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In the early days of residential and commercial electrical service, the most common method of installing and joining wires involved many different skills and trades. Mechanical workers installed the physical wires. And electricians followed up to strip, clean, twist, solder, and wrap the connections. This was a time-consuming, labor-intensive, and often dangerous process that involved dipping connections into a vessel of molten solder. Fortunately, today there are various reliable and easy-to-use wire connectors available for both professionals and DIYers. With so many types and varieties, how do you know which one is best for you?
In this blog, we’ll review three of the most common wire connector designs. We’ll rank them from “Good” to “Best” with a brief history + pros and cons. That way, you can make your own decisions about what’s best for you.
Wire Connectors Examined and Compared in this Article:
- Ideal Wire Nuts (assortment pack)
- Ideal Push-In Connectors (assortment pack)
- WAGO 221 Lever-Nuts (assortment pack, 2-wire only also available)
Rather watch than read? Check out this 14 minute video.
DISCLAIMER: This blog contains affiliate links, which means that if you click on one of the product links, I’ll receive a small commission.
1. Twist-On Connectors (Wire Nuts): Good
History:
Twist-on connectors go by many different names: wire nuts, cone connectors, and thimble connectors. Marrette, a brand of connector named for their inventor William P. Marr, is widely used in Canada as a genericized trademark to refer to twist-on connectors from any manufacturer.
Twist-on connectors have a long history of use in North America and parts of Europe going back to their invention in the early 20th century. They have become near ubiquitous, particularly in Canada and the United States. However, they’re now widely distrusted in many places internationally, due to issues with early porcelain versions outside North America cracking and failing, resulting in short circuits and fires.
Design & Use:
Twist-on connectors typically consist of a sharp-edged, conical metal spring set into a molded cap of insulating material. This material is usually plastic. Though, some use ceramic in specialized connectors designed for high-temperature applications like ovens or furnaces.
When you insert two or more bare wire conductor ends of appropriate size and length into the connector and they twisted on, the conical spring tightens down. This draws the conductors in. By squeezing them together, it creates a secure electrical connection between them. Additionally, the metal spring itself acts as a bus, helping to bridge the wire conductors together.
Twist-ons achieve a secure connection when tightened onto straight and even bare conductor ends by hand. Premium connectors may have tabs or wings to enable easier hand tightening. In fact, some DIY-ers and professionals may prefer to tighten connectors with pliers or a specialized wrench. This can be less fatiguing when there are many connectors to install.
The connectors work equally well with solid or stranded wire. However, you should pre-twist stranded wires to ensure proper mating inside the spring. (That said, generally, it’s not necessary to pre-twist all conductor ends together before installing the connector.)
Pro Tip: Unfortunately, it is common to find improperly installed wire nuts, especially among the less experienced. Always perform a “pull test” when making up electrical connections. Do this by gently tugging on the conductors to ensure they don’t easily separate.
Twist-on connectors come in a variety of different sizes. And they typically conform to a uniform color code. Red and yellow are the largest and second-largest respectively. Each are able to accommodate more than two conductors depending on the gauge.
You may see other sizes and colors of connectors from time-to-time.
Orange, for example, often goes with light fixtures where you join two 14 gauge wires. Though, a larger yellow or red connector would generally be equally suitable.
Overfilling a connector with too many conductors (or too low a gauge of conductors) will result in poorer, less secure connections. When mixed solid and stranded conductors are used without first pre-twisting the stranded conductors, it’s common for the individual strands to be pushed aside. Rather than being drawn into the spring, this results in a very poor connection.
Twist-on wire connectors are designed to be removable/replaceable. A connection may be made-up and undone or reconfigured any number of times. However, the spring inside the connector can eventually stretch and wear out. Conductor ends can become too marred or defaced to reconnect, requiring them to be trimmed back and re-stripped.
The Pros:
- Inexpensive
- Reliable connection when used properly
- Ubiquitous and widely available
The Cons:
- Somewhat bulky and inflexible
- Easy to make-up a poor connection by accident
- May require cutting and re-stripping conductors when re-making or modifying connections.
