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Electrical installation work demands great care. All connection work must be done meticulously and accurately to avoid short circuits and ma! functions. Code requirements and recommendations need to be followed strictly. It is for this reason that most municipalities don't allow electrical work to be done by anyone other than a licensed electrician. In cities, by code, a licensed electrician is a must. Those of you who live in multifamily dwellings will also find that the codes prohibit do-it-yourself electrical work. There is sound logic behind this requirement. The electrical systems of these buildings are far too complicated for the novice. Occasionally you will find a code that allows the owner of a single-family home to do his own electrical work. Even in this instance, we strongly recommend that you hire a licensed electrician to do your renovation. The following discussion is geared to those renovators in one-family houses who may be assisting a licensed electrician. A few tips on safety: Whenever you are working on the system, caution must be taken that the wires are dead. Make sure you disconnect all power to the area where you are working. Disconnect the circuits by flipping off the breaker or completely removing the fuse from the box. Use a voltage tester to make sure the circuit is dead. Let everyone know that electrical work is in progress by leaving a note on the service panel. “Hands off panel: electrical work in progress” will prevent any confusion. The last thing you want is for someone to go into the basement and flip the circuit breakers back on while there is work taking place. Always use tools with insulated handles. Rubber gloves and rubber-soled shoes are also good insulators. Never stand on a damp or wet surface while doing electrical work. Remember, electricity can be hazardous. The configuration of 115-volt and 230-volt outlets and plugs is different. Materials: You’ll need the following materials:
Tools: Here are some of the most widely used electrical tools:
We have divided the roughing-in stage of electrical installation into two sections: new work and old work. New work would apply to those of you doing a “gut” renovation and those building a new extension. Old work applies to renovators who are extending or adding to the existing sys tem. Whether you are doing new or old work, we suggest you read the entire section, since most of the techniques discussed are common to both types of projects. Like plumbing, electrical work takes place during both rough and finish stages of construction. Roughing in refers to concealed wiring; it usually takes place when the house frame is exposed. The finish work occurs after all wall and floor finishes are in place. The steps involved in an electrical installation are: Roughing In
Finish Work
Following are a few pointers to remember:
ROUGHING IN: NEW WORK The Service Panel The existing service panel may be inadequate to meet your expanded needs. If so, you may need an auxiliary panel or a new service. The service panel may be installed before, after, or at the same time as the interior wiring. Service panels are in stalled by licensed electricians—for very good reasons. Not all service panels are similar in design. As designs vary, so do the steps necessary for proper installation. Aside from this problem, the installation work itself is tricky. Its efficient operation, however, is essential to that of the rest of the system. A mistake in the installation of the service panel could become a hazard for the entire system. As a matter of fact, many electrical contracting companies allow the service panel installation to be performed by only their most experienced electricians. The Distribution System: The code requires that all connections between the cables and the devices (switches and outlets) and all wire splicing take place inside approved boxes or inside special conduit fittings. This is to reduce the possibility of fire or shock brought about by a defective connection left unprotected inside a wall. A few sparks could ignite paper, wood, other combustible construction materials, or accumulated dirt inside the wall cavity. A greater danger is a subsequent fire resulting from an incorrect installation and long-term heating of the wire or conduit. The roughing-in stage starts by locating and installing all the boxes for switches and outlets as indicated in the plan. Although these boxes have traditionally been made out of metal, the use of plastic boxes is becoming more popular. There are still many building codes that don't allow the use of plastic boxes. There are many boxes available to satisfy a number of different conditions. The most common ones are rectangular and octagonal. Octagonal boxes are generally used for lighting, and multiples of rectangular boxes are used for receptacles and switches. Square boxes are often used for junctions. (Junctions occur when electrical wires are spliced with no outlet or switch pro vision.) The size of the box is determined by the number of outlets or the number of connections and by the quantity of wiring to be contained. There