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What is a GFCI Electrical Outlet?

Written by Brett Kayzar on Monday, 21 September 2009 7:00 pm
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As a home inspector I am often asked, "What is a GFCI Electrical Outlet?" Let us start with the name, GFCI stands for Ground Fault Circuit Interrupter. Now that answered all of your questions, right?

Ground Fault means that this type of receptacle, or outlet as they are more commonly known, can detect if electrical current escapes from the intended flow.

Circuit Interrupter means that this type of electrical outlet will trigger an automatic shutoff or reset switch within the circuit flow to protect you from any escaping electricity.

Simply put the GFCI electrical outlet's primary design is to provide additional protection from improper electrical flows which could shock or harm a person near the area around the outlet.

To better explain the principles behind how the GFCI works, let's take a step back to explain the general principles of your homes' electrical system. Much like your plumbing system, the electrical system brings in a "flow" or current of electricity into a location such as a light fixture to illuminate a bulb, or to an outlet whereby the electricity can be channeled into use to run an attached device like a kitchen toaster or bathroom hairdryer. Then any unused electricity "flows" back out safely from the light fixture or electrical outlet back into the electrical system of your home. Electricity flows into each location, and then any unused electricity flows back out, all in a continuous distribution process.

Incoming Power - the homes' electrical service uses primary supply wires, often called the "hot wires", to route the power current from the electrical meter through the panel's circuit breakers and then out to its intended locations for use through a series of wires, switches, and outlets.

Returning Current - again through the adjoining primary supply wires, often called the "neutral wires", all unused electricity is routed back to the breaker panel and ultimately back out into the originating electrical transformer and power grid from which it came.

Grounding System - since the early 1960's, most residential home electrical systems began adding a third wire called the "ground wire", as an additional or secondary neutral wire. This third wire works in conjunction with the neutral wire to make sure that all electrical currents stay routed within its fixture or device. The ground wire/system also routes electrical current back to the panel box should the neutral wire fail to carry the entire flow.

What is the GFCI's roll in the electrical system? If the electrical system is working properly the GFCI reset switch remains "on" or in the open position indefinitely. It is only when the GFCI outlet detects a loss of current, meaning electricity has found an alternate path, say through to your wet hands while using that hairdryer in the bathroom, then the GFCI switches "off" in a matter of milliseconds to shutoff the flow of electricity.

GFCI designs vary slightly, but most GFCI switches and outlets use a series of sensors to continually monitor the magnetic fields generated when electrical current is flowing in and out, and as long as the magnetic fields are equal or balanced at the in-flow verses out-flow, then the GFCI allows the flow to continue. If the magnetic field becomes unbalanced, that is when the outlet triggers the shutoff or reset of its internal safety switch. Some GFCI systems also measure for current loss detection, which also then triggers the need for a reset. The aim of the GFCI is to manage this reset locally at the area of use, such as near the bathroom sink for example; so that once the problem has been corrected the person can quickly reset the GFCI outlet/switch and resume activities. Build codes and standards vary among municipalities, but generally all exterior receptacles/outlets, pool & spa equipment, garage or basement outlets, bathroom outlets, wet bars and kitchen counter outlets should be connected to a GFCI. At a minimum, any outlet or switch within 5-feet of a water source should provide for GFCI protection. Note that older homes may not have GFCIs installed, but most electrical systems can be upgraded to add them as a retrofit and they are strongly recommended for added safety.

A standard home inspection process will typically look to see that GFCI outlets have been installed, and most inspectors will test the GFCI outlets to ensure they "trip or reset" properly. A simple hand-held electrical circuit tester can indicate whether or not an outlet is wired correctly, and most testers can safely trigger a reset function, thus indicating a protected circuit.

As always, home owner safety is one of the home inspector's primary goals, and checking for the safe operation of electrical outlets for GFCI protection is one of the services home inspections provide!

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