Electrical outlets (more properly known as receptacles) are the workhorses of your home's electrical system. The outlet receptacles are where lamps, electronic equipment, small appliances, space heaters, and many other devices tap into the home's electrical circuits to fulfill their duties. Over time, an outlet receptacle can see cord plugs inserted and withdrawn hundreds of times, and like any other mechanical device, they eventually wear out or become damaged. Changes in electrical code requirements may also mean that, when an existing receptacle is being changed or worked on, it may need to be upgraded to meet code.
Here are some of the common problems with outlet receptacles and what to do about them.
Although receptacles have no moving parts, they do have metal contact points inside the body of the device, which are designed to firmly grip the hot, neutral, and grounding prongs on cord plugs. Over time, these contacts begin to wear and lose their gripping power. As the exposed contact points lose their ability to grip the plug, it creates greater electrical resistance and heat, which can cause problems in the wiring and may cause circuit breakers to trip. You may also begin to hear audible crackling in the receptacle due to sparking, and appliance plugs will feel loose within the receptacle slots.
Solution: Turn off the power and replace the receptacle with a new one. Often, replacing the receptacle may require bringing the new one up to code, particularly when GFCI and arc-fault requirements are involved.
Loose Wire Connections
Another very common problem with receptacles that receive a lot of use is that the circuit wire connections begin to loosen. Each time current is drawn through a wire connection, a small amount of heat is generated, and this repeated expansion and contraction of the wires can eventually cause the screws to loosen. You may hear the receptacle begin to crackle when this happens, and if the wire connections come loose entirely, a short circuit may cause the circuit breaker to trip. More dangerously, the circuit may even try to maintain a connection and heat to the point of starting a fire.
Loose wire connections are especially common if a receptacle has been wired using the push-in fittings on the back of the receptacle. These connections are notoriously insecure, which is why professional electricians almost never use these fittings to make wire connections.
Solution: Turn off the power and tighten all wire connections. If you discover back wiring, clip and strip the wires, wrap them around the proper screw terminals, and tighten them securely. Also make sure that the receptacle mounting strap is tightly secured, so that the device cannot wiggle around when you insert or extract plugs.
A damaged receptacle is a dangerous receptacle. Modern receptacles use a tough vinyl in the bodies and they rarely crack or break, but older receptacles were made with a rather brittle bakelite plastic that is susceptible to cracking. Sometimes cracks or chips will be visible on the front face of the receptacle, especially around the slots, but it is also possible that the side or back of the receptacle can crack.
Solution: Turn off the power and replace the damaged receptacle with a new one.
A surprising number of homeowners don't realize that outlet receptacles are rated for a particular amperage. In standard household circuits, the receptacles are rated for either 15-amps or 20-amps. A 20-amp receptacle can be identified by a small horizontal "T" that juts out from one of the vertical slots on the receptacle. This design accepts special 20-amp plugs that are found on some heavy-demand appliances, such as space heaters.
It is a very common error to use receptacles with the wrong rating for the circuit amperage. While there is no danger at all when a 15-amp receptacle is attached to a 20-amp circuit (this is allowed by the National Electrical Code), there is a notable hazard when a 20-amp receptacle is connected to a 15-amp circuit. In this situation, there is the potential for plugging in a 20-amp appliance to a circuit that can provide only 15-amps of power. The result, if you are lucky, will be a tripped circuit breaker, but damage to the wires and possible fire is also possible.
Solution: Review the amperage of the circuit and make sure the receptacles match the rating. If necessary, replace them with properly-rated devices.
A cheap, bargain receptacle may work fine for a time, but it eventually will be susceptible to problems. Devices mass-produced overseas can be suspect unless they carry an approval listing from a recognized testing agency, such as UL (Underwriters Laboratories).
Solution: Inspect receptacles and replace any that do not have an approval listing from a well-known testing agency. Such ratings will be stamped on the body of the receptacle.
Receptacles are designed with hot and neutral wire connections, so that the polarized plugs found on most lamps and small appliances, will route the hot and neutral current in the correct direction through the device. If those wire connections are reversed, the appliance will still work, but there is an increased danger of fire or shock should a short circuit occur.
Reversed hot and neutral wire connections are known as "reversed polarity," and this situation is often not recognized until problems occur.
Solution: Test receptacles with a plug-in circuit tester. If reversed polarity is identified, turn off the circuit and change the circuit wire connections to the proper positions.
No Ground Connection
Another very common problem with receptacles is the lack of a ground connection, which occurs either because the receptacle has not been properly connected to the circuit grounding wire, or because the system itself is not grounded, such as happens in very old wiring systems that do not have grounding protection. The lack of grounding can be identified by using a plug-in circuit tester. If your outlets use two-slot receptacles without a round grounding slot, it's a signal that the system itself may not be grounded.
Solution: Test the outlets, and if they indicate no grounding, shut off the power, inspect the receptacle's ground connections and make corrections if necessary. Or, have a professional electrician review an old wiring system and make necessary improvements to ground the system.
No AFCI/GFCI Protection
Today's electrical code requires that most outlets in living areas have AFCI (arc-fault circuit interrupter) protection and that outlets in some locations also have GFCI (ground-fault circuit interrupter) protection. Existing wiring installations are generally "grandfathered in"—you don't have to make the corrections unless work is already underway on the system. But any time a professional electrician makes a repair or improvement to the system, he or she will be required to add the required AFCI or GFCI protection to that circuit. When doing your own work, you should also make the required changes.
GFCI protection is generally required in all outdoor locations, all finished below-grade locations (such as in a finished basement), garages, unfinished attics, and all locations where there is a nearby presence of a water source (such as countertops near a sink, laundry rooms, and bathrooms). AFCI protection is now required for virtually all receptacles in living spaces.
Solution: Replace standard receptacles with GFCI or AFCI receptacles in locations where the electrical code requires them. Or, install GFCI or AFCI (or combined GFCI/AFCI) circuit breakers for any circuits feeding receptacles that require this protection.
Fish, Raymond M, and Leslie A Geddes. Conduction of electrical current to and through the human body: a review. Eplasty vol. 9 e44. 12 Oct. 2009