Twist-on Electrical Wire Connectors

You may have heard of the term “Wire connectors” before. You may have even heard of “wire nut,” “wire joint,” “marr connector,” or even “splice connector.” Technically, they all mean the same thing. Typically, an electrical wire connector is known as a “twist-on wire connector.” For short, we’ll refer to it as a TWC for this blog to save time.

English: An illustration of wire nuts

English: An illustration of wire nuts (Photo credit: Wikipedia)

TWCs are used to secure two or more electrical wires together to keep a continuous flow of energy or information. For example, say the cord running into a lamp broke and the inner wires are now not only disconnected but are exposed. To fix the connection, you would need to reconnect the wires, and to subtract fire hazards, you would need to keep them covered and protected. So how do TWCs help with this?

Made for such instances, TWCs are usually made from hard plastic to act as protective shells –hence the name, wire nut; the shell protects the important material inside, in this case, the newly spliced wires. Inside of the TWC is a coiled metal insert or a steel spring that expands and wraps around the spliced wires to secure them and hold them tight. Upon installation of a wire nut, the spring twists around the exposed wires and creates a new connection: electrical continuity maintained by the direct wire-to-wire contact and the conductivity of the metal spring.

The Design behind Wire Connectors

We’ll touch more upon installation of TWCs later. For now let’s talk a little more about the various designs of a wire joint and what they do. Most TWCs look like wide marker caps, basically like this.

Average look of Electrical Connectors

These are Thomas and Betts electrical wire connectors; most TWCs follow this design of grooves to give the user a good grip, it’s rare to see TWCs that are smooth. Note the width of the Thomas and Betts TWC, it’s not very wide. In fact, the largest model can hold a diameter of roughly 11mm of twisted wire.

Before we go any further, you may have noticed the terms “spliced wires” and “twisted wire” thrown around a bit. In case you’re not quite sure what any of those mean, allow me to catch you up. Spliced wires are primarily a minimum of two wires that have had their insulation stripped and the bare copper conductors have been twisted around one another to create a new connection, as stated above. That’s all it is really, simple.  In other blogs, you may have read about UTPS, unshielded twisted wire pairs; this is relatively the same idea, although done for a different function. Here’s a good idea of what it looks like inside of a TWC.

Diagram of what twisted wires look like inside of a wire nut

Are you ready for another abbreviation? As to not be confused with UTP, a group of spliced wires will be referred to as TWP for “twisted wire pair.” Now as mentioned above, a TWC can only hold up to a certain diameter of TWPs. If you’ve been reading our blogs or are familiar with our products, then you know that the cumulative diameter comes from the American Wire Gauge (AWG) of the wires being used.

Not every TWC can hold the same amount of AWGs, but they are all pretty similar. For instance, the smallest Thomas and Betts TWC will hold a minimum of two 22AWG and a max of two 16AWG, and so will Ideal Wire-Nut Wire Connectors. In contrast, Ideal Twister TWC and Wing-Nut TWC need a little more for a secure hold, having a minimum of three 22AWG and two 17AWG, respectively. As you may also know when it comes to AWG, the bigger the number the smaller the diameter.

So, each TWC can hold a number of TWPs securely and create a connection to keep up electrical continuity. If you looked at some of the products linked to, you may have noticed that some TWCs are smooth or flat at the bottom of the base, while some have wings or “skirts.” These are molded grooves intended to assist the user in hand installation and give the ability to use a tool during installation, such as a TWC socket tool. Now we’re getting to the meat of TWCs, the individual design features of different brands and styles, and the applications they are intended for.

Different Wire Joints, different features

First, let’s do a quick review of the general characteristics of most if not all TWCs. Most of the time, according to the brand/manufacturer, or a Universal rule, TWCs are color-coded to indicate the wire nut’s size and its AWG holding capacity. Not all TWCs come with different colors as you can clearly see on some of our product pages, but they tend to follow the same rule. Another characteristic you will find with many TWCs is their ability to be removed and reused. I can’t confidently say ALL TWCs are reusable, some are made to stay put forever; those that are reusable however make it easier on your wallet.

Another common characteristic you will find is that almost every TWC has at least one certification by the CSA or another federal standards organization. The most common approval comes from the UL, rating products for fire safety. This is because a lot of TWCs, especially the ones we carry on our website, are flame retardant. Some of them are made out of thermoplastic material, some are just very resistant to high temperature conditions, and others are just prone to fire in case of a short circuit or spark. Other TWCs may be made out of self-extinguishing plastic or have specific designs to protect against combustion, but overall the majority of them are made for hot applications and therefore are usually flame retardant.

