What Kind of Junction Box Do I Need for 6 Gauge Wire?

Junctions Defined

• A junction box is a metal or plastic open-faced box that can be surface mounted, or inset into a wall to contain a splice, outlet, switch or turn in a wiring run. All splices inside residential homes must be inside such boxes by law. The boxes themselves are made from either a heavy weight plastic, typically blue or gray, or galvanized metal. They come in round, square and rectangular styles. The outside edges of the box have multiple entry holes, some of which can open up to more than one size, to fit your cabling. The box is mounted with screws, and covered over with a screwed-down metal, or plastic cover.

New Construction

• In new construction, 6-gauge wiring can go in either metal, or plastic boxes. Typically the cabling is mounted to the framing with staples, or small metal straps. The box itself mounts to the frame, so that the front edges will be even with the finished face of the wall. Plastic new construction boxes are often fitted with attached nails, that you can drive into the stud. Others have angled holes that you can drive screws through. The metal boxes are mounted with screws through holes in the back, or sides, of the box.

Upgrades

• When installing 6-gauge in remodeling and reworking to existing systems an "old work" box works best. These are typically of heavy plastic and have a screw clamp that fastens to the front edge of the drywall, rather than attaching to the frame, for easy installation in previously finished walls. You can fit the face of the box with the standard junction covers so that there is no visible difference.

Box Sizing

• To calculate box size, you must account for the size of all wires running into your box. Typically multiple cables will run into your box in a wiring chase, or conduit. Building codes dictate the space that must exist inside a junction box. The minimum requirement is related to the largest conduit coming in. Measure the diameter of the largest chase coming into your box. The box must be 8 times longer than the diameter of the largest conduit.