Module 2: Electrical Terms PDF

Bulacan State University College of Architectecture and Fine Arts BU 313 Utilities 2: Electrical and Mechanical Systems Module 2: ELECTRICAL TERMS Access Fitting – is a fitting that permits access to conductor or enclosed wiring, elsewhere than at an outlet. Active Electrical Network – is a netwo...

Bulacan State University College of Architectecture and Fine Arts BU 313 Utilities 2: Electrical and Mechanical Systems Module 2: ELECTRICAL TERMS Access Fitting – is a fitting that permits access to conductor or enclosed wiring, elsewhere than at an outlet. Active Electrical Network – is a network that contains one or more sources of electrical energy. Admittance – it is the reciprocal of impedance. Air Circuit Breaker – a circuit breaker in which the interruption occurs in air. Air Switch – a switch in which the interruption of the circuit occurs in air. Air-Blast Transformer – a transformer cooled by force circulation air through its core and coil. Alive – electrically connected to a source of emf, electrically charged with a potential different from that of the earth. Also: Practical synonym for current-carrying Alternating Current – a periodic current, the average value of which over a period is zero. Alternator – (Synchronous Generator, a synchronous alternating-current machine, which changes mechanical power into electrical power. Ammeter – an instrument for measuring electrical current. Ampacity – current currying capacity. Ampere – a charge flow of one coulomb per second. Annunciator – an electromeagnetically operated signaling apparatus, which indicated whether a current is flowing or has flowed in one or more circuits. Apparent Power – in a single phase, two wire circuit, the product of the effective current in one conductor multiplied by the effective voltage between the two points of entry. Appliance – current-consuming equipment, fixed or portable such as heating or motor operated equipment. Armor Clamp - a fitting for gripping the armor of a cable at the point where the armor terminates, or where the cable enters a junction box or other apparatus. Armored Cable – a cable provided with a wrapping of metal, usually steel wires, primarily for the purpose the mechanical protection. Arrester, Lighting – a device which reduces the voltage of a surge applied to its terminals and restores itself to its original operating condition. Autotransformer - a transformer in which part of the winding is common to both the primary and secondary circuit. B X Cable – trade name for armored cable made by General Electric Co. commonly used to refer to armored cable. Back Connected Switch – a switch in which the current- carrying conductors are connected to studs in back of the mounting base. Bidirectional Current - a current that has both positive and negative values. Bond, Cable – an electric connection across a joint in the armor or lead sheath of a cable, or between the armor or sheath to ground, or between the armor or sheath of adjacent cables. Box, Conduit – a metal box adapted for connection to conduit for connection for installation of wiring making connections, or mounting devices. Box, Junction (Interior Wiring) – a metal box with blank cover for joining runs of conduit, electrical metallic tubing, wire-way or raceway, and providing space for connection and branching of enclosed conductors. Box, Junction – an enclose distribution panel for connection or branching of one or more electric circuits without making permanent splices. Branch Circuit – the portion of a wiring system extending beyond the final automatic overload protective device. Branch Circuit Distribution Center – a distribution circuit at which branch circuit are supplied. Branch Circuit, Appliance – a circuit supplying energy either to permanently wired appliances or to attachment- plug receptacles such as appliance or convenience outlets, and having no permanently connected lighting fixtures. Branch Circuit, Lighting – a circuit supplying energy to lighting outlets only. Branch Conductor – a conductor that branches off at an angle from a continuous run of conductor. Branch Joint – a multiple joint for connection of a branch conductor or cable to a main conductor or cable, wherein the latter continues beyond the branch. Break – the break of a circuit opening device is the minimum distance between the stationary and movable contacts when the device is n its open position. Breakdown – also termed “puncture”, denoting a disruptive discharge through insulation. Breaker, Line – a device that combines the functions of a contractor and a circuit-breaker. Buried Cable – a cable installed under the surface of the soil in such manner that it cannot be removed without digging up the soil. Bus – a conductor or group of conductor, which serves as a common connection for three or more circuits in a switchgear assembly. Bushing – also termed insulating bushing”, a lining for a hole for insulation and /or protection form abrasion of one or more conductors passing through