What are the most common problems/defects found with electric receptacle outlets during a home inspection?
Friday, October 19, 2018
We call them electrical receptacles. Some people call them wall plugs or outlets; and, yes, home inspectors do check them. Not every single one because receptacles are often behind furniture or stored items that are not readily movable; but we try to spot-check at least one in each room.
Two circuit analysis tools, one low-tech and one high-tech, are used: a simple 3-light tester that checks wiring configuration, and also a more sophisticated circuit analyzer that checks voltage, voltage drop under load, resistance to ground, plus tests GFCI and AFCI receptacles.
Before we go into what defects the electrical receptacles are tested for, let’s review the basics of receptacle wiring. A modern receptacle that accepts a 3-prong plug has a specific designation for each opening: the shorter of the two narrow slots connects to the “hot” wire (the one that can shock you), and the taller slot is the “neutral” (which completes the circuit), and the round hole is the “ground” (an alternate safety route for electricity that has gone astray, not found in pre-1960 2-slot receptacles). Each of the three wires in a typical 120-volt electrical cable must be connected securely to the right receptacle terminal for it to function correctly.
Here’s some typical defects we find:
If the wires going to the hot and neutral terminals are switched, you have reverse polarity. While this defect does not affect the operation of simple appliances like a lamp, it can make them more dangerous. In the correct wiring configuration, the hot wire is connected to the button at the bottom of the light socket and the neutral is connected to the socket threads. When replacing a bulb in lamp that is connected to a receptacle that is wired properly, it is difficult to be shocked by the small button at the bottom of the socket. But a reverse polarity receptacle electrifies the threaded socket, making it more likely that you will be shocked when changing a light bulb.
Older 2-Slot Receptacle
Two-slot receptacles, the ungrounded type that were typical in homes before 1960, are considered safe and we do not list them as needing repair. However they are noted, because 2-slot receptacles will not accept the 3-prong plug on the cord of many new appliances, that require a ground connection to work properly, and this may prove to be an inconvenience.
Homeowners in older homes sometimes succumb to an easy, but unsafe, solution to plugging the 3-prong cord on their new refrigerator to the 2-slot receptacle behind it. They use a conversion gadget we call a “cheater plug.” It has 2 prongs on the back side and three-slots on the front, along with a short wire for connection to the screw at the front of the receptacle box cover--although the receptacle box is rarely actually grounded. We always call out cheater plugs for repair.
Another shortcut for upgrading older homes to accept 3-prong plugs is replacement of 2-slot receptacles with 3-slot receptacles, even though there is no ground connection available. This is a typical defect in older homes that have had a quick, cheap remodeling to be “flipped,” and it is a serious safety defect.
Yet another shortcut to installing 3-slot receptacles in an older home is a “false ground,” where the ground slot is connected to the neutral terminal of the receptacle. Again, no ground connection exists and we call it out for repair.
When our circuit tester indicates no neutral connection, it usually a loose wire in the receptacle box or the main panel.
High Resistance to Ground
In order for the ground to work properly as a safety device, it must have a low resistance to the flow of electric current so that a breaker is tripped quickly when electricity starts flowing to the ground. Electrical resistance is measured in ohms, and 1.0 ohms is the recommended maximum resistance.
The nominal voltage for household receptacles is 120 volts, but between 114 and 130 volts is acceptable. We note if the voltage at receptacle is outside this range.
Excessive Voltage Drop Under Load
Voltage is a measure of electrical force, which is comparable to water pressure in a plumbing system. When a standard 15-amp load (approximating a large household appliance or several smaller ones) is applied to a 120-volt household circuit, the voltage drops somewhat. The maximum acceptable voltage drop is 5%. More than that indicates poor wire connections, damaged, or undersize wires.
These will only be found in very old homes. Unlike modern polarized receptacles, both slots are the same height. Polarized two-prong plugs and grounded three-prong plugs won’t fit into them and, of course, they are always ungrounded. Some lamps and other devices have unpolarized prongs (same size) but, because of the age of these receptacles they always also suffer from loose connections with plugs.
Loose Plug Connection at Receptacle
The spring metal in the receptacle that grabs the prongs of an electrical plug eventually wears out over time. Then the plug sits loosely at an angle or slides out of the receptacle, causing arcing. This happens most often at receptacles that are plugged and unplugged often, such as at the kitchen counter.
We “pop” and reset GFCI receptacles and breakers to test them. Like any mechanical device, they begin to fail as they age.
We “pop” and reset AFCI-breakers to test them. They also begin to fail with age and, occasionally, we find defective new ones.
Any receptacle that is not supplying current is marked for repair.
Sometimes they just aren’t there. For example, pre-1960 homes often had a 2-slot receptacle built into the base of the wall light over the bathroom sink, and it was the only power source in the room. Those combination light/receptacle fixtures aren’t made anymore. When the bathroom gets modernized with a new light fixture, the sole convenience receptacle is lost--unless the remodeler spends the extra money to have an electrician install a wall receptacle. Having a receptacle in the bathroom wasn’t a big deal 50 years ago, but it is today.
Too Few Receptacles
The maximum spacing between receptacles, according to the National Electric Code, has been set at 12 feet since 1956—with no point along a wall being more than 6 feet from a receptacle. The logic behind that number is that an appliance with a standard length cord could then be plugged in anywhere along the wall. The prior maximum spacing was 20 feet.
Several other standards also come into play: each wall more than 2 feet long needs a receptacle, and hallways more than 10 feet require one. Also, kitchen counters now have a more stringent standard: no point along the back of the counter can be more than 2 feet from a receptacle, and any counter more than 1 foot long requires a receptacle.
These tighter standards have developed over the years in response to the increasing use of plug-in electric appliances around the home. Home electric consumption has been increasing at a rate of about 5 percent per year for a while now. And, obviously, older homes have fewer receptacles. It’s not uncommon to have one receptacle per bedroom in a 1940s era bungalow, and only one receptacle at the kitchen counter. Extension cords snaking along the walls behind the furniture is an omen.
Receptacles in the Wrong Place
Equally important, though, are locations where an electric receptacles should not be placed:
•• Receptacles should not be placed lower than 18 inches above a garage floor. Gasoline fumes from a car parked in the garage are heavier than air, and accumulate at the floor. The slight arcing that happens when a cord is plugged in can set off an explosion.
•• Although one receptacle should be placed near each bathroom sink, it should not be placed behind the sink, like in the photo below, to avoid the possibility of the cord drooping into a sink full of water.
•• Receptacles directly over a baseboard electric heater are a no-no. The cord could come in contact with the top of the heater and melt.
•• A receptacle should not be flush-mounted on a horizontal surface where it may have water splashed on it, like at a kitchen counter. And a floor receptacle in a dry area, like a living room, should have a special “rated” cover that protects the slots when not in use.
As electric technology has evolved over the years, so have receptacles. The latest improvement is a receptacle that only opens to allow standard cord prongs—but not any metal object that a curious child may try to stick into it. Unfortunately, they can be difficult for grownups to use too, if they are unfamiliar with how they function, or the prongs of a cord they are trying to plug-in are bent or damaged. To learn more, go to our blog How do the new tamper-resistant electric outlets work?
Also, see our blog posts Where are GFCI receptacle outlets required? and Does a home inspector remove receptacle outlet cover plates?
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To learn more about electrical wiring, devices, and receptacles, see these other blog posts:
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