Summary:
Twist-on connectors are the “Good” option. Why? Because while they’re often reliable, easy to use, and inexpensive, they also tend to be bulkier. They can also be unreliable or difficult for do-it-yourselfers.
2. Push-In Connectors: Better
History:
Since as early as the 1950’s, push-in connectors have been available as an alternative to twist-ons. These were originally developed to combat the problems caused by vibration and thermal cycling (repeated temperature changes) that can cause screw-based connections like twist-ons and screw terminal blocks to work loose over time.
A push-in connector uses the constant compressive force of a spring to press the inserted conductors firmly and securely against a metal bus bar. The spring mechanism remains under constant compression, even with expansion and contraction from changes in temperature. On the other hand, a screw tightened to a fixed position and torque could never accomplish this.
Design & Use:
Push-in connectors are composed of a single spring steel clip and tinned copper bus bar assembly enclosed in a transparent plastic housing. A plastic end plug with holes for the conductors keeps the metal spring captive inside the housing. And it acts as a guide to direct wires as they’re inserted.
Depending on the number of wire conductors a connector is designed for, the spring clip will have a corresponding number of tab-covered openings. The tabs act like one-way pet doors. And the harder a wire is pulled out, the more firmly the bottom edge of the tab bites into the softer metal of the conductor, keeping it in place.
On the surface, the connection might not look very sound. However, it’s not the small area of contact between the conductor and the tab which matters. Rather, the connection below where the conductor presses into a larger, flat bus bar is more important. The tab holds the conductor firmly in contact with the bus, so it doesn’t pull out.
Push-ins are easier and quicker to install and make a repeatably reliable and consistent connection. The form factor is also somewhat more compact than a twist-on. And the conductors are free to move rotationally inside each port of the connector. This provides surprising flexibility to maneuver conductors and devices in and out of junction boxes.
(Note: the push-in connectors I’m referring to here are specifically engineered for safely joining and splicing electrical cable. Please don’t confuse these with the “backstab” connectors on lower grade or lower spec receptacles and switches in North America.)
Pro Tip: Backstab device connections are generally less reliable. Unlike transparent push-in connectors, it’s impossible to visually verify the connection quality of a backstab-wired device. For these reasons, it’s always best to wire switches and receptacles using a clockwise-hooked conductor end and the terminal screw, or a straight conductor end under the terminal’s screw-down plate if equipped.
Be careful to check the manufacturer’s instructions if you are using solid and stranded copper wires. Some of the push-in connectors are designed for both stranded and solid with others only being designed for solid wire.
Although it may be possible with sufficient patience and muscle to twist and pull the wire conductors out of a push-in connector, their design is intended to prevent this, and the same connector won’t be able to be reused as it and the conductor ends will have been damaged. Push-in connectors are designed to be installed once (and completely replaced with a new termination and connector if disconnection/reconnection are ever required).
The Pros:
- Easier to make a consistent reliable connection.
- Smaller and more flexible than twist-ons.
- Ability to visually verify a proper connection.
The Cons:
- More expensive than twist-ons.
- One-time-use.
Summary:
Push-in connectors are the “Better” option. Why? Because although they’re more expensive, the increase in cost is offset by the ease of making a secure and reliable connection, especially for do-it-yourselfers. A smaller form-factor and added flexibility to maneuver connected conductors are additional benefits.
3. Lever-Nuts: Best
History:
While there are many different brands and manufacturers of twist-on connectors and even push-in connectors, the “lever-nut” is a special case. Invented and released by the German electrical components company WAGO Kontakttechnik in the early 2000’s, the connectors quickly gained acceptance and use worldwide and are increasingly becoming more available in the United States.
What makes the lever-nut unique, is that it incorporates the ease of use and secure connection of a push-in connector, with a mechanism that makes the connector reusable near indefinitely, all without damage to either the connector or conductor.