it. Cabinet – an enclosure for either surface or flush mounting provided with a frame, mat, or trim. Cable Fault – a partial or total local failure in the insulation continuity of the conductor. Cable Joint – also termed a “splice”, a connection between two or more individual lengths of cables, with their conductors individually connected, and with protecting sheaths over the joints. Cable Service – service conductor arranged in the form of a cable. Cable, Electric - an inequality of positive and negative electricity in or on body. The charge stored in a capacitor (condenser) corresponds to a deficiency of free electrons on the positive place, and to an excess of free electrons on the negative plate. Capacitor – a device specifically designed to exhibit the effect of capacitance. Choke Coil – a low conduction path through which electric charges may flow. A DC circuit is a closed path for charge flow, an AG circuit is not necessarily closed, and ma conducts in part by means of an electric field (displacement current). Circuit – the path taken by an electrical current in flowing through a conductor from one terminal at the source of supply to the other. Circuit Breaker – a device used to open a circuit automatically. Circular Mil – the area of circle one-thousands of an inch in diameter, are in circular mils = diameter in mils, squared or multiplied by itself. Cleat – an assembly a pair of insulating, material member with grooves for holing one or more conductors at a definite distance from mounting surface. Clip, Fuse – contact on a fuse support for connecting a fuse holder into a circuit. Closed Electric Circuit - a complete electric circuit through which current will flow. In an AC closed circuit, charge flow may be changed into displacement current “through” a capacitor (condenser). Closed-Circuit Voltage- the terminal voltage of a sources of electricity under a specified current demand by electric charge flow. Coil – a conductor arrangement (basically a helix or spiral) that concentrates the magnetic field produced by electric charge flow. Composite Conductor – a conductor consisting of two or more strands of different metals, operated in parallel. Concealed – to be made inaccessible by the structure or finish of a building, also wires run in concealed raceway. Condenser – also termed “capacitor”, a device that stores electric charge by means of an electric field. Conductor – a substance that has free electrons or other charge carriers, which permit charge flow when an emf is applied across the substance. Conduit - a structure containing one or more duct; commonly formed from iron pipe or electrical metallic tubing. Conduit Fittings - accessories used to complete a conduit system, such as boxes, bushings and access fitting. Conduit Run – a duct bank, an arrangement of conduit with a continuous duct between two points in a electrical installation. Conduit, Flexible Metal – a flexible raceway of circular form for enclosing wires or cables, usually made of steel wound electrically and with interlocking edges, with a weather-resistant coating. Conduit, Rigid Steel – a raceway made or mild pipe with a weather-resistant coating. Contactor - an electrical power switch not operated manually and designed for frequent operation. Contacts - conducting parts, which employ a junction that is opened or closed to interrupt or complete a circuit. Control Relay – a relay to initiate or permit predetermined operation in a control circuit. Converter – a machine that changes electric current of one kind into current of another kind by the use of rotating parts. Coulomb - an electric charge of 6.28 x 10 electrons. One coulomb is transferred when a current of 1 ampere continuous past a point for one second. Counter EMF – (CEMF), the effective emf within a system, which opposes current in a specified direction. Current - the rate of charge flow. A current of one ampere is equal to a flow rate of one coulomb per second. Cycle – the complete series of values, which occur during one period of a periodic quantity. The unit of frequency, the hertz is equal to one cycle per second. Dead – functionally conducting parts of an electrical system that have no potential difference or charge (voltage of zero with respect to ground). Degree, Electrical - an angle equal 1/360 of the angle between consecutive field poles like polarity in an electrical machine. Diagram, Connection – a drawing showing the connections and interrelations of devices employed in a electrical circuit. Dielectric - a medium or substance in which a potential difference establishes an electric field, which is subsequently recoverable as electric energy. Direct Current – a unidirectional current with a constant value. “Constant Value” is defined in practice as a value that has negligible variation. Direct EMF – also termed “direct voltage”; an emf that goes not change in polarity and has a constant value that (one of negligible variation). Discharge – an energy conversion involving electrical energy. Example: discharge