How to Wire a Lamp

One of the most basic electrical fixtures in your home is a floor or table lamp. If you ever have to rewire a broken lamp or socket, there are some important lamp socket wiring basics you need to understand to correctly connect hot and neutral wires when you replace a lamp switch and socket to keep your lamp safe. Most lamp cords and plugs have marking to identify the neutral wire. You should verify that your lamp is wired correctly especially if it is old or you purchased it second-hand.

One of the most basic electrical fixtures in your home is a floor or table lamp. If you ever have to rewire a broken lamp or socket, there are some important lamp socket wiring basics you need to understand to correctly connect hot and neutral wires when you replace a lamp switch and socket to keep your lamp safe. Most lamp cords and plugs have marking to identify the neutral wire.

Lamps and Electricity

With incandescent light bulbs, the lamp will work with the hot and neutral wires reversed, but safety is compromised. CFL and LED light bulbs may not work with reversed wiring. If you switched out your traditional light bulbs with new CFL or LED style bulbs and they will not work you may have to check the wiring of the lamp.

Under normal conditions the electricity flows into the tab on the socket base (brass) and into the base of the light bulb. The electricity then goes through the filament of the bulb and then exits through the threaded side of the bulb and into the threaded socket (aluminum) which is the neutral. In this condition, when the switch is off, the part of the lamp that is hot, the hot terminal screw is protected. When the switch is turned on, only the tab at the bottom of the socket is energized.

Reversing the wiring creates a potentially dangerous situation as the hot side goes to the threaded socket since the threaded socket is always energized whether the switch is on or off. In this configuration there is a much greater potential electric shock, especially when changing a bulb. Another dangerous situation occurs in older lamps and fixtures that contain cardboard insulation between the socket shell and the bulb socket. This cardboard can wear out and the outer metal shell of the socket can touch the threaded socket. If the threaded socket is energized then every metal part of the lamp is energized.

If you attempt to repair a lamp you need to determine which wire is the neutral. The neutral wire in the lamp cord is usually marked with a rib or ribs and it connects to the wide blade of the plug and to the neutral screw which is usually silver in color at the other end.

Correct lamp switch wiring

How to Wire a Three-Way Lamp Socket

Wiring a three-way lamp socket is similar to wiring a standard socket. While a regular lamp socket turns your light off and on, the three-way socket is used with special three-way bulbs to vary the wattage of the bulb from low, medium and high.

Tools and Materials

Phillips or flat-head screwdriver

Replacement three-way lamp socket

Wire Strippers, if necessary

Directions

Caution: Always unplug any electrical device before attempting to repair it.

1. Remove the light bulb, lamp shade and lamp shade holder called a harp. Squeezing the harp sides in toward the socket and lifting it up will free it from the harp base.

2. Grab the socket sleeve and gently pull it up and out of the socket base. To expose the interior three-way socket and socket wiring.

3. Remove the three-way interior socket by gently pulling up and away from the lamp base to expose the wiring and allow you to make the new connections. Loosen the terminal screws on the side of the three-way socket and remove the wires. Discard the old three-way interior lamp socket.

4. Install the new three-way interior lamp socket. The neutral conductor is ribbed down the entire length of the cord. Wrap the neutral wire around the silver screw on the side of the replacement three-way socket. The remaining smooth wire is connected to the brass screw. Tighten both screws. Note: Make sure that there is a knot in place where the two conductors are separated. This is often referred to as an “Underwriter’s Knot” and it is used to relieve strain from the cord and prevent the cord from being pulled out of the lamp and off of the terminal screws creating a short.

Underwriter's Knot

Tying an underwriter's knot.

5. Gently pull the cord at the base of the lamp to lower the socket back into the socket base.

6. Slide the socket sleeve over the three-way socket body and firmly push it into place.

7. Replace the harp, the light bulb and the lamp shade.

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Posted on Apr 10, 2012