should be enough room in the box to work on the connection, to comfortably house the device, and to store all loose wiring. Avoid working with small boxes. They not only will make the installation work more difficult but will hardly leave sufficient room to house the wiring and the de vice. (See square-inch requirements in the code.) Cables enter the boxes through knockout holes. Knockouts are circular sections of metal or plastic that have been pre-punched and can be opened by tapping with a screwdriver and a ham mer. The piece of metal is then twisted loose with a pair of pliers. Each box is equipped with more knockouts than required to accommodate various installation conditions. It is important to remove only those knockouts necessary for the connection work. Don’t leave an unused knockout open. If you pull one open by mistake, close it with a closure washer. Switch, receptacle, and junction boxes are attached to the woodwork with mounting brackets. These brackets are generally built in as part of the box. Ceiling boxes are attached to the frame with hanging bars. Both the bars and the built-in mounting brackets automatically adjust the boxes to be flush with the outside edge of the finish wall surface. It is helpful to know the heights commonly used for installation of boxes. Those used to house floor outlets are usually 12” to 14” above the floor. Over-the-counter outlets are generally placed at approximately 40” (to the bottom of the outlet) or 42” (to the center of the outlet) above the floor. Switches are installed at 48” above the floor (to the center of the outlet). Outlets and switches to satisfy special conditions should be placed accordingly. With all the boxes in place, the next step is to string the cable to the various boxes according to the circuitry design. (The 115-volt circuit is customarily strung before the 230-volt circuit.) Electrical cables, like plumbing pipes, snake through and around the house structure. (It is a good idea to keep the paths of the electrical cables and the plumbing pipes separate from each other to avoid problems should leaks develop in the pipes.) To minimize interference with the building’s structural capacity, keep in mind the tips for drilling outlined. In addition, placing electrical cables in the center of studs or joists helps to prevent finish nails or screws from puncturing the cables during the installation of finishes. To prevent the cables from sagging and causing possible damage, they are secured to the wood work by means of special staples. These staples are specifically designed for use with non-metallic sheathed cable or armored cable, making the installation work considerably easier. (Care should be taken to use the right type of staples for the type of cable you are using; you may otherwise damage the cable.) Check your code for the required spacing of the cable supports. Fig. 3 shows ways in which to run the cables in relation to the house structure. Avoid sharp bends. A few tips on stringing cable: Cable comes wound in big rolls. Unwind only as much cable from the roll as you will need to make a run between two boxes. When too much cable is unwound at a time, it tends to twist, making the stringing job more difficult. To further avoid twists and bends, unwind the cable by turning the spool. Begin by stringing the cable from the ser vice panel (or projected location of the service panel) to each outlet box along a particular circuit. To avoid a mix-up later on, tag all circuits at the service panel end. Leave 4’ to 6’ of cable behind for later installation to the panel. Once you get to the box, cut the cable, allowing about 11/2’ extra length for both the incoming and the outgoing cable. (Extra cable comes in handy in case an outlet must be moved to accommodate a molding, cabinet, or other unforeseen construction.) Strip 8” of cover from the cable, leaving the wire exposed. Remove two knockout plates from the box and carefully connect the cable to the box. = = = = -BASIC SKILLS- CUTTING CABLE The procedure varies with the type of Cable. We will discuss nonmetallic sheathed cable and armored cable. Nonmetallic sheathed cable: This type of cable can be stripped with a knife. Slit the outer covering, being careful not to damage the insulation of the wires inside. Once a slit is started on the outer cover, you can pull it off as far as you want with a pair of pliers. A cable ripper can be used instead when type NM cable is used. It will save you some time. For type NMC cable, only a knife is needed. Armored cable: Armored cable is more difficult to cut than nonmetallic sheathed cable. With a fine-toothed saw, start a diagonal cut on the cable where the armor is to be removed. Be careful as you are sawing the armor not to damage the wire insulation or the bare grounding strip in side. Grab the cable with one hand at either side of the cut and twist the cable against the spiral until the armor breaks off. The bushing is slipped between the armor and the wires. Make sure that the grounding wire is bent back over the outside of the armor. It is very important that a bushing be provided; otherwise, the danger of damaging the wires