If there is enough of an amperage difference between the wire with current running through it and the neutral wire, the GFCI will trip, thereby stopping the current altogether. This is to ensure that all of the amperage stays within the closed circuit.

If there is any difference between the two that could indicate that amperage may be flowing somewhere in the living area of a house (such as through a person). If there is a difference, as a safety precaution the GFCI will trip thereby shutting off the circuit entirely, eliminating the danger of electrocution. GFCIs are usually required around areas that are more likely to get wet or experience pooling water.

GFCIs are located in areas that are more likely to get wet due to the fact that water offers less resistance for electricity and if that water is in contact with a person then any electrical shock will be magnified and may result in much greater injury or death.

See the below list for common areas that require GFCIs for newly installed receptacles on 15 and 20 amp circuits:

• Any outlet is connected to a dishwasher
• Within 6 feet of any sink, bathtub or shower stall
• Laundry rooms
• Unfinished basements
• Crawl spaces
• Outdoor outlets
• Garages
• Kitchen Countertops

GFCI installation

There are two ways to install a GFCI. One way is at the the service box as a GFCI breaker. The second way is at the receptacle. Both have advantages and drawbacks depending on the setup of your home, protection needed or desired and code adoption by municipalities.

GFCI Breaker
A GFCI breaker is installed directly to an electrical panel and offers ground fault protection on all of the outlets on the circuit that breaker protects. While more expensive than a single GFCI receptacle, a GFCI breaker is appropriate for the below reasons

• Accessibility issues with GFCI receptacle. A GFCI must be accessible so it can be reset if it is tripped in order to restore power to the receptacle (and any other receptacles that are affected on that same circuit. Therefore a GFCI must be in a place that is readily accessible (cannot be behind an appliance or any large pieces of furniture)
• Multiple receptacles require protection
• When a GFCI and AFCI are required on the same outlet (this would have to be a combination GFCI/AFCI breaker)
• GFCI receptacles are sometimes larger than the receptacle that it's replacing. Therefore, a receptacle replacement may not be a practical option so a GFCI breaker can be installed as a substitute

GFCI Outlet
A GFCI outlet is generally cheaper than a single GFCI breaker so if you need protection on only one outlet then the outlet variety may be the appropriate choice. Additionally a GFCI receptacle can be wired so it offers protection for all downstream appliances and receptacles as well. Installation of GFCIs at an outlet have the below advantages:

• Cheapest option if only one receptacle needs protection on a circuit
• Can be wired to protect other downstream receptacles and appliances on the same circuit
• Can be reset at the receptacle so if there is a ground fault then you will not need to go to the electrical panel to for a reset (which is the case with a GFCI breaker)

Finally GFCI requirements will always be dependent on whichever codes your local municipality has adopted. Maryland has adopted the 2017 National Electrical Code but if you live in another state that may not be the case.