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Common Electrical Wiring Mistakes to Avoid

According to the U.S. Fire Administration’s recent statistics, electrical fires accounted for 6.3% (nearly 24,000) of all residential fires. One of the leading causes of these fires is faulty wiring, meaning some of these fires might have been caused by preventable electrical wiring mistakes. Outdated wiring may not have the capacity to handle the increased number of electrical appliances and devices in today’s average home. Although breakers should be triggered when an overload occurs, there is a possibility that there are worn connectors which no longer function, greatly increasing the risk of an electrical fire.

Here are some common electrical wiring mistakes and how they can be fixed.

Mistake 1 – Making Connections Outside the Electrical Box

Junction boxes serve the purpose of protecting connections from accidental damage that may occur. They can also help contain sparks and heat due to a loose connection or short circuit. Wires should always be connected to the electrical box to ensure that they are being protected properly.

Solution: If you see a connection that is not made in an electrical box, install a box and reconnect the wires inside the box.

Mistake 2 – Cutting Wires Too Short

Cutting wires too short is a common electrical wiring mistake. Wires that are too short can result in poor connections. Wires should protrude at least three inches from the box.

Solution: Once a wire is cut, you may think there’s not much you can do to make it longer. However, there is an easy fix. You can add 6-inch extensions to existing wires. Wire extensions that are easy to install in tight spots can be purchased in hardware stores and home improvement centers.

Mistake 3 – Leaving Plastic Sheathed Cable Unprotected

Plastic sheathed cables that are left exposed between framing members are easily damaged. In fact, the electrical code requires that cables be protected in these areas. Cable can be especially susceptible to damage if run under wall or ceiling framing.

Solution: Protect the exposed cable by nailing or screwing a board that is 1-½ inches thick alongside the cable. The cable does not have to be stapled to the board. If you are running the wire along a wall, you can use a metal conduit for this purpose.

Mistake 4 – Poor Support for Outlets and Switches

Loose switches and outlets are not only an eyesore, they are also dangerous. Connections that are not secure can move around, causing wires to loosen from terminals. After some time, these wires can arc and overheat causing a fire hazard.

Solution: You can shim under the screws to make a tight connection to the box. This can be done using spacers. You can also use small washers, or a coil of wire wrapped around the screw for this purpose.

Mistake 5 – Installing a Three Slot Receptacle without a Ground Wire

Two slot outlets are outdated because they are not grounded. To update to new safety regulations and accommodate modern appliances, you should be replacing them with three slot receptacles. However, if you do not install a ground wire, these outlets are no safer than their two slot alternatives.

Solution: A tester can help you determine if your outlet is grounded. In a worst-case scenario, simply put the two slot outlets back where they were originally placed. This is safer than having a three-slot receptacle without a ground wire.

Mistake 6 – Recessing Boxes Behind the Wall Surface

Electrical boxes should be flushed to the wall surface if the surface is made of a combustible material. If they are recessed behind walls that are made of wood, they can heat the surface which can lead to sparking and fire.

Solution: If you find an electrical box that is recessed behind the wall, it is best to install a metal or plastic box extension to solve the problem. If you are using a metal extension on a plastic box, it is a good idea to connect the metal extension to the ground wire in the box using a grounding clip and a short piece of wire.

Mistake 7 – Installing Cable Without a Clamp

If a cable is not secured with a clamp, it can move around and strain connections. In metal boxes, a sharp edge can cut the insulation of the wires if the wires rub against it. For single plastic boxes cable clamps are not necessary, but the cable must be stapled within eight inches of the box. A larger box should have built-in clamps, and the cable must be stapled within 12 inches of the box.

Solution: The relatively simple solution to this is to install a clamp. However, you must make sure that the sheathing on the cable is trapped under the clamp and about ¼ inch of the sheathing is visible inside the box. Some boxes have built-in cable clamps.

Mistake 8 – Overfilling Electrical Boxes

The increased number of appliances and devices being used in modern households require lots of cables, which sometimes may be stuffed in a box that cannot accommodate them. Although the National Electrical Code (NEC) specifies a minimum box size to reduce risk, this doesn’t eliminate the chances of overcrowding which can lead to short-circuiting and fire.

Solution: The solution to this electrical wiring mistake is to buy a larger box. However, this is easier said than done as many factors must be taken into consideration when trying to find the correct size box for your safety needs. You must first count all the items in the box, which include the hot and neutral wires, the ground wires, the cable clamps, and count two for each device (including switches and outlets but not light fixtures).

Multiply the total by 2.00 for 14-gauge wire and 2.25 for 12-gauge wire to get the minimum box size in cubic inches. Then, find a box that is at least this big. A plastic box will have the volume stamped on it, but steel boxes won’t be labeled. Therefore, you must measure the height, width, and depth and then multiply the three to come up with the volume.

Mistake 9 – Reversing Hot and Neutral Wires

Connecting a hot wire to a neutral terminal in an outlet can result in an electric shock that may be potentially fatal. You may not even realize anything is wrong until a shock occurs because the electrical system may function as expected despite the unknown danger.


  • White wires should always be connected to the neutral terminal of outlets and light fixtures
  • Neutral terminals always should be marked, usually by a silver or light-colored screw
  • Hot wires should be connected to the other terminal (not the neutral)
  • A green or bare copper wire should be the ground wire
  • The ground should be connected to the green grounding screw or to a ground wire or grounded box

Preventing Code Violations

Here are some of the more common code violations. Familiarize yourself with these to avoid the consequences of permit denials and/or fines.

Choose the Correct Circuit Breaker: Circuit breakers are protective devices, but different types will be effective in different applications. There are standard circuit breakers, ground fault circuit interrupters, and arc fault interrupters. It’s a good idea to familiarize yourself with how each should be used in accordance with National Electrical Code (NEC).

Use Tamper-Resistant Receptacles: These are installed to stop children from getting an electrical shock that may occur if they insert foreign objects into outlets. They are required in all locations, as stated in the NEC.

Don’t Install the Wrong Cover on an Outdoor Receptacle: There are several types of covers that can be used for outdoor receptacles. To determine an appropriate cover, figure out how likely the outlet is to become affected by the weather and dampness. The NEC requires that all 15- and 20-amp receptacles be rated as weather resistant and tamper resistant, if they are installed in wet or damp locations.

Make Sure There Are Enough Receptacles Installed: One of the missions of the NEC is to reduce the use of extension cords, as they can lead to fires and tripping hazards. The NEC mandates that a receptacle outlet needs to be within reach of a 6-foot appliance cord from any point along a wall line and cannot be measured across a passageway.

Use Sufficient Electrical Bonding: Electrical bonding is defined as the practice of intentionally electrically connecting all exposed metallic items that are not designed to carry electricity in a room or building. This is a measure that protects everyone against electric shock. It is not the same thing as grounding and must be done in addition to grounding.

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