Author: John M. Sharp; Category: Electronics; Length: Pages; Year: The Complete Guide to WIRING - Free ebook download as PDF File .pdf), Text File .txt) or read book online for free. The Complete Guide to WIRING. TLC recommends that you download and save this pdf document and . procedure or electrical safety textbook or a comprehensive source book on electrical .. a means of connecting apparatus that utilize electricity to the wiring system.
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PDF Drive is your search engine for PDF files. As of today we have 78,, eBooks for you to download for free. No annoying ads, no download limits, enjoy . ALL OF THE ILLUSTRATIONS IN THIS BOOK SHOW TYPICAL WIRING BREAKER BOX SUPPLYING POWER TO THE OUTLETS AND HOW TO CHANGE. Electric Wiring Domestic Book PDF Electric Wiring Domestic by Brian Scaddan Electric Wiring Domestic is the definitive guide to home wiring to professional.
Armored cable: An assembly of insulated wires enclosed in a flexible, interlocked metallic armor. Box: A device used to contain wiring connections. BX: A brand name for an early type of armored cable that is no longer made. The current term is armored cable. Cable: Two or more wires that are grouped together and protected by a covering or sheath.
Duplex receptacle: A receptacle that provides connections for two plugs. Commonly known as NM cable. A device used to measure the amount of electrical power being used.
The current term is flexible metal conduit. Screw terminal: A place where a wire connects to a receptacle. A device used to contain wiring connections. Watts can be calculated by multiplying the voltage times the amps. Also called a wire nut. A metal or plastic pipe used to protect wires. GFCI receptacles Separate volt circuit for water heater heater. Electric meter measures the amount the amount of electrical of electricity power consumed and displays the measurement inside a glass dome dome.
Bonding wire to metal water pipe pipe. Bonding wire to metal grounding rod rod. Wall switch Chandelier Receptacles Switch loop Separate volt circuit for microwave oven oven. Service panel distributes electrical power into circuits circuits.
Jumper wire is used to bypass the water meter and ensures an uninterrupted grounding bonding pathway pathway. Grounding rod must be at least 8 feet long and is driven into the ground outside the house house.
The grounding wire conducts current in the event of a ground fault see page and helps reduce the chance of severe electrical shock. Several switches. For safety. Current returns to the service panel along a neutral circuit wire. If a circuit carries too much current. Understanding Electrical Circuits Anatomy of a circuit A n electrical circuit is a continuous loop. A fuse or a circuit breaker protects each circuit in case of overloads.
Hot wires are black or red. Current then leaves the house on a large neutral service wire that returns it to the utility transformer. Household circuits carry electricity from the main service panel. These wires are color coded for easy identification. Current enters a circuit loop on hot wires and returns along neutral wires.
The service panel also has a bonding wire connected to a metal water pipe and a grounding wire connected to a metal grounding rod. A person could receive a fatal shock if he or she touches energized metal that is improperly bonded.
Ground Fault: Current is detoured by a loose wire in contact with the metal box. Most current in the bonding and ground system flows back to the transformer. Other grounding electrodes include reinforcing steel in the footing. These terms are often misunderstood. Bonding connects the non-current-carrying metal parts of the electrical system.
The most common grounding electrode is a buried copper rod. The dead circuit alerts people to a problem. Bonding is also a fire safety system that reduces the chance of electrical fires. Contrary to popular belief. Black hot wire Grounding wire Current returns to transformer White neutral wire Grounding screw Grounding wire Loose hot wire Grounding wire to grounding rods Grounding wire to grounding rods 8 ft.
Metal Service panel water and gas pipes are the most common examples. Grounding is accomplished by connecting a wire between the main service panel and a grounding electrode. Metal gas pipe could become energized by a ground fault in a gas appliance such as a furnace. In a household wiring system. Grounding also provides a secondary return path for electricity in case there is a problem in the normal return path.
You will see the terms grounding and bonding used in this and other books about electricity. Bonding is a very important safety system. The grounding wire and bonded metal conduit pick it up and channel it back to the main service panel.
If this metal becomes energized a ground fault. Current enters the electrical box along a black hot wire and then returns to the service panel along a white neutral wire. From the service panel. A metal water and gas pipe could become energized by coming in contact with a damaged electrical wire.
