Thomas & Betts 30P High Temperature Wire Connectors

The 30P is built for small conductors, #22 through #14 AWG. That covers fixture wire, thermostat and control wiring, and 14 gauge branch circuit conductors. If you are splicing #12 or larger, this is the wrong cap and you need a bigger twist-on.

That is what the 30P is for. The phenolic cap is rated 150 degrees C (302 F), well above the 105 C rating of a standard thermoplastic wire nut, so it holds up in fixture canopies, recessed housings, heating appliances and other high heat splice points.

Yes, the 30P carries UL E9809 and CSA 6591, and it is rated 300V. The 300V rating means it is for fixture, luminaire and control splices, not 600V building wire applications.

They pack 100 to the inner box and 1,000 to the master carton. Weight runs about 2.5 lbs per thousand, so a full carton of these caps is light. Inner box measures 2.31 x 1.62 x 3.87 inches and the outer carton 8.75 x 4.87 x 4.5 inches.

Use the phenolic cap wherever the splice sits in a high heat enclosure: fixture canopies, ballast compartments, recessed housings, heating equipment. A standard nylon or thermoplastic wire nut tops out around 105 C and can soften or craze at those temperatures. The 30P is rated to 150 C. For ordinary junction box splices at room temperature, a standard cap is fine and the 30P is more connector than the job needs.

The copper coating on the internal spring resists corrosion, which matters in damp or high heat locations where a bare steel spring can degrade. The spring is a round design that multiplies twist-on torque through leverage and wedge action, crushing the conductors into a solid joint.

The 30P cap is black. On Thomas & Betts high temperature caps the color identifies the model rather than following the common thermoplastic wire nut color scheme, so go by the #22-14 AWG conductor range and the 30P marking rather than by color when standardizing across a building.