A switch controls power to lights and devices by turning off the hot side of the circuit. Selection depends on design and load capacity.
A conventional switch makes or breaks contact when a mechanically connected tumbler or toggle bridges or breaks the line contacts in the switch.
* A single-pole switch is simplest and most frequently used in the home, controlling current on one circuit from one point. It features two terminal screws.
* Double-pole switches have four terminal screws.
* A three-way switch controls one circuit from two separate points, such as a garage light that can be turned on or off from the house or the garage.
* Four-way switches are used in connection with three-way switches to control one circuit from three or more points.
Single-pole and three-way switches are available with lighted handles that glow in the dark.
Dimmer switches control the amount of current in a lighting circuit, allowing the user to control the degree of light from off to full capacity.
Some dimmers control the amount of voltage going to the lamp, increasing or reducing the amount of light given off. Other dimmers control a portion of each alternating current cycle applied to the lamp. This means a solid state dimmer turns the light off and on approximately 120 times per second. The on-off rate has no noticeable effect on the life of the bulb or on the eyes of persons in the room.
It is normal for a dimmer to get warm during operation, which is why dimmers are built with a heat sink. If the load is not over the wattage rating of the dimmer and is a proper load for which the dimmer is designed to control, the dimmer does not need to be replaced.
* There are several styles of wall dimmer switches available. The most popular include a push on-off/dial-to-dim type, a rotary full-range type, a slide type and a toggle type that offers full-range control but uses toggle motion instead of a dial.
* Dimmers also come in single-pole or three-way construction. If two, three-way switches are involved, only one of them can be a dimmer. Otherwise, the setting will not work, although some toggle dimmers allow two three-way switches to be used.
* An air gap switch is built into all dimmers as a safety feature to ensure that power can be removed to the output--this is a UL requirement.
* Rocker switch--used in place of a standard wall switch, it is activated with a push-button mechanism. Useful near a doorway or area where hands might be full or for appearance and for range hood and appliances.
* Delayed-action switch--circuit remains active for a few minutes after switch is thrown. Useful in garage or breezeway, allowing individual to get into the house before light goes out.
* Programmable memory switch--set to go on and off at specific times far security or safety purposes.
* Photoelectric switch--operates by light striking cell. Usually used on yard lights. Daylight turns circuit off; it goes back on at dusk. Circuit usually has a delay device to prevent passing headlights from turning light off.
* Motion switch--turns the light on as you enter the room. Used for both convenience and security. Can be used to replace existing wall switches.
* Illuminated switch--is available in two types. One has a small light that is on when the switch is off so it can be easily found; these are usually used at entrances to rooms and in hallways. Pilot light switches are on when the light is off and usually used for out-of-sight lights such as those in the basement, garage and attic.
* Outdoor switch--enables electrical power to be used for outside applications. They feature a turning lever inside a weatherproof box cover with a toggle switch.
* A second type of tamper-resistant outlet utilizes an overlapping shutter system that limits improper access to its energized contacts.
* Voice-activated switch--offers a hands-free approach to illuminating dark areas quickly and safely. Voice-activated switches incorporate the latest technology in speech recognition to enable homeowners to control the brightness of the lights. Used in place of any standard wall switch, they can be programmed with any command or language.
* Silent switch--provides the same operation as many of the other switches with little or no noise. Silent switches are either mechanical or solid state. The mechanical switch is almost identical to the regular switch except for an extra bumper to reduce the noise. Prior to 1991, silent switches contained mercury and used no springs or mechanical devices. This resulted in smooth, silent operation and long life. Due to health concerns they were removed from the market.
The wall receptacle, or outlet, taps the circuit to provide electrical power at a given location. The slots in the outlet are designed to match the plug blades of the appliance or extension cord. Building codes specify number and spacing of outlets.
* Receptacles come in flush- and surface-mounted designs. Flush-mounted (recessed) is the style most commonly used for permanent installations.
* Configuration of a receptacle refers to the arrangement of slots or openings on the face of the outlet. These arrangements vary according to voltage and current rating of the receptacle.
The most common configuration is three-wire grounded. The most common outlets used in homes are standard 15-amp, 125V, three-wire designs. All outlets must be grounded (three prongs).
* A single- or double-wipe contact refers to the area of the inserted prong on which contact is made. In the case of a double wipe contact, contact is made on both sides of each blade.
* All outlets should have a faceplate to help prevent exposure to "live" wiring.
* There are three basic ways to terminate wiring in wall receptacles. First is the conventional binding-screw method where wires are stripped, looped and placed under binding screws and then secured by tightening down screws.
