Home Wiring and Electricity -- Planning the Work

Once you have drawn your floor plan, you are ready to plan which fixtures will be linked and where wire will be run, as well as what materials to use. Take your time and consider your options. Careful planning now will minimize work later.

Identifying and Sizing Circuits

Every receptacle on the floor plan should be identified by circuit number. Circuit-breaker spaces in the panel will have their load assignments as shown in the table below.

In this electrical system there are two general-purpose circuits present in each room except the kitchen, dining room, and laundry. This scheme adds to the cost of the system, but it also ensures that if a circuit blows, there will still be some power in every room. However, you should be aware that in some localities it's common practice, sometimes even a cede requirement, that lights and receptacles be put on separate circuits. Where possible, multiwire branch circuits (3-wire circuits that do the work of two 2-wire circuits) will be used. The wiring in the garage will be ex posed and everything else will be concealed.

The wire used must have sufficient ampacity, or capacity, to carry the load being served. The cooktop, for instance, can draw as much as 21 and a fraction amperes. The wire for this appliance must be capable of safely carrying this much cur rent, and the circuit breaker that’s to be used must be sized to properly protect the wiring.

This house will be wired with Type NM cable (commonly referred to by the trade name Romex®), which is an assembly of two or more insulated conductors and one bare ground wire enclosed in a jacket of moisture-resistant, flame- retardant, nonmetallic material. A mix of two-conductor and three-conductor, as well as different sizes, will be used.

Electrical wire is sized using American Wire Gauge (AWG) sizes. The lower the wire number, the greater its size and ampacity. All wires and cables are marked with the following information: the maximum rated voltage for which it's listed, a letter or letters that identify it as to type, the manufacturer’s name, and the AWG size or circular mu area. No. 14 is the smallest wire size allowed for general wiring. Choose cop per wire and cable for interior wiring jobs.

The following table lists ampacities for the copper wire sizes commonly used in house wiring. Note that ampacities for No. 4 and larger may be lower in the original wiring in older homes. This is because older houses were wired with 600 C and 75° C wire, the only wire available at the time. These wires have lower ampacities than the 90° C wire now in use.

Understanding Cable

Type NM, or nonmetallic- sheathed, cable is probably the most commonly used cable in residential wiring. There are other types available, each with special application features. Type NMC is also a nonmetallic cable, but unlike Type NM, which can be run in dry locations only, Type NMC can be used in moist, damp, and corrosive locations as well. This means that it can be fished into voids in outside walls of masonry block or tile and installed in shallow chases in masonry and covered with plaster.

Type UF, underground feeder, cable can be buried directly in the earth but can't be installed in poured concrete or plastered over. It can also be used in any dry, wet, or corrosive location.

Service-entrance cable is available in larger wire sizes, such as Type USE, for use in underground services, and Type SE, which is generally used to supply power to large ranges and clothes dryers.

Armored cable, commonly known as BX, is a fabricated assembly of insulated conductors in a flexible metal jacket that's intended for use in dry locations. Once a very popular material in house wiring, it has largely been replaced by nonmetallic- sheathed cable as a general- purpose wiring material. How ever, it's sometimes used to connect fixed appliances, such as food disposers, to the branch circuit wiring. It requires boxes with special clamps that keep the bushings in place.

All of these various cables, except for the service-entrance types, are available in two- or three-conductor configurations.

Table of Wire Sizes

25 Sizes and Types of Wire and Cable: #16 and #18 (unmarked) for low-voltage systems; Usually in 110V or 120v circuits; Usually in 240v circuits; #6 or #8 used as system grounding wires.

Determining the sizes and quantities of wire to buy must be done systematically. Most of the wire used in the example is No. 14 and No. 12. Plot each cable run on the floor plan with two or three slash marks, one slash to represent each conductor in the cable. Then scale the distances between boxes for all the two-conductor No. 14 (14-2) wire being used and add appropriate amounts for the up and down runs. Add these together along with any 14-2 home runs (final runs to the service panel). The result is a fairly accurate estimate of the amount of two conductor No. 14 wire needed for the job. Do the same for the 14-3, 12-2, and 12-3 cable runs. These four sizes are generally bought in 250-foot coils, and can be purchased ahead of time. For smaller jobs, shorter coils are usually available. The larger sizes are generally sold by the foot and are quite expensive. Wait until actual cable runs can be measured to buy them. Techniques for running the wire are explained in the next section, “Rough Wiring.”

Electrical Boxes

Electrical boxes are sold in a variety of shapes and sizes. Years ago metal boxes were the only type available. They’re still widely used, but today there is also a wide range of plastic boxes available.

