How to Wire an Unfinished Garage
- 1). Draw a diagram of your garage, and lay out the circuits you intend to pull. In general, 15-amp breakers are standard and will support up to 1,500 watts of electricity usage safely. This means that several light switches or outlets can be wired on one circuit. Design separate circuits for heavy-duty items, such as freezers and other appliances, and avoid wiring 220-volt circuits yourself for safety.
- 2). Turn off the main power to the garage sub-panel. Typically, there will be a lever to the side of the box with a red handle marked on and off; switch it to off, usually down. In some cases, the power is controlled by a larger breaker at the top of the breaker panel; flip this to the off position.
- 3). Assign breaker bays for each circuit, and stick temporary tape labels to the breaker box to indicate each location. Feed three conductor household insulated cables into the punch-out at the top of the box for each circuit. Cut your wires with wire cutters, long enough to run from the box, through the wall or ceiling to the outlet or switch intended, with at least 2 feet of slack.
- 4). Strip the end of each wire, cutting the outside casing away from the end for 4 to 6 inches and stripping each of the three conductors 1 inch back from the end by using the correct size hole in the jaw of your wire-stripping pliers. Squeeze the pliers shut and pull toward the end of the wire to remove the insulation.
- 5). Feed the green ground and the white wire into holes in the neutral bus block. This is a strip to one side of the box with square holes, each with a screw. Choose any hole, push the tip of one wire in and tighten the screw. Attach the black wire to the circuit breaker it will belong to. Loosen the screw at the bottom rear of the breaker, feed the wire into the hole, and tighten the screw again. Snap the breaker into the bay you chose, snapping the outside, or back, onto the rod first, then pressing the front in firmly to snap it into place.
- 6). Install all junction boxes for light fixtures, switches and outlets. Depending on the box, nail or screw these to a stud in the location where the outlet, junction or switch belongs. Outlets must be at least 12 inches from the floor. Mount them with the front edge 1/2-inch out from the face of the stud to account for drywall.
- 7). Run each circuit from the breaker box to its switch, junction or outlet. Drill holes through the frame or wall cap at the tops of walls with a 1-inch paddle bit where needed. Wires running horizontally will need holes through the studs. All wires must be inside the frame, with nothing running over the face of studs or ceiling joists. If the area above the garage will be floored, run wires through holes drilled in the joists; if not, run them above the joists for ease of installation.
- 8). Strip the wire at the ends as you did for the breaker box end, only cut the outside casing back 3 to 4 inches. Attach wires at the switch or outlet by inserting the tip into the appropriate hole and tightening the wire. Typically, nickel-colored screws receive black wires and copper-colored screws receive white. Green ground wires will attach to the green ground screw.
- 9). Make splices between wires in junction boxes using wire nuts. Twist like-colored wires together, twist an appropriate sized wire nut onto their ends and wrap it in electrical tape. Install wires from switches to fixture junctions last. Install covers on every switch, outlet and junction box. Turn on the power and test the circuits.
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