Stripping and Working With Electrical Wiring Cables

Stripping and Working With Electrical Wiring Cables

Here I’ll show stripping insulation because it is often done at the rough wiring stage. Splicing and joining wires are operations that happen during the finish wiring stage after drywall has been installed. Like PVC pipe, NM cable (also called Romex) is easy to work with,

but you still need to take care when stripping and joining. In particular, be sure not to nick the wire insulation when you strip the sheathing; bare wires could touch each other and cause a short.

This work is often done with a knife, but it pays to buy and use good tools, especially if you are a beginner. A number of good tools are on the market, but a pair of cable and wire strippers like the one shown on this page may be the best option.

It will make quick and easy work of stripping without nicking wires. It has slots for stripping 12/2 and 14/2 cable, as well as holes for stripping 14- or 12-gauge wire. If you need to strip other sizes of cable or wire, go ahead and buy a tool for those sizes.

For clarity, I show these stripping operations being performed prior to running the cable through framing to the box. However, it is often easier to run an unstripped cable to the box location and then do the stripping just prior to inserting into the box.

  • Measure to cut off a bit more than 6 in. of sheathing. To do this quickly, note where 6 in. comes on your tool, so you don’t have to repeatedly use a tape measure.

  • Slip the cable into the slot for its size (here, 14/2), squeeze the handles together, and give it a twist as you squeeze. Then slide the sheathing off.

  • Pull any paper or plastic strips off the wires, and cut them near the cut end of the sheathing. Or, it may be easier to simply tear off the paper. If you will strip the wires as well at this point (you may decide to do this later), measure 3⁄4 in. or so.
  • Slip the wire into the correct-size stripper hole, squeeze, twist, and pull the insulation off.

  • If you feel skilled and want to try doing it the way many pros do, you can practice until you get good at stripping both cable and wire ends using a pair of lineman’s pliers.

Once you are used to working this way, you can squeeze with just the right pressure so you quickly strip without nicking wires.

Splicing Wires

Some people splice solid wires together simply by poking them into a wire nut and twisting, but you’ll get a firmer connection by twisting them together first and then adding a wire nut.

  • After stripping about 3⁄4 in. of insulation from two or more wires, hold them tightly side by side with their ends aligned.
  • Grab the wire ends with the tip of a pair of lineman’s pliers and twist clockwise several times, to get a neat-looking, tight joint.

  • Pull on the wires to be sure the connection is tight; you should not be able to easily untwist. Snip the tip of the splice at an angle with the lineman’s pliers or diagonal cutters.
  • Insert the wires deep into a wire nut and twist clockwise to tighten.

When joining a fixture’s stranded “lead” wire to one or more solid wires, wrap the lead clockwise around the wire(s) so the lead extends about 1⁄8 in. past the solid wire. Insert the wires deep into a wire nut and twist clockwise until you achieve a firm connection.

Wrapping With Tape

Wrapping the bottom of a wire nut and the wires with professional quality electrical tape is not usually considered necessary, but doing this is a good idea. At the very least, make sure that no bare wire is exposed after the wire nut is attached.

Connecting Wires To Terminals

Many switches and receptacles have side-mounted terminals with screws. (They may have poke-in options as well, but most electricians don’t trust them to make reliable connections.) To connect wires,

  • strip off a full 1 in. instead of the 3⁄4 in. used for splicing. Use the tip of a pair of wire strippers (as shown) or longnose pliers to twist the stripped wire into a question-mark shape.
  • Loosen the terminal—brass for the hot wire and silver for the neutral—and slip the stripped end under the screw head. Squeeze the wire to tighten it around the terminal.
  • Tighten the screw firmly.

  • Also, tighten any other terminal screws that are loose. Wrap the device with electrical tape, so all the bare wires and terminals are covered. Some high-quality devices have push-in terminals that get tightened after inserting the wire end. These make for reliable connections.

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Simplest Ways for Understanding Wiring

Simplest Ways for Understanding Wiring

Installing boxes and running electrical cable or conduit for receptacles (outlets), switches, lights, small heating units, and other fixtures generally happens after the rough plumbing is finished, since the cable is easy to rout around pipes.

Once you have ensured that you are working on only nonenergized wiring, then the installations are surprisingly easy to learn. Attaching boxes, routing cable, and installing lights and other fixtures often can be accomplished in short order. This article hits only the high points of electrical work. if you are at all unsure of how to install something correctly, hire a professional electrician.