of a storage battery, discharge of capacitor; lightning discharge of a thundercloud. Displacement Current – the apparent flow of charge “through” a dielectric such as in a capacitor, represented by buildup and/or decay of an electric field. Disruptive Discharge – a rapid and large current increase through and insulator due to insulation failure. Divider, Voltage - a tapped resistor or series arrangement of resistor, sometimes with movable contacts providing a desired IR drops. (A voltage divider is not continuously and manually variable as in a potentiometer). Drop, Voltage – an IR voltage between two specified points in an electric circuit. Duet – a single enclosed runway for conductors or cables. Efficiency - the ration of output power to input power, usually expressed as a percentage. Electrical Units – in the practical system, electrical units comprise the volt, the ampere the ohm, the watt, the watt hour the coulomb, the mho, the Henry, the farad and the joule. Electricity – a physical entity associated with the atomic structure of matter which occurs in polar forms (positive and negative) and which are separable by expenditure of energy. Electrode - a conducting substance through which electric current enters or leaves in devices that provide electrical control or energy conversion. Electrolyte - a substance that provide electrical conduction when dissolved (usually in water). Electrolytic Conductor - flow of electric charges to and from electrodes in an electrolytic solution. Electromagnetic Induction - a process of generation of emf by movement of magnetic flux, which cuts an electrical conductor. Electromotive Force - (EMF) and energy-charge relation that results in electric pressure which produces or tends to produce charge flow. Electron - the subatomic unit of negative electricity; it is a charge of 1.6 x 10-19 coulomb. Electronics – the science treating of charge flow in vacuum, gases, and the crystal lattices. Electroplating – the electrical deposition of metallic ions as neutral atoms on an electrode immersed in a electrolyte. Electrostatics - a branch of electrical science dealing with the laws of electricity at rest. Energy – the amount of physical work, which a system is capable of doing. Electrical energy is measured in watt- seconds, or the product power and time. Equipment, Service – a circuit-breaker or switches and fuses with their accessories, installed near the point of entry of service conductors to a building. Exciter - an auxiliary generator for supplying electrical energy to the field of another electrical machine. Farad – a unit of capacitance that is defined by the production of one volts across the capacitor terminals when a charge of one coulomb is stored. Faults Current – a abnormal current flowing between conductors for connections, generating and substations, or a substation and a feeding point. Ferromagnetic Substance - a substance that has a permeability considerably greater than that of air; ferromagnetic substance has a permeability that changes with the value of applied magnetizing force. Filament - a wire or ribbon conduction (resistive) material which develops light and heat energy due to electric charge flow, light radiation is also accompanied by electron emission. Fixture Stud - a fitting for mounting a lighting fixture in an outlet box, and which is secured to the box. Flashover – a fitting for mounting a lighting, fixture in an outlet (but not through) an insulator. Fluorescence - an electrical discharge process involving radiant energy transferred by phosphors into radiant energy that provides increased luminosity. Flux - electrical field energy distributed in space, in a magnetic substance, or in a dielectric. Flux is commonly represented diagrammatically by means of flux lines denoting, magnetic or electric forces. Force - the number of periods occurring in unit time of a periodic process such as in the flow of electric charge. Frequency Meter - an instrument that measures the frequency of an alternating current. Fuse - a protective device with a fusible element that opens the circuits by melting subjected to excessive current. Fuse Cutout - an assembly consisting of a fuse support and holder, which may also include a fuse link. Fuse Element – also termed “fuse link” the current-carrying part of a fuse, which opens the circuit when subjected to excessive current. Galvanometer – an instrument for indicating or measuring comparatively small electric currents. A galvanometer has zero-center indication. Gap – (Spark Gap); a high-voltage device with electrodes between which a disruptive discharge of electricity may pass, usually through air. A sphere gap has spherical electrodes, needle gap has sharply pointed electrodes; a rod gap has rods with flat ends. Generator – machine that produces electricity. Ground Outlet – an outlet provided with a polarized receptacle with a ground contact for connection of grounding conductor. Ground – also termed “earth”; a conductor connected between a circuit and the