Different Types of Wires with Their Specification | Without wire, there would be no electricity, where we want and need it. The type, size, and insulation of cable affects the safety of the electrical operation for long periods. In addition to wire, it also takes boxes, fixtures, switches, plugs, and other electrical devices to wire any facility. In this article, we look at wire and some of the devices used in making an electrical cable or wiring system operate without damage to people or buildings.
What is a Wire?
A wire is a metal, usually in the form of a very flexible thread or slender rod that conducts an electric current.
|Different Types of Wires with Their Specification|
Conducting Materials and Their Specification
Two commonly used conductors are aluminum and copper. Both has advantages and disadvantages. Copper has high conductivity and is more ductile. It is relatively high in tensile strength and can be soldered easily. Although silver is the best conductor, its use is limited because of its high cost.
Copper is more expensive than aluminum. Aluminum wire has about 60% of the conductivity of copper. It is used in high-voltage transmission lines and sometimes in domestic and industrial wiring. Its use has increased in recent years.
However, most peoples will not use it to wire a house today. There are a lot of reasons for this, the most important being the safety of the installation and the possible deterioration of joints over the years due to expansion and contraction of the aluminum wire.
If copper and aluminum are connected together in a wire nut, it is possible for moisture to get to the open metals over time. Corrosion will take place, causing a high-resistance joint. This can result in a dimmer light or a malfunctioning motor.
|What is wire?|
The size of wire is given in numerals. The wire size usually ranges from 0000 (referred to as 4 aught) to No 40. The larger the wire, the smaller its number. Table lists the size of standard annealed solid copper wire in relation to its number. Note the relation of circular mils to square inches. A mil is 0.001 inch. Circular mils are often expressed by
Roman numerals. 212,000 circular mils is 212 MCM.
The first M stands for thousand (as with Roman numerals) and the CM stands for circular mils. Wire larger than 0000 is usually referred to according to MCM (thousands of circular mils).
A frequently used wire is 750 MCM (750,000 circular mils). Figure shows the various sizes of wire most often encountered by electricians. Note that. No. 6 and above consist of multi strands of wire. This allows the wire to be bent by hand. The larger sizes sometimes require a conduit bender to bend them to smaller radius.
Different Types of Wires
Many different types of wires are manufactured. Three major types are discussed here. They are,
- Service entrance cable
- Non-metallic sheathed cable
- Metallic or armored cable
|Types of wires|
Branch Circuit Wiring
General-purpose circuits should supply all lighting and all convenience outlets through the house, except those convenience outlets in the kitchen, dining room or dining area of other rooms, breakfast room or nook, family room, and laundry areas.
General-purpose circuits should be provided based on one 20-ampere circuit for not more than every 500 square feet or one 15-ampere circuit for not more than every 375 square feet of floor area. Outlets supplied by these circuits should be equally divided among the circuits.
Feeder circuits should also be used. Feeder circuits strongly recommended that consideration be given to the installation of branch circuit protective equipment served by appropriately sized feeders located throughout the house, rather than at a single location.
Small appliance branch circuits should also be installed. There should be in-home wiring service at least one three wire, 120/240-volt, 20-ampere small-appliance branch circuit that is equipped with split-wired receptacles for all convenience outlets in the kitchen, breakfast and dining room, and family room. Two two-wire, 120-volt, 20 ampere branch circuits are equally acceptable.
Several different types of wires can be used for branch wiring. Armored cable, commonly referred to as BX cable, is available in 250-foot rolls for use where local codes permit. BX cable is hard to work with and needs some attention to details once the metal shield has been cut.
Armored Cable Installation
Install armored cable fittings as follows:
• To protect wires, install anti short bushing in end of cable (754 series). Anti short bushings are not required when using screw-in connectors and couplings (044 and 045 series).
• Slip connector onto cable allowing 6 to 8 inches of wire to protrude from fitting.
• Tighten screw(s) (except 044 and 045 series).
• Remove locknut from fitting. Insert fitting (now with wires protruding) into knockout in outlet box.
• Turn locknut on fitting from inside the box and tighten by tapping with screwdriver blade until teeth bite into box.
• Tug on cable to test connection.
• Secure cable with staples (625, 720, and 730 series) within 12 inches of the box and one for every four 1/2 feet of cable run. Be careful not to damage cable insulation or conductors.
• 044 and 045 screw-in series are used for flexible metal conduit only.
• 05803 connector is to be used with armored cable only.
• 153 series combination couplings can be used for EMT and flexible metal conduit only.
• 15803 duplex connectors may be used on nonmetallic cable as well as armored and flexible metal conduit. Romex cable is used for branch circuits and is easier to work with.
A cable stripper is used to strip off the first insulation. Then, a knife or wire cutter is used to cut away any loose materials to expose the uninsulated copper wire and the black- and white-jacketed conductors, In three-wire cable there is also found a red-jacketed conductor.
Romex is used to wire a branch circuit with a receptacle. how to properly wire receptacles and switches in branch circuits. Illustrates how branch circuits are loaded to balance the load on different phases.
Single-phase and three-phase loading are shown. Of course, the proper wire should be used for each of the circuits.
Service Entrance Cable or SEU Wire
Power is brought from the pole or transformer into the rear of the house (in some cases the lines are underground) by means of three wires—one black, one red, and one white or uninsulated. These wires may be three separate ones, or they may be twisted together to look like one cable.
Once the cable is connected to the house, it is brought down to the meter by way of a sheathed cable with three wires: one red, one black, and one uninsulated (ground or neutral). The stranded, uninsulated wire is twisted at the end to make its connection.
Wire size depends on the load to be applied to the line. The square footage of the house determines the amount of minimum service capacity needed (125 amperes, 150 amperes, or 200 amperes). From the outside, the cable enters the house and is connected to the distribution box located somewhere easily accessible, such as in the basement.
From the distribution box, the branch circuits run to all parts of the house. Underground Feeders and Branch Circuit Cable. This type of cable is for direct burial and is made with polyvinyl chloride (PVC) insulation and jacket materials. It is available in many sizes.
In multiple-conductor cables the two- or three-circuit conductors are individually insulated and are laid parallel under a jacket to form a flat construction. A multiple-conductor cable may have, in addition to the circuit conductors, an uninsulated or bare conductor of the same wire size for grounding purposes.
Type UF cables are designed for use in wiring methods recognized by the National Electrical Code (NEC) in systems operating at potentials of 600 volts or less. The maximum conductor temperature in type UF cables is 60C. This type of wire may also be used for interior wiring in dry, wet, or corrosive locations.
Multiple-conductor-type UF cable may be installed as nonmetallic sheathed cable. Once every 24 inches along the conductor jacket will appear “sunlight resistant UF, size of the wire, and the number of conductors plus 600 V UL.
What is Cable?
Cable is a general term often applied to large conductors. They may be single-strand conductors or a combination of conductors (wires) insulated from one another but encased together. Many types of cable are used, two of the most common being Romex cable and BX cable.
|Romex cable and BX cable|
Romex cable is used to carry power from a distribution panel box to the individual outlets within the house. This nonmetallic sheathed cable has plastic insulation covering the wires to insulate them from all types of environments. Some types of Romex cable may be buried underground. Underground Romex has UF stamped on its outside covering.
BX cable is the name applied to armored or metal-covered wiring. BX sometimes meets the need in home applications for flexible wiring. It is used to connect appliances, such as a garbage disposal unit, which vibrates or moves a great deal. BX cable has to have special fittings to make sure its metal covering does not cut through the insulation of the wire it houses.
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