GFCI outlet being tested (C) Daniel Friedman Ground Fault Circuit Interrupters, GFCIs
Definition & performance of GFCIs, Electrical Code GFCI Requirements

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Ground Fault Circuit Interrupters, GFCIs:

Definition of GFCI, what is a GFCI, and when should a GFCI trip or turn off an electrical circuit? What is the level of electrical shock protection provided by a GFCI or ground fault circuit interrupter.

What are the electrical code requirements for GFCIs? Where are GFCIs required to be installed?

This article series discusses safety procedures for the electrical inspector, home inspector, or other professionals while examining GFCIs and AFCIs. Safe electrical inspection procedures and safe use of volt meters, DMMs, multimeters, and similar electrical test equipment is discussed at the end of the article.

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GFCI-Protected Electrical Receptacles

GFCI outlet being tested (C) Daniel Friedman

A GFCI or Ground-Fault Circuit Interrupter is a safety device intended to prevent electrical shock by detecting an improper flow of electrical current and shutting the electrical circuit off very quickly - in milliseconds.

The GFCI is designed to protect people from severe or fatal electric shocks by quickly detecting a small flow of electrical current between the electrical circuit (wires, switch, electrical receptacle or something plugged-in to the receptacle) and "ground" or the earth.

A GFCI also can protect against some electrical fires by detecting arcing and other faults to ground but a GFCI cannot detect hazardous across-the-line arcing faults that can cause fires.

[Click to enlarge any image]

A ground fault is an unintentional electric path diverting current to ground. Ground faults occur when current leaks from a circuit.

How the current leaks is very important. If a person’s body provides a path to ground for this leakage, the person could be injured, burned, severely shocked, or electrocuted.

If a person is touching a live electrical wire or is touching an electrical appliance inside of which a wire has come loose and is touching the appliance body while the person is also grounded (standing on a wet floor or touching a metal water pipe) that person could easily suffer a fatal electrical shock.

The U.S. National Electrical Code requires GFCI protection for receptacles located outdoors, in bathrooms, garages, kitchens, crawl spaces and unfinished basements;

and at certain locations such as near swimming pools where the risk of electrical shock is high because people are likely to be both near electrical circuits and device and in wet or damp or otherwise high-risk locations where they're also likely to be electrically grounded.

What is the "Trip Level" of GFCIs? - at what current should a GFCI device shut off the circuit?

Many sources describe the effects on a person of receiving an electrical shock at various levels of current, measured in amperes. Very low levels of electrical current, in the 50 mA to 4A range can cause heart fibrillation and at 4A or higher, heart paralysis, tissue or organ burning, i.e. death is very possible. Half of people in the general population will "freeze" or be unable to let go of an electrical device at 10-15 mA of electrical current.

Note: 1 mA is one milliamp or 1 one-thousandths of an ampere of current flow. A typical household lighting circuit or receptacle circuit is wired for a total electrical load or current draw of 15 Amps.

Therefore GFCIs are typically designed to trip in the 4-6 mA range. Setting GFCIs to trip or to turn off the electrical circuit at current leakage or flow rates lower than that would raise a convenience issue as electrical circuits would experience high nuisance tripping. - (ANSI/UL Standard 943, Class A GFCI Trip Level) (NEMA 2012)

How Quickly Should a GFCI Trip Off?

The speed at which a GFCI device should shut down the circuit is not a fixed amount of time. Rather, the higher the current-flow, the faster the device should trip. At 6 mA of electrical current flow, a typical GFCI will trip off in just under six seconds. At that level a person might just feel the tingle of electrical current flowing through their body.

At a much higher, potentially fatal current level of around 264 mA, the GFCI device should trip off in just about 25 milliseconds. (25 thousandths of a second).

Related Electrical Safety Devices: AFCIs & Combination AFCI/GFCI devices

AFCIs, a different types of electrical circuit safety device, arc faults or electrical circuit arcing and the use of AFCIs are discussed separately at AFCIs ARC FAULT CIRCUIT INTERRUPTERS - devices intended to provide improved fire protection.

A combination AFCI and GFCI can be used to satisfy the NEC requirement for GFCI protection only if specifically marked as a combination device.

Where are GFCI's Required to be Installed?

NFPA 70, the U.S. National Electrical Code (NEC) requires that Ground Fault Circuit Interrupters or GFCIs must be installed at high-risk locations where a person might touch an electrical device, circuit, or component and be close to water (piping, drains, wet floors, damp locations) or might be easily grounded:

thus where people are at extra high-risk of being shocked or killed by an electrical fault that allows electrical current to pass through their body. GFCIs used in residential buildings where electrical circuits are limited to 240V or less are designated as Class A devices.

