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Twist-On Connector Range Guide

How to read the wire combination chart on a twist-on wire connector package, and what to check before using a connector for a splice.

Ref EL-0065UL 486C

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Twist-on wire connectors (often called wire nuts) join two or more conductors by twisting a coiled spring or threaded insert onto the stripped ends. Each connector size is listed under UL 486C for specific combinations of wire sizes and counts. Those combinations are printed on the package or in the manufacturer's literature. There is no single industry chart. The combinations allowed for one brand and color do not apply to another brand, even if the colors match.

How to read it

Find the connector's combination chart. Each line lists a set of conductors that the connector is listed to join, such as two 12 AWG with one 14 AWG. Find the line that matches your exact splice, including the number of conductors, each size, and whether each is solid or stranded. If your combination is not on the chart, that connector is not listed for it.

What the chart shows

Chart item	What it tells you	What to check
Wire size range	Smallest and largest wire the connector takes	Your splice must fall inside it
Combination lines	Exact sets of conductors the connector is listed for	Count and size of every conductor
Solid or stranded	Whether stranded or fixture wire is allowed	Mixed solid and stranded may need a specific line
Minimum and maximum conductors	How few and how many wires one connector can hold	Do not exceed the maximum
Voltage rating	Maximum system voltage	Must meet the circuit voltage
Temperature rating	Maximum operating temperature	Must suit the location, such as inside a luminaire
Conductor material	Copper only, or listed for aluminum and copper	Aluminum needs a connector specifically listed for it
Strip length	How much insulation to remove	Too long leaves bare copper exposed

Key points

Color identifies size only within one manufacturer's line. Read the package, not the color.
Pre-twisting conductors is allowed by some makers and not needed by others; follow the instructions.
A good splice has no bare conductor showing below the skirt, and each conductor holds when tugged.
Wet and direct-burial locations need connectors listed for those conditions.

Common mistakes

Using a connector for a combination not on its chart, such as one more wire than allowed.
Joining aluminum and copper with a standard connector.
Assuming one brand's red connector has the same range as another brand's red connector.

Governing standards: UL 486C (splicing wire connectors); NEC 110.14 (electrical connections). Manufacturer's combination chart and instructions govern.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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