Switch boxes are used to house switches and receptacles. Some metal boxes have removable sides and can be “ganged,” that's , mounted side by side to accommodate two or more switches or receptacles. Plastic boxes aren't gangable, but they are manufactured in one-gang, two-gang, three-gang, or four- gang styles. All of these boxes are available in a variety of depths. Nailing is a common way of mounting these boxes in new work.

Round metal boxes and octagonal metal boxes are used most often with ceiling fixtures. Some employ integral mounting brackets and nail up, while others mount on a bar hanger that's attached to the house framing. One special type of ceiling box is listed for use with ceiling fans.

Metal and plastic square boxes are often used as junction boxes when surface-mounted.

26 Low Wire and Cable:

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Choosing the Right Box:

As evident in the illustration, the variety of boxes available is staggering. The two main categories are boxes for new construction and cut-in boxes for remodeling work.

Switch Boxes (Utility Boxes, Handy Boxes)

These are rectangular boxes that hold switches and receptacles. The basic size is 2 inches by 3 inches, which means the rectangular opening isn't much larger than the switch or receptacle to be mounted in it. Some metal switch boxes have removable sides so they can be ganged together to make larger boxes. Switch boxes are some times used where wall bracket lights are installed and for telephone outlets.

Ceiling or Outlet Boxes

These octagonal or round boxes are designed to be covered with a light fixture or porcelain lamp holder that has essentially the same shape. They also are sometimes used to hold receptacles.

Box Extension

This is a backless box that can be screwed onto another box, piggyback fashion, to make a deeper box.

Square or Junction Boxes

Square boxes serve a variety of needs. They are used with mud rings to flush-mount switches and receptacles where large box capacity is needed. When surface-mounted, they are used as junction boxes and covered with a blank cover, or used with raised covers that hold switches or receptacles.

Special Boxes

These boxes are designed to meet specialized needs. One such box is intended for use with ceiling fans. It is designed and installed so the framing, not the box, supports the weight of the fan. Another is the ceiling pan. Only ½ inch deep, it can be mounted directly on the ceiling joist or on the surface of the ceiling. Either way, a single cable enters through the back of the box, and the box is completely covered by the fixture attached to it. Shallow switch boxes, slightly over 1 inch deep, are made for use on concrete-block walls where 1-inch furring strips support the finished wall. Special waterproof boxes are made for use outdoors.

When square boxes are used to hold switches and receptacles in concealed work, they are combined with a flat cover that has a raised, switch box—shaped opening that's called a mud ring or plaster ring. Handy boxes are slightly longer than switch boxes and are intended for surface mounting a single switch or receptacle. A number of other boxes are available, mostly for special applications.

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27 Types of Boxes: Nail-on nonmetallic handy box; 2-gang nonmetallic box with front brackets; Square-corner metal switch box; Square-corner metal switch Square-corner metal switch box with side nailing bracket box with 16d nails in side; 3.5” nonmetallic ceiling box; Square metal junction box; Square metal junction box with side bracket; Square metal junction box with front bracket; Octagon metal junction box with side bracket; Octagon metal junction; Octagon metal junction box; box with front bracket; Octagon metal junction box extension; Square box flat cover; Square box flat device cover; Square box raised device cover; Round box cover; Octagon box cover; Stud bar hanger for ceiling boxes; Weathertight box

28a Reading a Receptacle: Acceptable wire; Break-off tab; Voltage and amperage ratings; Testers approval; Ground terminal; Side Wired, Back Wired:

28b GFCI Devices: GFCI breaker for insertion in the service panel; A plug-in GFCI can fit into any 3-slot outlet and give it GFCI protection. It is portable and can be used with power tools outdoors.

Receptacles

Receptacles are used to connect equipment with a cord and plug to the electrical system. Grounding receptacles are used in all new work. The most common type 120-volt receptacle is the duplex, one that has spaces for two plugs. Power is connected to its two parallel slots, and its U-shaped opening is connected to ground.

Ground fault circuit interrupters (GFCIs) provide greater protection than ordinary grounding-type receptacles. The NEC requires them in bathrooms, unfinished basements, garages, and along countertops within 6 feet of a sink. They’re also required for most outside electrical outlets.

A 20-amp receptacle will be used on the laundry circuit; all other 120-volt receptacles will be 15 amp. The oven and cooktop will be cord-connected to properly sized surface- mounted receptacles for ease of appliance servicing. A 120- volt, 20-amp circuit will be connected directly to a service switch on the furnace. Also, a 240-volt, 30-amp branch circuit will be run to a safety switch mounted close to the air-conditioning compressor.

