APE 131FARM ELECTRIFICATIONLABORATORY EXERCISE #4TITLE: WIRING PRACTICES: THE BRANCH CIRCUITOBJECTIVE: TO FAMILIARIZE WITH THE NATURE OF THE ELECTRICAL BRANCH CIRCUIT AND ITS COMPONENTS, AND BE ABLE TO FULLY ILLUSTRATE ITS APPLICATION AND USEFULNESS.METHODOLOGY:(1.) DISCUSS THE FOLLOWING COMPREHENSIVELY.a. RACEWAYS, CONDUITS AND CONNECTORS.Anelectrical conduitis a tubing system used for protection and routing ofelectrical wiring. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Flexible conduit is available for special purposes.Conduit is generally installed byelectriciansat the site of installation of electrical equipment. Its use, form, and installation details are often specified by wiring regulations, such as the USNational Electrical Code(NEC) or other national or local code. The term "conduit" is commonly used by electricians to describe any system that contains electrical conductors, but the term has a more restrictive technical definition when used in official wiring regulations.Comparison with other wiring methodsElectrical conduit provides very good protection to enclosed conductors from impact, moisture, and chemical vapors. Varying numbers, sizes, and types of conductors can be pulled into a conduit, which simplifies design and construction compared to multiple runs of cables or the expense of customized composite cable. Wiring systems in buildings may be subject to frequent alterations. Frequent wiring changes are made simpler and safer through the use of electrical conduit, as existing conductors can be withdrawn and new conductors installed, with little disruption along the path of the conduit.A conduit system can be made waterproof or submersible. Metal conduit can be used to shield sensitive circuits fromelectromagnetic interference, and also can prevent emission of such interference from enclosed power cables.When installed with proper sealing fittings, a conduit will not permit the flow of flammable gases and vapors, which provides protection from fire and explosion hazard in areas handling volatile substances.Some types of conduit are approved for direct encasement in concrete. This is commonly used in commercial buildings to allow electrical and communication outlets to be installed in the middle of large open areas. For example, retaildisplay casesandopen-officeareas use floor-mounted conduit boxes to connect power and communications cables.Both metal and plastic conduit can be bent at the job site to allow a neat installation without excessive numbers of manufactured fittings. This is particularly advantageous when following irregular or curved building profiles.Special equipmentis used to bend the conduit without kinking or denting it.The cost of conduit installation is higher than other wiring methods due to the cost of materials and labor. In applications such as residential construction, the high degree of physical damage protection may not be not required, so the expense of conduit is not warranted. Conductors installed within conduit cannot dissipate heat as readily as those installed in open wiring, so the current capacity of each conductor must be reduced (derated) if many are installed in one conduit. It is impractical, and prohibited by wiring regulations, to have more than 360 degrees of total bends in a run of conduit, so special outlet fittings must be provided to allow conductors to be installed without damage in such runs.Some types of metal conduit may also serve as a useful bonding conductor for grounding (earthing), but wiring regulations may also dictate workmanship standards or supplemental means of grounding for certain types. While metal conduit may sometimes be used as agrounding conductor, the circuit length is limited. For example, a long run of conduit as grounding conductor may have too high an electrical resistance, and not allow proper operation of overcurrent devices on a fault.Types of conduitConduit systems are classified by the wall thickness, mechanical stiffness, and material used to make the tubing. Materials may be chosen for mechanical protection,corrosionresistance, and overall cost of the installation (labor plus material cost). Wiring regulations forelectrical equipment in hazardous areasmay require particular types of conduit to be used to provide an approved installation.Metal conduitsRigid Metal Conduit(RMC) is a thick-walled threaded tubing, usually made of coated steel, stainless steel or aluminum.Galvanized rigid conduit(GRC) is galvanized steel tubing, with a tubing wall that is thick enough to allow it to be threaded. Its common applications are in commercial and industrial construction.[1]Intermediate Metal Conduit(IMC) is a steel tubing heavier than EMT but lighter than RMC. It may be threaded.Electrical metallic tubing(EMT), sometimes called thin-wall, is commonly used instead of galvanized rigid conduit (GRC), as it is less costly and lighter than GRC. EMT itself is not threaded, but can be used with threaded fittings that clamp to it. Lengths of conduit are connected to each other and to equipment with clamp-type fittings. Like GRC, EMT is more common in commercial and industrial buildings than in residential applications. EMT is generally made of coated steel, though it may be aluminum.Aluminumconduit, similar to galvanized steel conduit, is a rigid tube, generally used in commercial and industrial applications where a higher resistance to corrosion is needed. Such locations would includefood processingplants, where large amounts ofwaterand cleaning chemicals would make galvanized conduit unsuitable. Aluminum cannot be directly embedded inconcrete, since the metal reacts with thealkalisincement. The conduit may be coated to prevent corrosion by incidental contact with concrete. Aluminum conduit is generally lower cost than steel in addition to have a lower labor cost to install, since a length of aluminum conduit will have about one-third the weight of an equally-sized rigid steel conduit.