What is Ground Fault Circuit Interrupter (GFCI) and How it Works?

At home or outside, there is no way can we do without electricity and electrical devices. These are the indispensable necessities of our modern day lives. But sometimes their accidental “touch” can give a painful shock resulting in serious injuries which at times, sadly enough can have fatal consequences.

Do you know?

Thousands of children and adults are critically injured and electrocuted annually from electrical hazards in their own homes.

According to the National Fire Protection Association (NFPA), home electrical problems account for more than 51,000 fires each year, resulting in more than 490 deaths, 1,400 injuries, and $1.3 billion in property damage in the United States (US).

Of the over 400 electrocutions in the US each year, approximately 180 are related to consumer products.

A fewer than 200 people die annually from household electrocutions.

Electricity is the cause of over 140,000 fires each year, resulting in 400 deaths, 4,000 injuries and $1.6 billion in property damage.

Total economic losses due to electrical hazards are estimated to exceed $4 billion annually.

Causes of Electrical Hazards

Apart from ever–increasing use of electrical power and outdated home electrical systems lacking capacity to handle modern electrical appliances and devices, wiring hazards are a major cause of electrocutions and home fires.

Misuse of surge suppressors, power strips and extension cords is also a cause of electrocutions and fires.

Don’t worry: Electrical Hazards are avoidable!

Incidents of electrical shock are avoidable for sure. For making electrical devices “shock free” and eliminating chances of fires, electrocutions and injuries to users, all one needs to do is eliminate electrical hazards with affordable devices.

Ground Fault Circuit Interrupters (GFCIs): Shield against electrical hazards.

When it comes to preventing electrical fires and keeping your family members especially kids safe, a GFCI is the top home safety device to have.

No home is safe without proper wiring . Properly installed and used GFCIs form an important part of household electrical safety.

Related Post: How to wire a GFCI Outlet? – GFCI Wiring Circuit Diagrams

What is GFCI?

A GFCI (Ground Fault Circuit Interrupter) is an automatic device that offers personal protection against lethal electrical shock or electrocution.

It is a special electrical receptacle or outlet that can stop electrical power within milliseconds as a safety precaution.

Let’s see how?

It trips electrical circuits whenever it detects ground faults or leakage currents. So when a person’s body starts to receive a shock, the GFCI senses this and cuts off the power before he or she can get injured.

In general, GFCIs are installed wherever there is the potential for contact between a person and an electrical appliance in or near moisture, water, or water pipes.

One needs to ensure that GFCIs are installed in his or her kitchen, bathrooms, workshop, basement, garage, swimming pools, hot tubs, outdoor outlets and fixtures, and any other areas where water and electricity are likely to come in contact.

GFCIs are especially useful for cord-connected appliances and equipment used outdoors or near water.

Related Post: How to Wire GFCI Combo Switch and Outlet – GFCI Switch/Outlet Wiring Diagrams

How GFCI Works?

Simply put, usually a normal electrical outlet has two vertical slots and a round hole just below them. The larger “left slot” corresponds to “neutral and “right slot” is called “hot”. The third, round hole is the “ground”.

Normally, electricity flows from hot to neutral in the outlet. The GFCI works by measuring the current leaving the hot side of the power source and comparing it to the current returning to the neutral side.

If they are not equal, this means that some of the current is flowing along an unintended path possibly through water or through a person.

The GFCI detects imbalance in the current flowing from hot to neutral, imbalance in the current flowing from hot to neutral and quickly cuts off electricity, thus reducing the risk of electrical shock.

The sensor inside a GFCI detects the difference between the current flowing to the appliance and the current flowing from the appliance.

If the electricity flowing into the circuit differs by as small as 4 or 5 milliamps from that returning, a GFCI quickly turns off all power by tripping a relay within it within a few hundredths of a second, much before the user hardly feels the shock.

When the problem is corrected, GFCI’s can later be reset to restore power to the affected circuit.

If the problem still exists and GFCI continues to “sense” the difference in the amount of electricity flowing into the circuit to that flowing out, it will not reset.

Related Post: Wiring of the Distribution Board with RCD (Residual Current Devices)

Types of GFCIs

Three types of GFCIs are commonly used in homes – the GFCI outlet, the GFI circuit breaker and the portable GFCI. All of these GFCIs perform the same function but each has different applications and limitations.

1. The GFCI outlet:

It is like a standard electrical outlet and protects any appliance plugged into it. The GFCI outlet can also be wired to protect other outlets that are connected to it.

2. GFCI Circuit Breaker:

It controls and protects an entire circuit, and is installed as a replacement for a standard circuit breaker in a home’s main circuit board. Compared to multiple GFCI outlets, one GFCI circuit breaker can protect the entire circuit which may include all bathrooms or all outdoor fixtures.

Precautions to take: The GFCI circuit breaker should match the requirements of main electrical panel. For an older panel that utilizes fuses, GFCI outlets must be used instead of a GFCI circuit breaker.

3. Portable GFCI:

It is used for mobile applications and can work as well as the ones installed in a house. Portable GFCIs are frequently used by contractors on worksites. But Portable GFCI protection could also be put to use whenever electrically-powered equipment is used in garden related works and when using electric tools in and around the house.

Precaution to take: Portable GFCIs should not be used in place of permanent ones in home. They are intended to be used only in situations where you must bring power from an unprotected outlet into a hazardous situation.

Applications of GFCI

The National Electrical Code (NEC) requires GFCIs to be installed at following spots at home and outside:

Underwater Pool Lighting

Outdoor Receptacles

Bathroom Receptacles

Garage Receptacles

Kitchen Receptacles

Crawl Spaces

Unfinished basements

Wet Bar Sinks

Laundry Receptacles

Utility Sinks

NEC Code Requirements for GFCI



The NEC Code Requirements for GFCIs are aimed at providing protection to anyone who plugs into an electrical system. As per the NEC Code, the installation of GFCIs is a must in following areas:• 210.8(A) Dwelling Units

210.8(A) Dwelling Units

406.3(D)(2), (3) Receptacle Replacement

424.44(G) Electric Space Heating Cables

511.12 Commercial Garages

517.20(A) Healthcare Facilities

525.23 Carnivals, Circuses, and Fairs

527.6 Temporary Installations

547.5(G) Agricultural Buildings

555.19 Marinas and Boatyards

680.32 Swimming Pools, Storable

680.62 Therapeutic Tubs

680.71 Hydromassage Bathtubs

620.23, 620.85 Elevators and Escalators

680.43, 680.44 Spas and Hot Tubs

680.22(A), 680.23, 680.27 Swimming Pools, Permanent

680.51(A), 680.56(A), 680.57 Fountains

Thousands of lives saved:

Since the 1970s, GFCIs have saved thousands of lives and have helped cut the number of home electrocutions in half.

If GFCIs were installed in older homes, experts suggest 70 per cent of the electrocutions that occur each year in the home could be prevented.

Installing a GFCI in every home and workplace could prevent nearly 70 per cent of the approximately 400 electrocutions that occur each year.

Author Bio:

Jeson Pitt is a professional electrician with a keen interest in electrical products and how they work. He spends much of his time delving into the world of new electrical technologies and innovations in the industry, polishing his skills and expertise, as well as sharing his thoughts and learnings with other enthusiasts. Jeson works as an online marketing manager for D&F Liquidators, a leading electrical products supplier in CA.

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