How To Choose the Right Wire Nuts for Electrical Connections

Updated: Mar. 22, 2024

How important are wire nuts? Extremely! Make sure you're choosing the correct wire nuts every time you join together two or more electrical wires.

If you’ve spent any time DIY-ing around your house, you’ve probably seen wire nuts. They’re the colorful, twist-on connectors that join two or more electrical wires together.

Since the earliest days of electricity, electricians have needed a way to connect and extend circuits throughout a building. Before the invention of the twist-on wire nut, electricians joined wires with solder and tape. It was messy, inconvenient and time-consuming. Here are a few tips for soldering electronics.

I know this to be true because I found wires in my old house that had been soldered and taped, and it looked like a plate of spaghetti. Not a wire nut in sight.

In the 1920s, an enterprising electrician got sick of that whole setup and decided to patent a “electric wire connecter.” A few years later, Ideal Industries, a major manufacturer of electrical products in the United States, got into the game. “Wire-Nut” is actually their trademark. But much like Kleenex, wire nut has become a universal term that, in practice, refers generally to twist-on wire connectors.

What Are Wire Nuts?

Wire nuts are small, twist-on caps that join two or more wires together in an electrical connection called a splice. Every light, receptacle and appliance in your home relies on a splice, so it’s important they be strong and safe. Wire nuts are also used to cap the end of a single wire so the live end is protected against accidental contact.

While “wire nuts” usually refers to the twist-on variety, other connectors, called push-in connectors, also join electrical wires together. Another, called a Wago lever nut, uses the nut terminology but is more akin to a push-in. Below we’ll focus on traditional, twist-on wire nuts.

How Do Wire Nuts Work?

Wire nuts consist of two main sections: an outer cap made from non-conductive plastic, and an interior metal spring that serves as the gripping mechanism. When twisted over the stripped ends of electrical wires, the metal spring holds the wires tightly so the cap will not fall off and no wires will slip out of the splice.

Types of Wire Nuts

Wire nuts are all pretty similar in how they function, but there are a few varieties for different applications.

  • Standard wire nuts: These are what you’ll find in homes everywhere. They have different shapes and sizes for application, wire size and comfort.
  • Outdoor: Use these outside and in wet areas, like patios and pools.
  • Aluminum to copper: Splices between different metals are required to be protected from corrosion.
  • Underground: Splices that will be underground must have wire connections rated for direct burial.

How To Choose the Right Wire Nut Size

Sizing is one of the most important concepts in the electrical industry. Improperly sized wire nuts can fall off or not cover the conductors fully.

All wire nut packaging states the sizes of conductors (and how many) the wire nuts can be used on. It’s usually a broad range. As an example, these yellow wire nuts from Ideal can handle 20 combinations of wires.

There’s no set color scheme for all wire nuts, though — it depends on the manufacturer. Always read the packaging before purchasing or using.

How To Use Wire Nuts Properly

Wire nuts are only as good as the installation. Here’s how to make sure your wire nuts stay put.

(Before handling any electrical wires, make sure the power is OFF by checking them with a non-contact voltage tester.)

  • Choose the correct nut: Before starting a project, have the right type and size wire nuts on hand. Read the label.
  • Make a fresh cut: Snip off the ends of the wires you’re splicing with wire strippers. Besides resulting in a better splice, stripping off the insulation will be a breeze.
  • Strip the wires: Use your wire strippers to remove one half to three-quarters of an inch of insulation, using the slot on the strippers that corresponds to your wire size and type (solid or stranded).
  • Hold the ends together: Take the wires and gather them into a bundle. For wires of the same type (all solid or all stranded), hold the stripped ends flush with each other. When splicing wires of different types, it’s best to hold them slightly offset, with the stranded ones higher than the solid.
  • Twist solid wires together first: This is an ongoing debate among electricians, but I always had better success twisting solid wires together with my lineman’s pliers before spinning on a wire nut. This is not necessary or recommended for stranded wires.
  • Spin on the wire nut: Push the wires all the way into the nut until they can’t go any farther. Twist the nut clockwise with one hand while maintaining pressure with the other. Once you feel the wires catch, twist until it’s secure. Wire nuts should be tight!
  • Pull on the ends: Hold the wire nut with one hand. Grab the ends of the wires, one at a time, and make sure they’re seated and don’t come out of the splice. If anything feels loose, tighten and try again. If any come out of the splice, take the splice apart and start over.