The purpose of a GFCI receptacle is to trip when it senses that any electric current has leaked from the intended circuit, which may be causing someone to be shocked, and quickly to cut off the current to avoid possible electrocution. GFCI protection is required for receptacles in all the wet areas of a home, such as the kitchen, bathroom, garage, laundry and exterior, along with spa tubs and pools.

    The device will still function properly if the ground slot is not connected to a ground, which we see occasionally in pre-1960 houses that have GFCI-receptacles in the kitchen and bathrooms supplied by ungrounded two-wire cables. The GFCI is considered an alternative to grounding by the National Electrical Code (NEC) and a two-slot ungrounded receptacle is allowed to be replaced with a three-slot GFCI receptacle; however, the receptacle must be marked as having “NO EQUIPMENT GROUND” on the cover plate. This is because, although it is considered safe, some appliances require a ground connection in order to work properly, and the notification alerts a user of the receptacle. Manufacturers of GFCI receptacles include a sheet of small stickers in each box to help you comply with this safety requirement.   Because a GFCI-receptacle at the head of a string of receptacles will provide shock protection for all the receptacles downstream, it is typical for a GFCI-receptacle in one bathroom to protect the receptacle in another bathroom that does not have a GFCI-device. Also, one GFCI-receptacle in a kitchen can protect several others nearby. All the protected receptacles must have a “GFCI PROTECTED OUTLET” sticker on the cover plate, and any protected ungrounded receptacles are required to have a “NO EQUIPMENT GROUND” sticker too. 

 
   Although an ungrounded GFCI receptacle will function properly, it cannot be tested with a three-light circuit tester with a “GFCI TEST” button or most electronic circuit testers, like the ones shown below, because they shunt a small amount of current to the ground slot to simulate a ground fault. Unfortunately, when there is no ground connection the test won’t work. But the test button on the front of the GFCI-receptacle will trip when tested, and that is how we verify that they are alright.

    Also, see our blog posts What electrical hazards does a Ground Fault Circuit Interrupter (GFCI) NOT protect against? and Does a receptacle outlet that is not readily accessible still need GFCI protection? and Where are GFCI receptacle outlets required?

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Here’s links to a collection of our other blog posts about AFCI and GFCI RECEPTACLES AND CIRCUIT BREAKERS:

• Does a septic pump or sump pump require a GFCI-receptacle?

 • What is the difference between what trips a GFCI (ground fault) receptacle and a circuit breaker?

• Are Ground Fault Circuit Interrupters (GFCIs) really necessary and worth the trouble? 

• What is the code requirement for GFCI protection for receptacles near a wet bar sink?

• When was GFCI-protection for kitchen dishwasher receptacle outlet first required? 

• When did arc fault circuit interrupter (AFCI) breakers first become required?

• Does a washing machine receptacle outlet require GFCI protection?

• My spa tub stopped working. What's wrong?  

• How do I identify a combination AFCI (CAFCI) circuit breaker? 

• What does "listed and labeled" mean for an electrical component?   

• What is the difference between GFCI and AFCI circuit breakers?  

• When were GFCI receptacle outlets first required?

• What happens when you press the "TEST" button on a circuit breaker in an electric panel?

• What is the difference between the electric service to a mobile home and a site built home? 

• Why is there a wall switch next to the furnace or indoor unit of the air conditioner in the garage?

• What is a Dual Function Circuit Interrupter (DFCI)? 

• How I can tell if a receptacle outlet is tamper resistant?

• What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?  

• What is the difference between "grounded" and "grounding" electrical conductors? 

• What does it mean when a wire is "overstripped" at a circuit breaker?

• Why is there a GFCI breaker in the electric panel for the bathroom shower light and exhaust fan?

• What is the switch on the wall with two pushbuttons? 

• How far apart should kitchen counter receptacles be spaced?  

• How far above a kitchen countertop do electrical outlets have to be? 

• How is it possible to provide both GFCI (Ground Fault Circuit Interrupter) and CAFCI (Combination Arc Fault Circuit Interrupter) protection for kitchen and laundry circuits?

• My bathroom electric receptacle/outlet is dead and there are no tripped breakers in the electric panel. What's wrong?  

• My GFCI reset button is hard to push and won't reset. What's wrong?

• Why do some breakers in my electric panel have a "TEST" button on them?

    Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.