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Please copy/paste the following text to properly cite this How Stuff Works article:
Club, Fix-It. "How to Do Home Electrical Repairs." 02 May 2006. HowStuffWorks.com. <http://home.howstuffworks.com/how-to-do-home-electrical-repairs.htm> 15 May 2008.
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Fix-It Club
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How to Check Receptacle Polarity and Replace a Receptacle
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How to Check Receptacle Polarity and Replace a Receptacle
Residential wiring systems installed in older homes use a two-wire system in the 110-120-volt branch circuits. One conductor is hot, and the other is neutral. The neutral may also serve as a ground, but, unfortunately, it usually does not. When this is the case, the system is ungrounded and the situation is potentially hazardous.You can easily tell if your circuits are of this type by looking at receptacles. There are only two slots for each plug in ungrounded receptacles. Modern wiring calls for the installation of a third conductor. Receptacles used with this system have three openings: two vertical slots and a third, rounded hole centered below or above them.
 ©2006 Publications International, Ltd. A plug-in polarity checker can enable you to make sure your outlets are installed properly. |
For proper operation and safety, make sure all receptacles on each circuit are installed with the individual conductors going to the correct terminals so there are no polarity reversals along the line. Unfortunately, receptacles are not always connected this way, even in new wiring systems installed by professional electricians. Check out your receptacles with a small inexpensive tester called a polarity checker, designed for this purpose. It looks like a fancy three-pronged plug and contains three neon bulb indicators.
To check your receptacles for polarity, plug a polarity checker into a receptacle. The lights will tell you if the polarity is correct and, if not, which lines are reversed. If there is a reversal, turn the circuit off, pull the receptacle out of the electrical box, and switch the wires to the proper terminals. If the equipment-grounding circuit is open (discontinuous), trace the circuit with a continuity tester until you find the disconnection or missing link; reconnect it to restore the effectiveness of the circuit.
Replacing an Electrical Receptacle
Nearly everyone has come across an electrical receptacle that doesn't work as well as it should or one that doesn't work at all. How does it happen that a receptacle fails to do its job efficiently and safely? There are two possible explanations.
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You may never do anything as foolish as sticking a paper clip in an electrical receptacle, but you can do the same damage when you plug in an appliance with a short circuit. Regardless of how the damage occurred, the damaged electrical receptacle must be replaced.
Another possible explanation for an electrical receptacle that doesn't work efficiently and safely is that it is just so old and has been used so often that it's worn out.
There are two clear indications of a worn-out electrical receptacle: the cord's weight pulls the plug out of the receptacle or the plug blades do not make constant electrical contact within the receptacle slots. At that point, the old electrical receptacle should be replaced.
This is not difficult, but you must follow the correct installation procedures precisely. Here's what you should do:
 ©2006 Publications International, Ltd. When replacing a receptacle, see whether it accepts only plugs with two flat blades or whether it can take plugs that have a rounded ground prong. |
Step 2: Take off plate that covers receptacle by removing center screw with screwdriver. If cover doesn't come off easily, it's probably being held in place by several coats of paint. Carefully cut paint closely around edge of cover plate with razor blade or utility knife.
Step 3: Remove two screws holding receptacle in electrical box. Carefully pull receptacle out of box as far as attached line wires allow. Loosen terminal screws on receptacle and remove line wires. Caution: If wires or insulation is brittle or frayed, that part of circuit should be professionally rewired.
 ©2006 Publications International, Ltd. A replacement receptacle must match the one you are removing. If you have the grounded type, you must buy a receptacle that has a ground terminal screw and slots for three-prong grounded plugs. |
Step 5: Carefully fold wires into space in electrical box behind receptacle, then push receptacle into box. Although there's no such thing as right side up for a two-blade receptacle, there is a correct position for receptacles designed to handle three-prong grounding plugs. Grounding plugs often attach to their cords at a right angle, so you should position receptacle so cord will hang down without a loop.
Step 6: Tighten the two screws that hold receptacle in receptacle box, then replace cover plate. Restore fuse or trip circuit breaker.
Slots in some electrical receptacles are not identical; one is wider than the other. The wider one connects to the white or neutral wire, while the narrower slot connects to the black or hot wire. Some plugs, in fact, are designed with one wide and one narrow blade, and these plugs will fit into the receptacle in only one way. The idea behind such a polarized plug is to continue the hot and neutral wire identity from the circuit to the appliance.
Keep reading to learn how to do another useful home electrical repair: replacing a wall switch.
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Please copy/paste the following text to properly cite this How Stuff Works article:
Club, Fix-It. "How to Do Home Electrical Repairs." 02 May 2006. HowStuffWorks.com. <http://home.howstuffworks.com/how-to-do-home-electrical-repairs.htm> 15 May 2008.
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