soil; a chassis-ground is not necessary at ground potential, but is taken as a zero volt reference point. An accidental ground occurs due to cable insulator defect, etc. Ground Lug - a lug of convenient connection of grounding, conductor to a ground electrode or device to be grounded. Grounding Switch – a switch for connection or disconnection of grounding conductor. Ground Electrode – a conductor buried in the earth, for connection to a circuit. The buried conductor is usually a cold-water pipe, to which connection is made with a ground clamp. Guy – a wire or other mechanical member having one end secured and other end fastened to a pole or structural part maintained under tension. Hanger – also termed “cable rack”; a device usually secured to a wall to provide support for cables have equal and opposite reactance values. Heat Coil – a protective device for opening usually secured to a wall to provide support for cables have equal and opposite reactance values. Heater – in the strict sense, a heating element for raising the temperature of an indirectly heated cathode in a vacuum or gas tube. Also applied to appliances such as space heaters and radiant heaters. Henry – the unit for inductance; it permits current increase at the rate of 1 ampere per second and 1 volt is applied across the inductor terminals. Hickey – a fitting for mounting lighting fixture in an outlet box. Also a device used with a pipe handle for bending conduit. Horn Gap - a form of switch provided with arcing horns for automatically increasing the length of the arc and thereby extinguishing the arc. Hydrometer – an instrument for indicating the state of charge in a storage battery. Impedance – opposition to AC current by a combination of resistance, impedance is measured in ohms. Impedances, Conjugate – a pair of impedances that have the same resistance values, and that have equal reactance value. Impulse – an electric surge unidirectional polarity. Indoor Transformer – a transformer that must be protected form the weather. Induced Current – a current that results in a closed conductor due to cutting of lines of magnetic force. Inductance – an electrical property of a resistance less conductor which may have a coil form, and which exhibits inductive reactance to an AC current. All inductors have at least alight amount if resistance, also. Inductor – a device such a coil with or without a magnetic core which develops inductance, as distinguished form the inductance of a straight wire. Instantaneous Power – the product of an instantaneous voltages by the associated instantaneous current. Instrument – an electrical device for measurement of a quantity under observation, or for presenting a characteristic of the quantity. Insulator – a device used to insulate electrical conductors. Interconnection Tie – a feeder that interconnects a pair of electric supply systems. Interconnection, System – a connection of two or more power supply systems. Interlock – an electrical device depending on its operation from another device; for controlling subsequent operations. Internal Resistance – a connection of two or more power systems. Ion – a charged atom, or a radical. For example, a hydrogen atom that has lost an electron becomes a hydrogen ion; sulfuric acid produces H+ and SO-4 ions in water solution. IR Drop – a potential difference produced by charge flow through a resistance. Isolating Switch – an auxiliary switch for isolating the electric from its source of power; it is operated only after the circuit has been opened by other means. Joule – a unit of electrical energy; also electrical energy is proportional to the square of the current. Joule’s Law – the rate at which electrical energy is proportional to the square or the current. Jumper – a short length of conductor for making a connection between terminals, around a break in a circuit, or around an electrical instrument. Junction – a point in a parallel or series –parallel circuit where branches of into two or more paths. Junction Box – an enclosed distribution for the connection or branching of one or more electrical circuits, not using permanent splices. In the case of interior wiring, a junction box consists of metal box with a blank cover; it is inserted in a run of conduit, raceway or tubing. Kirchoff’s Law – the voltage law states that the algebraic sum of the drops around a closed circuit is equal to zero. The current law states that the algebraic sum of the sum currents at a junction is equal to zero. Knockout – a scored portion in the wall box of a box or cabinet, which can be removed easily by striking with a hammer; a circular hole is provided thereby for accommodation of conduit or cable. KVA – kilovolt-amperes, the product of volts and amperes divided by 1,000. Lag – denotes that a given sine wave passes through as peak at a later time than reference since wave. Lampholder – also termed “socket” or “lamp receptacle”, a device for mechanical support of and electrical connection to a lamp. Lay – the lay of a helical element of a cable