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Splicing Electrical Wires

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Summary: Splicing electrical wires can be done safely when you understand the method. This example shows you step by step the process of splicing electrical wires.

The Correct Way of Splicing Electrical Wires for Home Wiring

Splicing Electrical Wires

This electrical wire splice is being made in a 3 inch cut-in box that is mounted in a wall..

Use approved electrical boxes that have enough space for the number of wires that are needed.
See more about types of junction boxes

Use the correct size wire connectors for your splice.
See more about wire and wire connectors

After the splice is made be sure to cap off any remaining wires.

314.19 Wiring Methods junction boxes accessible Junction boxes shall be installed so that the wiring contained in them can be rendered accessible without removing any part of the building.

314.16 Electrical Junction Box Fill - The volume of electrical boxes shall be sufficient for the number of conductors, devices, and cable clamps contained within the box. Nonmetallic boxes are marked with their cubic inch capacity.

NOTE: This is a partial list of electrical codes. Other codes may apply. Some codes may be updated.

See the Electrical Code area for more information: Home Electrical Codes 

Splicing Electrical Wires

In this example two sets of wires are spliced inside a junction box where a light fixture will be installed.

Step 1: Always Identify The Electrical Circuit And Make Sure It Is Off

splicing electrical wires 1 Always be sure the circuit is off and test the wires before proceeding. The electrical cable should be installed so that 1 inch of sheathing is inside the electrical box and 6 inches of wire is showing outside of the electrical box.

Step 2: Splice The Ground Wires Together

splicing electrical wires 2 The ground wires must be spliced together in order to maintain the bond of the home electrical ground system. In this fixture box the ground wires are twisted together, then a crimp-sleeve is placed over the wires and crimped tight. The crimp sleeve is placed down over the wires past the half way area.

Step 3: Bond One Ground Wire To The Junction Box

splicing electrical wires 3 After bonding both ground wires together there will be two wires that can be used for the remainder of the ground process. This box has a ground screw and bracket built in so one ground wire is securely fastened under the ground screw.The other ground wire will be available to use once the fixture is ready to hang.

Step 4: Fold The Ground Wires Carefully Back Into The Junction Box

splicing electrical wires 4 Fold the ground wires and push them back into the box keeping the last one out. Straighten out the wires and trim them off evenly if needed, then strip back the insulation about 3/4 of of an inch removing the insulation to prepare the wires for the splice.

Step 5: Remove The Insulation From The Remaining Wires

splicing electrical wires 5 Use a pair of pliers to twist the bare wire in a clock-wise direction. In this example an additional wire has been added which will be used when installing the light fixture. After twisting the wires together trim the ends evenly to prepare them for the wire connectors. The total length of the bare copper wire area should still be about 3/4 inch.

Step 6: Install the Wire Connectors Onto The Twisted Wire Sets

splicing electrical wires 6 Select the right size wire connector, otherwise known as a "wire nut". Screw the splice connector onto the twisted set of wires in a clock-wise direction until each connector is good and snug. The bare wire should be all the way inside the wire connectors. Bare wire should not be seen. If bare wire is seen, back off the wire nut and trim more of the twisted wire sets and reinstall the connector.

Step 7: Fold The Spliced Wires Back Into The Junction Box

splicing electrical wires 7 Fold the spliced wires back into the junction box and pull the remaining lead wires and the ground wire out of the box and then trim off the ends to make them neat and even.

Step 8: Fold The Remaining Wires Into The Junction Box

splicing electrical wires 8 These wires are now ready for a light fixture to be installed. If a device will not be installed then wire connectors would be installed onto the wires that are not connected, and a blank cover would be placed on the junction box. In this project a wall fixture will be installed immediately so the junction box was left open and the wires are ready to attach to the light fixture.

More about Splicing Electrical Wires

Learn more about splicing electrical wires


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