When a cable is run through bored holes the cable must be How far from the nearest edge of the framing member?

While you might call this area inaccessible because it's small, dark, and difficult to enter. In this case, the codes definition of accessible is whether or not there's permanent stairs or a ladder.

Cable run across the top of joists

If the attic is accessible by permanent stairs or ladder, any cable running across the top of joists will have to be protected. Protecting the cable is as simple as installing "substantial guard strips", which can simply be a 1x2 furring strip on each side of the cable.

If there's no permanent stairs or ladder, this protection only has to be provided to cables within 6 ft. of the entrance of the attic.

334.23 In Accessible Attics. The installation of cable in accessible attics or roof spaces shall also comply with 320.23.

Article 320 Armored Cable: Type AC

320.23 In Accessible Attics. Type AC cables in accessible attics or roof spaces shall be installed as specified in 320.23(A) and (B).

(A) Where Run Across the Top of Floor Joists. Where run across the top of floor joists, or within 2.1 m (7 ft) of floor or floor joists across the face of rafters or studding, in attics and roof spaces that are accessible, the cable shall be protected by substantial guard strips that are at least as high as the cable. Where this space is not accessible by permanent stairs or ladders, protection shall only be required within 1.8 m (6 ft) of the nearest edge of the scuttle hole or attic entrance.

(B) Cable Installed Parallel to Framing Members. Where the cable is installed parallel to the sides of rafters, studs, or floor joists, neither guard strips nor running boards shall be required, and the installation shall also comply with 300.4(D).

Cable run through bored holes

You could always run the cable(s) through holes bored in sanw lumber joists, but you'll have to make sure the edge of the hole is more than 1 1/4" from the nearest edge (2" according to IRC).

300.4 Protection Against Physical Damage.

(A) Cables and Raceways Through Wood Members.

(1) Bored Holes. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (1 1/4 in.) from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate(s) or bushing(s), at least 1.6 mm (1/16 in.) thick, and of appropriate length and width installed to cover the area of the wiring.

NOTE: When dealing with engineered structural members, boring holes may not be an option.

Most of the wiring in a modern home consists of runs of nonmetallic sheathed cable, or NM cable (also known by the popular brand name Romex). NM cable must be supported by framing when running through walls, ceilings, and floors. The National Electrical Code (NEC) outlines specifications for securing NM cable and other electrical wiring. Most local building authorities follow the NEC recommendations, but in any case, the local rules are the ones you must follow, and they are the specific requirements you must meet to pass inspections. Securing cables prevents excessive movement that could loosen connections or lead to cable damage.

Runs of NM cable must be supported at least every 54 inches. They also must be secured within 12 inches of an electrical box that includes a cable clamp or within eight inches of a box or enclosure without a cable clamp. Keep in mind that "support" does not always mean fastening the cable to framing. For example, with a typical cable installation inside a framed wall, the cable passes through holes drilled into the wall studs for most of its horizontal run. When the cable approaches an electrical box, it makes a turn to run up or down the side of the stud toward the box and is fastened (usually with a cable staple) to the side of the stud within eight or 12 inches of the box, as required. In this common application, most of the cable is supported by the framing but is not fastened to the framing.

Use anything from a U-shaped staple to nail-on fasteners with plastic cable clips. There are a few important rules to follow when choosing and installing staples and other cable fasteners:

• Use the proper size of fastener for the size and number of cables being secured.
• Use insulated staples and fasteners. Avoid plain metal staples, and never use standard staples or other fasteners that are not designed for electrical installations.
• Position cables flat against framing before securing them; do not fasten cables on-edge.
• Secure cables snugly but not so tightly that the cable is damaged or indented from the fastener.
• Secure only one cable under each fastener, in most cases. Sometimes it is permissible to secure two 2-conductor (plus ground) cables under a single staple, for example, but it is preferable not to double up cables. It is not permissible to secure more than one 3-conductor cable under a single staple.
• Use stacker-type fasteners to secure multiple cables to the same framing member. These allow the cables to be stacked for a neater, safer installation. The clips are either nailed or screwed to the framing, and the cables are secured by clipping them into the slots.
• Avoid sharp bends in the cable immediately after a box, a drilled hole, or a staple or clip. Cables must not be bent in a radius smaller than five times the cable diameter.

