Whether you’re swapping in a new light fixture or adding an outlet in the garage, you’ll probably need to reconnect wires, connect a new wire to an old one, or extend a few wires. In other words, you’ll need to do some splicing.
This project involves making the cable connections inside a junction box with a blank cover that can be removed whenever you need to work on the wires. So be sure that the junction box is accessible. Learn how to perform this basic, essential household project safely and efficiently.
Step-by-step instructions for splicing wires
Before beginning any work, turn off the circuit breaker supplying electricity to the wire that you want to splice. Use extreme caution when working with electricity, as it can cause serious injury or even death when not handled properly.
Once you have turned the power off, you can cut the wires where the damage has occurred. Make sure there’s enough slack in the wires so that the two ends can go into the junction box. If enough slack is not available, you might need to use two junction boxes and connect them with a short piece of cable of the same gauge.
- Use a flathead screwdriver to remove two of the knockouts on the junction box, which will house and protect the spliced wires and contain any sparks that could cause a fire if something should go wrong. (Knockouts are partly stamped, quarter-size openings in the electrical boxes that service things such as outlets and switches.) Once removed, a knockout allows electrical wires to be run into and out of the box. The knockouts are pressed into the box in predetermined locations during manufacture for easy removal. Most junction boxes are universal and include knockouts of various sizes to accommodate different applications and a range of wire gauges. Once the knockouts are removed, feed the wires through and use the proper cable connectors to secure the cables to keep them from moving.
- Strip approximately 6 inches of the outer plastic sheathing from the end of the wires you’re splicing together. A utility knife is ideal for slicing and cutting away the outer insulation, making sure that the wire’s insulation does not get nicked or damaged. Remove the protective paper wrapping surrounding the insulated wires and ground wire.
- Strip 5/8ths of an inch of insulation from each conductor and ground wire.
- Using the electrician’s pliers, twist together in a clockwise direction the stripped ends of the corresponding wires from each strand, white wire to white, black to black, bare copper (ground wire) to bare copper.
- Twist them until they are tightly joined, making sure no bare copper is exposed, and secure each joint with a cap/wire nut. Fold both sets of wires neatly into the junction box.
- Align the protective blank cover with the mounting screws on the junction box and tighten the screws firmly using a screwdriver.
- Using the electrician’s pliers, twist together in a clockwise direction the stripped ends of the corresponding wires from each strand, white wire to white, black to black, bare copper to bare copper.
NOTE: All junction boxes must be made visible and easily accessible.
Safety warnings when splicing wires
Safety is of the utmost importance when doing any type of electrical project. When splicing wires, take these precautions:
- Ensure that the breaker to that cable is turned off and that there is no power to it.
- Ensure that all devices connected to those wires are turned off.
- Wear work gloves for additional safety.
- Consider using a voltage tester to confirm that there’s no power to the wires you’re going to work on.
The usual tools needed for this project are:
- Insulated electricians’ pliers with copper wire cutting capabilities
- Utility knife or cable rippers
- Wire stripping pliers for the proper gauge of wire
- Metal or plastic junction box
- Blank cover plate
- Wire nuts (wire connectors) big enough to wrap and cover the spliced conductors. Note: Wire nuts, or twist-on wire connectors, are used to connect two or more electrical wires in a junction box. Made of flame-retardant materials, wire connectors prevent wires from contacting other wires or exposed metal surfaces, which could cause a dangerous fault or short circuit.
- A voltage tester
Time and cost of this repair
It would take a homeowner 3 to 4 hours to make this repair, and the cost to buy the tools needed to complete this project would range from $30 to $100, depending on tool quality. A professional’s time to complete the job averages about 2 hours, and the cost of a professional repair could be between $250 to $500.
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