You should understand the difference to safely work on electrical circuits. When connected to metal junction boxes. Flexible metal conduit not shown is sold empty. A receptacle adapter allows three-prong plugs to be inserted into two-slot receptacles. Double-insulated tools have non-conductive plastic bodies to prevent shocks caused by ground faults. Use a receptacle adapter to plug three-prong plugs into two-slot receptacles. Tamper resistent three-slot receptacles are required by code for new homes.
Used with a polarized plug. Modern NM nonmetallic cable. The adapter should only be used with receptacles mounted in a bonded metal box. By plugging a three-prong plug into a grounded three-slot receptacle. The mounting screw connects the adapter to the grounded metal electrical box. Modern cable includes a green insulated or bare copper wire that serves as the bonding path. After The metal jacket around armored cable and flexible metal conduit.
The two-slot polarized plug and receptacle was designed to keep hot current flowing along black or red wires and neutral current flowing along white or gray wires. Polarized receptacles have a long slot and a short slot. Armored cable is sold pre-installed in a flexible metal housing. Because of these features. This grounding wire is connected to all three-slot receptacles and metal boxes to provide a continuous pathway for any ground-faulted current.
They are usually connected to a standard two-wire cable with ground. The materials used for electrical wiring have changed dramatically in the last 20 years. Home Wiring Tools T o complete the wiring projects shown in this book. The following pages show how to work with the following components for your projects. As with any tool download. Keep your tools clean. Electrical tapes in a variety of colors are used for marking wires and for attaching cables to a fish tape. C A B Diagnostic tools for home wiring use include: A touchless circuit tester A to safely check wires for current and confirm that circuits are dead.
A fish tape is useful for installing cables in finished wall cavities and for pulling wires through conduit. Products designed for lubrication reduce friction and make it easier to pull cables and wires. Create a circuit index and affix it to the inside of the door to your main service panel.
Follow the safety tips shown on these pages. Although most household electrical repairs are simple and straightforward. Common sense can prevent accidents. Update it as needed. These devices have been tested for safety by Underwriters Laboratories. The basic rule of electrical safety is: Always turn off power to the area or device you are working on. Use only UL-approved electrical parts or devices. Shut power OFF at the main service panel or the main fuse box before beginning any work.
Confirm power is OFF by testing at the outlet. Test a live circuit with the voltage tester to verify that it is working before you rely on it. Then check to make sure the power is off by testing for power with a voltage tester.
Restore power only when the repair or replacement project is complete. Wiring Safety afety should be the primary concern of anyone working with electricity.
Never attempt an electrical project beyond your skill or confidence level. At the main service panel. Use fiberglass or wood ladders when making routine household repairs near the service mast. If possible. Breakers and fuses must be compatible with the panel manufacturer and match the circuit capacity.
Cords must be rated for the intended usage. Do not penetrate walls or ceilings without first shutting off electrical power to the circuits that may be hidden. On damp floors.
Extension cords are for temporary use only. Never alter the prongs of a plug to fit a receptacle. This chapter introduces some of the many varieties of wire. Selecting the appropriate size and type and handling it correctly is absolutely necessary to a successful wiring project that will pass inspection.
Copper wire is the primary conductor of electricity in any home. In some cases. Conduit also known as raceway is used primarily in situations where the cables or wires are exposed. It also will demonstrate the essential skills used to run new cable. The insulated wires are frequently grouped together and bound up in rugged plastic sheathing according to gauge and function.
Multiple wires housed in shared sheathing form a cable. The electricity itself travels on the outer surfaces of the wire. Aluminum and copper-covered aluminum wires require special installation techniques.
The ampacity for aluminum wire is less. A group of two or more wires enclosed in a metal. Solid copper wires are the best conductors of electricity and are the most widely used. Old insulation that is cracked or damaged can be reinforced temporarily by wrapping the wire with plastic electrical tape.
Wire sizes shown actual size are categorized by the American Wire Gauge system. The ampacities in this table are for copper wires in NM cable.
This type of insulation is very durable and can last as long as the house itself. Conduit also protects wires. White means 14 wire. If so. The ampacity for the same wire in conduit is usually more. In some circuit installations. The insulation is color coded see chart. To check the size of a wire. The sheath protects the wires from damage. Individual wires are covered with rubber or plastic vinyl insulation.
