Before knowing what a GFI is, you should know one thing: GFIs can save your life. A GFI, also known as GFCI, stands for Ground Fault Circuit Interrupter; and it's a type of outlet that protects against electrical shock. GFI outlets are required in most states, and homeowners should change all older version outlets to GFI outlets.
GFI plugs or outlets are so important that I recall the sale of our old home being held up until we switched some of our outlets to GFIs. In homes built to comply with the National Electrical Code, GFCI protection is required for most outdoor receptacles (since 1973), bathroomreceptacle circuits (since 1975), garage wall outlets (since 1978), kitchen receptacles (since 1987), and all receptacles in crawlspaces and unfinished basements (since 1990). (Source: DoItYourself.com).
GFIs are inexpensive to purchase, (about $5 for one) and inexpensive to install. Find an electrician to install GFI outlets in your home. At the very least, GFI outlets should be installed where there is close proximity to water, such as in a kitchen or bathroom.
How a GFI/GFCI Works:
The GFI has a sensor inside that detects changes in current to the appliance that is connected to it (such as a toaster or blow dryer) by comparing the current flow to the appliance and the current flow from the appliance. If there is a potentially dangerous drop off in the current, then the GFI turns off all power by tripping a relay within it in less than one second. If a GFI turns off your appliance then you will need to unplug it, press the reset button and everything should be back to normal. A GFI outlet has two buttons:a test button and a reset button.
If a problem persists or you think something may be wrong with the electrical system in your home, then make sure to call an experienced electrician. If there is a serious problem with the affected circuit and the GFI will not reset, this is a sure sign to call an electrician to help diagnose the problem. In short: GFI outlets turn the power off before a shock can occur.
Testing Your GFI:
About every month or so you should consider testing your GFI outlets to make sure they function properly. Simply plug in a small appliance or even a clock or lamp, make sure it's on and then press the test button. If the GFI works properly then the clock or lamp should lose power and turn off, and the reset button on the GFI outlet should pop out, indicating the power is out. If the reset button pops out but the light does not go out, the GFCI has been improperly wired. Contact an electrician to fix the problem. If the reset button does not pop out, the GFCI is defective and should be replaced.
If the GFCI is functioning properly and the lamp goes out, press the reset button to restore power to the outlet. You can also purchase a GFI tester, available at most hardware stores. It plugs into the GFI outlet, and will supply you with information about yourconnections, indicating wiring problems and/or the condition of the GFI. This testing method is probably best for advanced do-it-your selfers.
Kinds of GFCI:
There are three kinds of GFCIs that can be used in homes: receptacle, circuit breaker and portable.
Receptacle: This is the basic GFI outlet, as pictured above, which is installed inthe place of older outlets.
Circuit Breaker: These are installed in a panel box in the circuit breaker to give protection to selected circuits. The circuit breaker GFCI can shut off electricity in theevent of a problem and will also trip when a short circuit or an overload occurs.
Portable: Portable GFCIs are used when there is no GFI nearby. For example, you may want to plug your electric lawn trimmer into a GFI outlet, but your garage does not have one. Simply plug in the portable GFI to the outlet and then plug in the trimmer.
For additional GFI information, visit: GFI questions and answers.