitable for installation in a kitchen or bathroom countertop. They are provided with one or more receptacle outlets. The outlets may be fixed or retractable for storage below the counter surface.