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Project Difficulty:
Easy
Estimated
Project Time: 1 hour
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| Tools and Materials: |
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Screwdriver
Utility knife (or wire stripper)
Lamp cord (and plug, as needed)
Multipurpose tool
Strong string (to act as fish tape)
Electrical tape, as needed
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Several different types of cords are available for lamps and appliances. Although a cord with an integral plug is preferable, you can purchase appliance cord by the foot, and then attach a plug to it. This alternative lets you choose the length of cord you want (but it should not exceed 6 feet beyond the base of the lamp). In either case, select a cord that is appropriate for the appliance and matches the original type of cord. Do not use a light-duty cord in place of a heavy-duty one, and if the original cord contains a ground wire, be sure the replacement cord also includes a ground wire. This will have a green covering in a round three-wire cord.
If you need a new plug, be aware that plugs come in a variety of different styles and shapes, including those for flat and round cords. Quick-connect plugs are for smaller gauge wire and "snap" together in some manner. Round-corded plugs are typically used on larger appliances that require a heavier gauged wire and a three-pronged plug; smaller appliances commonly use flat-corded plugs. All 120-volt plug ends are now polarized, with one wide and one narrow prong, and can only be inserted into a receptacle so that the neutral and hot cord wires properly align with the neutral and hot receptacle wires. If your cords and plugs no longer meet NEC standards, it is safer and less expensive for you to replace them, rather than attempting to repair them. When you do replace a plug or cord, be sure that the new device meets current code requirements (NEC Article 400).
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1.
Remove the Old Cord
Unplug the lamp, remove the lampshade, harp, and bulb, and separate the brass shell and insulation jacket from the socket. Disconnect the wires; unknot them if necessary. Securely tie or tape a strong cord or thin rope to the end of the old wire, and then pull the old wire down and out through the center pipe and lamp base. (Fig. 1)
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2.
Thread the New Cord
At the base of the lamp, tie the end of the new wire to the string that is now threaded through the lamp. Pull the string back up through the base and stem of the lamp, feeding the wire carefully while gently pulling on the string, so as to not disturb or pull apart the tie connection. Once it is through the socket base, untie the string, separate the last 2 inches of the cord wires, and strip the insulation jacket 1/2 inch off each wire end. (Fig. 2)
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3.
Knot the Wires
Using an Underwriters' knot (also known as a Hartford loop), tie the wire ends together. This knot will prevent the wire from pulling loose from the terminals in the socket. To form an Underwriters' knot, first separate the wires (split the cord lengthwise if using zip cord), form a large loop with each wire, and thread the end of each wire through its opposing loop (Fig. 3). Pull on the ends of the wires, tightening the knot. Then pull the wire down to set the knot into the socket.
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4.
Rewire the Socket
Attach the hot side of the wire pair to the brass or dark-colored terminal. If using common lamp wire (zip cord), this will be the smooth side. The neutral conductor will have ribbing or have other markings and will be screwed to the silver terminal. If the lamp or appliance had a third wire (ground) then the replacement wire must contain a third wire, which will have a green jacket, and this must be connected to the grounding screw or clip. Reassemble the socket by replacing the insulation jacket over the socket, and then slipping the brass shell into place over the insulation jacket (Fig. 4). Put in a new bulb, and then reattach the harp and lampshade.
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5.
Wire the Plug
If the replacement wire did not come with a prewired plug end, then you will have to wire the plug, making sure that all polarity rules are followed. Thread the wire through the new plug. Most plugs are supplied with some form of clamping mechanism to hold the cord securely, but if your plug does not come with one, you can strengthen the physical connection by making an Underwriters' knot (see Step 3), before making any connections within the plug.
Be aware that the wires may need some precise trimming to make them fit exactly because there is very little space for any extra wire within a plug. Strip 1/2 inch of the insulation off the wire ends, and then twirl the strands of each wire so that there are no stray ends. Clip the ends evenly and make loops that can be tucked neatly under the correct screw so that as the screw is tightened, the wire will tend to tighten as well and not splay out. (Silver for the neutral wire and brass for the hot wire; green goes to the ground prong screw.) During trimming and stripping, be careful that there are no strands lost and that there are no stray bits of wire that can touch any other area or part of a wire within the plug. It does not take much to blow the circuit.
Reinstall any cardboard insulating plate over plug prongs, and check that any wire-clamping device is secure.
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