and a consequent short circuit or ground is increased. No inspector will approve an installation without bushings. SPLICING THE WIRE To splice is to join together two or three wires in such a manner that the resulting wire remains as strong mechanically, as good a conductor electrically, and as well insulated as a continuous piece of wire. The first step in making a splice is to remove the insulation from the wire. You can do this with a pocketknife (being careful not to dam age the conductor) in the same manner in which you sharpen a pencil. The insulation should de crease smoothly toward the conductor. It shouldn't be a right-angle cut. Make sure that there are no traces of insulation left on the wire. The splice can be soldered or solderless. Soldered splices start by mechanically joining the wires. This can be done in a couple of different ways. The most common one is the pigtail splice, which joins two wires. There are instances in which three wires are joined together, and a slightly more complex version of the pigtail called the bunch splice is used. When the wires have been joined mechanically, flux is applied over the splice. Be careful to apply the type of flux used for electrical purposes. Check with your supplier. Hold the wire splice with a pair of pliers and heat it with a soldering iron until the solder melts on contact. Push the solder inward to provide enough solder for a good bond. Make sure that the splice is well soldered on all sides. After the solder has hardened and cooled, tape the entire splice over with rubber tape (then plastic tape). Wrap the tape spirally to completely cover the splice and overlap the wire insulation. The proper application of tape is very important since it provides the insulating jacket for the splice. Solderless splices are easier to do than soldered ones. “Wire nuts” are the most common, al though “pressure” connections are sometimes used as an alternative. Both save considerable time. Check the code to see if it allows their use. A wire nut is a small insulated cap that's screwed onto the ends of wires. Only enough wire is stripped to fit into the connector. The wires are placed side by side and screwed onto the cap. Be careful not to leave any bare wire exposed. A “pressure” connection is made with an insulated copper thimble and a special pressure hand tool. Plastic, vinyl, and friction tape have no accept able insulating qualities. To prevent the sharp edge of the cut armor from damaging the insulation of the wires, you must install a bushing. A bushing is a small cylinder with one side having rounded edges. It is made out of a tough fiber with a high insulating value. == == Keep in mind that the grounding wire, or the ground system, isn't the same as the neutral. See Section 20. When using plastic boxes, care must be taken to follow the grounding procedures as directed by local codes. Since plastic isn't a conductor like metal, the grounding techniques for plastic versus metal boxes differ significantly. To provide a continuous ground, the cable is grounded at each box. The grounding procedure varies with the code. Generally, however, if you are using nonmetallic sheathed cable, the grounding wires in the incoming and outgoing cables are secured or connected together with a wire nut and fastened with a screw to an unused hole in the box. (Grounding wire may be bare or insulated.) There are several ways in which the connection to the grounding screw can be done. There are boxes that come equipped with a “pig tail” wire already attached. Another method is to allow one of the grounding wires to be longer than the other and use the longer section as the connection to the screw. Yet a third method is to snip off a piece of grounding wire or buy precut grounding wire and use it as the attachment between the twisted grounding wires and the screw. Most likely the local code will specify the method to be used. In any event, it's very important that the grounding wire be wrapped around the screw in such a manner that as the screw is tightened, the wire is being wound and “lays” in the same direction on the binding screw. This screw should be used only for grounding. The other end of the grounding wire will later on be connected to the neutral bar in the service panel. If you are using armored cable, the grounding will be accomplished together with the connection of the cable to the box. The last step in the roughing-in process is to strip about 1” of insulation at the end of the wires. These ends will be connected to the de vices during the finishing stage. Before moving on to the next box, bend the wires back into the box to keep them out of the way. Repeat the same procedure at every box in the circuit. With all the circuits in place, the electrician will install the service panel (if he has not done so already). He will also conduct a few tests to check for short circuits, proper current flow, and good circuit ground. Before any of these tests are done, make sure that the power has not been connected at the service panel. The electrical inspector is now called in to check and approve the wiring. ROUGHING IN: OLD WORK The basic principles