Rough Wiring for New Construction

Drilling Holes

Holes for the cable runs are drilled in the framing after all the boxes have been mounted. They should be bored in the center of the stud so their edges aren't less than 1½ inches from the edge of the framing. If this clearance can't be maintained, or if it's necessary to notch studs, the cable must be protected from nails by a steel plate that's at least 1/16 inch thick and large enough to cover the wiring area. These plates are called nail plates, and should be available wherever wiring supplies are sold.

Drill holes for cable runs that will connect wall receptacles about 1 foot above the boxes. Use drill bits that are large enough to accommodate the wire size to be used. You can use a hole for more than one cable if the hole is large enough. Usually a ¾-inch hole is large enough for one or two cables to be pulled through it. As you work, keep the holes aligned to make it easier to pull cable through them later. This requires conscious effort because the locations for holes usually aren’t marked on the framing. Snap a chalk line across the bottoms of the ceiling joists or the front of the wall studs to provide a guide, then work backward toward your destination while keeping an eye on the first couple of holes you drilled. Remember to always wear safety goggles and head protection when drilling overhead.

A ship auger is superior to most other drill bits for rough-in work. This bit is designed to pull itself through wood, let ting the drill motor do the work. Most other types of drill bits require a lot of pressure to bore through the wood. This is an important consideration when there is a lot of drilling to be done, especially in tight quarters. Avoid nails; they ruin drill bits.

Pulling NM Cable

Before you start pulling cable, familiarize yourself with the rules listed below that govern the securing and stapling of cable. These rules are important. They determine what supplies you must have on hand before you begin the work, as well as how you will do that work.

Pull the long cable runs first; use any leftover short lengths of cable for the runs between the boxes. Don’t permit the cable to sag excessively between holes, but don’t pull it too tight, either. Open new boxes of cable as they are needed. Lay the cable alongside the run and cut it so there will be 8 or 10 inches of free cable inside each switch box. Use a cable ripper to remove enough jacket so that about ½ inch of the jacket will show inside the box, or beyond the internal cable clamps if they are used. The electrical inspector will probably want the cable ends left outside the panel until after the rough-in inspection. Leave them long enough to easily reach any point inside the panel, and identify them by circuit number.

Where cable types NM, NMC, and UF are used in ex posed work (in garages and unfinished basements, for example), they should be run along the center of the sides of the joists, or through bored holes, or on running boards nailed across the joists, providing a surface for cable to be fastened to. Take care not to bend the cable too tightly. The minimum radius bend allowed is five times the diameter of the cable.

The NEC requires that cable types NM, NMC, and UF be secured at least every 4½ feet wherever they aren't run through bored holes, and within 12 inches of every box or panel where clamps are used to secure the cable. Clamps aren’t required in plastic one- gang switch boxes if the cable is secured within 8 inches of the box.

Select and use the correct staple sizes for the cables being installed. Application charts are usually printed on the staple package. Both bare and insulated staples are available. Choose whichever is used locally. Take care not to drive staples into the cable jacket.

Special Runs

Some special rules govern the installation of wiring in attics, crawl spaces, and garages. Where cable is run across the top of floor joists in attics that are accessible by permanent stairs, the cable must be protected on both sides by guard strips at least as high as the cable. Where only a scuttle hole leads to an attic, this protection is required only within 6 feet of the entrance. In garages and basements where cables aren't run inside walls, they must have physical protection wherever they are exposed within 8 feet of the floor. The most common form of protection is thin-wall conduit. A thin-wall connector and bushing are needed on the upper end of the conduit. The conduit is attached to the box using a standard thin-wall connector, which also serves to ground the conduit. Wiring in crawl spaces sometimes requires special mechanical protection, too. Consult the local electrical cede.

It’s a common practice to plan runs from the panel to a few boxes located in the center of areas where there are to be a number of receptacles, and then to wire from box to box in that area. These runs to the panel are called home runs, and they are shown on electrical drawings as short arrows connected to the home-run boxes and pointed toward the panel.

42 Running Cable; Cable — staple; Stud; Don’t staple through or into small cable; Receptacle for next room; Drill 3/4” holes for cable 1 1/4” from edge; Sheathed cable; Wires after sheathing is removed

Step 1. Nail the box to the stud so its center is on your mark and its front edge is the thickness of the wallcovering beyond the stud.