is equal to the axial length of a turn. Lead – denotes that a given sine wave through its peak at an earlier time than a reference sine wave. Leakage, Surface – passage of current over the boundary of an insulator as distinguished from passage of current through its bulk. Leg of a Circuit – one of the conductors in a supply circuit between which the maximum supply voltage. Len’z Law –states that an induced current in a conductor is in a direction such the applied mechanical force is opposed. Lighting Rod – a rod that is run from the ground up above the highest point of a building. Limit Switch – a device that automatically cuts the power off at or near the limit of travel of a mechanical member. Limit Switch – a switch that opens the circuit when a device has reached the end of its travel. Load – the load on an AC machine or apparatus is equal to product of the rms voltage across its terminal and the rms current demand. Locking Relay – a relay that operates to make some other device inoperative under certain conditions. Loom – see tubing, flexible. Luminosity – relative quantity of light. Magnet – a magnet is a body, which is the source of magnetic field. Magnetic Field – a magnetic field is the space containing distributed energy in the vicinity of a magnet, and in which magnetic forces are apparent. Magnetizing Force – number of amperes-turns in a transformer primary. Mass – quantity of matter; physical property which determines the acceleration of a body as the result of an applied force. Matter – matter is a physical entity that exhibits mass. Megger – an instrument that measures the resistance in megaohms. Meter – a unit length equal to 39.37 inches: an electrical instrument for measurement of voltage, current, power, energy, phase angle, synchronism, resistance, impedance, capacitance, etc. Mho – the unit of conductance defined as the reciprocal of the ohm. Mica – a transparent mineral substance used for insulating commutators. Motor – a machine that changes electrical energy into mechanical energy. Mounting, Circuit-Breaker – supporting structure for a circuit breaker. Multiple Feeder – two or more feeders connected in parallel. Multiple Joint – a joint for connecting a branch conductor or cable to a main conductor or cable, to provide a branch circuit. Multiplier, Instrument – a series resistor connected to ammeter mechanism for the purpose of providing a higher voltage-indicating range. Mutual Inductance – an inductance that is common primary and secondary of a transformer, resulting from primary magnetic flux that cuts secondary winding. Negative – a value less than zero; an electric polarity sign indicating an excess of electrons at one point with respect to another point; a current sign indicating charge flow away from injunction. Network – a system of interconnected paths for charge flow. Network, Active – a network that contains one or more source of electrical energy. Network, Passive – a network that does not contain a source of electrical energy. Neutral – not positive or negative although it may act as positive to one circuit and negative to another. No-Load Current – the current demand of a transformer primary, when no current demand is made on the secondary. Normally Closed – denotes the automatic closures of contacts in a relay when deenergized (not applicable to a latching relay). Normally Opened – denotes the automatic opening of contacts in a relay when deenergized (not applicable to a latching relay). OHM –the unit of resistance; a resistance of one ohm sustains a current of one ampere when one volt is applied across the resistance. Ohm’s Law – states that current is directly proportional to applied voltage, inversely proportional to resistance, reactance or impedance. Ohmmeter – an instrument for measuring resistance values. Open-Wire Circuit – a circuit constructed from conduction that is separately supported on insulators. Open-Circuit Voltage – the terminal voltage of a source under conditions of no current; demand the open-circuit voltage has a value to the emf of the source. Oscilloscope – an instrument for displaying the waveforms of AC voltages. Outdoor Transformer - a transformer with weatherproof construction. Outlet – a point in wiring system from which current is take for supply of fixtures, lamps, heaters, etc. Outlet Receptacle – an outlet used with one or more receptacles, which are not have, the screw-shell type. Outlet, Lighting – an outlet used for direct connection of a lamp holder, lighting fixture, or a cord that supplies a lamp holder. Overload Protection – interruption or reduction of current under conditions of excessive demand, provided by a protective device. Panel Box – the box in which switches and fuses for branch circuit are located. Peak – to – Peak Value - the value of an AC waveform from its positive peak to its negative peak. In the case of a sine wave, the peak – to – peak value is double peak value. Peak Current – the maximum value (crest value) of an alternating current. Peak Voltage – the