This month I am going to discuss one of the more critical mechanical components of a house, the ground-fault interrupter (GFI).
GFI’s (also called gfci for “ground fault circuit interrupter“) are generally found only on homes of relatively recent construction (since about 1980). However, one can be installed in any home and is recommended. GFI’s were included in the National Electric Code in 1973 but may not have been adopted by various city building codes until later. They were developed due to the large number of injuries and fatalities caused by relatively minor shocks from hand held appliances and power tools.
GFI’s come in two types. The first is similar to a normal electrical outlet except the device contains the GFI mechanism and test / reset buttons. The second is similar in appearance to a normal circuit breaker with the addition of a test button and is found in the breaker box. Both types can sense current leakage as small as 5 milliamps. In comparison, a regular circuit breaker will only trip at its rated amperage (a minimum of 15 amps.) A shock from a 15 amp circuit is very strong and can be lethal.
The National Electric Code requires GFI circuits at all accessible garage, bath, outside & kitchen countertop plugs as these are areas where people may come in contact with water or an improperly grounded tool. Any outlets UNDER a home, at a spa tub motor, pool or sink must be this safety type outlet as well.
It is strongly recommended that you test the GFI plugs or breakers in your house often by pressing the test button. An even better way to test the GFI is to purchase a GFI tester which can be found at Home Depot or Lowes for about $10. Use the tester on the plugs to determine if the GFI is tripping at the proper level. In my experience, fully 1/4 of the GFI circuits we test weekly are improperly wired or defective, which constitutes a hidden shock hazard to all occupants of the house. Have you checked yours recently? GFI outlets are relatively inexpensive ($12) and are easily installed.