Step 2. Pull the cable through a knockout hole in the box so it protrudes 6” to 8” out of the box. Tighten the box clamp on the cable and staple the cable to the stud.

Step 3. Strip the sheath from the cable and remove the paper separation material. Strip ½” to W’ of insulation from each wire.

Wall T studs; Receptacle; Staple cable within 8” of plastic box; Knockout holes Box clamp; Staple

Using BX Cable

Years ago, armored cable, commonly known as BX, was used extensively in residential wiring, but nonmetallic cable has largely replaced it as the wiring method of choice. However, BX cable is often used in confined spaces such as inside cabinets, cupboards, and for runs to range hoods and food disposers, because it's superior mechanically to nonmetallic cable.

Actually, BX can be used in any dry place above the bottom of the basement ceiling joists. It can’t be used in damp or wet locations because paper spacers are used to maintain separation of conductors inside the jacket, and the paper is vulnerable to moisture. Red anti-short bushings are inserted into the cable ends to protect the conductors from the edge of the metal jacket; and special connectors, which are designed to keep the bushings in place, are used to connect the cable to the boxes.

Wiring Smoke Detectors

Smoke detectors have become standard equipment in homes. Originally, all smoke detectors were battery powered, and that type is still most commonly found in older homes. Information about types and location requirements is available through your local building- inspection department. Ideally, a house should contain a mix of battery-powered and hard- wired alarms because it’s unlikely that a battery and the home’s electrical system would fail at the same time.

43a Installing Armored Cable

1. Cut armor with a hacksaw

2. Strip armor

4. Slip a fiber bushing over the wires and into the end of the armor

5. Thread wires and cable through knockout hole in box and tighten clamp onto cable

43b BX Cable Applications: permanent appliance box

When hard-wiring smoke detectors, it’s advisable to put them on the same circuit as lights which are turned on several times a day so that you will know and respond quickly if the circuit goes out.

Wiring for Specialized Equipment

Doorbells and thermostats are wired with low-voltage wire, usually No. 18 or smaller (bell wire). This is usually installed after the 120/240-volt wiring is in place. The thermostat is in a circuit that's powered by a 24- volt source located in the furnace, and it should be mounted about 4 feet off the floor on an inside wall near the center of the house.

A separate transformer must be installed for the doorbells. This is a small 12-volt unit that usually mounts in a knockout in the side of a ceiling box in the basement or garage, where it’s accessible for future re placement if necessary. Small holes are drilled for the cable where needed, but whenever possible the cable is run through the holes used for the main house wiring. Insulated staples are used to secure the cable where it's run along the framing of the house.

Wiring for telephone, stereo, security systems, intercoms, remote-control systems, and so on, should be installed before the walls are closed up. De tailed installation instructions are always included with pack aged systems; follow such instructions exactly.

Cables that terminate in the service panel should be marked with their circuit numbers or destinations using indelible felt-tipped markers. Most of the boxes in the example house have one cable entering and one cable leaving them. Connections here should be obvious, and any question about the circuit number involved can be answered by checking the electrical layout on the floor plan. Real confusion can occur at ganged boxes where more than one switch is to be mounted; to minimize this, gently twist together the wires that go to each switch. When it comes time to do the finish work, the connections will be obvious.

Splicing

All splices must be made inside an electrical box or other approved housing. Most splices in residential wiring are made using wire nuts. These wire nuts are available for wires as large as No. 6. Color is used to identify size. Two of the most frequently used sizes are yellow and red, with red being the larger of the two. Wire nuts available now are generally approved for copper-to-copper connections only. Wire-nut packages contain charts that list allowable wire combinations:

Three No. 14s, two No. 12s, a No. 9 and a No. 10, etc. Additional information from the manufacturer includes strip length and whether the wires are to lay side by side or be twisted together before turning on the wire nut. Follow all of these instructions carefully.

The wire nuts used to connect circuit conductors together.

44 Stripping Wire: If you use a wire stripper or multipurpose tool, place wire in the proper-sized groove, squeeze handles and rotate tool to cut through insulation; Pull insulation off end of wire

Labeling and Marking Wires

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45 Splicing Wire

Joining Wire to a Screw Terminal

Strip ¾” of insulation from the wire ends.

Use needle nose pliers to form a ¾-loop in the stripped wire.

Joining Wires with Wire Nuts

Strip about ½” of insulation from the ends of wires you’re joining. Stick the ends into the wire nut and turn it clockwise until tight.