maximum value (crest value) of an alternating voltage. Pendant – a fitting suspended| ended from overhead by a flexible cord which may also provide electrical connection to the fitting. Pendant, Rise and Fall – a pendant that can be adjusted in height by means of cord adjuster. Period – the time required substance that has substantial retentivity. Permeability – the ratio of magnetic flux density to magnetizing force. Phase – the time of occurrence of the peak value of an AC waveform with respect to the time of occurrence of the peak value of a reference waveform. Phase is usually stated as the fractional part of a period. Phase Angle – an angular expression of phase difference it is commonly expressed in degrees, and is equal to the phase multiplied by 360 degree. Plug – a device that is inserted into a receptacle for connection of a cord to the conductor terminations in the receptacle. Polarity – an electrical characteristic of emf, which determines the direction in which current, tends to flow. Polarization (Battery) – polarization is caused by development of gas at the battery electrodes during current demand, and has the effect of increasing the internal resistance of the battery. Pole – the pole of a magnet is an area at which it flux lines tend to converge or diverge. Positive - a value greater than zero; an electric polarity sign denoting a deficiency of electrons at one point with respect to another point; a current sign indicating charge flow toward a junction. Potential Difference – a potential difference of one volt is produce when one unit of work is done in separating unit charges through unit distance. Power Circuit – wires that carry current to electric motors and other devices using electric current. Power, Real – real power is develop by circuit’s resistance, or effective resistance. Primary Winding – the input winding a transformer. Primary Battery – a battery that cannot be recharged after its chemical energy has been depleted. Proton – the subatomic unit of positive charge; a proton has a charge which is equal and opposite to that of an electron. Pull Box – a metal with black cover for insertion into a conduit run, raceway, or metallic tubing, which facilitates the drawing conductors. Pulsating Current – a direct current that does not have a steady value. Puncture – a descriptive electrical discharge through insulation. Quick-Break – a switch or circuit-breaker which has high contact-closing speed. Raceway – a channel for holding wires or cables, constructed from metal, wood, or plastics, rigid metal conduit, electrical metal tubing, cast-in-place, under floor surface wooden types wireways, busways and auxiliary gutters. Rack, Cable – a device secured to the wall to provide support for a cable raceway. Rating – the rating device, apparatus, or machine states the limits of its operating characteristics. Ratings are commonly stated in volts, amperes, watts, ohm, degrees, horsepower, etc. Reactance – reactance is an opposition to AC current based on the reaction of energy storage, either as a magnetic field or as electric field. No real power is dissipated by a reactance. Reactance is measured in ohms. Reactor – an indicator or capacitor. Reactors serve as current-limiting devices such as in motor starter, for phase- shifting applications as in capacitor star motors, and for power-factor correction in factories or shops. Receptacle – also termed “convenience outlet” a contacting device installed at an outlet for connection externally by means of a plug and flexible cord. Rectifier – a device that has a high resistance in one direction, and low resistance in the other direction. Regulation – denotes the extent to which the terminal voltage of a battery, generator, or other source decreases under current demand. Commonly expressed as the ratio of the difference of the no-load voltage under rated current demand, usually expressed a percentage. Relay – a device operated by a charge in voltage or current in a circuit, which actuates other devices in the same circuit or in another circuit. Reluctance – an opposition to the establishment of magnetic flux lines when a magnetizing force is applied, usually measured in rels. Resistance – opposition or friction to the flow of current. Resistor – a resistive component, may be of the wire wound carbon-composition, thyrite, or other type of design. Rheostat – a variable resistive device consisting of resistance element and a continuously adjustable contact arm. Safety Outlet – also term “ground outlet” and outlet with a polarized receptacle for equipment grounding. Secondary Battery – a battery that can be recharged after its chemical energy is depleted. Sequence Switch – a remotely controlled power-operated switching device. Series – connected one after another so that same current will flow through each one. Series Circuit – a circuit that provides a complete path for current and has its components connected end-to-end. Series Parallel – an arrangement where several devices are connected into