Wires must be large enough for the amperage rating of the circuit see chart. The larger the wire size. Before New cable sheathing is also color coded to indicate the size of the wires inside. A wire that is too small can become dangerously hot. Rubber insulation has a life expectancy of about 25 years. In most wiring systems installed after An exception is a bare copper grounding wire.
It is designed for installations in damp conditions. Metal conduit was installed during the middle of the 20th century as a way to protect hot and neutral conductors. UF underground feeder cable has wires embedded in a solid-core plastic vinyl sheathing and includes a bare copper grounding wire. Wires are covered with a layer of rubberized cloth. Early NM nonmetallic cable was used from until The Modern MC contains an insulated ground wire along with the conductors. NM cable nonmetallic was developed cable was around developed around Early versions had no grounding function.
Later armored cable products either had ground wire twisted in with the flexible metal cover or relied on the metal cover itself for connecting to ground. NM cable greatly simplified installations because separate wires no longer had to be pulled by hand through a conduit or armored cable. It features a rubberized fabric sheathing that protects individual wires.
The conduit itself often was employed for connecting to ground. Metal clad cable MC and armored cable AC have been around since the s. Early NM cable had no grounding wire. Eight-wire cable has extra wires that are left unattached. NM nonmetallic sheathed cable should be used for most indoor wiring projects in dry locations. Telephone cable is used to connect telephone outlets. Your phone company may recommend four-wire cable shown below or eight-wire cable.
UF cable underground is used for feeder wiring cable in damp is used locations. Cat 5 Category 5 cable is used mostly for information and data networks. It is similar to NM cable. Service entrance cable SE is used between Large-appliance cable.
NM cable is allowed. Each wire. It is available in lengths up to 25 ft. SE cable is available in both 3-wire types. Large-appliance conducting wire is made from fine-stranded cable is available in both 2-wire and copper wires. The cable contains four pairs of twisted copper wire with color-coded insulation. NM cable is available in a wide range of wire sizes. NM cable is sold in boxed rolls that contain from 25 to ft.
Coaxial cable is used to connect cable television jacks. These extra wires allow for future expansion of the system. Or you can download bulk cable B in any length.
It can also be used or amp appliances that require 8-gauge for kitchen ranges and other amp or amp or larger wire. Wire connectors are color-coded by size. Green wire connectors are used only for grounding wires. Wire coded with an N is impervious to damage from oil or gas. The wire connectors shown above come from one major manufacturer. W denotes wire suitable for wet locations. To ensure safe connections. Ampacity varies by the size of the wires.
The bare grounding wire is not counted. For dedicated appliance circuits. H stands for heat resistance. Wire insulation is coded with letters to indicate resistance to moisture. NM cable also is stamped with a maximum voltage rating. T indicates thermoplastic insulation. When installing a new circuit.
For example. Code requires certain letter combinations for certain applications. These connectors can be used to connect both conducting wires and grounding wires.
Cut individual wires as needed using the cutting jaws of the combination tool. Choose the opening that matches the gauge of the wire. Slide the cable ripper onto the cable. Strip insulation for each wire using the stripper openings. Instead of twisting the bare wire ends together. Hook each wire around the screw terminal so it forms a clockwise loop.
Tighten the screw firmly. Never place the ends of two wires under a single screw terminal. Choose the stripper opening that matches the gauge of the wire. These connectors are perfect for inexperienced DIYers.
Insulation should just touch head of screw. The wire should have no scratches or nicks. Choose staples sized to match the cables. Pull the wire firmly to remove plastic insulation. The connectors come with two to four holes sized for various gauge wires.
Push-in connectors are a relatively new product for joining wires. There should be no bare wire exposed beneath the collar of the connector. Few professional electricians use tape for purposes other than tagging wires for identification.
Twist a wire connector over the ends of the wires. Rotate the pliers clockwise two or three turns to twist the wire ends together. Gently tug on each wire to make sure it is secure. Hand-twist the connector as far onto the wires as you can. Make sure the connector is the right size see page By code.
The ends of the wires should be flush and they should be parallel and touching. Pigtailing is done mainly to avoid connecting multiple wires to one terminal.
Fold the wires neatly and press the fitting into the box. Join one end of the pigtail to the wires that will share the connection using a wire nut. Connect the pigtail to the appropriate terminal on the receptacle or switch. If you are pigtailing to a grounding screw or grounding clip in a metal box. Use plastic grommets to protect cables on steel studs inset.