Crimp made with a crimp tool

Strip insulation as you would for a wire-nut splice. Insert the wires and crimp the connector.

Note: Some manufacturers of wire nuts require you to pre-twist the wires before screwing on the nut

Hook the bent wire clockwise around the screw terminal and tighten the screw.

Metal insert with points

This connector is molded from one piece of plastic and has a metal insert with points. You insert the wires and close the clam shell, forcing the metal points through the insulation into the metal wire.

Clamshell connector

Joining Several Wires to a Screw Terminal

The electrical code requires that no more than 1 wire be attached to a screw terminal. To attach more wires to a terminal, splice them together along with another short piece of wire (the pigtail) with a wire nut. Then attach the pigtail to the screw terminal.

Clamp connector; Pigtail

Bare wires and connector must be wrapped with electrician’s tape or enclosed in a junction box.

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Split-bolt connector in NM cable may also be used to connect grounding conductors together. A special wire nut is available for grounding purposes in metal boxes. It resembles an ordinary wire nut, except that it's green and has a hole through its top. A bare grounding wire passes through the hole, with one end connected to the ground screw in the box and the other end connected to the ground terminal on the switch or receptacles being wired. The ends of the ground wires from the cables entering the box are pushed into the wire nut, and it's then twisted tightly over the entire group of wires until it's tight.

Crimp-on terminals are needed for certain applications, in which an ordinary screw is used to connect a stranded wire to a terminal, for example. Without the crimp-on terminal, the stranded wire would flatten out, and some of the strands would not be covered by the screw head. Terminals are classified by wire size and screw size. A 10-10 terminal is meant to be used with No. 10 or No. 12 wire and a 10-24 or 10-32 screw. These terminals are available both bare and insulated in a number of configurations. A crimping tool, preferably one that also strips wire, is a worthwhile investment for the home electrician.

Using Conduit

It’s often wise, and sometimes required, to install conduit and wire rather than cable in basements, garages, and some outdoor wiring situations if the cable will be subjected to physical damage. Conduit is used in all service installations, al though this hasn’t always been true. Conduit systems are continuous from box to box, which means that future wiring changes and additions can be made easily.

Conduit runs must be complete before wire is pulled into them. Wire is usually fished from outlet to outlet with a fish tape. To do this, first, push the fish tape through the conduit. Then strip about 4 inches of insulation from the end of each of the wires that will be pulled through the conduit. Push these bare ends halfway through the eye of the fish tape, fold them back 180 degrees, and tape the group closed with two or three wraps of electrical tape. All of the bare wire should be covered. Now, one person pulls the fish tape through the conduit while a helper feeds the wire into the conduit and keeps it straight. Wire usually can be pushed into short, straight conduit runs with ease if the wire ends are taped together as described above and the group is kept relatively straight while pushing.

EMT (Thin-wall) Conduit

Electrical metallic tubing, commonly called EMT, thin-wall, or steel tube, is a popular, rather easy-to-install conduit that's often used in basement and garage wiring. It’s also approved for outdoor installations when used with weathertight couplings and connectors. EMT

is cut with a hacksaw using a fine-toothed blade; never use a tubing cutter. After the conduit is cut it must be reamed and de-burred. Use channel lock pliers for both operations. To deburr, gently close the pliers over the cut end of the conduit and rotate the pliers back and forth while holding the EMT in your other hand. To ream, open the pliers until the tips of the handles come together, and then insert them into the conduit and twist back and forth, or if the pliers’ handles are cushioned, insert the upper jaw into the conduit and twist. Either way, it’s easy; the material is soft.

EMT is never threaded. In stead, it's coupled together and connected to boxes using couplings and connectors that slide ¾ inch or so over the thin- wall and are held firmly to it using set screws (indoors) or a compression arrangement (out doors). Fittings using an in denting tool were once popular because of their low cost, and you may find this kind in your home. A locknut is threaded onto the connector to hold it securely to the box. Generally, bushings aren’t required.

Because it bends easily, ½-, ¾-, and 1-inch EMT can be bent with a hand bender; 1” can be bent by hand, but is more difficult. Larger sizes require mechanical bending. Use the correct-sized bender for each EMT size. Factory-bent el bows are available in all sizes. Offset connectors can be used when only a small amount of offset is needed where the EM enters a box.

