Splicing electrical wires is an essential skill for any DIYer working with electrical circuits. Properly splicing wires ensures safe, reliable connections in lighting, appliances, outlets, switches and more. While it may seem intimidating, splicing wires is actually quite straightforward with the right materials and techniques. In this comprehensive guide, we’ll cover everything you need to know to splice electrical wires like a pro.
Gather the Right Materials
Splicing wires begins with having the proper supplies on hand. Here’s what you’ll need:
- Wire strippers – A must-have tool for stripping away insulation so you can access the inner copper wire. Choose self-adjusting strippers designed for common 12 to 14 gauge electrical wire.
- Needle-nose pliers – Allows you to easily maneuver and twist wires together. Look for pliers with insulated handles for protection.
- Wire nuts – These plastic, twist-on connectors secure wire splices. Make sure to get the right size wire nuts for the gauge of wires you’re using.
- Electrical tape – Used to wrap splice connections for a more secure hold and added insulation. High-quality vinyl electrical tape is best.
- Wire cutters – Clean cuts make for easier stripping and splicing. Invest in sharp, heavy-duty wire cutters.
- Safety glasses – Protect your eyes from debris and wire bits when stripping. Clear lenses give you the best visibility.
- Flashlight – Illuminates dark electrical boxes and wire connections. Choose a compact LED flashlight.
- Voltmeter – Lets you double check wires are dead before splicing. Get a digital model for precise readings.
- Replacement wire – Has many uses like extending short wires or replacing damaged wire. Keep 12-14 gauge THHN/THWN-2 wire on hand.
With the right supplies gathered, you’re ready to move on to preparing the wires for splicing.
Prepare the Wires
Proper wire preparation ensures clean, conductive splices. Here are the key steps:
Turn Off Power
Start by turning off power to the circuit at the breaker box. Verify power is off by testing wires with a voltmeter or circuit tester. Working on live wires can lead to serious shock or electrocution.
Cut Back Insulation
Use your wire strippers to remove about 3/4” of insulation from the ends of each wire you plan to splice. Take care not to nick or cut into the inner copper. Damaged wires won’t make solid connections.
Clean Wires
Use needle-nose pliers to gently twist each stripped wire end. This helps tighten any loose wire strands. You can also shine the wire ends with fine sandpaper or emery cloth to reveal shiny copper.
Arrange Wires
Position wires in a single layer, side-by-side, with frayed ends all facing the same way. This makes it easier to join aligned wires for optimal conductivity.
Secure Wires
Have needle-nose pliers handy to hold and maneuver wires. If needed, use electrical tape to temporarily bind wire ends, preventing them from unraveling as you work.
With prep work complete, it’s time to make the mechanical and electrical connections.
Join the Wires Together
Splicing requires securely connecting copper wires so current can effectively flow between them. Here are proven techniques for joining wires:
Twist On Wire Nuts
Wire nuts are the go-to choice for most basic wire splices in electrical boxes. To use them:
- Align stripped wire ends so they overlap about 1/2”.
- Twist a properly sized wire nut over the wires, turning clockwise until tight.
- Use needle-nose pliers to tightly twist the nut 1-2 more turns until wires are fully mated together.
Twist and Tape
An alternative is twisting wires together manually:
- Hold stripped ends together, evenly aligned.
- Use pliers to twist wires around each other in a clockwise direction.
- Add 3-4 tight twists to join the wires securely.
- Tape the twisted section with electrical tape for a stronger connection.
This method works for two-wire splices. For more than two wires, wire nuts are much easier.
Use Lever Nuts
Lever nuts provide a push-in splicing option. They’re ideal for joining many wires quickly, like in junction boxes:
- Strip 1/2” of insulation from each wire end.
- Arrange wire ends evenly around the lever nut’s opening.
- Push in wires until fully seated then press the nut’s lever down hard.
The internal spring pushes against wires to create a tight mechanical splice.
Solder Connections
For mission-critical applications, soldering wires provides a permanent, low-resistance splice:
- Strip wires, thoroughly clean ends with sandpaper, apply flux paste.
- Hold wires side-by-side and melt solder against the intersection.
- Let solder fully wick into the joined wires to create a conductive splice.
- Insulate the soldered connection with heat shrink or electrical tape.
Soldering makes very durable splices but requires more tools and skill to master.
No matter the technique, a properly executed wire splice will be strong, conductive and insulating.
Insulate Your Splices
Once wires are securely joined, it’s essential they’re properly insulated for safety and longevity. Here are some insulation tips:
- Wrap all wire nuts and wire twists with 2-3 layers of high-quality electrical tape. Stretch tape tight as you wrap for a snug fit.
- With wire nuts, wrap tape around each joined wire individually, then over the nut in a criss-cross pattern.
- For soldered splices, slide heat shrink tubing over and apply heat to seal. Or tape over thoroughly.
- Avoid exposed copper or splice points coming into contact, which risks dangerous shorts.
