Ground Fault Circuit Interrupters — Fact and Fiction


Everywhere in Canada a Ground Fault Circuit Interrupter (GFCI) is required in different parts of homes and businesses. A whole article on the building code requirements and interpretations could be written, but today I want to focus strictly on the facts and fictions surrounding GFCIs.

In layman's terms, a GFCI measures the flow of current between the wires (hot and neutral) that are powering whatever is connected to the circuit. This is the same regardless of how simple or complex the circuit might be. The GFCI “trips”, cutting off the flow of electricity, when there is a current flow imbalance between those wires. It assumes the current is going through you to the “ground” and cuts the flow off to prevent or reduce injury.

Here are some facts and fictions you should know:

1. A GFCI can be used to protect computers and other sensitive electronic equipment.


A GFCI is not designed to protect equipment connected to the circuit. Granted, if there is a problem with the equipment and the GFCI trips it could prevent further damage, but the sole purpose of the GFCI is to protect humans from electrical shock. This type of equipment is protected by installing a surge suppressor to protect for high voltage spikes or an Uninterruptable Power Supply (UPS) to protect from low voltage (brown outs).

2. A GFCI is better at protecting wires than the breaker because it trips at a lower level.


The job of the breaker is to protect wires from being stressed by excess current. Even in a combination GFCI/breaker, the overcurrent and the fault protection elements are separate.

3. A GFCI receptacle provides a ground for an old style two-wire circuit.


Although the Canadian Electrical Code (CEC) recommends the installation of a GFCI when replacing ungrounded type receptacles (rule 26-700(8)), the GFCI does not provide a ground and anything that is connected to the GFCI or further downstream on the same circuit is still not “grounded”. Please consult with a reputable electrician for advice on replacing/upgrading receptacles on old two-wire circuits.

4. A GFCI will trip if I drop my hair dryer into the sink or tub full of water.

Fact, but not always.

We all know that water and electricity don't mix and that when the two meet the GFCI will normally trip. However, there are situations where it won't. This can happen in new construction or renovations where both the water lines and the drain lines are plastic. The sink or tub acts as an insulator; meaning there is no direct path to ground for the current to flow. Think of it as a plastic bucket sitting on something not touching the ground. In these situations the GFCI does not detect an imbalance between the two wires and doesn't trip. That doesn't mean that the installation is faulty, it just means there is no direct path for the current to flow. In most cases if the water was flowing or if you got caught in between the sink and some metallic object that is grounded, the GFCI would trip and save your life.

5. A GFCI will prevent you from getting an electrical shock.


Even though a GFCI is manufactured to detect relatively tiny imbalances, no more than 4 milliamps (mA) of current, it is still possible to be shocked before it trips. The National Electrical Manufacturers Association (NEMA) has an excellent presentation called Understanding GFCIs that illustrates the threshold at which you could still receive a shock. With a GFCI, even if you still get a shock it shouldn't be enough to be harmful in a vast majority of cases. You likely won't even notice it if it does happen.

6. A more expensive GFCI receptacle or breaker is better than a cheap one.


Even though GFCI related products are supposedly manufactured to the same specifications, over the years I have noticed differences in the quality provided by certain manufacturers. As a contractor I am the last guy who wants to spend money on “name brands” if it is all the same. Almost all companies will tell you why their GFCI is better than their competitors'; however in my experience the GFCI receptacles and breakers made by the big names like Hubbell, Leviton, Pass & Seymor, and so on are of a far better quality than what you can buy off no-name suppliers on the internet. They tend to be more robust in multiple trip and overcurrent situations, as well as more durable during hard usage and exposure.

7. A GFCI will save lives.


Despite some of the fictions noted above, it is a fact that a properly installed GFCI receptacle or breaker will save your life. Research from both the Canadian Standards Association (CSA) and the Underwriters Laboratory (UL) show that both injury and death by electrocution has decreased from the introduction and increasing use of GFCI devices.

I always tell my clients that the GFCI breaker or receptacle is a life-saving device and should be treated as such. It may seem simple to install or replace, but I always recommend that you seek advice from a trained professional. That last thing you want is an improperly installed life-saving device killing you.

About the Author

John Kuehnl-Cadwell is a Master Electrician and an owner of Datawise Solutions Inc., an electrical contracting company located in Ontario. He has been licenced as a Journeyman Electrician since 1992.

Posted by: John Kuehnl-Cadwell
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