Project Overview
Total Time: 5 – 15 mins
Safety Considerations: Making wire splices is not a difficult technique, but it requires a good understanding of electrical systems and experience with basic electrical repairs. Any project involving circuit wires must start with turning off the power to the circuit at the service panel (breaker box).
Electrical splices should never be left exposed; they must be contained within an approved junction box or fixture electrical box. The box must remain accessible and not be hidden behind drywall or other building materials. Junction boxes provide a safe environment for splices, protecting them from impact and containing sparks and fire if something goes wrong.
What You’ll Need: The necessary equipment and tools include a cable ripper, wire stripper, hammer, screwdriver, pliers, cordless drill with driver bit, and drill bit extender if needed. Materials needed are one metal junction box with cover, two cable clamps for the box, UL-approved wire connectors, wood screws for mounting the box, and grounding pigtail wire.
Instructions: How to Splice Electrical Circuit Wires. The project assumes that wall surfaces are open for access and electrical cables are already run inside the wall cavities. If not, the process of fishing cables will complicate and prolong the project.
Examine Wiring: Ensure that you are joining two similar cables that match in terms of wire gauge and the number of individual conductors. Modern wiring up to 50 years old will have the gauge and number of wires printed on the outer sheathing.
Remove Outer Sheathing From Cable: Expose the individual conducting wires within the tough outer plastic jacket using a cable ripper to slice through the sheathing. Do not use a utility knife to avoid cutting into the individual wires. Trim away the severed portion of the sheathing and paper filler with the cutting jaws on a wire stripper or a utility knife.
Strip Insulation From Conductors: Every conducting wire, except for the ground wire, will be coated with color-coded plastic insulation.
Use a wire stripper to remove about 1/2 inch of insulation from each wire. The wire stripper tool has slots for various wire gauges. Use the slot that matches your cable wires.
Inspect the Cables: Check both cables for damage like cut, chewed, or burned insulation and nicked wiring. When properly prepared, about 6 inches of wire should protrude beyond the remaining sheathing, and individual wires should be stripped back and smooth. Remove Knockouts From Junction Box: Use a screwdriver and hammer to loosen two opposing knockout disks. Pry off and remove the discs with pliers. Rock the disk back and forth until it comes free. Dispose of the disks. Attach Cable Clamps to the Junction Box: Plastic cable clamps snap into knockout openings. For metal clamps, remove the threaded tightening ring, insert the clamp through the opening, and screw the ring back on. Tighten securely with pliers. Don’t turn too hard or you may break the clamp. Insert the Cables: Insert one cable into each junction box knockout through the clamp. Ensure the cable is flat on the clamp. Cable sheathing should extend past the clamp into the box by 1/4 to 1/2 inch. Close plastic clamp tabs or tighten metal clamp screws. Attach the Box and Cover Plate: The junction box has holes for screwing to a wood framing member. Use a bit extender if needed. Ensure the box is attached securely at a depth for the cover plate to fit. For example, if the wall has 1/2-inch drywall, the box should extend 1/2 inch beyond the stud. Make the Wire Connections: Use approved wire connectors to join wires with similar insulation colors. Some electricians twist wires with pliers first then use wire nuts. Others hold parallel wires and twist wire nuts clockwise. Ensure the wires are securely connected so they don’t come free when tugged.There should be no bare wire exposed at the bottom of the wire nut. Some electricians like to wrap a loop or two of electrician’s tape around the base of the wire nut and wires to help reinforce the wire connection.
Another type of approved wire connector is the push-fit connector. With these connectors, you simply push the bare end of the wire into a grip-fit socket on the connector. The bare copper circuit grounding wires should also be joined together in the box, using an approved connector. For metal electrical boxes, run a third grounding pigtail (bare copper or green insulated) to the two bare copper circuit grounding wires, using a wire connector. The free end of the pigtail is then connected to a threaded screw opening on the metal box, using a green grounding screw. This technique grounds the electrical box and improves the safety of the circuit. After completing the connections and finishing the wall or ceiling surface around the box, attach the cover plate securely. Some cover plates have a matte surface that allows them to be painted. The safest way to join electrical wire is detailed above using approved electrical boxes and connectors. The most critical step regarding safety is turning off power to the circuit at the service panel in the breaker box first. When in doubt, hire an electrician, which would truly be the safest way to join electrical wire. There is no standard answer to how many times you can splice electrical wire. It depends on the quality of the wire and your DIY skills. That said, many suggest not to splice electrical wire more than three times. It is against code to splice wires that are not contained in a junction box. You should hire a professional to splice wires if you aren’t confident in your personal electrician skills. Even if you are knowledgable on the topic, if the wires have already been spliced a couple of times, you should consider hiring a professional. Article Sources: The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. How to Deal With Unsafe Electrical Wiring. Coyne College.