- When splicing within boxes, fold and position wires carefully to avoid straining connections.
- Keep wire splice points accessible rather than burying them in packed electrical boxes.
- Cap unused pigtail wires with wire nuts to protect until needed for future connections.
Proper insulation lasts for years, preventing shorts that can damage circuits and electronics while also improving safety. Take your time taping for best results.
Splice Wires in Common Locations
Understanding where electrical splices occur helps ensure you make reliable, code-compliant connections:
Lights and Ceiling Fans
Lights often have wire splices made within the fixture box itself during installation. These include joining hot supply wires to the fixture’s wires and neutral connections.
Switches
Switches involve splicing hot wires (black typically) coming from the breaker panel to traveler wires going to lights. Neutral and ground wires are spliced through without interruption.
Outlets
Receptacles splice hot and neutral supply wires to hot and neutral wires running to an appliance plugged into the outlet. Ground wires splice straight through.
Appliances
Any appliances like disposals or microwaves will have splice connections joining the appliance’s internal wires to the hot, neutral, and ground supply wires.
Junction Boxes
Splices here extend wiring from one box’s circuit to another downstream box, joining hots, neutrals, and grounds as needed.
Understanding typical splice scenarios helps ensure every wire gets connected properly for optimum safety and circuit performance.
Tips for Safe, Durable Splices
Follow this collection of dos and don’ts for flawless wire splicing:
DO:
- Turn off power at the breaker before splicing. Verify with a voltmeter that wires are dead.
- Use wire nuts and electrical tape rated for the wire gauge and type you’re splicing.
- Stagger splice locations to avoid an overly thick bundle when insulating connections.
- Splice like-colored wires together – hot to hot, neutral to neutral, ground to ground.
- Tug hard on each spliced wire to check it’s secure before insulating it.
- Trim stripped wire ends flush with wire nuts using end cutters. No copper strands should be exposed.
DON’T:
- Attempt to splice aluminum and copper wires together. Use special connectors made for this purpose.
- Discard the paper inside wire nuts. This insulates connections to prevent shorts.
- Use electrical tape without first installing wire nuts to join conductors. Tape alone is insufficient.
- Splice more than 4-5 wires within a single wire nut, which can cause loose connections.
- Leave splice points uncovered or unprotected. Exposed copper can short and poses a shock hazard.
With attention to detail and adherence to basic procedures, you can achieve splice connections that keep your circuits safe and working reliably for years to come.
Frequently Asked Questions About Splicing Wires
Splicing electrical wires isn’t difficult, but it’s common to have questions arise, especially for first-timers. Here are answers to some frequently asked questions:
Do I need to match wire gauges when splicing?
It’s ideal to splice the same gauge wires, which ensures a consistent fit in wire nuts and similar conductivity. But it is possible to splice different gauges using code-approved, multi-gauge wire nuts. The splice’s current capacity will match the lower gauge wire.
What’s the maximum wires I can join in one splice?
Inside most wire nuts, you can safely join up to 4 or 5 wires, any combo of solid or stranded copper wires. Exceeding this risks loose connections and overheating. For more wires, use a larger junction box with multiple splices.
Is it okay to flatten twisted wire strands before splicing?
It’s actually best to ensure wire strands remain rounded rather than getting flattened. Round wires bundle together better within wire nuts for a tighter splice. Flattened strands tend to fan out and don’t join as evenly.
Can I use electrical tape instead of wire nuts sometimes?
While tape alone can bind wires together, it doesn’t provide the same strong mechanical and conductive connection you get from wire nuts or other connectors. Tape should only go over wire nuts as added insulation.
What’s the flexible conduit coming off my ceiling wires?
That’s BX or MC “smurf tube” cable housing the wires inside. You can snip and strip it back like normal insulation to access the inner conductors when splicing at a light or fan.
My wires are really short. Can I splice in extra wire length?
Absolutely. Use same-gauge wire to create “pigtail” extensions giving you more slack to work with in tight electrical boxes. This involves splicing in an extra 6 to 12 inches of wire for at least one of the conductors.
Is it normal for a splice to feel loose at first?
It’s very common for a fresh splice to feel a little loose initially. As you wrap the connection with electrical tape, it tightens up nicely. The stiffness of the tape binds everything together firmly.
For any other questions about splicing wires, don’t hesitate to consult an electrician to be sure your connections meet code and are completed safely.
Conclusion
Connecting electrical wires by splicing is a crucial skill that any homeowner will eventually need to master. While it may seem daunting if you’ve never worked with household electrical before, rest assured that following basic procedures and having the right tools on hand will set you up for success. The most important steps to remember are turning off power, properly stripping and preparing wire ends, selecting suitable connectors, joining copper-to-copper conductors, and completely insulating your completed splices. Take things slow, double-check your work, and don’t be afraid to call in an electrician if you’re ever uncertain. Mastering wire splicing takes practice, but being comfortable making these vital electrical connections will serve you well for a lifetime of DIY electrical projects ahead.