If your house was built within the past few years, it must, by law, be equipped with ground-fault circuit interrupters, or GFIs. If it isn't, you are leaving yourself and your family vulnerable to dangerous electric shocks.
What's a GFI? Essentially, a very sensitive circuit breaker. Installed in your electric line, a GFI senses and compares the current flowing through the hot (black) wire and the neutral (white) wire. If all is well, the flow will be the same through both wires.
But if a ground fault exists in this circuit, current will leak from the hot wire to the ground. The flow through both wires will no longer be equal, the GFI will detect the difference and will immediately shut off the power.
Great, but how does this protect you from shock?
Let's say you're outdoors with your electric drill, fixing a downspout. If that drill has a frayed wire, current from that wire will want to flow to the ground. If the grounding circuit is working perfectly, that's what will happen. If not, the current will take the alternate route to ground--right through our body.
But if there's a GFI in the circuit, it will sense this flow and shut off the current in a fraction of a second, quick enough to prevent a serious shock.
GFIs are fairly new. Not long ago they were required only in the high-risk wiring around swimming pools. Now they are required in all new construction for outdoor circuits, bathrooms, laundry rooms and garages. Although you are not required by law to retrofit them in such locations, it's a wise safety precaution to do so. There are a couple of ways to get the job done.
GFI RECEPTACLES: For the bathroom and other indoor locations you can simply replace your existing receptacles. But some may be too big to fit the boxes your existing receptacles are housed in. To solve this problem you can either look for one of the compact GFIs, or get an adapter plate to increase the useful space in your old box. The compact GFI will give a neater installation.
Since GFI receptacles are not watertight, you can't use them for outdoor circuits. Here you'll have to use a circuit breaker GFI. This type goes right into your main electrical service panel, replacing the standard breaker presently protecting your outdoor line.
Circuit breaker GFIs will also work for indoor circuits, such as bathrooms, but for those, the receptacle type may be a better choice. At any rate, installing circuit breaker GFIs is best left up to an electrician.
PLUG-IN UNITS: If you don't want to bother installing a GFI on your existing outdoor circuits, you should at least consider buying a plug-in GFI. This is an extension cord with a GFI receptacle at the end. Plug it into an outlet, plug your tool into the GFI, and you're protected.
TEST BUTTONS: Even a GFI can't protect you if the GFI becomes damaged. To prevent this sense of false security, all GFIs come equipped with test buttons. The Underwriters Lab suggests that GFIs be tested as a matter of routine, once every month. To do this, just push the test button. When you do, the GFI should trip off. If it doesn't, it is faulty and should be replaced.
Unfortunately, it's easy to forget to perform this test on a circuit breaker GFI, because it's out of sight, out of mind, tucked away in some gray box down in your basement. Receptacle types, however, are out where you can see them, and their test and reset buttons serve as handy reminders. That's why they may be your best choice for indoor circuits.