series groups and these groups are connected in parallel with each other. Service – the conductors and equipment for supplying several devices are connected into series groups and these groups are connected in parallel with each other. Service Entrance – the place where the service wires are run into a building. Service Switch – the wires that connect the wiring in a building to the outside supply wires. Serving of Cable – a wrapping over the core of a cable before it is leaded, or over the lead if it is armored. Shaded Pole – a single heavy conduction loop placed around one-half of a magnetic pole that develops an AC field, in order to induce an out-of-phase magnetic field. Sheath – the outside covering that protects a wire or cable from injury. Sheath Cable – a protective covering (usually lead) applied to cable. Shell Core – a core for a transformer or reactor consisting of three legs, with the winding located on the center leg. Short-Circuit – a fault path for current in a circuit the conducts excessive current; if the fault path has appreciable resistance, it is termed a leakage path. Shunt – denotes parallel connection. Sine Wave – variation in accordance with simple-harmonic motion. Sinusoidal – having the form of a sine wave. Slate – a rock that is cut into slabs and used for switchboards it is a fair insulator. Sleeve Wire - a circuit conductor connected to the sleeve of a plug. Sliding Contact – an adjustable contact arranged to slid mechanically over a resistive element turn of a reactor, series of taps or around the turns of a relay. Snake – a steel wire or flat ribbon with a hook at one end, used to draw wires through conduit etc. Solenoid – a conducting helix with a comparatively small pitch, also applied to coaxial conduction helices. Spark Coil – also termed “ignition coil” a step-up transformer designed to operate from a DC source via an interrupter that alternately makes and breaks the primary circuit. Sparkover – a disruptive electrical discharge between the electrodes of a gap, generally used with reference to measurement of high voltage value with a gap having specified types and shape of electrodes. Splice – also termed “straight-through joint”, a series connection of a pair of conductors or cables. Station Automatic– a generating station or substation that is usually unattended and which performs its intended functions by an automatic sequence. Surge – a transient variation in current and/ or voltage at a given point in a circuit. Symbol – a graphical representation of a circuit component also, a letter or letters used to represent a component, electrical property, or circuit characteristic. Tap – in a wiring installation, a T joint (Tee Joint), Y joint, and multiple joint. Taps are made to resistors, inductors, transformer, etc. Terminal – the terminating end(s) of an electrical device source, or circuit, usually supplied with electrical connection such as terminal screws, binding post, up jacks, snap connectors soldering lugs, etc. Three Phase System – an AC system in which three sources energize three conductors, each of which provides a voltage that is 120 out of phase with the voltage in the adjacent conductor. Three Phase – a generator or circuit delivering three voltages that are 1/3 of each cycle apart in reaching their maximum value. Three Phase Circuit – a circuit delivering three-phase current. Three Phase Motor – an alternating current motor that is generated form three-phase circuit. Three Pole – a switch that opens and closes three conductors or circuit at one time. Three-Way Switch – a switch with three terminals by which the voltage a circuit can be completed through any one of two paths. Three-Wire Circuit – a circuit using a neutral wire in which the voltage between neutral wires is twice that between neutral and each side. Tie Feeder – feeder that is connected at both ends to sources of electrical energy. In an automatic station, load may be connected between the two sources. Time Delay – a specified period of time form the actuation of a control device to its operation of another device or circuits. Tip, Plug – the contacting member at the end of a plug. Torque – mechanical twisting force. Transfer Box – also termed “pull box”, a box without a distribution panel containing branched or otherwise interconnected circuits. Transformer – a device that operates by electromagnetic induction with a tapped winding, or two or more separate windings, usually on an iron core, for the purpose of stepping voltage or current up or down, for maximum power transfer, for isolation of the primary circuit form the secondary circuit and in special designs for automatic regulation of voltage or current. Transient – a non-repetitive or arbitrary timed electrical surge. Transmission (AC) - transfer of electrical energy form a source to a load, or to one or more stations for subsequent distribution. Trough(ing) – an open earthenware channel, wood or plastic in which cables are installed under a protective cover. Tubing, Flexible – also