EMT can't be installed with more than the equivalent of four quarter bends (360 degrees) between boxes. Bend it more than this and it may be impossible to get a fish tape through it for pulling wire. EMT must be supported with approved straps at least every 10 feet and within 3 feet of each box or panel.

Rigid Metal Conduit

This type of conduit is often used for the mast in overhead services, and is always used in low-roof services, that's , where the mast extends above the roc of the home. Rigid metal conduit is threaded and reamed on both ends. It joins together with couplings that thread over the conduit, and is fastened to boxes and panels with a lock nut or locknuts (one outside and one inside the box) and a bushing on the inside to protect the wire from abrasion.

Small sizes can be bent by hand, but larger sizes should be bent mechanically. A variety of factory elbows and L- and T-shaped conduit bodies are available. The rules for sup porting rigid metal conduit are the allowable number of bend: between openings are the same as for EMT.

Rigid is truly the “use everywhere” conduit. It offers maximum mechanical protection of the wires within it, indoors, outdoors, and in the ground. Black enameled conduit is sometimes found in older homes; this is ordinary conduit that has had a coat of enamel applied to it by the manufacturer. It can be used only indoors because it isn't galvanized.

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47a Conduit

Thin-wall conduit (EMT); Thin-wall connector; Thin-wall weathertight coupling; PVC coupling; Thin-wall coupling; Setscrew connector; Plastic conduit (PVC); Rigid metal conduit

Note: Rigid conduit is different Rigid coupling from plumbing pipe— they Rigid connector aren't interchangeable

Bending Conduit

1. Insert the conduit in the bender so the hook is where you want the bend to start.

2. Hold the bender and conduit in place with your feet but do not stand on it. Pull the handle back until the conduit is bent to the required angle.

Hint: Because bending to precise measurement is difficult, it's easier to bend the conduit first and then cut each leg to exact length.

PVC (Rigid Nonmetallic) Conduit

This nonmetallic conduit is a PVC product that's used primarily outdoors, especially for service-entrance conductor raceways and wiring to swimming pools and spas. Like EMT and rigid metal conduit, it's manufactured and sold in 10- foot lengths.

This rigid PVC conduit can be cut with a hacksaw, and the rough edges can easily be trimmed inside and out with a knife. Sections are joined together with couplings that are attached to the conduit ends with solvent cement. Connections at boxes and conduit bodies are made by solvent- welding the conduit to the hub of the enclosure; or where the conduit enters an ordinary knockout, a connection is made by solvent-welding a threaded adapter to the conduit and using a metal knockout to secure it to the enclosure.

A variety of PVC elbows, boxes, and L- and T-shaped conduit bodies and service heads are available for use with PVC conduit. PVC must be heated for bending, which means the do-it-yourselfer is limited to using readily avail able factory items for turning corners and changing elevations. The 360-degree limit between openings also applies to PVC conduit. Supports must be no farther than 3 feet apart for ½- to 1-inch sizes, 5 feet apart for 1.5- to 2-inch sizes.

Rigid nonmetallic conduit is manufactured as Schedule 40 and as a heavier-walled Schedule 80 for use where greater physical strength is needed. PVC for use above ground is marked “sunlight resistant.” Local practices determine which type is used where. Check with your electrical- inspection department or with a reliable local supplier before installation.

Flexible Conduit

Three types of flexible conduit are found in home wiring. They are flexible metal conduit, often called Greenfield, liquid- tight flexible metal conduit, and liquid-tight flexible non metallic conduit. Special fit tings are required for each of these types.

Greenfield is a fine, but ex pensive, general home-wiring material, once used exclusively in some geographical areas. It is pulled from box to box in concealed work through the holes bored in the framing of the house in much the same way cable is pulled. There can be no more than 360 degrees total in the bends between boxes, and the conduit must be supported at intervals not exceeding 4½ feet and within 12 inches of each box or panel. Properly in stalled Greenfield provides grounding at all the receptacles in the system.

Liquid-tight flexible conduits in the home are usually limited to short lengths, such as between a disconnect and an air- conditioning compressor, or in wet or damp conditions where the lengths of conduit are no more than 6 feet and flexibility is needed.

Installing High-speed Broadband and Telephone Cable

Red, Blue, Black, Yellow, Green; Telephone cable; Regular electric box nailed to stud; Plastic snap-in connector secures cable to box; FM radio coaxial cable

Jack Types: Cover plate; Telephone jack; Coax Cable jack; Ethernet jack