Setback rules apply when cables run through holes in the framing or when they run parallel to and are secured to, the sides of the framing. This includes most cable runs in finished areas of the home. The general setback rule is that cables must be at least 1 1/4 inches from the face of the framing members. In a wall, ceiling, floor, or roof framed with standard lumber (2x4, 2x6, etc.) the faces are the narrow edges that get covered with drywall or other surface material. If the setback requirement cannot be met, you must protect the cable by installing a steel plate that fastens to the face of the framing, centered over the cable location. The setback requirement also means that cables cannot be fastened side-by-side on the broadsides of 2x4 studs; there isn't enough room to provide sufficient setback for both cables. That's where stacker-type fasteners come in most handy.

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The number and the content of "Code Question of the Day" submissions concerning the installation of nonmetallic sheathed cable suggests vast differences among, or lack of proper inspection of, electrical installations using Type NM cable as the wiring method. This, coupled with some electrical installers' seemingly indifferent attitude toward keeping a "neat and workmanlike manner," suggests a need for improved education relating to the installation requirements for nonmetallic-sheathed cable. Following are some questions submitted to "Code Question of the Day." QUESTION: We have a new inspector in our area and he's driving me nuts. "Mr. Gung Ho" says that, in the attic of new homes, he wants the NM cable that is run across the joists to be protected by guard strips. He told me to check the Code, but I can't find anything in Article 336 where he told me to look. What should I do? ANSWER: Three cheers for Mr. Gung Ho. Take another look in Article 336, specifically Section 336-6(d). This tells us, "The installation of cable in accessible attics shall also comply with Section 333-12." Article 333 relates to "Armored Cable: Type AC," but Section 333-12 is applicable by reference from Section 336-6(d). Section 333-12 requires, "where run across the top of floor joists (meaning the attic floor joists), the cable shall be protected by substantial guard strips that are at least as high as the cable." This is a "performance" requirement because you are not told how to do it, just that you must do it. It can be readily accomplished by fastening 1 x 2 furring strips on each side of the cable. You could also protect the cable by not running it across the top-of-floor joists. Instead, the cable could be run through bored holes in the joists. Remember Section 300-4(a)(1) when doing this. Holes shall be bored so that the edge of the hole is not less than 1-1/4 inches from the nearest edge of the wood member. If you can't maintain this distance you must protect the cable with a steel plate at least 1/16 inch thick. Another point to remember is that Section 333-12 requires this protection in the entire attic space only if it is accessible by permanent stairs or ladders. Where the attic space is accessible through a scuttle hole, the protection is required only within 6 feet of the scuttle hole. QUESTION: When installing nonmetallic sheathed cable at the main panel in a residence, how is it possible to fasten each cable within 12 inches of the cabinet as required by Section 336-18? If I bring all the cables to the studs to fasten them, then I can't keep the required clearance from the edge of the stud. ANSWER: Section 300-4(d) requires a steel plate at least 1/16-inch thick to be installed where 1-1/4-inch clearance from the edge of the framing member cannot be maintained. A header between the studs could be installed to secure the cables to. QUESTION: Table 370-16(a) is titled "Metal Boxes." How do I determine the box fill requirements when using NM cable and nonmetallic boxes? ANSWER: Section 370-16(a)(2) requires nonmetallic boxes to be durably and legibly marked by the manufacturer with their cubic-inch capacity. Using this information, together with Table370-16(b) requirements, the installer is required to comply with the box conductor fill requirements. Then of course, there is the clamp fill, support fittings fill, device or equipment fill, and the equipment grounding conductor fill. If you're looking for the cubic-inch capacity of a nonmetallic box, you will find the durable and legible marking inside the box at the back. QUESTION: The building I am wiring has steel studs. The inspector says I have to install grommets or bushings to protect the cable where I run the Type NM cable through holes in the studs. I can't find this anywhere in the Code. Is he right? ANSWER: Yes, Section 300-4(b)(1) requires that, where nonmetallic cables pass through holes or slots in metal framing members, the cable shall be protected by bushings or grommets covering all metal edges and securely fastened in the opening prior to installation of the cable. SYNOPSIS: Every effort has been made through the Code-making process to establish requirements for the installation of nonmetallic-sheathed cable to ensure that complying installations will be safe. There's no reason for inspection or installation procedures not to be consistent with these requirements. TROUT is a technical consultant For Maron Electric Company of Chicago, and he is Chairman of the National Electrical Code-Making Panel 12, representing NECA. He is also the principal author of Electrical Contractor magazine's on-line feature, "Code Question of the Day."