Prevent kinks by straightening the cable before pulling it through the studs. NM Cable N on-metallic NM cable is used for most indoor wiring projects except those requiring conduit and those in damp areas such as against concrete or masonry walls with dirt on the other side.
When boring holes. In general. Manufacturers of I-joists and engineered beams have limits about the size and location of holes. Joists can be notched only in the end third of the overall span. Do not install wallboard or attach light fixtures and other devices until this inspection is done. Cut and install the cable after all electrical boxes have been mounted.
When inserting cables into a circuit breaker panel. Different rules apply to wood I-joists. Check with your building inspector before using NM cable. Cable runs are difficult to measure exactly. Cable splices inside walls are not allowed by code. Some areas. Refer to your wiring plan to make sure each length of cable is correct for the circuit size and configuration. After all cables are installed and all the ground wires spliced. This is done easily with a right-angle drill.
Insert a cable clamp into the knockout. Use a cable ripper to strip the cable. Measure and cut all cables. Open a knockout in the circuit breaker panel using a hammer and screwdriver.
Tighten the mounting screws on the clamp so the cable is gripped securely but not so tightly that the sheathing is crushed.
Clip away the excess sheathing. At corners. Run the cable to the first electrical box. Remove sheathing from the marked line to the end using a cable ripper. Different types of boxes have different clamping devices. Insert the cable through the knockout in the box. Hold the cable taut against the front of the box. Retrieve the cable through the other hole using needlenose pliers inset.
Where the cable runs along the sides of framing members. Take care not to nick the copper. Clip back wires so there is 8" of workable length.
From inside the fixture. At metal boxes and recessed fixtures. Label the cables entering each box to indicate their destinations.
After all cables are installed. Mark the floor so the cable will be easy to find after the walls are finished. If the box has internal clamps.
In boxes with complex wiring configurations. At each recessed fixture and metal electrical box. From the unfinished space below the wall. From above the finished wall. Drill a 1" hole up into the stud cavity. Choose a location for the new cable that does not interfere with existing utilities. Apply cable-pulling lubricant to the taped end of the fish tape. This job will be easier if you have a helper feed the cable from below as you pull.
Drill a 1" hole down through the top plate and into the stud cavity using a drill bit extender. Bend the wires against the cable. If walls do not line up right. After running the cable. Extend a fish tape into the joist cavity between the walls and use it to pull the cable from one wall to the next. If the walls line up one over the other left. Use a flexible drill bit. Drop the line into the stud cavity from above. Cut small openings in the wall near the top and bottom plates. This often occurs in two-story homes when a cable is extended from an upstairs wall to a downstairs wall.
Be sure not to tap into a restricted circuit such as the kitchen counter top and bathroom receptacles. When you are finished pulling the cable. New fixture location Nail guard New switch location Existing receptacle Access holes shown larger than necessary for clarity 2 Fish a cable from the existing receptacle location up to the notch at the top of the wall.
After having your work inspected. Remove drywall on the wall and ceiling surface. To begin. Use a fish tape to pull the new cable up through the wall cavity and the notch in top plates. Make a notch in the center of the top. Be sure to plan a location for the new switch. Remove short strips of drywall from the wall and ceiling. Where cable must cross framing members.
Next use the fish tape to pull the cable through the ceiling to the fixture hole. Protect the notch with a metal nail stop. Elbow fitting is used in tight corners or for long conduit runs. Conduit should be supported within 3 ft. Cables that are exposed and are within the reach of an adult and most cables installed outside are often considered subject to physical damage. Compression fittings are used in outdoor IMC installations. Use UF cable instead or pull individual wires rated for wet area use.
Conduit and tubing installed outdoors must be rated for exterior use. Pigtail Pigtail Install a green insulated grounding wire for any circuit that runs through metal conduit.
The interior of conduit and tubing installed outside is considered a wet area. It often is used to connect permanently wired appliances. Although code allows the metal conduit to serve as the grounding conductor. The grounding wires must be connected to metal boxes with a pigtail and grounding screw left or grounding clip right.
The cover can be removed to pull long lengths of wire. Whether a location is subject to physical damage depends on the judgment of the electrical inspector. Other exposed locations may also qualify. Screw-in connectors or setscrew connectors are used to connect flexible metal conduit. Nail straps are driven into wooden framing members to anchor conduit.