involved in roughing in are common to new work and old work. The primary difference lies in the need for breaking through finish surfaces and routing the electrical wire within the existing walls and floors (with a mini mum of disruption in rewiring existing installations). Most commonly, the cable runs in the spaces between studs and joists. There are other possibilities, such as the corners of stairwells. Routing wires behind baseboards, door trim, or other moldings is yet another option. (Wiring should never be run through ducts.) “Fishing wire” isn't easy. The steps involved are more difficult than they sound. This is a two- person job: one person feeds a length of metal or “fish” tape into an opening in the wall, while a second person (with another fish tape) tries to catch the first tape. Once both tapes are connected, a length of electrical cable. is attached to one fish tape and pulled through the opening. Cutting out a series of small openings in the finish surfaces at various locations along the wiring run is usually necessary to snake the wires through. To minimize disruption, find out where the studs and joists are. The openings can then be cut in the spaces between these members. Start by getting access into the wall by means of a new or existing outlet. If you are using an existing outlet, cut all power to the outlet and remove the receptacle. To open up a hole for a new outlet, trace the box itself onto the wall (including all protrusions from the box). The next step is to cut out the space for the box. Where the wall is gypsum board, you can use a keyhole saw to cut out the hole. Plaster walls are trickier. Drill holes at the corners of the box. Cut into the holes very gently (plaster is delicate and can easily crack) with a plaster cutting blade. It is important to point out that there are codes which don't allow extending circuits from existing boxes. If the code al lows you to do so, don't exceed the ampacity (amperage capacity) of the individual circuit and make sure that additional outlets don't exceed the ampacity of the wire. If extending an existing circuit, be sure to install the new device before returning power to the circuit. If this isn't possible, temporarily install wire nuts to the wire ends. Renovators should also keep in mind that all wire splicing must be made in accessible junction boxes. == == CABLE CONNECTORS Cable connectors are used to fasten the cable to the outlet boxes. The type of connector varies to accommodate different conditions—for example, straight-run and right-angled connections. They are installed by slipping the connector over the end of the cable. The screws (on the connector) are tightened. Before inserting the connector through the knockout in the box, remove the locknut. Once it's in the box, fasten the locknut and connector tightly to each other— and therefore the box. Some boxes come with built-in clamps, eliminating the need for connectors. When installing connectors to armored cable, be sure to push the cable into the connector as far as it will go to prevent the bushing from falling out of place. The bare grounding strip should be in the connector. This way, when you tighten the screws on the connector to anchor it to the cable, the grounding wire will be squeezed. It shouldn't lie loose. This is very important in order to obtain a good continuous ground. == == Once the holes are in place, insert the fish tape above. The next step is to drill a hole either through the sole plate (if you are trying to get to the space between the joists) or through other studs (if you are working along the wall). As a general rule, the most difficult part of wiring is drilling the holes through plates, studs, or other structures. A 3 drill bit at the shallowest possible angle is generally used for this task. A second fish tape is then inserted from below (or from the sides). This tape has to make its way through all the holes until it hooks up with the original fish tape. When the two engage, pull the tape into the living space. Using electrical tape, wrap the electrical cable securely to the end of the fish tape (you don’t want it to come apart and have to start fishing all over again!). The other person can now pull the cable and bring it into the new outlet location. The easiest route for wiring the ceiling is to cut an opening directly from above. This is relatively easy for those who have an unfinished attic directly above the area being rewired. Where there is no attic space, you will need to cut into the finish surfaces where the wall meets the ceiling. The space behind baseboards is a convenient place to run cable, since cuts will later be covered during the installation of the trim. Wires can sometimes be easily snaked by removing moldings, installing the wires, and later covering the damage with the reinstalled molding. Care must be taken, however, that finish nails don't accidentally puncture the cable. One way to help pre vent this is to chisel out the bottom of the studs (check the local code for allowable depth of cut) and then cover these notches with a steel plate. FINISH WORK With the rough work checked and inspected and the