* Second is the pressure-lock method, which eliminates binding screws. In this method, connection is made by inserting a stripped conductor, which pushes the conductor into and against the terminal channel for a strong connection. Release slots permit easy removal of conductors.
* A third method involves clamp-type terminals. Stripped wire is inserted into an open clamp beneath a screw that is then turned down to lock connection.
* Some receptacles have small "pilot" or guide lights. Appliance receptacles consist of one vertical slot and two slanted slots and are designed to be surface-mounted. Specialty receptacles include twist lock, childproof, surge suppressor, isolated ground and RV.
* Any flush-mounted receptacle may be installed outdoors if covered by a protective plate. These weatherproof covers have hinged or threaded caps that cover the outlet face. A self-sealing gasket fits between the plates and the wall surface to add further protection.
* Safety outlets have spring-loaded caps to prevent children from inserting objects into them. To insert an attachment plug, its prongs must be placed into the slots of the protective cap, then turned 90[degrees] or until the slots of the outlet are exposed. When the plug is withdrawn, the cover automatically returns to its original protective position. A slight variation of this uses an overlapping shutter system.
Also available is an outlet that removes the hassle of fitting more than one large plug in a standard wall outlet. You connect the large plug and give it a turn to make space for another plug--large or small. Each receptacle clicks and holds in many different positions and maintains power even during rotation.
New to the market is a product that makes it easy to install new lighting fixtures and ceiling fans. It consists of a female receptacle and a male plug. The female receptacle attaches to the electrical outlet box and the male plug is pre-installed into the light fixture or ceiling fan. With the female receptacle installed into the outlet box, the lighting fixture or ceiling fan plugs into the receptacle and requires no additional wiring for installation. The lighting fixtures can then be easily replaced and removed for cleaning, painting or redecorating.
GROUND FAULT CIRCUIT INTERRUPTERS
Even with proper wiring and fusing or circuit breaking equipment, danger exists from ground faults, which are the most common cause of electrical shock.
* Ground fault occurs when a person comes into contact with a live electrical wire. This can happen by touching an exposed wire, or by operating a faulty appliance or power tool. Worn insulation, hidden damage or faulty connections can make the metal housing of an appliance a hot electrical conductor. Technically, this happens when a wire develops a small leak that will flow to the ground through any path, including a human body. This can cause serious shock, even death. Ground faults can also cause electrical fires.
This hazard is so serious that the National Electrical Code requires all new homes to be equipped with ground fault circuit interrupters (GFCI) in bathroom, kitchen, workroom, outdoor, basement and crawl space, garage and swimming pool receptacles. It is a good idea to suggest that homeowners install such a device in older homes. The GFCI interrupts power quickly enough to help prevent someone from receiving a lethal dose of electricity.
GFCIs are available in receptacles, modules, breakers and extension cords. Receptacles work for 15- or 20-amp circuits. GFCIs should be tested monthly to ensure they are working properly.
For convenience, a portable GFCI can be plugged into any existing outlets, either two-wire or three-wire, without rewiring. Circuit breaker GFCIs can be added in electrical panels to replace ordinary circuit breakers. They should be installed by a qualified electrician.
With increasing use of home computers and other sensitive electronic home entertainment equipment, there is a growing need for protection from voltage surges, often called spikes or transients. Surge protection is also needed because of the sheer number of potentially destructive spikes and surges that occur in the home every day. Surges can cause equipment to malfunction and in severe cases cause catastrophic damage or fire.
A surge is a transient increase of current, voltage or power on an electrical system. The larger, more destructive surges, generally caused by lighting, can reach thousands of volts. Surges can also come from utility transformer switching, air conditioner operation, inductive and power switching, distant lightning strikes and static discharges. They put extreme stress on solid-state components. Unchecked, such surges can quickly destroy wiring, appliances, telephones and other electrical devices.
* Transient voltage surge suppressors (TVSS) help protect sensitive electronic equipment. Surge protectors limit surge voltages by discharging surge currents to ground. Proper grounding is the strongest prerequisite for proper surge protection.
* The key component in almost all surge protectors is metal oxide varisters (MOVs). Under normal conditions, MOVs offer high resistance to currents, preventing normal currents from discharging to the ground. Under surge conditions--typically 115 percent or more of a normal current--the MOV's resistance drops within nanoseconds, creating a path with far less resistance than the facility's wiring for the current to flow to the ground.
* Basically, there are two types of suppressors. One--also known as a surge strip--is similar to a grounding adapter, and the appliance plugs into it at the wall outlet. Surge strips are not capable of suppressing a powerful surge. The other type, designed primarily to prevent lightning damage, is mounted at the service panel and protects the home where the electric, telephone and cable lines enter. The Institute of Electronics and Electrical Engineers recommend whole-house surge suppression as the most effective way to protect against damage in the home.