Cables and wires that are subject to physical damage must be installed in conduit or some types of tubing to protect them. Plastic PVC conduit and tubing are allowed by many local codes. Do not use PVC plumbing pipes. Use material approved for use in electrical applications. Rigid metal conduit provides the greatest protection for wires. IMC is rated for outdoor use but can also be used indoors.
IMC has thicker galvanized walls and is a good choice for exposed outdoor use. It is assembled with solvent glue and PVC fittings that resemble those for metal conduit. It has watertight threaded fittings and a removable cover. LB conduit fitting is used in outdoor conduit installations. Setscrew coupling connects lengths of indoor metal conduit.
Offset fitting connects an indoor metal electrical box to a conduit anchored flush against a wall. It is available in ft. EMT is the preferred metal material for home use.
EMT is lightweight and easy to install. EMT is available in ft.
It is connected with watertight fittings. When wiring with PVC conduit and tubing. EMT is used primarily for exposed indoor installations.
Liquid-tight flexible conduit LFC is used in outdoor applications. RNC rigid nonmetallic conduit. IMC intermediate metallic conduit. The cement should be applied past the point on the conduit where it enters the fitting or coupling.
Insert the conduit into the fitting or coupling and spin it a quarter turn to help spread the cement. Allow the joint to set undisturbed for 10 minutes.
Wipe the cut ends with a dry rag. Also wipe the coupling or fitting to clean it. Wear latex gloves to protect your hands. Remove any rough inside edges with a pipe reamer or a round file. Drill pilot holes with a masonry bit. You can also use a conduit bender inset to make your own sweeps and bends. Continue attaching additional lengths. Open one knockout for each length of conduit that will be attached to the box. Conduit should be anchored within 3 ft.
Attach the conduit to the offset fitting on the box. Laundry receptacles usually are mounted at 48". Attach an offset fitting to each knockout using a locknut. Boxes for receptacles in an unfinished basement or other damp areas are mounted at least 2 ft. Open a knockout in the panel. The cover on the elbow fitting can be removed to make it easier to extend a fish tape and pull wires.
Leave at least 2 ft. Remove the cover on an elbow fitting when extending the fish tape around tight corners. Use extreme care when using a metal fish tape inside a circuit breaker panel. And After the boxes that house the switches and receptacles tend to be very shallow and more difficult to work with than ordinary boxes.
Before Surface-mounted wiring circuits are networks of cable channels and electrical boxes that allow you to run new wiring without cutting into walls. If you are tying into a standard switch box for power. Surface-Mounted Wiring S urface-mounted wiring is a network of electrical circuits that run through small.
But more often. They are not allowed for some specific applications damp areas such as bathrooms. If you have a room with too much demand on a single receptacle inset. The main advantage to a surface-mounted wiring system is that you can add a new fixture onto a circuit without cutting into your walls. The systems include matching elbows. The tracks house THNN wires that run from the new box to new receptacles and light switches. For home wiring.
Both systems include box extenders for tying in to a receptacle C. Lighter-duty plastic raceways A. Remove the receptacle from the box by unscrewing the two long screws that hold it to the box. Remove the cover plate from the receptacle by unscrewing the screw that holds the plate to the electrical box. If the sensor does not beep or light up. If your existing receptacle is not a tamper-resistant model replace it with one see page Once the screws are out.
Depending on how your receptacle has been wired. download a surface-mounted starter box.
Set the screws and the plate aside. If the sensor beeps or lights up. Measure from the power source to the new receptacle or switch. With the cover plate off. download enough raceway to cover this distance plus about 10 percent extra. Detach these wires and set the receptacle aside. Often the prepunched knockouts have two profile options—make sure the knockout you remove matches the profile of your track.
Pull all the wires you just disconnected through the opening. Screw the mounting plate to the existing receptacle box with the included mounting screws. Drive the mounting screws through the holes in the box and into the threaded openings in the mounting plate.
Secure the track or conduit in a vise or clamping work support. If the plate is not located over a wall stud. Position the mounting plate for the receptacle box up against the reference line and secure it with screws driven through the mounting plate holes.
Some work better than others. Mark screw locations on the wall. For best results. Of course. For this. At the new receptacle location. The common tapered plastic sleeves that are driven into guide holes will work for lighter duty. Once the cut is made. Ideally anything you attach to a drywall wall should be anchored at a wall stud location. Use a stud finder to locate and mark all of the wall framing members between the old receptacle and the new one.