[2]In extreme corrosion environments where plastic coating of the tubing is insufficient, conduits may be made fromstainless steel,bronze, orbrass.Non-metal conduitsPlastic tubing for use as electrical conduit.PVCconduit is the lightest in weight compared to other conduit materials, and usually lower in cost than other forms of conduit. In North American electrical practice, it is available in three different wall thicknesses, with the thin-wall variety only suitable for embedded use in concrete, and heavier grades suitable for direct burial and exposed work. Most of the various fittings made for metal conduit are also available in PVC form. The plastic material resists moisture and many corrosive substances, but since the tubing is non-conductive an extra bonding (grounding) conductor must be pulled into each conduit. PVC conduit may be heated and bent in the field, by using special heating tools designed for the purpose.Joints to fittings are made with slip-onsolvent-weldedconnections, which set up rapidly after assembly and attain full strength in about one day. Since slip-fit sections do not need to be rotated during assembly, the special union fittings used with threaded conduit (such as Ericson) are not required. Since PVC conduit has a highercoefficient of thermal expansionthan other types, it must be mounted to allow for expansion and contraction of each run. Care should be taken when installing PVC underground in multiple or parallel run configurations due to mutual heating effect of densely packed cables, because the conduit will deform when heated.Rigid Nonmetallic Conduit(RNC) is a non-metallic unthreaded smooth-walled tubing.Electrical Nonmetallic Tubing(ENT) is a thin-walledcorrugated tubingthat is moisture-resistant and flame retardant. It is pliable such that it can be bent by hand, and is often flexible although the fittings are not. It is not threaded due to its corrugated shape, although some fittings might be.Flexible conduitsFlexible metallic conduit used in an underground parking facility.Flexible conduits are used to connect to motors or other devices whereisolation from vibrationis useful, or where an excess number of fittings would be needed to use rigid connections. Electrical codes may restrict the length of a run of some types of flexible conduit.Flexible Metallic Conduit(FMC, often informally calledgreenfieldorflex) is made by thehelicalcoiling of a self-interlocked ribbed strip of aluminum or steel, forming a hollow tube through which wires can be pulled. FMC is used primarily in dry areas where it would be impractical to install EMT or other non-flexible conduit, yet where metallic strength to protect conductors is still required. The flexible tubing does not maintain any permanent bend, and can flex freely.FMC may be used as an equipment grounding conductor if specific provisions are met regarding the trade size and length of FMC used, depending on the amperage of the circuits contained in the conduit. In general, an equipment grounding conductor must be pulled through the FMC with an ampacity suitable to carry the fault current likely imposed on the largest circuit contained within the FMC.Liquid tight Flexible Metal Conduit(LFMC) is a metallic flexible conduit covered by a waterproof plastic coating. The interior is similar to FMC.Flexible Metallic Tubing (FMT)is not the same as Flexible Metallic Conduit (FMC) which is described in National Electrical Code (NEC) Article 348. FMT is a raceway, but not a conduit and is described in a separate NEC Article 360. It only comes in 1/2" & 3/4" trade sizes, whereas FMC is sized 1/2" ~ 4" trade sizes. NEC 360.2 describes it as: "A raceway that is circular in cross section, flexible, metallic and liquidtight without a nonmetallic jacket."Liquid tight Flexible Nonmetallic Conduit(LFNC) refers to several types of flame-resistant non-metallic tubing. Interior surfaces may be smooth or corrugated. There may be integral reinforcement within the conduit wall. It is also known as FNMC.Underground conduitConduit may be installed underground between buildings, structures, or devices to allow installation of power and communication cables. An assembly of these conduits, often called a duct bank, may either be directly buried in earth, or encased in concrete (sometimes with reinforcingrebarto aid againstshear forces). Alternatively, a duct bank may be installed in autility tunnel. A duct bank will allow replacement of damaged cables between buildings or additional power and communications circuits to be added, without the expense of re-excavation of atrench. While metal conduit is occasionally used for burial, usuallyPVC,polyethyleneorpolystyreneplastics are now used due to lower cost, easier installation, and better resistance tocorrosion.Formerly, compressedasbestosfiber mixed with cement (such asTransite) was used for some underground installations. Telephone and communications circuits were typically installed in fired-clay conduit.Surface Mounted Raceway (wire molding) This type of "decorative" conduit is designed to provide an aesthetically acceptable passageway for wiring without hiding it inside or behind a wall. This is used where additional wiring is required, but where going through a wall would be difficult or requireremodeling. The conduit has an open face with removable cover, secured to the surface, and wire is placed inside.Plasticraceway is often used fortelecommunicationwiring, such asnetworkcables in an older structure, where it is not practical todrillthroughconcrete block.

