GFCI (ground fault circuit interrupter) receptacles were invented in 1961 by Charles Dalziel, a professor of electrical engineering at the University of California. These outlets are not the same as AFCI which are designed to address fire hazards. Instead, GFCI outlets are intended to prevent accidental electrocution by cutting off the flow of power when they detect that it is flowing along an unintended path (such as through water or a person) to prevent electrical shock and electrocution.
How They Work
By monitoring the difference in current flowing in and out of an appliance or tool, GFCI outlets will automatically shut off the flow in as little as 0.025 seconds if a difference exceeding 5 milliamps occurs. Once it is safe, they can be turned back on by pressing the Reset button found on the unit.
As they will protect you whether or not the wiring is grounded, they can be used to replace old two-prong outlets with three-pronged outlets without additional wiring be required. Safer than using an adapter, this is a great solution for older homes that do not have grounded wiring.
This type of outlet is usually installed where they may accidentally come into contact with waterdue to the potential for power leakage and electrocution.As such, GFCI receptacles are required by the National Electric Code in:
- Crawl spaces;
- Unfinished basements; and
- Outdoor areas or basements.
Because GFCI outlets will shut off the flow of electricity if there is a discrepancy in the power flowing in and out of the outlet, they are not recommended for certain types of appliance and lighting due to the high potential for false positives (tripping the safety mechanism when it is not necessary.) To prevent this nuisance tripping, keep GFCI circuits shorter than 100 feet and do not use these outlets for fluorescent lighting or permanently installed electric motors.
Simply having GFCI receptacles installed is not enough as power surges and lightning can damage their internal circuitry. To ensure they are functioning as intended, perform monthly tests on all of your GFCI outlets:
- Press the Reset button to ensure the outlet is on.
- Plug in a light and turn it on.
- Press the Test button on the GFCI outlet and the light should turn off.
- Press the Reset button on the GFCI outlet and the light should turn back on.
Used properly, GFCI outlets can save your life so take a look around your home and make sure you have them installed wherever necessary.