How to Splice Electrical Circuit Wires

Wire splicing is a standard electrical procedure that allows you to extend wires and add devices, while often reducing drywall demolition and repair.

Wire splicing can be done inside a standard fixture box, such as an outlet or ceiling light box. Wire splicing can also be done outside a standard fixture box. The cable connections are made inside a junction box that is installed expressly for the purpose of splicing. The box has a blank cover that can be accessed whenever you need to work on the wires.

When to Splice Wires

Many electrical projects require you to join (splice) circuit wires together. Wherever possible, the best method is to run a solid, uninterrupted cable from the service panel to the device or from device to device. This is preferable in many ways: it reduces the possibility of severed wires in an emergency, provides a smoother wall or ceiling surface, and eliminates confusion.

But this is not always possible, and this is where wire splicing comes into play. Learning how to splice wires makes it possible to tackle countless projects that enhance your living space.

• Moving an outlet
• Moving a light fixture
• Removing a wall
• Finishing a basement
• Dealing with loose wires
• Bringing improperly connected wires up to code
• Branching a circuit into two or more directions
• Leaving a junction box in place for future devices

Type of Materials to Use

Junction Box

Junction boxes come in both plastic and metal varieties. Some electricians prefer the durability of metal boxes, but if you use a metal junction box, remember that it will need to be connected to the ground system with a grounding pigtail wire.

One end of the pigtail is grouped together with the circuit grounding wires, while the other end is screwed directly to the metal box.

Plastic junction boxes may also be acceptable. Do-it-yourselfers often prefer plastic boxes because they are lighter weight, have softer edges, and the punch-outs are easier to remove. No grounding pigtail is required with plastic junction boxes.

Wire Connectors

The method demonstrated here is the correct way to splice electrical wires using UL-approved wire connectors joined inside an approved electrical box.

These connectors can be the familiar twist-on wire nuts or newer-style push-fit connectors. This is the method approved by the National Electrical Code (NEC). Either wire nuts or push-fit connectors are acceptable, as long as there is sufficient space in the box to contain them.

The old, informal method of splicing wires with electrical tape should never be used. Splicing wires with electrical tape creates a bond that is less solid than with wire nuts or push-fit connectors. Do not splice wires with electrical tape.

While you should not splice wires with electrical tape, tape is often used to bind wire nuts to the wires.

Safety Considerations

Making wire splices is not a difficult technique. But like any electrical repair that involves handling circuit wires, DIYers should have a good understanding of electrical systems as well as some experience with basic electrical repairs.

Any project that involves working with circuit wires requires that you first turn off the power to the circuit at the service panel (breaker box).

Electrical splices can never be left on their own in a wall or ceiling cavity. Instead, all splices must be contained within an approved junction box or fixture electrical box. The box itself must remain accessible and cannot be hidden behind drywall or other building materials that would require removal to get to the box. The junction box provides a safe environment for your splices, protecting them against impact and containing sparks and fire if anything should go wrong. While junction boxes may at first seem unwieldy and unnecessary, you will find that they are easy to work with and will make your work safer.