finishes up, you can start to install the de vices* (receptacles, fixtures, and switches) to the wires in the boxes. As a general rule, similar-color wires are connected to each other: black (“hot”) is connected to black, white (neutral) to white, red (“hot”) to red, and grounding strip to grounding strip. The white or neutral wire runs, without interruption by a switch, circuit breaker, fuse, or other device, up to each point where current is being consumed. This continuity is very important since the white wire is the one connected to the grounding or neutral bar in the service panel. There may be instances where a white wire may need to be connected to a black one to respond to a particular wiring condition. You will find, however, that in these instances there is always provision for maintaining the continuity of the white (neutral) wire. Remember: Neutral wires are always continuous, and hot wires are interrupted by switches. Most devices are connected to the wires by means of two sets of terminal screws, a brass and a chrome set. The black wires are attached to the brass screws and the white wires to the chrome screws. Fig. 9 shows a device wired in parallel. This means that should the wire slip off the terminal screw, the power will continue to flow to the rest of the circuit. Terminal screws are wired with the aid of small-nosed pliers (wrap the jaws with tape to avoid damaging the wire). Make a loop in the end of the wire and place it around the screw. The open end of the loop should be in a clockwise direction so that when you tighten the screw, you wind the wire, not the opposite. Make sure that all bare wire is wound in the screw. Any bare wire left exposed could cause short circuits. Should you have more bare wire than you need to go around the screw, trim it off. The National Electrical Code defines a device as a unit of an electrical system which is intended to carry but not utilize electrical energy. To install wire nuts, hold the wires together with a pair of pliers and twist the exposed ends in a clockwise direction. Snip the twisted ends slightly so that the wires end evenly. (There should be about 1/2” of bare wire.) Put the wire nut in place and twist it until snug. (Wire nuts come in a variety of sizes and are usually color- coded to indicate the number of wires they are designed to hold.) The wire nut should cover all exposed wire. Make sure that the wire nut is “socked up” solidly; otherwise, it can come loose. Switches have brass screws as a reminder that only black wires are connected to each other. (Keep in mind that switches don't consume current.) An exception to this occurs when a switch is located at the end of a circuit. Whenever you have this condition, you will find yourself with only one black wire with which to effect the connection instead of the two you need. To solve this problem, the National Electrical Code allows you in this particular case to connect a black and a white wire to the switch, providing you with the two wires needed. You will note, however, that since the switch is at the end of the circuit, the continuity of the white wire up to the point where the current is being consumed isn't bro ken. If you have such a condition, paint the ends of the white wire black as a reminder that it's no longer serving as a neutral wire Three-way switches have a pair of brass terminals and a single darker one called the common terminal. The common terminal is attached inside to a switch arm that can connect internally to either one of the two terminals, depending on which way the outside switch lever is pushed. You will need three-wire cable to make these connections. Three-wire cable comes with a red and a black wire (both hot) and a white (neutral) wire. Some of the most common wiring conditions are shown in the schematic drawings. Following are a couple of tips on device installation: There are instances when too many wires in a box may cause the screw terminals in the receptacle to be pushed against the side of the box. This can result in a short circuit. A good way to help prevent this problem is to wrap electrician’s tape around all the sides of the device. To avoid working in cramped quarters, pull the wires out of the box. Once the device has been installed, gently curl the wires back into the box, being careful to move them out of the way of devices to be pushed in. Push the device back into the box, making sure that no strains are being induced on the connections. The finish work is completed with the installation of the cover plate (). A number of devices are available to simplify the finish wiring. Generally, they are more expensive than the ones we’ve already described and they are often not allowed by code. The most common one is the back-wired type. In back- wired devices, the bare wires are inserted in the back of the device. Once inside, the wire is sandwiched between two plates, which when pushed together grip the wire to make contact. This is done by tightening two screws located at the side of the receptacle. This device also has a stripping guide to measure the amount of wire that needs to be bared. Next: Applying Interior Finishes |