29a Beading a Switch: Note: All information for choosing the proper switch is either stamped into the mounting yoke or molded into the back of the plastic case.

29b Some Special Switches: Lighted-handle switch; Pilot-light switch; Locking switch; Dimmer switch; Clock switch

Switches

An ordinary two-way switch is used to control a light from a single point. Controlling that light from two points requires a pair of three-way switches. A four-way switch is required for each additional control point. Dimmers are often used in place of single-pole and three- way switches in dining rooms and kitchens. Note that fluorescent fixtures require special, more expensive dimmers. So- called “quiet” switches and “touch” switches are available for use where desired. Illuminated switches require no special wiring and can be used as direct replacements for most ordinary switches. They are common in bedrooms and bathrooms.

Low-voltage relay systems are sometimes used in houses where complex light switching is desired. These systems use a separate relay to control the 120-volt power to each lighting outlet. Low-cost low-voltage switch loops are used to energize the individual relays. When a relay is energized, its light turns on. Complete systems include a master control panel, usually installed in the master bedroom, that can control all the lighting in the house from one location.

The list of electrical options available for the home is nearly endless. The most common and necessary are doorbells, telephones, and smoke detectors. As previously mentioned, smoke detectors should be in stalled near the furnace and on every habitable level. Exhaust fans are desirable in bathrooms and kitchens. Often an exhaust fan is combined with a ceiling light and heater in bathrooms. Other useful options include garage door openers, driveway floodlights, yard lights, under ground lawn sprinkler systems, television cable, and intercoms.

Where to Buy Materials

An all-service building-supply house that’s geared toward do-it-yourselfers is an excellent source of electrical supplies. Such outlets usually are well stocked and their merchandise is well labeled and backed up with good point-of-purchase information. Time spent in the electrical department can be quite an education. The best of these stores usually have experts on hand to answer questions and help with material selection.

A well-stocked hardware store is another excellent place to buy electrical supplies. Plenty of sound advice is usually available at no cost, and the staff may take a personal interest in your project as well.

Dealing with a wholesale house can be difficult if not impossible. Wholesalers sell to contractors, manufacturers, and other industrial accounts, and usually aren’t interested in re tail sales. They often have a minimum-purchase policy as well. Also avoid buying through catalogs because catalog descriptions often confuse even the most knowledgeable do-it-yourselfer.

How to Purchase Materials

Buy No. 14 and No. 12 wire by the 250-foot coil unless you are doing a very small project; it's far cheaper that way. Larger sizes are generally bought by the foot. Avoid buying the least-expensive switches and receptacles. Usually spending just a bit more buys much better equipment. Finally, the best rule is to buy more than you think you will need.

Obtaining a Permit

Always inquire about a permit before beginning any electrical installation. In fact, apply for the permit before buying any material. Permits are generally issued by a municipal building- permit department upon application and payment of a fee. An inspection or inspections are part of the permit process. Final approval of your installation by an inspector is a good indication that the installation is free from hazard.

Inspection schedules vary. If you have any questions about specifics, especially if a service is involved, ask the electrical inspector for clarification be fore you begin work. This public official is the best local resource you have and should be available to you by prior appointment.

There is a rough-in inspection that takes place when all the boxes have been installed and the wiring has been run to them. This is always done be fore finish materials are applied to interior walls in new work. A new service is usually inspected at this time, although the service inspection may be separate. A final inspection takes place after all connections have been made and all switches, receptacles, and so forth are in place, and branch- circuit connections in the panel are complete. It’s the installer’s responsibility to notify the inspection department that the installation is ready for inspection at each stage.

Plan carefully, read, and perhaps even visit a local project to see how work is being done before applying for a permit. Spend time with the inspector before starting the work, especially if a service is involved. There will be many questions about specifics, and the inspector is the best local resource there is.

Expect the inspection of the service to be stringent. This shouldn’t be a problem if it has been installed employing specifics provided by the inspector (regarding grounding, bonding, connections at the terminals, and so on). The inspector will look at cable and conduit routing, protection, and sup port, and will check to be certain that box sizes are large enough for the number of conductors entering them, that there’s adequate free conductor length in every box, and most important, that proper ground continuity is maintained throughout the system. Also, the inspector will want to see that the entire installation has been done in a workmanlike manner. This simply means he’ll check to see that your work is done neatly, as a journeyman electrician would do it, with no twisted cable, disorderly or oversized loops, or boxes out of plumb, for example. Read the section on Rough Wiring for some helpful tips on passing inspection.

