GFCI Prevention And How It Works

Posted on: August 19, 2016
By: Alan O'Neill
Posted in: Electrician

Home Inspections and Ground Fault Circuit Interrupters (GFCI) For Houston Homeowners

One of the most important aspects of being a home inspector is detecting safety hazards. One area of the electrical inspection in particular is Ground Fault Circuit Interrupters (GFCI). Depending on which state you live in or which inspection association’s standards of practice you are following, the majority of them address GFCI.

This video shows Prevention of GFCI and Protecting a Home

How GFCI’s Work

You may know in what situations the NEC requires you to install a ground-fault circuit interrupter (GFCI), but do you know how a it works? A GFCI is specifically designed to protect people against electric shock from an electrical system, and it monitors the imbalance of current between the ungrounded (hot) and grounded (neutral) conductor of a given circuit. Don’t let the name confuse you — these devices will operate on a circuit that does not have an equipment-grounding conductor.

A ground-fault circuit interrupter (GFCI) is the only protection device designed to protect people against electric shock from an electrical system. Because of this, we need to understand what a GFCI is, how it works, and what its limitations are.

We need only to look to the NEC for the definition of a GFCI. The NEC defines it as “a device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.”

A GFCI protection device operates on the principle of monitoring the imbalance of current between the circuit’s ungrounded (hot) and grounded (neutral) conductor. It does not monitor the grounding conductor, and so it will still operate in a circuit without a ground.

However, a GFCI doesn’t give you a license to be careless. Severe electric shock or death can occur if you touch the hot and neutral conductors in a GFCI-protected circuit at the same time because the current transformer within the protection device won’t sense an imbalance between the departing and returning current and the switching contacts will remain closed.

GFCIs will also fail if you wire them improperly. The most important thing to remember when wiring them is to connect the wire originating at the breaker to the line side of the GFCI and the wire connecting downstream to the load side of the device. The GFCI terminals are clearly marked “Line” and “Load.” As an added safety improvement, one manufacturer markets a 15A, 125V receptacle with a built-in line-load reversal feature that prevents the GFCI from resetting if the installer mistakenly reverses the load and line connections.

One final thought on GFCI protection: Press the test button of the protection device to ensure it turns off the power to the connected load. You should do this whenever you install one, but also before relying on it to protect you when using it. Do not assume a GFCI protection device is operational unless you properly test it!


Ground faults are very dangerous when a person becomes part of the electrical path or circuit to ground. When electrical current escapes through a faulty connection, it seeks a path to ground. The person touching that connection while standing in a wet or damp environment, or touching a sink or tap, becomes a good path to ground. The electrical current flowing through a person’s body to ground can result in serious injury or death. Call (713) 812-7070 us for your home service and repair needs.

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