Electrical Devices: How They Work & How To Wire Them

Common Electrical Devices

• Main Power Box or Power Panel
• Single and Duplex Receptacles
• Toggle and Dimming Switches
• Fixed Lighting & Appliances

WARNING: When working with electricity, removing covers, or examining your wiring, be certain to turn the power OFF first. The main power box may not have a disconnect and you may have to call the power company to pull the meter or turn off your electricity at the pole.

CAUTION: Depending on the local building codes and laws, some or all of your work must be done by a licensed electrician. In some areas, the homeowner is allowed to do some or all of the work when supervised by a licensed electrician. Most likely, the work will have to be inspected by a local building inspector and if any of the work fails to pass, it will have to be replaced and done correctly.

Main Power Box or Power Panel

This has many names, depending on locality and manufacturer. It's where the power comes in to your home and usually there will be a main disconnect along with over-current protection. Fuses or breakers provide over-current protection for the many smaller circuits.

For 110/120 volt circuits, it is common to use cable that has three wires. A wire that is bare is used for the safety ground, a wire with white insulation for the neutral lead, and a wire with black insulation for the "hot," or power lead. Inside the power panel, the black wire is connected to the lug on the breaker, the white wire is connected to the neutral block of lugs, and the safety ground wire is connected to the ground block of lugs.

For 220/240 volt circuits, an extra wire is needed for power. Some appliances, such as an electric water heater doesn't need a neutral wire, and often the same type of cable is used as in 110/120 volt circuits. It is common to use a red marker to color the white wire, indicating that is carries power. Inside the power panel, a larger 220/240 volt breaker is used which has two power lugs; the black and red wire is connected to these, while the ground wire is connected to the ground block of lugs.

Other 220/240 volt appliances, such as an electric clothes dryer, require the neutral wire, too. In this case, a different cable is used which has a red, black, white, and bare wire. Again, the red and black are connected to a larger 220/240 volt breaker, the white wire is connected to the neutral block of lugs, and the safety ground wire is connected to the ground block of lugs. You should never use the bare ground wire for the neutral wire.

Single and Duplex Receptacles

These are often called outlets, and modern ones can accept a plug with two straight blades, a polarizing plug with two straight blades, one of which is larger so it cannot be plugged in the wrong way, or a grounding plug with two straight blades and a grounding prong.

These have two brass, or gold, colored screws for the black wire(s), two silver colored screws for the white wire(s), and one screw, often painted green, for the bare ground wire.

When connecting receptacles "in line," where more than one receptacle is used in the same circuit, the extra screws for the black and white wires are used to "feed" the next receptacle(s) in line.

Two separate circuits can be included in one duplex receptacle by removing the tab that connects between the screws for the black wire and also between the screws for the white wire. This would commonly be used in a kitchen, where more circuits are needed, or where an outlet is switched for a floor lamp. In this case, removing the tabs separates the receptacle so wiring from two different circuits can be connected.

Toggle and Dimming Switches

These are commonly used to control lighting. Sometimes toggle switches are used for other purposes, such as switching an outlet or for a garbage disposal. Dimmer switches should only be used for incandescent lighting that is permanently installed.

Switches are always wired so that the hot, or black, wire is the one that gets switched. Due to how wire is made, often the physical color of the insulation may be white, but in reality, it is carrying the hot side of the circuit. Often, folks use a black marker to color the white wire black.

When physically running wiring, there are two methods used. One is called a "switch leg," where the wiring runs directly to the lighting fixture or device, and then more wiring runs to the switch — one carries power to the switch and the other returns power back from the switch to the fixture or device.

The other method is done "in line," where the hot wire goes to the switch, and continues on to the hot wire that feeds the circuit; the two the white, or neutral, wires are connected together.

Fixed Lighting & Appliances

These are normally permanently installed and "hard wired," instead of using a receptacle and plugging them in. Some examples are light fixtures, built-in dishwashers, ceiling fans, etc. The wiring size should be adequate to handle the amount of current, with the proper size breaker or fuse. Most of these devices come with a wiring diagram and information about the minimum circuit requirements, usually rated in amps, and sometimes watts.

Replacing Devices

First, always turn off the power. Before removing any wires, it is a good idea to make a wiring diagram, and mark all of the wires using masking, or other light colored, tape. Sometimes it is easier if you have the new device on hand. If the number of connectors or terminals are not the same for both devices, you need to get help before you connect anything. Remember that the color of wire in the wall may not be what you expect — a white colored wire is often used for power in a switch leg. Draw a picture of the device and terminals, label each with a letter or number, and mark each wire the same. Often, when devices look different they still work the same but the physical locations of the terminals or colors of the wires may be different.

When connecting two wires, use a "wire nut" that has a metal connector (looks like a spring) inside. Tighten to the right (clockwise from the bare ends)and for extra safety, use black electrical tape to secure the wire nut. All connections should be made inside of an electrical box with a cover.

If you blow a fuse or breaker after installing a new device, it's time to call an electrician. Most likely, you connected something wrong, and with electricity, you ought not to play "eenie, meenie, miny, moe," trying to guess how to make it work.

A schematic, or electrical diagram, only shows the logical connections. Wiring diagrams show the physical location and connection of the wires. If you don't know the difference, get help before you start.