Below, using the U.S. 2008 NEC as an example we will list the locations where GFCI devices are required in residential properties.

The NEC also requires class A GFCI's to be installed on all 5-Amp and 20-Amp 120V utility receptacles ("electrical outlets") in high risk commercial locations such as in restrooms, kitchens, b asements, roofs, and outdoor receptacles.

The U.S. NEC has required GFCIs in various locations since 1971, or beginning in 1965 if we include underwater lighting, with the latest updates and changes to GFCI requirements in the 2014 NEC.

2014 NEC 210.8 GFCI Protection for Personnel, Dwelling Units

Excerpting from the NFPA,

GFCI protection is required by the 2014 NEC for newly installed and replacement 15 and 20 amp receptacles on kitchen countertops, in bathrooms, outdoor areas, unfinished basements and crawl spaces, garages, boathouses, laundry areas, and within 6’ of sinks, bathtubs and shower stalls.

GFCI protection is also required for certain appliances that have a history of being a shock hazard. Drinking fountains, vending machines, dishwashers and boat hoists are examples of appliances that require GFCI protection.

In 2014 additional details on GFCI protection were added to prior code specifications such as the following: [Note that this is an example, not a complete citation of the entire 2014 NEC code on GFCIs]

Any 125 V, single-phase, 15- or 20- amp receptacle within 6 ft. of the outside edge of a sink in a dwelling unit must now have ground-fault circuit-interrupter (GFCI) protection. This requirement is now for kitchens as well as other areas of the dwelling unit.

This includes receptacles for a garbage disposal, refrigerator, or range hood, if they are within 6 ft. of the sink. The distance does not have to be horizontal, so a receptacle on a kitchen island would require GFCI protection if the shortest route to the sink was less than 6 ft.

2008 National Electrical Code (U.S. NEC) Changes Affecting Ground Fault Circuit Interrupters GFCI's

NEC 210.8 is the code section pertaining to GFCI's. (AFCI's are addressed in NEC 210.12.). These GFCI requirements are intended to address residential electrical wiring using 15A or 20A 120V electrical receptacles and circuits. Heavier-duty circuits such as a 30A welder circuit are excluded.

Basically GFCI protection requirements have been expanded to all basement, garage, and accessory building receptacles, and a wording change to drop "receptacles" and keep "outlets" expands GFCI coverage in other areas.

For 2008 the NEC deleted Nos. 1 and 2 to 210.8(A)(2) and Nos. 1 and 2 to 210.8(A)(5) from the prior NEC version.

210.8(A)(2) & (A)(5): Expanded GFCI protection requirements by deleting exceptions for receptacles that are not readily accessible and receptacles located in dedicated spaces to supply an appliance.

Deleting "receptacle" and leaving "outlet" in the NEC expands the required coverage of any device being discussed. That's because a "receptacle" is taken to mean an electrical outlet (a wall socket) while "outlet" is any place in the electrical wiring system from which electrical power is taken (a ceiling fan, a hard-wired smoke detector, etc.).

• 210.8(B)(4): Expanded GFCI protection requirements to include all outdoor 15- and 20-ampere, 125-volt receptacles, and added a conditional exception to permit use of assured equipment grounding conductor program in industrial establishments.

• 210.8(B)(5): Added GFCI protection requirements for all 15- and 20-ampere 125-volt receptacles installed within 6 ft of the outside edge of sinks, and added exceptions for receptacles in industrial laboratories where the loss of power would introduce a greater hazard and for receptacles in patient care areas where critical care equipment may be utilized.

Basement GFCI changes: The GFCI protection requirements for receptacles in basements, garages, and accessory buildings have been expanded to all 125-volt, single-phase, 15- and 20-ampere receptacles regardless of accessibility or movability of an appliance from one location to another. - Minnesota Electrical Association

A Summary of Current (2008) Residential Ground Fault Circuit Interrupter GFCI Requirements

GFCI's are required safety devices to be installed in the following locations:


Continue reading at AFCI GFCI TESTING & SAFETY or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BUILDING CODE DOWNLOADS - free downloadable PDF files of building codes & standards


Or see AFCIs vs. GFCIs - what's the difference between an arc fault circuit interruptor and a ground fault circuit interrupt or?



See FREEZE-PROOF A BUILDING where we describe GFCI protection on heat tape circuits powering heat tapes for manufactured and mobile homes.

Similar issues regarding building water entry control are discussed at SUMP PUMP PROTECTION




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