Drive the anchor into the guide holes until the flange is flush with the wall surface. Snap the raceway into the clip below the knockout. Install the mounting plates directly below the pieces of track entering the receptacle boxes. Repeat this same procedure at the new receptacle box. The clips should line up with the knockouts. The elbow piece will have two parts. Corners are available for inside or outside corners and consist of a mounting plate and a cap piece.
Measure the distance between the ends of the horizontal parts of the elbows. Line up one end of the track with the end of an elbow and tap the track with a rubber mallet until it is snapped into all of the clips.
Use corner pieces to guide around corners. Be sure to measure all the way to the base of the clip. Snap the long piece of track into the mounting clips. There should be about 3" of wire coming out at each box. Snake the end of each wire into the starter box. Now you can wire the receptacles.
Wrap the end of the black wire around the bottom gold screw on the side of the receptacle. Begin at the new receptacle location. Make sure all of the wire fits completely within the cover pieces. Then snake the wire all the way through the long piece of track so about 12 to 16" comes out on each end. You may need to rap the plate with a rubber mallet to get enough force to snap it on.
You can use straight connector pieces to join two lengths of track. Cut black. Much like an elbow piece. Attach the cover plate. Tighten the screw. Connect the green wire to the green-colored screw on the bottom of the receptacle.
Wrap the end of the white wire around the silver screw opposite the gold one you just used. First make sure the power is still off with your touchless circuit tester. Use a screwdriver to drive the two long mounting screws that hold the receptacle to the box. Wrap the end of the black wire around the top gold screw on the side of the receptacle.
Install the cover plate. You can now restore the power and test your new receptacle. Join one end of the pigtail with the ends of the bare and green wires in the box using a wire connector. Wrap the other end of the pigtail around the green screw on the receptacle. Take the black wire that goes into the raceway and wrap the end of the wire around the bottom gold screw on the side of the receptacle.
The smallest common boxes. It is typically rectangular. Electrical panels function like other electrical boxes insofar as they house connections. Be sure to refer to a box fill chart see page 60 to learn which size and shape box is required for your job.
But they are not one-size fits all. Subpanels are smaller electrical panels that perform the same function but are supplied by the main service panel so they can distribute power into multiple circuits in a remote spot. The box may be as simple as a small handy box for making a splice or as complex as a amp main service panel. Installing a box that is too small is an extremely common wiring mistake that is easy to understand: In addition to the maximum box fill allowed by the chart. Electrical boxes come in several shapes.
Replace an undersized box with a larger box using the Electrical Box Fill Chart right as a guide. Octagonal electrical boxes contain wire connections for ceiling fixtures. This is an important fire safety rule. Do not overfill the box inset. Electrical Boxes T he National Electrical Code requires that wire connections and cable splices be contained inside an approved metal or plastic box.
A box must be deep enough so a switch or receptacle can be removed or installed easily without crimping and damaging the circuit wires. The box shields framing members and other flammable materials from electrical sparks and protects people from being shocked. A properly installed octagonal box can support a ceiling fixture weighing up to 35 pounds.
Any box must be covered with a tightly fitting cover plate. Rectangular and square boxes are used for switches and receptacles. The box must also be large enough to safely dissipate the heat from wires. Because the ceiling fixture attaches directly to the box. The NEC also says that all electrical boxes must remain accessible. Electrical boxes are available in different depths. Never cover an electrical box with drywall.
Rectangular boxes are used with wall switches and duplex receptacles. Single-size rectangular boxes shown above may have detachable sides that allow them to be ganged together to form double-size boxes.
They are used for cable splices and ganged receptacles or switches. To install one switch or receptacle in a square box, use an adapter cover. Braced octagonal boxes fit between ceiling joists.
The metal braces extend to fit any joist spacing and are nailed or screwed to framing members. Old work boxes can be installed to upgrade older boxes or to allow you to add new additional receptacles and switches. One type above has built-in clamps that tighten against the inside of a wall and hold the box in place. Plastic boxes are common in new construction. The box may include preattached nails for anchoring it to framing members. Wall switches must have grounding screws if installed in plastic boxes.