The Service Panels

Understanding your electrical service begins with a look at the service panel. (You don’t have to remove your service panel cover, but you will need to if you install new circuits for new service.) Unless you have an old house with outdated equipment, three thick wires enter your panel. One “neutral” wire connects to a strip of metal called a neutral or hot bus bar. The two “hot” wires connect to the two hot bus bars, which run down each side of the panel; individual breakers are connected to the bus bars.

Each breaker is connected to a hot wire that sends power to an individual or “branch” circuit. A breaker is a safety device that turns itself off when there is an overload, short, or other problem with the wiring. To restore power, some breakers turn back on with a single flip; others must be flipped one way, then the other. Inside a service panel, you will find a mass of wires. Hot wires, which are black, red, or another color, attach to breakers and carry power to electrical outlets throughout the home. Neutral wires, which are almost always white, carry power back from the outlets to the panel, where they hook to a neutral bus bar. Bare copper or green ground wires also lead back from the outlets to the panel, where they attach to the same bar as the neutrals or to a separate grounding bus bar.

You’ll find a lot of wires in a service panel—hot, neutral, and ground. Be sure you know what each wire is before working in a panel.

If you have a fuse box instead of a panel with breakers, don’t panic. It may work fine, as long as you don’t have heavy electrical users. But if you will be adding service in your basement, you will need new electrical circuits. It’s probably time to hire an electrician to install a new breaker panel with at least 100 amps—200 is even better. When opening a service panel, be extra safety-conscious: Wear gym shoes or other rubber-soled footwear, and be sure to stay dry. And don’t touch any bare wires in the panel.

Safety Alert: If you suspect any problem with the wires that run to your house, or to your electrical meter, do not touch anything; call your electrical utility to come out and assess the situation.

Volts, Amps, and Watts

To put things as simply as possible, “volt” refers to the force with which power is pushed through wiring. Residential wires all carry between 115v and 125v, which is called 120v. Most devices and fixtures in a home use 120v, but some heavy users, such as air conditioners, electric stoves, or electric water heaters, use 240v. This amount of voltage is provided by two 120v wires.

Though voltage is the same throughout a house—120v per wire—the amount of power used varies quite a bit. This amount is measured in amperes or amps. A light fixture—especially an LED—uses a tiny amount of amperage, while a window air conditioner or refrigerator can use a lot.

Most 120v circuits have breakers and wires that can handle either 15 amps or 20 amps. A 15-amp circuit uses #14 wire, while a 20-amp circuit uses thicker #12 wire. (These are also called 14-gauge and 12-gauge wires, or 14 AWG and 12 AWG.) It is important that a #14 wire not be attached to a 20-amp circuit, or it can overheat dangerously before the breaker shuts off. Some very heavy 240v circuits use larger-amp breakers and correspondingly thicker wires. Thirty-amp circuits call for #10 wire, and 40-amp circuits require #8 wire.

Wattage (or “watts”) is a measurement of the power used by fixtures or devices. It is calculated by measuring volts times amps. So for instance, a 15-amp/120-volt circuit has a capacity of 1,800 watts. Codes require that it be loaded with no more than a “safe capacity” of 1,560 watts. And a 20-amp circuit should supply no more than 1,920 watts.

Circuit Wiring

Power passes from the hot bus bar to a breaker, and from there to a branch circuit via a hot wire. Each branch circuit supplies power to a number of outlets. Modern codes call for separate circuits (and separate breakers) for receptacles, for lights, for certain appliances, and so on. But in many homes, a single circuit may supply some receptacles, some lights, and maybe even an appliance as well.

In homes with well-organized circuitry, it is fairly easy to determine which users are controlled by which circuit: It may be a group of receptacles or lights, or it may be a certain room. However, don’t be surprised if your circuits go all over the place and if a single circuit controls receptacles in one room, lights in another, and so on.

Contemporary electrical codes call for many more circuits than used to be required. For instance, in a kitchen, you may need two circuits for countertop receptacles, as well as dedicated circuits for the refrigerator, the microwave, and an exhaust fan. And a bathroom’s receptacle may need to be on its own circuit. A duplex receptacle—the most common type, with two outlets— may be “split,” so that the outlets are on separate circuits.

