Wire nut

Twist-on wire connectors are a type of electrical connector used to fasten two or more low-voltage (or extra-low-voltage) electrical conductors. They are widely used in North America in residential, commercial and industrial building power wiring.

Twist-on connectors are also known as wire nuts, wire connectors, cone connectors, or thimble connectors. One trade name for such connectors, Marrette, is derived from the name of their inventor (see History) and, in Canada, this type of connector is often referred to as a marrette regardless of the actual brand of the product.

In the UK, items similar to those used in North America, but made from ceramic materials, were sold under the brand "Scruit". Such ceramic connectors are currently sold in South Africa under the name "Porcelain Scruits".

Twist-on wire connectors are available in a variety of sizes and shapes. While their exterior covering is typically made from insulating plastic, their means of connection is a tapered coiled metal insert, which threads onto the wires and holds them securely. When such a connector is twisted onto the stripped and twisted-together ends of wires, the wires are drawn into the connector's metal insert and squeezed together inside it. Electrical continuity is maintained by both the direct twisted wire-to-wire contact and by contact with the metal insert.

Twist-on wire connectors are typically installed by hand. They may have external grooves to make them easier to handle and apply. Winglike extensions are commonly molded into higher quality connectors to reduce operator muscle fatigue when installing a large number of the connectors. Such extensions also allow these connectors to be installed with a common nut driver or a specialized tool.

Twist-on wire connectors are commonly color-coded to indicate the connector size and, hence, their capacity. They are commonly used as an alternative to terminal blocks or the soldering of conductors together, since they are quicker to install and, unlike soldered connections, allow easy subsequent removal for future modifications.

Twist-on connectors are not often used on wire gauges thicker than AWG #10 (5.26 mm²), because such solid wires are too stiff to be reliably connected with this method. Instead, set screw connectors, clamps or crimp connectors are used.

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