Outdoor boxes have sealed seams and foam gaskets to guard a switch or receptacle against moisture. Corrosion-resistant coatings protect all metal parts. Code compliant models include a watertight hood that protects even when the outlet is in use. Common styles include single-gang A , double-gang B , and triple-gang C. Double-gang and triple-gang boxes require internal cable clamps.
Metal boxes should be used for exposed indoor wiring, such as conduit installations in an unfinished basement.
Metal boxes also can be used for wiring that will be covered by finished walls. Plastic retrofit boxes are used when a new switch or receptacle must fit inside a finished wall. Use internal cable clamps. Additional electrical boxes include, cast aluminum box A for use with outdoor fixtures, including receptacles that are wired through metal conduit these must have in-use covers if they house receptacles ; old work ceiling box B used for light fixtures; light-duty ceiling fan box C with brace that spans ceiling joists; heavy-duty retrofit ceiling fan box D designed for retrofit; PVC box E for use with PVC conduit in indoor or outdoor setting; vapor-proof ceiling box with foam gasket F.
A variety of adapter plates are available, including junction box cover plate A , single-gang B , double-gang C , and light fixture D. Adapter plates come in several thicknesses to match different wall constructions. After installing cables in the box, tighten the cable clamps over the cables so they are gripped firmly, but not so tightly that the cable sheathing is crushed. Metal boxes must be bonded to the circuit grounding system. Connect the circuit grounding wires to the box with a green insulated pigtail wire and wire connector as shown or with a grounding clip page Cables entering a metal box must be clamped.
A variety of clamps are available, including plastic clamps A, C and threaded metal clamps B. Most are sold prefitted with installation hardware—from metal wings to 10d common nails attached at the perfect angle for a nail-in box.
The bulk of the nonmetallic boxes sold today are inexpensive blue PVC. You can also download heavier-duty fiberglass or thermoset plastic models that provide a nonmetallic option for installing heavier fixtures such as ceiling fans and chandeliers.
In addition to cost and availability, nonmetallic boxes hold a big advantage over metal boxes in that their resistance to conducting electricity will prevent a sparking short circuit if a hot wire contacts the box. Nonmetallic boxes generally are not approved for exposed areas, where they may be susceptible to damage.
Their lack of rigidity also allows them to compress or distort, which can reduce the interior capacity beyond code minimums or make outlets difficult to attach. Low cost is the primary reason that blue PVC nail-in boxes are so popular. Not only are they inexpensive, they also feature built-in cable clamps so you may not need to download extra hardware to install them.
The standard PVC nail-in box is prefitted with a pair of 10d common nails for attaching to exposed wall studs. These boxes, often called handy boxes, are too small to be of much use see fill chart, page Nonmetallic boxes for home use include: A box for a ceiling fan is another type of outlet.
Circuit: A continuous loop of electrical current flowing along wires. Overload: A demand for more current than the circuit wires or electrical device was designed to carry. This should cause a fuse to blow or a circuit breaker to trip. Circuit breaker: A safety device that interrupts an electrical circuit in the event of an overload or short circuit.
Pigtail: A short wire used to connect two or more wires to a single screw terminal. Conductor: Any material that allows electrical current to flow through it. Copper wire is an especially good conductor. Polarized receptacle: A receptacle designed to keep hot current flowing along black or red wires and neutral current flowing along white or gray wires.
Conduit: A metal or plastic pipe used to protect wires. Power: The work performed by electricity for a period of time. Use of power makes heat, motion, or light. Continuity: An uninterrupted electrical pathway through a circuit or electrical fixture. Current: The flow of electricity along a conductor. Receptacle: A device that provides plug-in access to electricity. Duplex receptacle: A receptacle that provides connections for two plugs.
Romex: A brand name of plastic-sheathed electrical cable that is commonly used for indoor wiring. Commonly known as NM cable. Screw terminal: A place where a wire connects to a receptacle, switch, or fixture.
Fuse: A safety device, usually found in older homes, that interrupts electrical circuits during an overload or shortcircuit. Service panel: A metal box usually near the site where electricity enters the house.
In the service panel, electrical current is split into individual circuits. In residences, the service panel has circuit breakers or fuses to protect each circuit. Greenfield: A brand name for an early type of flexible metal conduit. The current term is flexible metal conduit. Note: flexible metal conduit is different from armored cable.
Short circuit: An accidental and improper contact between two current-carrying wires or between a current-carrying wire and a grounding conductor.