Avoiding Overloads

When adding new service in a basement, you may be able to extend an existing electrical circuit, but only if it has enough “room” for new users. If you add too much in the way of electrical users, you can overload the circuit, and the breaker will trip regularly. To determine if you can piggyback onto an existing circuit, add up the wattage or amps of the light bulbs, the plugged-in appliances, and the fixtures already being used, and add in the users that you plan to add. The result should be less than the “safe capacity” for the circuit.

For a 15-amp circuit, safe capacity is 12 amps or 1,440w. For a 20-amp circuit, safe capacity is 16 amps or 2,400w. If users will be over the safe capacity, then you need to install a new circuit. Check that your service panel has empty spaces where you can install new breakers; if not, you may need to hire an electrician to install a new panel.

Do You Need a New Service Panel?

Determining whether you need a new, larger service panel calls for some complicated calculations, which I cannot get into here. I can say this: If you have a 100-amp service panel, and the amperage of all your breakers adds up to more than 160 amps, you should consult with an electrician or your building department to see if you need a new 200-amp panel.

Common Codes

Electrical codes are constantly changing, usually in the direction of greater stringency. Here are some of the more common ones that you should be aware of. The following are based on the latest National Electrical Code® (NEC) regulations, but be sure to check with your local building department to be certain you comply with their regulations.

  • The service panel must have enough amperage. A 100-amp panel is usually sufficient for a medium-sized home, but a 200-amp panel is preferred. Circuits should be labeled on the panel.
  • Wire sizes must match the breakers: 14-gauge for a 15-amp breaker, and 12-gauge for a 20-amp breaker, for instance.
  • Nonmetallic (NM) cable is allowed in most areas, but conduit or metal-clad cable is required in other locales. Where wiring is exposed rather than hidden in walls, it should run through conduit.
  • The cable should be run in areas where drywall screws cannot reach it or should be protected with metal nailing plates.
  • There are specific rules for running NM cable. You may need to staple it within 8 in. or 12 in. of a box, depending on whether the box has a cable clamp.
  • Electrical boxes must be within 1⁄8 in. of flush with the surrounding drywall, tile, or other finished surfaces.
  • Inside a box, there should be at least 6 in. of unsheathed wire. All splices must be made with wire nuts, not tape.
  • Only one wire can be connected to a single terminal on a device or fixture.
  • You may be required to wrap switches and receptacles with electrician’s tape to protect wires and terminals.
  • Install GFCI receptacles wherever the area may get damp.
  • In most cases, there should be separate circuits for lights and receptacles.
  • In a bathroom, there should be an exhaust fan. You may or may not be allowed to put a fan/light on the same circuit as a receptacle.
  • Install at least one receptacle every 12 ft., and at least one receptacle on every wall that is at least 6 ft. long.

Wiring Supplies And Tools

In most areas, NM cable is allowed with either metal or plastic boxes. The supplies and tools shown here should handle most common wiring situations in a basement. If you live in an area where the conduit is required.

How to Install Wiring Boxes and Cables

How to Install Wiring Boxes and Cables

Installing Boxes

Plastic boxes come in single-, double, triple, or even four-“gang” sizes, referring to the number of switches or receptacles you will install in them. They have integral screw holes for attaching devices.

Some metal boxes also come in different gang sizes. However, it is most common to install a “square” metal box whether you will install one or two devices. After the cable is run into the box, you add a “mud ring” (also called a device extender ring) that is either one or two gangs so you can install one or two devices. This arrangement allows for plenty of room for wires.

 

 

A hammer makes for an easy and convenient height gauge for receptacle boxes.

Determine where you want your receptacles and switches. Receptacles should be no farther apart than 12 ft., and there should be at least one on every wall that is longer than 6 ft. Think through the placement; avoid putting receptacles where they will be hard to reach, and perhaps increase the number behind a desk and other places where you use lots of power.

Also, think through switch placements. Avoid placing a switch where it will be hidden when a door is opened. Where a switch is near a door (as often happens), be sure it is not so close to the door as to interfere with the door molding. As a general rule, a switch box should be at least 3 in. away from the inside of the door’s rough opening.

 

 

To attach this plastic box, simply position it using the guide, so it extends 1⁄2 in. out from the stud, and drive the nails.

