Wiring problems and mistakes are all too common and, if left uncorrected, can lead to short circuits, electric shocks, and even fires. Here's what to look for and how to fix what you find.
Mistake: No electrical box| Never connect wires outside an electrical box. A junction box (or J-box) protects the connection from accidental damage and contains sparks and heat from a loose or shorted connection.
Solution: Add a box| If the electrical box does not contain a connection, install a box and reconnect the wires in it. The photo shows a method of mounting an exterior light on a wooden wall panel.
Myth 2: Wires are too short| Cutting wires too short can make wire connections difficult and - because you are more likely to make poor connections - dangerous. Leave the cord long enough to stick out of the box at least 3 inches.
Solution: Extend the cord| If you encounter a short cord, there is a simple solution. Simply add 6 in. extensions to the existing cord. The photo shows a wire connector that is easier to install in tight locations. You will find these at hardware shops and home centers.
Mistake: unprotected cables| Plastic-sheathed cables exposed between framing members can be easily damaged. This is why the electrical code requires that cables are protected in these areas. As shown here, it is particularly vulnerable when running above or below a wall or ceiling frame.
Solution: Install a 2 x 2 | Protect the exposed plastic sheathed cable by nailing or screwing a 1-1/2 inch thick plate next to the cable. You do not have to nail the cable to the plate. Running wires along a wall? Use metal conduit.
Mistake: Loose outlets| Loose switches or sockets look bad, but even worse, they are dangerous. A loosely connected outlet can move around and cause wires to come loose from the terminals. Loose wires can arc and overheat, creating a potential fire hazard.
Solution: Add rigid electrical box spacers| Secure loose sockets with spacers underneath the screws to create a tight connection to the box. You can purchase special gaskets that we have on display in our home centers and hardware shops. Other options include small washers or coils that wrap around the screws. You can also add some insulation when you get back in there.
Solution: Install a two-slot socket | If you have two-slot sockets, it's easy to replace them with three-slot sockets so you can plug in a three-hole plug. However, do not do this unless you are sure that there is an available ground. Use a tester to see if your socket is grounded. A series of lights indicate whether the socket is wired correctly or if there is something faulty. These testers are readily available at home centers and hardware shops. If you find a three-slot socket in an ungrounded box, the easiest solution is to simply replace it with a two-slot socket as shown in the diagram.
Mistake: Exposed combustible material| If the wall surface is combustible, the electrical box must be flush with the wall surface. Boxes hidden behind combustible materials such as wood are a fire hazard because the wood is exposed to potential heat and sparks.
Solution: Add a box extension| The solution is to simply install a metal or plastic box extension. If you are using a metal box extension on a plastic box, use a grounding clip and a small length of wire to connect the metal extension to the ground in the box.
Mistake: Missing clips| Unsecured cable will pull the connection tight. In metal boxes, sharp edges can cut the insulation on the wires. Individual plastic boxes do not require internal cable clips, but cables must be bound within 8" of the box. Larger plastic boxes require internal cable clips and the cable must be bound within 12 inches of the box. Cables must be attached to the metal box using approved cable clips.
Solution: Install clips| Ensure that the sheath on the cable is clamped under the clip and that approximately 1/4" of the sheath is visible inside the box. Some metal boxes have built-in cable clips. If you are using a box that does not include clips, purchase the clips separately and install them when you add the cable to the box.
Mistake: too small a box| Too many wires crammed into one box can lead to dangerous overheating, short circuits and fires. The National Electrical Code specifies a minimum box size to reduce this risk.
Solution: Install a larger box| To calculate the minimum box size required, add up the items in the box.
1 - for each fire and zero wire entering the box
1 - for all combinations of earth wires
1 - for all cable clamp combinations
2 - for each device (switch or socket? but not the luminaire)
Multiply the total number of 14 gauge wires by 2.00 and the total number of 12 gauge wires by 2.25 to obtain the minimum box size in cubic inches. Then choose a box that has at least that much volume. The volume is printed on the inside of the plastic box, usually on the back. Steel box volumes are listed in the electrical specifications. Steel boxes will not be labeled, so you must measure the height, width and depth of the interior. Then multiply this to find the volume.
Solution: Identify the zero terminal| Connecting a black hot wire to the neutral terminal of a socket creates the potential for a fatal electric shock. The problem is that you may not realize the mistake until someone is shocked because the lights and most other plug-in devices still work; they just don't work safely.
Always connect the white wire to the neutral terminal of the socket and the lamp. The neutral terminal is always marked. It is usually marked by a silver or light-colored screw. Connect the hot wire to the other terminal. If there is a green or bare copper wire, it is earthed. Connect the earth to the green earth screw or an earth wire or earth box.
Solution: Connect the power supply to the "line" terminal| GFCI (Ground Fault Circuit Interrupter) receptacles protect you from fatal shocks by switching off the power when they sense a small difference in current. They have two pairs of terminals. One pair, labeled "line", is used for input power to the GFCI receptacle itself. The other, labeled "load", protects the downstream outlet. If you confuse the line and load connections, you will lose your protection against shocks.
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