The ABC’s of a GFCI

The GFCI or Ground Fault Current Interrupter was invented by Charles Dalziel, an Electrical engineering professor at the University of California in 1961. A GFCI measures how much current is flowing from hot to neutral. If there is any imbalance, it trips the tiny circuit in the outlet and that cuts the power. Imbalances are caused by appliances in a wet environment, frayed or damaged electrical wiring, or some other electrical ‘leak’.

If you examine a GFCI outlet, the first thing you notice is that the left side is the larger slot. Left is neutral. Right is hot. The hole is ground.

Bathrooms, kitchens, outdoors-anyplace where water and electricity can meet is a good place for a GFCI outlet. As you walk around testing each of your GFCI outlets, take a moment and look to see if you can find any places in your home where there may be the potential for an electrical appliance to come in contact with water. If that electrical outlet isn’t a GFCI, you will want to upgrade, because any potential for shock is too much. It only takes the tiniest amount of electricity  and a fraction of a second to kill a human being.

Fortunately, this outlet, which was in an older home, didn't kill anyone.

Fortunately, this outlet, which was in an older home, didn't kill anyone.


How to test a GFCI


In order to test a GFCI, push the ‘reset’ button. On many devices the reset button is red, however, on some, the buttons are the same color as the outlet.  Then, plug in a testing device, such as a lamp. Press the ‘test’ button. If the light goes off, the test is a success. If the light stays on, the unit has been damaged.

Hit the reset button and the light should go on again.

If the light doesn’t go off when you hit ‘test’, the GFCI isn’t working. The GFCI may have been damaged by lightning or could fail because the circuitry of GFCI’s doesn’t have a long life. These units need to be replaced. This type of failure actually happens quite often, which is why they need to be tested every month.


Testing older models

Unfortunately, you have to test older models with a meter such as a circuit tester, which comes with a GFCI tester. (They cost about $10) The power will work on some older GFCI’s even if they fail the test, as counterintuitive as that may be. Post 2006-GFCI’s have a different set of specifications, and will simply stop working.

Replacing a GFCI, either an old model or swapping out regular outlets in unsafe  conditions isn’t difficult, but it’s much safer to leave it in the hands of a professional. What I tell my customers is that whether it’s one item, or ten items, we are always happy to come out and help them when they have an electrical issue.