* Some of these suppressors also feature filters that reduce or eliminate line noise distortion that is picked up on radios, televisions and tape recorders. These filters also help guard against accidental data loss in home computers triggered by spikes or line noise.
* A whole-house surge protector mounted at the service panel also protects secondary distribution wiring and electrical appliances such as ovens, air conditioners, dishwashers and refrigerators from most sudden power surges. To increase the protection of electronic equipment, it is also recommended that a plug-in surge suppressor be installed at the point of use to supplement a secondary surge arrester.
* Surge protectors are rated in Joules and clamping voltages. Once surge protection has been provided at the maximum levels, the unit must be replaced. Look for audible or visual indicators.
When selling surge protection devices, stress the low cost of these products compared to the high cost of repairing or replacing branch wiring and electrical appliances and equipment. However, a surge protector will not protect against a direct lightning strike.
Transfer switches have become more popular for new construction and aftermarket installations due to weather storms or accidental power outages. Transfer switches are wired up to specific load center circuits that will be utilized when there is an emergency power outage. A portable generator is then plugged into it, and the switch transfers generator power through the home's existing electrical circuits. There is no backfeed when power is restored.
Transfer switches eliminate unnecessary extension cords and are easy to install. Available in choice of watts and number of circuits, plus optional accessories.
Lampholders are used to hold light sockets where design is not a concern. They are often used in garages or basements as a temporary fixture. One type has a pull chain to turn it on. The other, a keyless lamp-holder, does not have a chain. Another type has a socket, two receptacles and a pull chain that turns off the lamp but not the receptacles.
* Typically they are a round porcelain fixture with a socket with prowired leads ready for connecting to a circuit. They also have screw holes for mounting to a box.
* Another type is the pigtail, which is merely a socket with wire leads and without a fixture. It is also used for temporary lighting or for testing.
APPLIANCE AND HEATER CONNECTORS
Connectors are used to connect older style, heat-generating, small household appliances with heat-resistant neoprene-type HPN cords.
The connectors are molded of strong, heat-resistant materials and come in a variety of styles, such as switchless, armored (or heavily protected), side outlet and monopull. All have spring cord protectors.
There are two standard sizes: 11/16" and the miniature 1/2". Standard 11/16" connectors generally fit on irons and toasters. The 1/2" connectors are for coffeemakers, corn poppers, some electric skillets and other similar appliances.
BOXES, FITTINGS AND CONDUIT
According to the National Electrical Code, every break or termination in an electric cable must be enclosed in an appropriate box. This rule applies to switches and fixture connections as well as to splices and junctions.
Wall boxes, ceiling boxes (junction boxes) and weatherproof (outdoor) boxes are the main types of electrical boxes.
The three types of boxes are switch and outlet, ceiling and utility boxes. Some are made of galvanized steel with knockouts to bring cable into the box. Non-metallic (plastic) boxes are also available. Clamps are included in some boxes to hold cables in place.
* Switch boxes are 2" x 3" in size and can be used to house receptacles (outlets) as well as wall switches. Switch boxes are designed so that two or more may be fastened together to form a larger box. The side walls must be removed where the boxes join.
* Octagonal ceiling boxes are used primarily in ceilings to hold overhead light fixtures and splices.
* Utility boxes are used for the same purpose as switch boxes, but their rounded corners make them suitable for surface wiring.
* All boxes require covers. Box covers can be made of metal or plastic and come in several different shapes. The box covers may be solid or feature knockouts for receptacles.
* Electrical fittings are used to couple, connect, fasten or ground conduit or cable. Refer to local codes for requirements.
* Cable is sometimes held in place by straps or staples that are designed to handle different sizes and is terminated by the use of cable connectors. A number of other fittings are available for service entrance installations, for grounding purposes or for hazardous locations. Fittings can be installed easily with a screwdriver, hammer or pliers.
* Conduit is a raceway in which wires are installed and protected. Types of conduit include metal, nonmetallic and flex. Each conduit and size requires its own family of fittings.
* Metal conduit can be electrical metallic tube (EMT); intermediate metallic conduit (IMC); rigid or surface raceway.
* Non-metallic conduit can be surface raceway or polyvinyl chloride (PVC).
* Flex conduit types include flexible (steel and aluminum); electrical non-metallic tube (ENT); and liquid tight (metallic end non-metallic).