b. THE OVERHEAD LIGHT AND SWITCHESi. THE OVERHEAD LIGHTThe overhead light are commonly used for providing good 'general illumination' and are very practical in high traffic areas as well as rooms with lower ceilings. Ceiling lights are as attractive as they are practical.

ii. THE FULL-CHAIN SWITCHESApull switchis aswitchthat is actuated by means of achainorstring.An electric pull switch is attached to a toggle type switch: one pull to switch on and next pull to switch off.The most common use of a pull switch is to operate a ceilingelectric light. Theceiling fanis another appliance often operated by pull switches. Pull switches may be either two-position (open or closed) or multi-position (allowing for different fan speeds or levels of illumination).Mounted inside a pull switch, there could be two types of two-position toggle switches. (In both cases the stable physical open- or closed -situation would be switch in outer and string in upper position.) One type would switch to closed (alternatively open) already during the initial pull in the string. The other type would switch to closed (or open) only when releasingaftera full pull. With the first type, the weight of the string and handle could accidentally switch the load intermittently on and off, when still around the initial position (depending on the internal spring). This could potentially increase the danger of overheating in the switch.In a damp environment, electrical pull switches have a safety advantage because the user is separated from the electricity by a significant distance and if the lead is made of an electrically insulating material, such as cotton string.Most commercially available pull switches use a short length of ball chain, which may then be connected to any number of optional leads for added length or decoration. Leads for decoration or utility are usually made of metal or plastic. They can come in many different shapes ranging from animals, geometric shapes, or look just like a weight.

iii. 3-WAY AND 4-WAY SWITCHESc. THE JUNCTION BOXAn electricaljunction boxis a container for electrical connections, usually intended to conceal them from sight and deter tampering. A small metal or plastic junction box may form part of anelectrical conduitorthermoplastic-sheathed cable(TPS) wiringsystemin a building. If designed for surface mounting, it is used mostly in ceilings, under floors or concealed behind an access panel - particularly in domestic or commercial buildings. An appropriate type (such as that shown on the right) may be buried in theplasterof a wall (although full concealment is no longer allowed by modern codes and standards) or cast into concrete - with only the cover visible.It sometimes includes in-built terminals for the joining of wires.A similar, usually wall mounted, container used mainly to accommodate switches. Sockets and the associated connecting wiring is called apattress.The termjunction boxmay also be used for a larger item, such as a piece ofstreet furniture. In the UK, such items are often called a cabinet. SeeEnclosure (electrical).Junction boxes form an integral part of a circuit protection system wherecircuit integrityhas to be provided, as for emergency lighting or emergency power lines, or the wiring between anuclear reactorand acontrol room. In such an installation, thefireproofingaround the incoming or outgoing cables must also be extended to cover the junction box to preventshort circuitsinside the box during an accidental fire.