Plastic boxes are often installed with their bottoms 12 in. to 16 in. above the floor. Many electricians use this simple and quick technique for getting all the receptacles at the same height: Place the head of a hammer on the floor and set the box on top of the handle.

Plastic boxes have side indentations or other guides so you can easily install them with their front edges 1⁄2 in. out from the framing—so they will be flush with the wall surface once 1⁄2-in. drywall is installed.

Many plastic boxes come with nails attached; simply drive the nails into the side of a wood stud to attach.

Metal boxes take just slightly more time to install than plastic boxes. There are several types, but for the most common type, use its guide to hold the front edge flush with the framing. The mud ring that gets installed later will bring it out 1⁄2 in. Drive two small tabs to hold the box in place temporarily, then drive a screw into each flange to secure the box to a wood stud.

 

 

Hold this type of metal box against the stud at the correct height, and tap in the little pointed tabs to temporarily hold the box in place. 
Drive at least two 11⁄4-in. screws to hold the box firmly in place.

Plastic and Metal Boxe Sizes

Plastic boxes are common, but in many areas, metal boxes are required. Some metal boxes come in different gang sizes.

However, it is most common to install a “square” metal box whether you will install one or two devices. After the cable is run into the box, you add a “mud ring” (also called a device extender ring) that is either one or two gangs, so you can install one or two devices. This arrangement allows for plenty of room for wires.

WORKING WITH METAL STUDS

  • If you have metal studs, attach by driving self-tapping pan head screws.
  • Or, screw a block of wood to the stud and attach the box to that.
  • Metal studs have holes for running cable, but the holes have sharp edges. Buy bushings to fit the hole size, and snap them in before running cable.

Running NM Cable Into Plastic Boxe

As shown in the top center photo, the cable is often run through holes drilled in the centers of studs where drywall screws cannot reach. (However, in the case of an outside wall where there is a space behind the framing, you can simply run the cable behind the framing.)

  • Drill 3⁄4-in. or larger diameter holes through studs. They should be reasonably level with each other. A quick way to gauge this is to drill all the holes at hip height.
 

 

1 Drill holes for the cable at hip height.
  • At a corner, drill holes through both studs, angling them slightly toward the inside corner. Bend the cable to roughly approximate the path it must take, and thread it through the two holes.
 

 

2a At a corner, drill slightly angled holes in both directions.
  • At a plastic box, strip the sheathing if you have not already done so. Poke the cable through the openings, which have flaps that keep them from backing out. The sheathing should show in the box just a bit—1⁄2 in. to 1 in. Staple the cables within 8 in. or so of the box and tuck the cable(s) into the box.
 

 

3 Poke cable into the openings until the sheathing enters the box slightly. Many electricians find it easier to strip the cable and wire ends at this point, rather than before running the cable.

Hooking Cable To Metal Boxes

Metal boxes come with various means of clamping the cable, and here we show the three most common types.

  • If the box has integral clamps, use a screwdriver to remove a tab for each cable A.
 

 

A Remove knockout tabs from a box with integral clamps.
  • Strip the sheathing, insert the cable(s) so the sheathing just shows beyond the clamp, and tighten the clamp B.
 

 

B Insert the cable and tighten the integral clamps.
  • On a box without integral clamps, check with local codes to see if you need to use metal cable clamps, or if plastic clamps are allowed. Use a pair of lineman’s pliers or a hammer and screwdriver to tap open a knockout slug and remove the slug by wiggling it out with the pliers C.
  • To use a metal clamp, unscrew its nut and slip it into the knockout hole D.
  • With the screw heads facing you so you can tighten them later, screw on the clamp’s nut. Use a screwdriver to tighten the nut E.
 

 

C1 Poke opens a knockout slug.
C2. . . then wiggle it out. 
D Insert a metal cable clamp and slip on the nut.
E Tighten the nut by pushing or tapping a screwdriver.
  • Either push hard on the screwdriver or tap with a hammer until the nut is firmly connected. Slide the cable in so the sheathing is visible inside the box and tighten the clamp screws F.
  • If plastic clamps are allowed, things go faster. Poke the clamp up through the hole from the inside of the box G.
  • You may need to tap it with a hammer. Slip the cable down through the clamp, taking care not to go too far; you cannot pull it back H.
 