Conduit can be held in place by a variety of straps and hangers that are designed to fit a specific size diameter. The diameter of rigid and EMT conduit differs, so the correct strap or hanger must be specified. Lengths of conduit are joined together by couplings (either rigid or EMT) and terminated by connectors. Couplings and connectors generally are either a set-screw type, threaded for rigid conduit or rain-tight compression type for damp locations.
PVC, EMT with rain tight fittings, liquid tight, rigid and IMC conduit can be used outdoors. For underground applications, only PVC and rigid conduit can be used.
SURFACE WIRING DEVICES
Surface wiring switches, receptacles, lampholders, etc., are installed entirely on the surface of the wall as opposed to a normal flush-mounted installation.
The device includes a box, cover and electrical device in one unit. The unit is molded of an attractive and sturdy plastic insulating material, which makes it suitable for use in the home as well as in barns, garages and basements.
On-the-wall wiring systems created for do-it-yourselfers allow the consumer to run electrical wires to the point of use in the home without breaking into the wall or ceiling.
These systems have adapters that alter existing outlet boxes, so consumers can tap wires off them and snap together vinyl channels that carry the wires to the new outlet or switch. The channels hide unsightly wiring and can be painted to blend into any decor. Quick and easy installation and economy are its major advantages.
FUSES AND CIRCUIT BREAKERS
A fuse or circuit breaker box, commonly called a main service entrance panel or load center, is located between incoming power lines and house wiring. It divides the main power line into branch circuits. Load center applications vary, depending on local codes.
Fuses and circuit breakers are safety devices that break an electrical circuit when it is overloaded. The fuse or circuit breaker is sized to protect the branch circuit wiring between the breaker and the outlet and does not protect anything plugged into the outlet.
* Circuit breakers come in three main types: single, double end thin.
You can generally tell if a fuse is blown by looking at it. If the fuse is blackened, that indicates a short circuit has occurred; if the metal is melted, then an overload has occurred.
* There are several types of fuses. Plug fuses are available in 5- to 30-amp sizes and are the most commonly used fuse.
* Another fuse is the Type S, which provides a minimum time delay for the starting of small household motors. Type S fuses prevent anyone from replacing a lower-rated fuse with a higher one. It consists of two parts: the fuse and the adapter, which has a different diameter for each fuse ampere rating. Once an adapter of a particular size has been inserted into the fuse socket, it cannot be removed and only the same rating fuses can be used in that socket.
* Cartridge fuses are used in high-current applications, such as the main service box and in clamp- or bar-type fuse boxes that serve electric ranges, water heaters, clothes dryers and air conditioners. Round cartridge fuses have ratings to 60 amps; greater capacity (to 600 amps) requires a cartridge fuse with knife-edge contacts.
* A screw-in breaker can replace a fuse. When a circuit malfunctions, a button en this device pops out; it must be pushed in to reset.
* A circuit breaker contains a bi-metal strip that breaks the circuit when current exceeds a predetermined rating. A broken circuit is indicated by the breaker's switch being in the mid-point position. This is commonly referred to as a "tripped" breaker. After the overload has been corrected, reset the circuit breaker by switching it to the "off" position and then to the "on" position.
* A time delay fuse is similar in appearance to a plug fuse. It provides a minimum time delay for small household motors that cause an electrical surge when started. That surge would cause a regular fuse to blow needlessly.
* Fuse pullers are used to remove cartridge-type fuses.
ARC-FAULT CIRCUIT INTERRUPTERS
* Existing circuit breaker technology does not protect against an occurrence known as an arc fault. Arc faults are believed to cause a significant percentage of the more than 43,000 electrical home fires, 330 deaths and 1,800 injuries annually.
An arc fault can occur when insulation around cords, wires or cables is damaged or deteriorates. In many cases, arc faults are the results of aging wire. Are faults can flare at temperatures in excess of 10,000[degrees]F, igniting surrounding combustible material.
In many cases, conventional circuit breakers do not respond quickly enough to arc fault situations. By the time a circuit breaker responds, a fire may have begun to smolder.
* An arc-fault circuit interrupter (AFCI) is a device that recognizes the unique characteristics of many types of arcing faults and acts instantly to interrupt the circuit. In some devices, the arc-fault circuit interrupter is integrated into state-of-the-art circuit breaker design.
In 1999, the National Electrical Code mandated that arc-fault interrupters be installed on all 15- and 20-amp circuits in bedroom outlets in new home construction starting in 2002. Some states mandated the change earlier.
* Now available is a combination AFCI/GFCI circuit breaker that is certified by Underwriter's Laboratories. The breaker protects against electrical fires and dangerous electrical shock hazards, enhancing electrical safety in the home. It also simplifies the installation process for electrical contractors since there is no need to wire two separate devices.