d. THE SERVICE-ENTRANCE SWITCHThecircuit breakerorswitch, withfusesandaccessories, located near the point ofentranceof supplyconductorsto a building and intended to be themaincontrol and cut-off for the electrical supply to that building.

e. WIRESi. TYPES OF WIRESSolid wireSolid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. Solid wire is useful for wiring breadboards. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. Solid wire also provides mechanical ruggedness; and, because it has relatively less surface area which is exposed to attack by corrosives, protection against the environment.Stranded wireStranded wire is composed of a number of small gauge wire bundled or wrapped together to form a larger conductor. Stranded wire is more flexible than solid wire of the same total cross-sectional area. Stranded wire tends to be a better conductor than solid wire because the individual wires collectively comprise a greater surface area. Stranded wire is used when higher resistance tometal fatigueis required. Such situations include connections betweencircuit boardsin multi-printed-circuit-board devices, where the rigidity of solid wire would produce too much stress as a result of movement during assembly or servicing;A.C.line cords for appliances; musical instrument cables; computer mouse cables; welding electrode cables; control cables connecting moving machine parts; mining machine cables; trailing machine cables; and numerous others.At high frequencies, current travels near the surface of the wire because of theskin effect, resulting in increased power loss in the wire. Stranded wire might seem to reduce this effect, since the total surface area of the strands is greater than the surface area of the equivalent solid wire, but ordinary stranded wire does not reduce the skin effect because all the strands are short-circuited together and behave as a single conductor. A stranded wire will have higher resistance than a solid wire of the same diameter because the cross-section of the stranded wire is not all copper; there are unavoidable gaps between the strands (this is thecircle packingproblem forcircles within a circle). A stranded wire with the same cross-section of conductor as a solid wire is said to have the sameequivalent gaugeand is always a larger diameter.However, for many high-frequency applications,proximity effectis more severe than skin effect, and in some limited cases, simple stranded wire can reduce proximity effect. For better performance at high frequencies,litz wire, which has the individual strands insulated and twisted in special patterns, may be used.Braided wireA braided wire is composed of a number of small strands of wire braided together. Similar to stranded wires, braided wires are better conductors than solid wires. Braided wires do not break easily when flexed. Braided wires are often suitable as an electromagnetic shield in noise-reduction cables.

ii. WIRE SPECIFICATIONS

iii. WIRE APPLICATION: SCHEMATIC AND WIRING DIAGRAMS, SPLICING AND OTHER WIRING PRACTICES.

Awiring diagramis a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified shapes, and the power and signal connections between the devices.A wiring diagram usually gives more information about the relative position and arrangement of devices and terminals on the devices, to help in building the device. This is unlike aschematic diagram, where the arrangement of the components' interconnections on the diagram usually does not correspond to the components' physical locations in the finished device. A pictorial diagram would show more detail of the physical appearance, whereas a wiring diagram uses a more symbolic notation to emphasize interconnections over physical appearance.A wiring diagram is used to troubleshoot problems and to make sure that all the connections have been made and that everything is present.

(2.) SKETCHES, DRAWINGS, OR PICTURES MAY BE USED TO ILLUSTRATE WHAT IS NEEDED TO BE SHOWN PICTORIALLY.

Service Entrance Switch

Wiring Application: Wiring Diagram

Wiring Application: Schematic Diagram

Wiring Application: Splicing Diagram

CONCLUSIONSTo sum up everything, this massive research has found out that there is an imperative nee to familiarize the nature of the electrical branch circuit as well as know its basic components. Having all of these, one can fully illustrate its practical application and be able to appreciate it usefulness.

REFERENCES

http://ehstoday.com/safety/don-t-be-shocked-static-electricity-qhttp://en.wikipedia.org/wiki/Atomhttp://www.sciences360.com/index.php/the-components-of-an-atom-2-12400/http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.intro.htmlhttp://inspectapedia.com/electric/Electrical_Definitions.htmhttp://en.wikipedia.org/wiki/Direct_current