Ground Fault Circuit Interrupters (GFCI's) 

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Electricity and water don’t mix however our lifestyles demand we have blow dryers in the bathroom, irons near the laundry, toasters near the sink, and even power tools in a possible rainy backyard. Electrical safety authorities became concerned starting in the 1960’s with the number of personal injuries due to electricity and water and started to require the install of ground fault circuit interrupters (GFCI’s) to prevent injuries and deaths.


What is a Ground Fault Circuit Interrupter (GFCI)?

A GFCI is a safety device on an electrical circuit that can constantly measure the electricity in both the hot and neutral lines of a circuit at the same time. If it detects a difference in the electricity between each side, it presumes there is a leak and it shuts the circuit off. GFCI’s measure the electricity leak so quickly that it can detect an electrocution nearly instantly which is why it is such an effective safety device.


Doesn’t a GFCI Do the Same Thing as a Breaker or Fuse?

No. Breakers and fuses are designed to protect our circuits from becoming overloaded. Overloaded circuits happen when we are trying to use too much power (see this article on kitchen outlets), we drive a nail accidentally into the wire creating a short, or an appliance fails resulting in a short circuit. Overloaded circuits can melt wire and wire insulation and start electrical fires.


The human body can be killed with as little electricity as 50 milliamps (0.05-amps). Typical household fuses or breakers won’t trigger unless there is at least 15 or 20 amps of electricity which is why they are not effective at preventing electrocution. GFCI’s are looking for a much smaller electrical ‘leak’ than a breaker of fuse adding an extra measure of safety protection to the circuit than a breaker or fuse alone can provide.


What Circuits are Often Protected by a GFCI?

Electricity, such as lightning, is always trying to reach a discharge point which universally is called ‘ground’ because the earth is a neutral point for electricity to dissipate. Our household water systems have piping and connections that are often connected to ground which makes them a desirable path for electricity to follow. Combined with the fact that dry human skin is a much better insulator against electricity than wet skin, and we have the dangerous situation where a wet human can become a good conductor of electricity to ground.


GFCI’s circuits are found in places where water, humans, and electricity may meet. Commonly, bathrooms, exterior, kitchens, laundry, whirlpool tubs, hot tubs, swimming pools, and garages. Electrical codes dictate where these GFCI’s must be located. In the earliest codes, it was often just bathrooms and exterior but in some modern homes today they are found in all potentially wet areas.


Where do I Physically Find a GFCI in My Home?

Breaker Style GFCI

This GFCI breaker provides GFCI protection to the whole circuit. Test button is on the breaker.

GFCI’s can be integrated into a circuit breaker allowing the tripping feature to turn the breaker off to stop electricity in the circuit. While these were common in the 70’s and 80’s, they are less common today as the more common outlet based GFCI’s are a much less expensive option and more convenient to test and reset circuits. GFCI’s at circuit breakers tend to be well labelled and have a ‘trip’ button on them. Do not confuse arc fault circuit interrupters (AFCI’s) with GFCI’s (see our information on AFCI's).


Only one GFCI device needs to be on a circuit in order to protect the entire circuit. It is very common for example for all bathrooms and an exterior plug in a 70‘s home to be connected to one GFCI outlet. In kitchens, one GFCI plug may protect multiple outlets in reach of the sink.


Why is there a Test Button on the GFCI?

Outlet Style GFCI

Only one of these is needed on a circuit to protect the entire circuit.

GFCI’s are a sensitive mechanical device and in time, corrosion, dust, or even an originally defective GFCI may not operate in an emergency situation. GFCI’s should be tested monthly by simply pressing the ‘test’ button on the GFCI outlet or the breaker. When this button is pressed, a test ‘leak’ is given to the circuit and an audible snap should be heard as the circuit is turned off. Use a lamp or nightlight to confirm the circuit is off then you can turn it back on by pressing the ‘reset’ button at the GFCI outlet or by turning the breaker back on.


During home inspections, we often run across GFCI’s that do not trip when tested or respond very slowly to a test (it should be instant). In these cases, the GFCI is not functioning correctly and replacing the GFCI is a matter of life safety and should be done immediately. 


Is an AFCI the same as a GFCI?

No, an arc fault circuit interrupter (AFCI) is a very different electrical safety device than a GFCI. (See our article on AFCI's)


Final Thoughts

GFCI’s are a very effective safety device in the home and they are also very inexpensive. Best practice is to have these located anywhere within 3’ of a water source or in any wet environment but at a minimum. If you need any help identifying GFCI circuits, you should always call in a professional home inspector or electrician and as always with electricity, leave it up to the professionals to make any changes.


By James Bell - Owner/Operator of Solid State Inspections Inc.