Wall plates include all plates used to finish or cover switches, receptacles or combination devices. Standard plastic wall plates are constructed with durable, smooth surfaces. Builders in new homes often install inexpensive ones. There are also designer and decorator plates, switches and receptacles with smooth plastic faces in contemporary colors.
* Chrome-plated wall plates are made of steel and brightly finished for lasting appearance and durability.
* Decorative wall plates come in many styles and materials such as ceramic, aluminum, brass, wrought iron, stainless steel, copper, wood and die-cast metals. Die-cast products include switch and receptacle plates made in finishes and designs to match other functional hardware items such as door handles, cabinetware and bath fixtures.
Timers turn on lights and appliances at specified intervals end times, making them a useful security product. They are available for outdoor or indoor applications and can be electronic or mechanical. Spring-wound timers for bath fans and spas have a manual on-off switch.
* Some doorbell models are battery operated and are wireless; wireless are easiest to install. If not battery operated, they require AC step-down transformers to reduce household voltage to the proper operating voltage. Standard doorbells operate at 10V or 16V.
* Push buttons are easily installed and replaced. Push buttons are available in lighted or unlighted, recessed or surface-mounted styles.
* Non-electric chimes are also available. Wireless doorbells are all on the same frequency, although some offer adjustable frequencies.
PLUGS, ADAPTERS AND TAPS
Plugs connect devices to the power supply through a receptacle. The typical plug includes two blades or prongs, a molded plastic body holding the two blades apart and a blade/cord connection within the plug body. When inserted into an outlet, the blades become energized. Electricity flows through the blades, through the blade/cord connection and through the cord, thus energizing the appliance.
Plugs come in polarized and non-polarized varieties. Polarization helps reduce the potential for shock. With polarized plugs, one blade is wider than the other. Three-conductor plugs are automatically polarized because they can only be inserted one way. Two-prong plugs do not have a grounding pin.
Older homes may not have polarized receptacle outlets. If net, the receptacles will not accept polarized plugs. A qualified electrician should replace the old receptacles and put in wiring consistent with polarization.
Safety Tips For Electrical Boxes
* Always turn off power at the circuit it breaker box or fuse box before changing a receptacle or switch. You can double check that the circuit is dead by using a tester.
* Never attempt repairs near the service head
* Don't drill into walls or ceilings blindly Without shutting off power. Use a detector to determine if there are wires be hind the walls.
* If the homeowner has small children, suggest safety covers for wall receptacles They are a small plastic device With two blades that fit into the slots of the receptacle and prevent title fingers from reaching in.
Choose the plug based on the gauge of wire on the appliance or tool. Male plugs have prongs while female connectors have slots.
There are plugs for different applications, such as exterior, interior and marine. A twist lock prevents accidental disconnection.
* Attachment plugs fit on the ends of cords of portable appliances and permit them to be connected to wall receptacles or extension cords. Plugs and connectors are used to build extension cords or for replacement on extension cords.
* The arrangements of slots and blades on connectors, receptacles and plugs must match the configuration of the devices with which they will be used. The number of slots or prongs on these devices must be the same as the number of wires in associated cords.
Socket adapters screw into the socket, while taps plug into the outlet.
* Adapters are generally used for temporary application to provide two outlets where a light socket is in use.
* Taps are used to increase the number of attachment plugs that can be used on a single receptacle face.
Caution must be exercised when tapping additional attachment plugs into the same line. If the power rating of the circuit is exceeded, fuses will blow (if the circuit is properly fused).
* Multiple taps plug into existing outlets and can accommodate four to six plugs. Some come with built-in surge protectors. Other types of taps are table and cube.
* Plug-in strips feature multiple outlets placed at regular intervals. If used in a workshop, it should have grounded outlets and be attached to a grounded circuit.
Quick-clamp devices do away with screw terminals and the necessity of stripping wire. If a plug needs replacing, insert the cord into the clamping mechanism as shown on the instructions. The clamp forces the cord into the proper position and onto sharp contact points that pierce the insulation and make contact with the conductors.
Clamp devices include both attachment plugs and cord connectors of various styles. They are used with portable lamps and small appliances. They cannot he used on kitchen or large appliances because of their low amperage rating.
Wire nuts or connectors are used to connect the bare ends of two wires inside e lighting fixture or box. They connect wire with a twisting action.
The size of the wire nut must correspond to the size wire being used. Wire nuts are available in a variety of sizes and colors.
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|Title Annotation:||Electrical Supplies|
|Date:||Aug 1, 2006|