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What is GFCI- Ground Fault Circuit Interrupter

What is GFCI- Ground Fault Circuit Interrupter


Electrician installing GFI plug in kitchen.
Pamela Moore/E+/Getty Images

What is GFCI- Ground Fault Circuit Interrupter

What is a GFCI? A ground fault circuit interrupter is an electrical device installed to protect against severe electric shocks. GFCI’s could also reduce electrocutions and minimize electrical burns and shock injuries. A GFCI integrates a ground fault protection in receptacles where electrical equipment is near water or might be in contact with water. Ground fault circuit interrupter also detects ground faults and interrupts the flow of electric current. A GFCI is not and might not be used to replace a fuse.

How a GFCI Works?

A normal 120-volt outlet has two vertical slots and a round hole just below them or to the sides. Usually the left slot is larger than the right, and it corresponds to the neutral while, the right slot is called hot. The round hole is the ‘ground’. When the outlet is working properly the electricity is flowing from hot to neutral, and that’s when the GFCI enters into action. The GFCI measures the amount of current flowing from hot to neutral, so when there is imbalance, the circuit trips. Normally ad GFCI can detect variations as small as 4 milliamps, and it trips quickly cutting off electricity.

Where to Install a GFCI

A GFCI is required by the National Electrical Code and is required in:

  • Underwater Pool Lighting
  • Outdoor Receptacles
  • Bathroom Receptacles
  • Garage Receptacles
  • Kitchen Receptacles
  • Crawl Spaces
  • Unfinished basements
  • Wet Bar Sinks
  • Laundry Receptacles
  • Utility Sinks
Portable GFCI protection could also be required whenever electrically-powered equipment is used in garden related works and when using electric tools in and around the house.

Replacing a GFCI

Sometimes you will need to install a new GFCI where an old unprotected receptacle was installed. These receptacles can be replaced with one of the following:

  • Another non-grounding type receptacle.
  • · A GFCI-receptacle, if marked “No Equipment Ground.”
  • A grounding type receptacle, if GFCI protected and marked “GFCI Protected” and “No Equipment Ground.”

Three Types of GFCI’s

GFCI’s can be found in three different ways. The most common one is the GFCE receptacle, very similar to a common wall receptacle. In addition circuit breakers GFCI’s are used as replacement for standard circuit breakers, providing ground fault protection to all receptacles in that same circuit. The last type of GFCI’s are temporary, and they should not be used to replace regular GFCI.

How to Avoid GFCI Tripping

In some cases GFCI’s will trip, but not related to normal operation of the GFCI. Having a long circuit, longer than 100 feet, can cause the GFCI to trip. Also whenever the circuit has many splices, fluorescent lighting fixtures or permanently installed electric motors can cause the GFCI to trip. Before installing a GFCI, the loss of power might be considered when using the protection with freezers, garage door openers and others.

Does a GFCI is the same as an ACFI?

AFCI’s are used to address fire hazards, while GFCI are installed to prevent shock hazards. AFCI’s are required since 2020 for bedroom circuits in new residential construction. AFCI’s can be installed in 15 or 20 ampere circuits in a home and are available as circuit breakers. We expect soon to have combination devices including both AFCI and GFCI protection in one single piece.

GFCI National Electric Code Requirements

NEC requires that GFCI must be installed for the following areas:

  • 547.5(G) Agricultural Buildings
  • 525.23 Carnivals, Circuses, and Fairs
  • 511.12 Commercial Garages
  • 210.8(A) Dwelling Units
  • 424.44(G) Electric Space Heating Cables
  • 620.23, 620.85 Elevators and Escalators
  • 680.51(A), 680.56(A), 680.57 Fountains
  • 517.20(A) Healthcare Facilities
  • 680.71 Hydromassage Bathtubs
  • 555.19 Marinas and Boatyards
  • 406.3(D)(2), (3) Receptacle Replacement
  • 680.43, 680.44 Spas and Hot Tubs
  • 680.22(A), 680.23, 680.27 Swimming Pools, Permanent
  • 680.32 Swimming Pools, Storable
  • 527.6 Temporary Installations
  • 680.62 Therapeutic Tubs
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