How to Splice a Cable
Whether you’re lighting a hobby project or installing a new home fixture, any electrical project will eventually call for one very specific task: The cable splice. Splices are simply a join between two separate cables or wires. In the case of installing an electrical fixture, a splice is used to connect the lead wires of your fixture (it doesn't matter whether it’s a ceiling fan, ballast, or downlight housing, they all have cable leads) to your house’s line voltage. Smaller projects like low-voltage lighting or even repairs to small electrical devices such as toys typically require an occasional spliced wire to fix the problem. Knowing how to affect a proper splice can save you money on replacing a fixture, and you’ll be able to install your own fixtures safely.
It needs to be mentioned that each of these splices is for connecting a single wire to a single wire (cables with multiple wires would need each individual wire to be spliced). This means they should be carrying equal loads and are used for the same purpose. Splices should always be done from hot wire to hot wire and from neutral to neutral. When working on a project, be sure that you aren’t adding source voltage or current that exceeds the rating of the wires or components used.
Traditional Cable or Wire
The safest way to splice a wire is with a splice connector. It’s a simple tube of plastic or vinyl with a metal center. The center helps maintain connectivity with the wires, while the two ends can be crimped over the insulation of each wire to hold them together tightly. To use a splice connector simply:
Strip the wires – Wire strippers make this simple, simply place the wire in the properly marked gage slot and pull the insulation from the wire. Otherwise, take a sharp knife and score (cut into) the insulation around the wire. Then pull the insulation away. Be sure to strip the wire roughly ¼ inch from the end of the wire.
Place the stripped ends of each wire into a splice connector, making sure to leave no bare metal exposed.
Using pliers, crimp the ends of the connector by closing each end of the connector with pressure from the pliers. Crimping the ends holds the wires in place.
Twist-On Electrical Wire Connector
Twist-on wire connectors are typically used for splices in home fixtures or lighting wiring to make quick connections between wires. Ceiling fans and wall switches use these plastic splices extensively since those fixtures are switched out more often than others. A twist-on cap is also a great way to end an exposed lead in house wiring to safely prevent a short. You should never leave any wires exposed for any reason when working with electrical wires. Splicing two cables with a twist-on connector is similar to the splice connector, but with a twist:
Strip wires as before, by removing the insulation ¼ inch of the way from the end.
Twist the bare ends of both wires together.
Insert twisted pair into wire connector.
Twist connector to secure the splice.
Emergency Splice – Low Voltage ONLY
An emergency splice should only be used on low voltage systems (5-10 volt systems). You should always replace it with a proper splice as soon as possible. Never leave an emergency splice in place in any kind of industrial or home wiring. If there’s a problem with your house wiring, do not use an emergency splice and call a licensed electrician instead.
Strip both wires by removing insulation ¼ inch from end.
Twist ends together.
Wrap in insulating electrical tape.
Replace with formal splice as soon as possible.
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