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About 10 or so years ago the National Electric Code came out with a change that made it permissible to do away with those annoying adapters for converting 2-prong outlets to 3-prong outlets. It also provided a method which makes this possible with no wiring changes. If you are familiar with GFCI outlets, if you have a bathroom with an outlet in it you are, that is the key ingredient to this fix. A GFCI receptacle works on the difference in potential between the hot and neutral that is why a 3rd wire, or ground, is not required.This fix while relatively simple will require a little detective work.
In all my articles I stress the importance of maintaining your panel schedule this project is a very good reason why. You will first need to identify your receptacle circuits. Get a count of how many receptacle circuits you have and how many 2-prong outlets you have. Don't count the kitchen that is an entirely different situation and project. For each circuit you will need 1 GFCI outlet and the corresponding number of 3-prong outlets to replace the 2-prong outlets. It is important to note that GFCI outlets come in 15 amp and 20 amp so you will need to know your wire size to size your outlets correctly. extruder screw and barrel14 requires 15 amp outlet, bimetallic screw barrel12 requires 20 amp outlet. All non-GFCI outlet amperages should match GFCI amperage.
Now the detective work begins. The first step is to find the first outlet in the circuit. Chances are good that the outlet closest to your panel is first in the circuit, but not always. This is the outlet that will be replaced withe GFCI outlet. After shutting off the breaker, # safety first, remove the suspected first outlet and cap off all wires with approved wire nuts. Plug in a tester or if you don't have a plug-in tester a lamp will do. Make sure you test the lamp on another live circuit to make sure it works. Now turn your breaker on, if your light is on install a 3-prong outlet where you removed the outlet and try another outlet. If your light is off congratulations you found it on the first try. Go ahead and install your GFCI outlet there and replace all others with the 3-prong outlets. Make sure when you are working with the wiring and installing the outlets your circuit breaker is OFF! Do not attempt to make any wiring changes on an energized circuit!
When you are installing your outlets you will find 2 sometimes 3 sets of wires in the box. Do not attach all the wires to the receptacle. There should only be one set of wires on all receptacles except for the GFCI. When you find more than 1 set of wires you must twist the like wires together and make pigtails to the outlets. Simply stated twist all the blacks together with one added black to attach to the receptacle (the pigtail), then twist all the whites together again with one added white to attach to the receptacle (the pigtail), and attach the pigtails to the receptacle. The black wire attaches to the brass screw if you can't tell which screw is brass, then look at the front of the receptacle, the short # slot is the black slot. Attach the white to the silver screw again if you can't tell it is the long slot on the front of the receptacle. The GFCI is a little different.
When installing a GFCI it is very important that you pay attention to LINE and LOAD. Line being the wires coming from the panel, and Load being the wires going out to the other outlets. If they are swapped the receptacle will not function properly. The screw colors are the same as well as the slot size. This time when you will only need to pigtail if there are 3 sets of wires, if there are only two no pigtailing is necessary. Install the GFCI and turn the breaker on. If the GFCI resets you are done, if it won't reset it is probably installed incorrectly (LINE and LOAD swapped). A GFCI will not reset if power is not supplied to the LINE side. When you have wired your receptacle correctly, turn your breaker on then press the test button on the GFCI. All the receptacles on your circuit should be off.
As with any electrical project, if you are uncomfortable or unsure of what you are doing, contact a qualified electrician to assist you. Always be SAFE!