The electrical system in a home is about as good as it will ever be on the day the first owner moves in. This is because the local building department requires that a licensed electrical contractor be hired for the wiring of a new house. The professional electrician is listed on the building permit paperwork, and is responsible for the safety and code-compliance of the work. Then it gets in-progress and final inspections by a municipal or county building inspector. 

    Even professionals occasionally make mistakes and maybe everything is not perfect, but it’s pretty close. After that, things tend to head downhill over time for two reasons: 1) failure and obsolescence of components as they age, and 2) electrical repair work and additions done by homeowners and handymen.

   Here’s our “Top 10” list of the most common electrical defects found at a home inspection, and each of them fits into one of those two categories:

1) Double Tapped Circuit Breakers - Most breakers in an electric panel are designed to accept a single wire, with the exception of certain ones manufactured by Square D and Cutler Hammer. The breaker shonw below is only rated for one wire connection. When two or more wires are connected under the lug at a “1 pole” breaker,the connection may not be secure or have adequate contact surface.

If you read the tiny print on the side of the breaker, it will say “2 pole” or have a graphic showing two wires, for the breakers that are rated for more than one wire connection.  

2) Receptacles Wired Incorrectly - There are three wires connected to a modern electrical outlet: hot, neutral, and ground. They are, in order, the black, white, and bare copper wires you see in the back of the box. When they get mixed up or poorly secured by an amateur electrician, you can get reversed polarity, open neutral, open ground, false ground, high resistance to ground, or excessive voltage drop under load. 

In the photo below, the receptacle is mounted forward of the box on wood paneling, which creates a fire hazard. 

3) Ungrounded 3-Slot Receptacles In An Older Home - This is a particular type of incorrect wiring that deserves its own place on the list because it is so common, and also it is not a mistake. It’s a deception. The NEC (National Electric Code) mandated that electrical outlets go from 2-slot (ungrounded) to 3-slot (with the third, round hole for grounding) in 1960. Some homeowners and less-than-ethical remodelers upgrade to new 3-slot receptacles when renovating an older home, but the ground slot is connected to nothing. An ungrounded receptacle will light make only the center light glow in a three-light plug tester, as shown below. 

4) Non-Functional GFCI or AFCI-Protection - GFCI stands for Ground Fault Circuit Interrupter, and a GFCI-device can be integral with a circuit breaker in the electric panel or at the center of a wall receptacle. It provides shock protection for wet areas of the home, such as bathrooms, kitchen, garage, and exterior. Each GFCI-breaker and receptacle has a test button to verify that it is still working. You push the test button, it trips the circuit, then you push an adjacent reset button at a receptacle, or throw the breaker switch back to the “on” position at a panel, to re-energize the circuit. Like any mechanical device it eventually stops working, usually after 10 to 20 years, and requires replacement.

    AFCI is an acronym for Arc Fault Circuit Interrupter. This device is integral with some circuit breakers in homes built since 2002, and trips the circuit whenever it recognizes any arcing or sparking in the wiring, as protection against electrical fires. Newer versions of this device are called CAFCI for Combination Arc Fault Circuit Interrupter, and have been required since 2008. They also have a 10 to 20 year lifespan, and need to be replaced when the test button does not trip the breaker. 
5) Open Splices and Open Electrical Boxes - An “open” wire splice is when a connection of two wires is not protected inside a fire-resistant box, such as a receptacle box or electric panel. An open box (shown at the top of the page) is one that is missing a cover plate to seal the box, often because there are so many wire connections in the box that it cannot be closed. 

6) Extension Cords - When we see extension cords running along the baseboard around the rooms of home, it actually not so much a defect in itself as a symptom of different problem: too few receptacles. The required spacing for wall receptacles in a home has been set at a maximum of 12-feet since 1956 by the NEC, under the logic that the average power cord for a lamp or appliance is 6-feet long—so, anywhere along a wall with correctly spaced receptacles should have an outlet within reach of a standard cord. 

    Because fewer receptacles were needed in older homes, sometimes have only one receptacle in a bedroom and none in the dining room. Also, when a homeowner encloses a back porch, installing receptacles along the new exterior walls sometimes get forgotten. The worst offender is an extension cord running under a carpet, which is a fire hazard when the cord becomes frayed from being walked over.  When extension cords appear to be a permanent installation in the home, it means more outlets are necessary. 

7) Unprotected Electrical Cables - Electrical cables below 8-feet above the floor (in other words, within reach) are required to be protected—either inside a wall or running in conduit. The cable running to the bottom of the disposal under a kitchen sink or to a water heater in an older house is often unprotected. If the appliance is connected by a cord to a receptacle, it is not a defect.

8) Unsecured Cables Entering Electric Panel - Because a loose wire connection can begin to spark at a circuit breaker if it is only slightly pulled away from the connection, it is required that all electric cables be secured where they enter an electric panel. The clamp that is used is called an NM-connector, and when wiring is connected to a panel without an NM-connector, there is the potential for someone climbing through the attic to trip over a cable and yank the connection loose in the panel. The wrong way to connect a cable in a panel is shown below: pop open one of the perforated “knockouts” and just pull it through, with no securing clamp.

9) Obsolete Equipment - Forgotten, but not gone in some older homes,  screw-in fuse panels and knob-and-tube wiring go unnoticed until an inspector points them out to a homebuyer. 

10) Improperly Wired Panel - Any electric panel downstream from the main service panel is defined as a subpanel, and must be wired a little differently from the first panel: neutral and ground wires should be on separate bus bars, with the neutral bar isolated. Also, many subpanels are “backfed,” meaning that the power comes into the panel through a breaker located in the same column with the other breakers feeding power out. While a backfed panel is acceptable, the backfeed breaker must be clearly marked as “MAIN” breaker and mechanically secured to the box. The red plastic clamp shown in the photo below is an example of correctly securing a backfed main breaker. And the photo below it shows a subpanel bus bar with neutral and ground wires on same bus, along with multiple neutrals under one lug, both of which are not allowed.

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

• Which house appliances need a dedicated electrical circuit?

• Can a short circuit cause a high electric bill?

• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

• What causes copper wires to turn green or black in an electric panel?  

• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

• Why is it unsafe to bond neutral and ground wiring at subpanels?

• Should I get a lightning rod system to protect my house?

• Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

• Does a wire nut connection need to be wrapped with electrical tape?

• What is the minimum clearance of overhead electric service drop wires above a house roof?

• What are the requirements for NM-cables entering an electric panel box? 

• What is the color code for NM cable (Romex®) sheathing?

• Why is undersize electric wiring in a house dangerous? 

• What causes flickering or blinking lights in a house?

• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

• How can I find out the size of the electric service to a house?

• Can old electrical wiring go bad inside a wall? 

• What is an open electrical splice?

• What is the life expectancy of electrical wiring in a house? 

• What is an "open junction box"? 

• How dangerous is old electrical wiring? 

• What is a ground wire? 

• I heard that aluminum wiring is bad. How do you check for aluminum wiring?  

• What is "knob and tube" wiring?  

• What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.