Installing a Ground Fault Circuit Interrupter

Electrical | Last modified on: 01 Nov 2009 @ 15:17:50

Now here is some shocking news: According to This Old House Magazine more than two-thirds of all accidental electrocutions in homes can be prevented with a simple electrical upgrade. Do I have your attention? Good, because every year about 200 people in the U.S. die from accidental electrocution.

Upgrading your electrical system with a device called a Ground Fault Circuit Interrupter (GFCI) may the best investment you can make in improving the safety of your old house. GFCIs are now required by code in certain locations in new homes, but they can be easily added to old houses, as well. The cost is quite reasonable, too.

Invented in 1961 by a University of California electrical engineer, a GFCI has internal circuitry that monitors the electricity that flows into and out of an electrical device (like a drill, a hair dryer or that electric fondue pot you got as a wedding gift). If the difference between the inflow and the outflow drops by more than 5 milliamps indicating a ground fault (a short in the circuit) the GFCI trips an internal breaker and cuts off the electricity to the device in as little as twenty-five thousandths of a second. Once the offending device is unplugged, the GFCI can be reset with a simple push of a button.

Code requirements for new houses mandate GFCI outlets in kitchens, bathrooms, laundry rooms, crawl spaces and for outdoor outlets. These locations are recommended places to add GFCIs in old houses, too. But another application for GFCIs for old houses is installing them in places where adding a grounding wire isn't feasible-a great way to add a safety margin that might not otherwise be possible. I ran into that situation recently in a third floor bedroom which is a long way away from the grounding strap in the basement breaker box. At one time, the solution to a lack of a ground wire in old houses was to run a wire to the nearest cold water pipe, but that is now prohibited under the electrical code. The code does allow a GFCI outlet to be installed without a ground wire present, because of how the circuitry works. However, while it's okay use GFCIs for a few remote outlets, I would not recommend GFCIs for a whole house in lieu of upgrading to properly grounded circuits.

There are two ways to add GFCI protection. One option is a GFCI receptacle which replaces a wall plug-in receptacle and fits into the same electrical box. GFCI receptacles cost about ten bucks and an electrician can install one in about half an hour or if you're comfortable with light duty electrical repairs you can install them yourself. The other option is GFCI circuit breakers that install in your service panel. The cost is higher-between $50 and $100 per breaker-but you are protecting an entire circuit with one breaker. If your old house still has a fuse box, you're out of luck on this second option.

To install a GFCI receptacle yourself, turn off the electricity to the outlet you are replacing and double-check the outlet with a circuit tester to be sure it's off. Remove the outlet cover plate. Remove the screws holding the existing receptacle in place and then loosen the screws to release the electrical wires. Attach the black (hot) wire to the brass colored screw on the new GFCI receptacle and the white (neutral) wire to the silver screw. Make sure you get a good snug connection with the wires wrapped tightly around the screw. The "U" shaped loop in the wire should wrap clockwise around the screw, so as you tighten the screw it will pull in toward the shank of the screw and not be pushed away from it. Carefully feed the wires the receptacle and into the wall box, secure the device with the new screws that came with it, put on the cover plate, test the outlet by pressing the "Test" and "Reset" buttons and you're done. Because power surges can damage a GFCI's internal circuit, outlets should be tested monthly.

In an old house there can be a hitch in this procedure: The wires in the outlet box may be so old and dirty that you can't tell the white wire from the black wire or-as it is in my old house-both wires are black. There is a way to determine which is the hot wire and which is the neutral wire, but if you don't already know how to do this, my advice is to put this project in the capable hands of a licensed electrician. I believe you will find the cost quite reasonable especially when you factor in the protection of your family.