31 Using a Voltage Tester: A voltage tester has no power of its own but tests for the presence of power in wires or appliances. Use it to be sure the power is off before making repairs, to see if an outlet is hot, or to test for proper grounding. Testing for power at a switch. Testing for power at an outlet. Checking for grounding. For grounded receptacles, left-hand probe should be in U-shaped grounding hole. Finding a hot wire

The Proper Tools

Home electricians need very few specialized tools to do small electrical projects. Installing an additional receptacle is probably the first do-it-yourself electrical installation project done in most homes. In homes with wallboard walls and the electrical panel in an unfinished basement, the only tools needed to install a receptacle in a first-floor wall are a pair of pliers for cutting wire and cable, a saw for making the cut out in the wall, an electric drill with a bit large enough for the cable being used, a screwdriver, hammer, knife, and ruler of some sort.

More complex jobs require additional tools, which may need to be purchased, including a voltage tester and a continuity tester; both are inexpensive. Finally, buy a cable stripper, a wire stripper, needle nose pliers, a wood folding rule (safer than a metal tape for electrical work), and a 9-inch nonmetallic torpedo level. If you are tackling a large, complex project, consider buying a low-cost amp-volt meter. The voltage tester is rugged and can be carried in a shirt pocket, but it can’t indicate voltages below about 60 volts or above 250 volts, whereas a volt-amp meter can accurately measure a great range of voltages. A continuity tester can read only through low-resistance circuits and devices when the electricity is turned off. A switch is an example of a low-resistance device. Amp-volt meters allow the user to check motor windings, solenoid valve coils, trans former windings, and other high-resistance devices for continuity or ground.

32 Basic Wiring Tools:

If work is to go beyond a small nonmetallic-sheathed cable installation, especially if the work will be in masonry or plaster, additional tools needed will include a variety of screw drivers, diagonal-cutting and side-cutting pliers, a pair of 9- or 10-inch pump pliers, a crimping tool for attaching terminals to wire, and a scratch awl. You will also need a hack saw and a wallboard saw as well as a narrow-bladed, fine toothed jab saw for cutting lath. Also include a variety of wood bits, twist drills, and masonry bits along with a variable-speed 3/8-inch electric drill. A 1-inch wood chisel and a 6-inch cold chisel that's ½ inch wide should also be part of the electrical tool kit.

Electronic stud finders are far superior to the older magnetic models, and they’re in valuable for work in old walls. A 25- or 50-foot fish tape is another must. It’s best to rent tools needed for any work requiring bending and threading conduit.

Electrical work requires planning—don’t rush it. Re member that any mistakes you make can usually be corrected without too much difficulty. Start small because a big project can be overwhelming. Confidence comes with experience. Professional electricians spend up to six years in school and on the job before they’re eligible for licensing, so don’t expect to learn everything you want to know about electrical wiring in a day or in a single project.

If, after much planning and rethinking, you’re still not comfortable about doing the job, you should probably call an electrician. Or, if half the power in the house goes out and a look in the panel shows that a main lug has burned off—unless you have lots of time and your skill level is very high—call an electrician.

There are other situations in which it’s best to call in a con tractor. Some work requires special equipment, for instance, pushing conduit beneath a 20- foot concrete drive to provide power for outdoor lighting, or bending and threading conduit for a large service. An electrician can also put his experience to work for you when a problem arises that just won’t go away. Strange things do hap pen, such as some bulbs in the house burning brightly while others are dim, or a clothes dryer that checks out as sound but continues to blow fuses. When faced with such puzzling circumstances, you need the help of a professional.

Always keep safety uppermost in your mind when you are doing electrical work. Turning off the power protects you from electrical shock, but you should be alert to other possible hazards and work carefully. Use only properly grounded or double-insulated power tools and three-wire cords with plugs and bodies that aren't frayed or cracked.

Take care when working with ladders; if outdoors, level the feet of the ladder with pieces of wood or other rigid material and , if possible, tie the top of the ladder to the building it’s leaning against. While aluminum ladders are lightweight and relatively inexpensive; they have the significant drawback of conducting electricity.

Remember that the tools being used to cut and drill material can cut and drill you, too. Always wear safety glasses or goggles when working with power tools.

33 Using a Continuity Tester: A continuity tester is a battery-powered device that tests for complete circuits when the appliance to be tested isn't hooked up or when the power is off. Testing a cartridge fuse; etc.