One characteristic that is fairly rare to find is a TWC that is chemical or moisture resistant to fight corrosion. One of these has been mentioned already, can you guess which one? The Thomas and BettsTWCs are chemical resistant and won’t break if exposed to household solvents, diluted acid or alkaline solutions. For moisture resistance, or TWCs that can be used in wet conditions, you’re going to want something gel-filled, like Platinum Tools Gel-filled Splicing Connectors. These will keep TWPs protected from water damage.

Okay so you now know that a TWC, simply put, is a cap or shell that holds a TWP of two or more wires of varying AWG sizes. You also know about TWCs from an in-depth perspective and the different characteristics some of them have and the reasons for these features. But, do you know how to install a TWP into a TWC? You can probably guess, it’s been hinted at all throughout this blog article. However, I hate to leave things unfinished, so here’s a quick crash course.

Installing a Wire Nut

Look over your wires for a quick second before we get started. This will help you with a few of the steps below. How big are the cords, what is the total diameter of the AWGs, how large or small should the wire nut be? Things like that will help narrow down the right size of TWC you need and whether you’ll need additional tools, such as pliers or crimpers. In addition, what application are you using the TWC for? Is this a simple repair, what environment will the wire nut be in, or are you being a bit brave and splicing together an audio cable and a visual cable?

Don’t worry about that last one, I don’t even know how that works. Let’s make it easy, say we’re using our earlier example of repairing a lamp cord. I don’t think the AWG would be too big for this, so no need for extra tools, your hands should do just fine. Now, let’s say the problem is perhaps a pet chewed through the cord, or some natural accident that exposed the wires in the cord, and caused some damage disrupting the electrical continuity between the two. Well, you can’t just leave it like that, especially with the notable fire hazards, so let’s get to work!

1. Turn Off the Power1

Just because a light switch, or in this case, the lamp is turned off doesn’t mean all electricity is halted. As long as the lamp is plugged into the wall, there is electricity flowing to it. Unplug it, or better yet, turn off all power to that area via the circuit breaker to avoid electrical shocks.

2. Choosing the Right Wire Connector

If you read the above directions, then you should know what kind of TWC you need. This is just as a necessary step as turning off the power. Too small, and the TWC can pop off when the lamp is turned back on; too big, and the TWP might just fall out and disrupt the connection. Either way, you need to make sure the TWC you are using is the correct size for repairing the lamp cord.

3. Exposing the Wires for the Connection

Now usually when splicing wires, you’d need to take a wire stripper and remove the wire insulation or coating. In this scenario, the wires are already exposed and the cable sheath is damaged. For future reference, no more than ½ an inch of bare wire needs to be exposed, but you can go up to ¾” if you wish2.

4. Place the Two Stripped Wires Together

Line up the two wires so that they are parallel to one another.

Parallel wires below a wire connector (credit to family handyman).

Now, you can twist the wires together before installing the wire joint, or you can let the TWC do that itself. Really, it’s preference. With larger AWGs, you may want to pre-twist the wires to make sure it’s a nice snug fit and no wires are loose. You can do the same for this repair, but it’s not required.

5. Place the Connector over the Wire Pair

Regardless of whether you have a TWP or parallel wires, place the cap of the marr connector over the exposed wires. Make sure both wires are in the plastic shell of the TWC; if some is protruding out, remove the cap, trim the wire a bit, and try again.

Twist the Connector On

6. Once the wires are safely in the TWC, twist the connector clockwise until it tightens. You twist clockwise because turning counter-clockwise would unscrew the TWC and thus, be counter-productive. After you’ve got the cap twisted on, hold the TWC and lightly tug on each wire. This is a test of the quality and strength of the newly spliced wires. If you can’t get them free with a firm pull, then you can be sure that normal conditions will leave it be also. Remember Step 2; better safe than sorry and test this TWC connection.

If you’ve done it all correctly, then it should look a little like this:

Finished installation of a Wire Nut

That about wraps up this blog article, I know it was a lot of information, but hey! I bet you feel a little smarter now knowing all about wire connectors, right? Who needs electricians when you’ve got our blog? But seriously, don’t get in over your head; hire a professional for the big stuff.



Knowledge +1

Skill + 1



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