Design & Use:
The WAGO “221” lever-nut is a similar design and form-factor to push-in connectors. A transparent connector body contains the metal internals and a lever mechanism for each port.
Earlier versions of the lever-nut, the “222” are constructed similarly, with a somewhat larger gray plastic body and larger/longer orange levers. Although the 222’s remain available, it is the 221’s that we’ll be referring to in this article.
A popular misconception about lever-nuts, is that pressure applied by the closed lever is what holds the conductor in place. In actuality, the reverse is true.
For each wire conductor, a spring is held under constant compression against a bus bar inside the connector housing. As the lever opens, the spring compresses and temporarily opens up a space between the spring and the bus for a conductor.
As the lever closes, additional compression on the spring releases and it moves back to its resting position, pressing the inserted conductor against the bus bar. The small amount of “play” left in the closed lever is intentional, to prevent incidental movement of the lever from accidentally actuating the spring and releasing the conductor.
Similar to the push-in connector, the small contact area between conductor and spring is immaterial. Springs for each conductor are separate, and the actual connection occurs between the conductor and the bus bar.
Lever-nuts work exceptionally well with both solid and stranded conductors. This is because they’re frictionless when in the opened position. By comparison, insertion of a conductor into a push-in connector is always working against the friction of the spring pressing on the bus bar.
Lever-nuts are transparent, allowing easy visual verification of proper conductor insertion similar to push-ins. They even include a probe hole that allows the insertion of a multimeter or voltage tester. inserted. Because lever-nuts are repositionable and reusable, connections can be made-up and modified near indefinitely without damaging the wire connector or the conductors.
The Pros:
- All of the benefits of push-in connectors.
- Probe hole for multimeter or voltage tester.
- Frictionless conductor insertion.
- Nearly infinite reusability without causing damage to conductors.
The Cons:
- Most expensive option.
- Limited (though increasing) availability in the US.
Summary:
Lever-nuts are the “Best” option because of all of the benefits they offer over both twist-ons and push-ins. Although they’re the most expensive option (perhaps making them cost-prohibitive to many professionals) their benefits make them ideal for do-it-yourselfers and novices especially.
The Wrap Up – Considerations and Conclusions of Wire Connectors
In addition to how well it functions and how easy it is to use, the wire connector type you choose is dependent on other factors; mainly, cost and availability. Twist-ons are typically the choice of professionals who need to be cost-efficient to maintain their profitability.
For professionals adept at using them, twist-ons are almost as fast and convenient as anything else. So the cost savings for them makes sense. However, for the average DIYer, the value of an easily repeatable and secure connection is usually worth the cost of push-ins or lever-nuts.
When considering push-ins vs. lever-nuts, where the choice is already between two more “premium” products, the lever-nuts just edge out push-ins due to their reusability and frictionless conductor insertion. When considering cost, specifically, lever-nuts can be far and away the most expensive option, however the smart shopper may find them costing little more than push-ins, so it pays to shop around and buy in larger quantities if you know you’ll use them.
Wire Connector Cost Ranges
Twist-ons cost 5-15 cents, push-ins 15-25 cents, and lever-nuts 30-55 cents each (prices in USD).
According to a recent Everyday Home Repairs poll, the vast majority of both professionals and “average Joes” still prefer to use twist-on wire connectors at about 80% of each group. Lever-nuts come in at a distant second place. But surprisingly an equal number of “Pros” and “Joes” are most comfortable with them at or near 13% each.
What Is the Most Common Wire Connector?
Twist-ons were by far the most popular wire connector type among both “Pros” and “Joes” in the Everyday Home Repairs community.
Not terribly far behind, Lever-Nuts are Push-Ins at 6% of both Pros and Joes followed by all other methods combined, accounting for 4% of Pros and 2% of Joes. No matter which wire connector you choose for your project or why, as long as you follow the manufacturer’s instructions and best practices you’ll have no problem making-up secure and reliable electrical connections each and every time.
