Electricity: Running Cable

In New Construction

For installing new cable, you’ll need a 3/4-in. (20-mm) spade or auger bit, a drill (right- angle drill, if possible), wire stripper and basic hand tools. Select the proper types arid sizes of boxes, then lay out and fasten them to framing members at the code-required and desired locations. Fasten boxes so their faces will be flush with the finished wall surface. Lay out, line up and drill holes—holes should be drilled in the center of framing members. Cables must always be at least 1-1/4 in. (32 mm) from both faces of studs to prevent damage from nails and screws. If not, install metal protector plates. Before pulling the wire through the holes, unroll and straighten a long length of it, so it slides through the holes with out tangling. Staple cable within 8 in. (20 cm) of boxes and every 4 ft. (1.2 m), when running along joists or studs.

1. Bore 3/4-in, holes through center of framing members about 12 in. (30 cm) above outlet boxes.

2. Pull cable through holes between boxes, leaving 12 in. (30 cm) of excess cable at each box.

3. Fish cable around corners by bending a sharp hook in it. Use your finger as a guide.

4. Secure cable with a staple 1-1/4 in. (32 mm) from front edge of stud and within 8 in. (20 cm) of box.


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In Thin Walls

Protect cable in 1-1/2-in. walls by running it through 1/2- in. thin-wall metal conduit. Fasten 4 x 4 x 1-1/2-in, metal boxes (drill extra hole in wall for ground screw) and attach a length of conduit with a conduit connector. You’ll need one conduit for each cable entering the box. Install a conduit connector at the top of the conduit to protect the cable from sharp edges where it exits the conduit. Secure the conduit with a strap within 3 ft. (90 cm) of the box and at a maximum of 10 ft. (3 m) thereafter. Attach the ground wire to the threaded hole in the back of the box with a green ground screw. Install a plasterring. continued...


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In Unfinished Garages

Special rules apply and extra care is required when installing Type NM cable in unfinished garages, sheds, workshops or other structures with unfinished walls and ceilings. In finished areas, wiring is protected by drywall or wood. The key to safe wiring in unfinished areas is to properly route the cable and use the framing members for protection. Remember these guidelines:

• Don't span stud or joist spaces where cables could be damaged. Run cables so they closely follow framing members. This often means taking a longer route between boxes, but cable is relatively cheap and easy to install.

• Unwind and straighten cable before installing it to avoid potentially damaging twists. Don’t bend the cable too sharply around corners -- gentle bends look better and won’t damage the cable.

• Secure cable within 8 in. (20 cm) of boxes and every 4 ft. (1.2 m). Use lots of staples at bends and where necessary to prevent cables from sagging.

• Use metal boxes and thin-wall metal conduit where cable is installed on masonry walls or already finished walls.

Follow framing members closely, bend cable gently around corners and secure cable often with plastic staples.

Run cables perpendicular to ceiling joists by securing them to the sides of wood braces.

Run cable on face of gable-end framing where it remains visible and not subject to damage.

Last modified: Saturday, 2007-11-03 1:15 PST