 

F slip
in the cable and tighten the screws to secure the cable. 
G Push or tap a plastic clamp up through a knockout hole.
H Carefully poke cable into the box; be sure you don’t push too far.

Ceiling Boxes

 

 

A flush light with a metal box uses a mud ring like a wall box. To line it up with other ceiling lights, string lines in two directions. You’ll likely need to install blocking pieces so you can locate the boxes precisely.

Ceiling boxes may be plastic or metal, or they may be recessed canister bodies. In most respects, they attach to framing and receive cable in the same ways as wall boxes.

If you will have a series of ceiling lights, take the time to measure carefully and string layout lines, so they will be evenly spaced and lined up in neat rows. Recessed canister lights often come with brackets that allow you to slide them from side to side, so you can fine-tune their positions.

 

 

Around or octagonal box like this nails on easily but is difficult to position precisely. However, it can work well if a row of lights all align with the same joist.

Installing a Canister Light Body

Canister lights also called can or pot lights, have their own electrical boxes. Run the cable to the area. Open the electrical box, which has a cover that may be attached with a clip or a screw.

  • Strip the cable sheathing and wire ends, and clamp the cable in the box. Connect the ground, neutral, and hot leads to the cable wires and close the box.
  • (In this example, push-in connectors are provided with the unit.) Tuck the wires back into the box and replace the cover.
 

 

1 Run wires into the canister light’s electrical box and make connections.
2 Tuck the wires into the box and replace the cover.
  • Attach the canister light by driving nails through the brackets into two joists; the bottom of the light housing should be 1⁄2 in. below the framing to allow for the drywall thickness.
  • Now you can slide the light to adjust its position.
 

 

3 Drive nails to attach the light to the joists.
4 Slide the fixture to align it.

See “Splicing Wires,” , and “Connecting Wires to Terminals,”

Wiring With Conduit

Conduit pipe often referred to as EMT, is required for electrical work in some areas of the country. And if you will be installing wiring that is exposed, the conduit is a very good idea, because it encases wires far more securely than NM cable. Joining conduit pipe to electrical boxes is not difficult, but bending it takes some skill, which you can learn with practice.

Make bends using a conduit bender of the right size for your conduit. Take some time to practice your technique, so you can make smooth, fairly accurate bends.

Make your bends so that the conduit will end up a few inches longer than needed; you will cut it off later. Most bends are made on the floor:

  • Insert the conduit, step on the footpad, and pull or push the bar to make the bend.
 

 

1 Step on the footpad of a conduit bender and pull the bar to make bends in conduit.
  • When making multiple turns, it may be easier to work with the bender upside down.
 

 

2 Multiple bends are sometimes easier to make with the bender positioned upside down.
  • At the box, remove a knockout slug and insert a conduit clamp. Hold the conduit in place and mark for a cut.
 

 

3 Mark for cutting conduit so it enters the box’s clamp.
  • Secure the conduit, then cut with a hacksaw or a reciprocating saw equipped with a metal blade.
  • Then-and this is important- remove all burrs from inside the cut end. (Burrs will dig into the wire insulation and perhaps even strip it off.) Use a hand tool like lineman’s pliers or a screwdriver, or—better—a reaming tool attached to a drill.
 

 

4 Cut conduit with a metal-cutting blade. 
5 Be sure to remove all burrs with a reaming tool.
  • Slip the conduit end into the clamp and tighten the setscrew.
 

 

6 Insert the conduit and tighten the setscrew.
  • Once all the pipes are attached to the boxes, it’s time to fish wires. Insert a fish tape into one end of a run and push until it pokes out the other end.
 

 

7a Push the fish tape…
7b. . . until it emerges at the other end.
  • Attach the wires to the end of the fish tape: Bend one of the wires over, then arrange the others in descending order, and wrap tightly with electrical tape.
 

 

8 Bend one of the wires around the fish tape, neatly arrange the others, and tightly wrap the tape around them all.
  • Have one person gently push wires through while another person pulls with force at the other end.
  • If pulling gets tough, apply wire-pulling lubricant to the wires at the front end.
  • Once the wires are pulled through, cut them off.
 

 

9 While one person pulls the tape, someone at the other end pushes wires gently. 
10 Lubrication helps wires pull smoothly, especially if they must make multiple turns. 
11 Once the wires are pulled through, cut them off.
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