Wire Connectors | Wire Connector Types
Wire connectors are electrical fasteners that are essential to help you join (splice) electrical conductors so you can connect household wiring to outlets, switches, and light fixtures. Using a wire connector to make such a splice is easy. Even those of us who aren’t electricians can do it. On the other hand, if you get it wrong, it’s possible you could create a short circuit because the wires have come loose or the connector has cracked in half, exposing live electrical components to their surroundings. In the worst case, you can start an electrical fire, with catastrophic results. The circuit breaker or fuse may or may not provide protection against a meltdown caused by an improperly applied wire connector.
To help you achieve a safe, tight, and electrically sound splice, we have done several things. Below we show some reliable electrical connectors; all are listed by Underwriters Laboratories (UL) or similar rating agency. Simply put, don’t use any connector that lacks this. Second, we’ve provided links to stripping tools (since you need to strip the wire without damaging it before applying the connector that will do the splice). These are tools that we have used and that we can attest to.
In addition to relying on our own experience (for example, when we have worked on volunteer construction projects under the supervision of a licensed electrician), we also interviewed David Shapiro, a licensed electrician, electrical inspector and expert who has spent countless hours as a member of various electrical code advisory groups. Having worked as an electrician for the past 40 years, he has made thousands of electrical splices and investigated almost as many faulty splices in old homes. His book on old house wiring and improvement of the wiring of the old house are considered by many to be industry classics and the definitive works on these subjects.
More Popular Mechanics
Types of wire connectors
The tools for the job
The splicing process
Using a twist-on wire connector comes down to three basic steps: stripping the wires (conductors), aligning them, and twisting the connector.
And as part of those steps, Shapiro suggests additional quality checks.
1. Look inside the connector. You should see an intact spring in place. If in the unlikely event the spring has fallen off, discard the connector.
2. Strip the correct length of wire. This varies greatly and can range from ¼ inch all the way up to 7⁄8 inch, depending on the type of connector.
3. Check the nicks before splicing. A nick created from the stripping tool leaves a stress focal point and an area of hardened material. Both of these can cause a crack to propagate in the spliced wires, leading to electrical failure, overheating, and possibly an electrical fire.
4. With the conductors stripped to the correct length, align the insulation over the conductors.
5. Place the connector over the conductors and twist very firmly in a clockwise tightening motion. Some manufacturers even recommend that the connector not only be fully tightened, but that the conductors themselves have two to three twists. There are several types of screw-on wire connectors with fins that facilitate both twisting by hand and using a connector-tightening tool, which can be anything from a specially fitted screwdriver or as simple as a nut driver. Shapiro warns, however, “These (clamping) tools are really handy, but you can break a connector with them if you’re not careful.”
6. Check the connection by pulling firmly on the conductors. Do not jerk the wires; instead, apply firm, increasing force. Shapiro notes that the UL standard for these connectors ranges from 25 pounds for 14-gauge wire to 35 pounds of pulling force for 12-gauge. That’s a lot of force. As for the pull test, Shapiro says, “Don’t be shy.”
To pre-twist or not to pre-twist
Want to trigger (if you allow me the pun) a lively debate between electricians? Ask if they pre-twist conductors before applying a screw-on connector. That is, if they twist the wires together beforehand and then add the connector as insurance or if they allow the connector to twist the conductors together. The UL requirement for listing is that the connector itself must provide sufficient bond strength for it to form an electrically reliable connection without this pre-twist.
Shapiro, with countless splices behind him, is firmly in the pre-twist camp. “I pretty much always pre-twist,” he says.
Other electricians reject the idea because the pre-twisting makes it virtually impossible to untwist the wires without damaging them in case you need to modify the circuit.
The Push-In versus Twist-On debate
Additionally, plug-in connectors are flourishing in the electrical aisle because they are simpler and faster to use than their screw-on cousins. You strip the wire and push it into the connector. Push the wire (or wires) you want to tie into it. Do.
With some connectors, like the Wago above, you open a small lever on the device, insert the stripped wire, and close the lever.
Still, Shapiro is not a fan of plug-in wire connectors and prefers twist-on types because, when done properly, they provide more contact area between or among conductors. “Still, I know colleagues who swear by pluggable connectors,” he says.
Connecting stranded conductors to solid conductors
Both DIYers and electricians have been frustrated with the inability to form a good splice when connecting stranded conductors to solid conductors. The stranded conductor does not seem to braid very easily.
The solution is simple, Shapiro says. When splicing stranded cable to non-stranded cable, strip some more stranded wire. Try adding an extra 1⁄16 inch to the stripped wire length, line up the insulation, and twist the wire connector (or pre-twist the conductors first). Then try the pull test.
Roy Berendsohn worked for over 25 years at Popular Mechanics, where he wrote about carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care , chainsaw use and outdoor electrical equipment. When not working in his own home, he volunteers with Sovereign Grace Church to perform home repairs for families in rural, suburban and urban areas of central and southern New Jersey.