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An overview of GFCI Ground-fault circuit interrupter

Normal looking outlet you say? Well, this puppy is a 15 amp GFCI outlet and costs much more than your average 15 amp outlet, but itprotects you in wet areas, i.e. bathroom & kitchen. Protection: I'm for it. (photo by zoolpsu via Flickr)

Protecting persons from ground faultsThe NEC requires that Ground-Fault Circuit Interrupters (GFCIs) be installed in many different rooms andlocations in both public and private buildings. They are now required in bathrooms, kitchens, appliance rooms orspaces, and garages.

In addition, they are required in basements, near swimming pools, hot tubs, or fountains, and in outdoor receptacles.While these requirements are most commonly met with GFCI dual receptacles, they can also be met with GFCIbranch circuit breakers.

GFCI circuit breakers and receptacles protect persons from ground faults.

These are typically caused by hot conductors with inadequate insulation coming in contact with an ungroundedmetal object such as an appliance cabinet. If the metal surface is not electrically grounded, a ground faultwill becreated.

Any person touching that metal object while standing on a conducting surface ( for example, a wet floor) could get a

The Square D by Schneider Electric QO Qwik-Gard 20Amp Two-Pole GFCI Circuit Breaker is intended for

protection of entire branch circuits where dAmp-locationshock hazards may exist, providing overload and short-

circuit protection of your electrical system.

fatal electrical shock because his or her body has effectively become the grounding conductor.

The current required to trip a standard circuit breaker is many times greater than the amount needed to inflict a fatalshock. It was clear that smaller, less expensive, and more sensitive GFCI circuits were needed because early GFCIcircuits were clumsy and expensive.

However, later versions that included solid-state electronics were small and could be mass-produced cheaply.

To comply with UL Standard 943, Class A, a GFCI must trip in the presence of a ground fault as small as 5 mA (1mA) within about 25 ms. The NEC requires that GFCI protection be available in the locations previously listed.

This can be accomplished by installing approved GFCI receptacles at those locations.

Alternatively, GFCI circuit breakers in the load center can protect downstream standard receptacles in branchcircuits serving locations where GFCI protection is required. GFCI circuits are now included in GFCI receptacles andminiature circuit breakers (MCBs).

GFCI circuit breakers have the same outline dimensions and areinstalled in the load-centers in the same way as standard units. Theonly visible difference is that they have two built-in leads.

Available in ratings from 15 to 60 A, the 15- and 20-A units arethe most popular.

Their amperage ratings must match the amperage ratings of thewire gauge of the branch being protected. One of the two leads of theGFCI circuit breaker is connected to the load neutral and the other,identifiable by its black-and-white stripe, is connected to the neutralbus to establish a zero reference.

The disadvantage of GFCI circuit breakers is that after a groundfault has been detected, a GFCI circuit breaker will disable theentire branch circuit. The branch circuit will remain inoperative untilsomeone finds and corrects the fault and then goes to the loadcenterto reset the circuit breaker manually. This can be awkward and time-consuming.

By contrast, under the same circumstances a GFCI receptacle willdisable only itself and any standard receptacles downstream of it, butnot the entire branch circuit. After correcting the fault, the protectedreceptacles can be reactivated manually simply by pushing the resetbutton on the face of the GFCI receptacle.

The NEC requirement that all outside outlets be GFCI-protected can be met with GFCI receptacles, but they arevulnerable to:

Water from rain,Snow,Lawn sprinklers, andCondensation.

Consequently, if used outdoors they must be protected by gasketed metal or plastic weatherproof enclosures.

An advantage of GFCI circuit breakers is that they can protect outside receptacles without the need forweather protection.

GFCI Outlet How it works and how to test (VIDEO)Cant see this video? Click here to watch it on Youtube.

Resource: Handbook of electrical design details Neil Sclater, J. E. Traister(Get this book from Amazon)

An overview of GFCI Ground-fault circuit interrupterProtecting persons from ground faultsGFCI Outlet How it works and how to test (VIDEO)