termed “loom” a mechanical protection for electrical conductors; a flame resistant and moisture-repellent circular tube of fibrous material. Twin Cable – a cable consisting of two insulated and stranded conductors arranged in parallel runs and having a common insulating covering. Underground Cable – a cable designed for installation below the surface of the ground, or for installation in an underground duct. Underground System – also termed “insulated supply system”, an electrical system that “floats” above ground or one that has only a very high-impedance conduction path to ground. Unidirectional Current – a direct current or pulsating direct current. Units - established values of physical properties used in measurement and calculation; for example, the volt unit, the ampere unit, the ampere-turn unit, the ohms unit, etc. Value – the magnitude of a physical property expressed in terms of a reference unit, such as 117 volts, 60 Hz, 50 ohms, 3 henrys, etc. VAR – denotes volt-amperes reactive; the unit imaginary power (reactive power). Volt – the unit of emf; one volt produces a current of one ampere in a resistance of one ohm Volt-Ampere – the unit of apparent power; is the product at the pressure times the current. Voltage – in a circuit the greatest effective potential difference between a specified pair of circuit conductors. Voltage Drop – the difference in pressure between two points in a circuit caused by the resistance opposing the flow of current. Voltage Loss – the voltage drop. Voltage Regulator – a device for keeping the constant voltage at a certain point. Voltammeter – voltmeter and ammeter combined in on case and using the same movement, but having separate terminates. Voltmeter – an instrument for measurement of voltage values. Watt – the unit of electrical power, equal to the product of one volt and ampere in DC values, or in rms AC values. Watt-Hour Meter - an instrument that records the power used in watt-hours Watt-hour – a unit of electrical energy, equal to one watt operating for one hour. Wattmeter – an instrument for measurement of electrical power. Wave – an electrical undulation, basically of sinusoidal form. Weatherproof – a conductor or device designed so that water, wild, or usual vapor will not impair its operation. Wiper – an electrical contact arm. Work – the product of force by the distance through which the force acts; work is numerically equal to energy. Working Voltage - also term “closed-circuit voltage”; the terminal voltage of a source of electricity under a specified current demand, also, the reacted voltage of an electrical component such as capacitor. Bulacan State University College of Architectecture and Fine Arts BU 313 Utilities 2: Electrical and Mechanical Systems Module 3: ELECTRICAL MATERIALS A) Components of Electrical System Electrical wiring of buildings requires a varied assortment of equipment and auxiliaries for adequate, safe and efficient operation. a) Service switch for main service control, protection and metering. b) Panel boards (near the load end of feeders) for control and protection of branch circuit. c) Outlets for local connections to lamps, motors and devices. d) Starting switches and or control devices for motorized equipment. e) Conduit and wiring system which interconnects all the preceding apparatus. National Electrical Code Defines the fundamental safety measures which must be followed in the selection, construction and installation of all electrical equipment. Economics of Material Selection The selection of electrical material involves not only choosing a material or assembly that is functionally adequate and where necessary visually satisfaction but also consideration of economic factors. Equipment Ratings All electrical equipment is rated for normal service it is intended to perform. The ratings are specifically and characteristically electrical are those of voltage and current. Voltage – voltage rating of an item / electrical equipment is the maximum voltage that it can be safely applied to unit continuously. Current - the current rating of a device is the basic heat capacity rating but it is not always given in amperes. B) Electrical Conductors Conductors (wiring) are use to carry the current at certain voltage through the electrical system. There are two categories of conductors: a) AWG – American Wire Gauge is preceded by a number which indicates the size of wire example : 14 AWG means American Wire Gauge number 14. AWG runs in reverse order to the size of conductor. It starts with 14 AWG the 12 AWG, 10, 8, 6, 4,2,1,0,00,000,0000 AWG.There are two categories of AWG systems:  Wire – a single conductor number 14 AWG, 12 AWG, 10 AWG and 8 AWG is called wire.  Cable – a single conductor number 6 AWG to 0000 AWG is called cable; two or more wires assembled in a single jacket are called cable, conductors 6 AWG and larger are stranded.  Electrical Design Ampacity Equipment/Raceway Wire Size PVC Conduit Rigid Steel Conduit Grdng Elec Grounding Conductor trode 60° 75° 90° Conductor 2- 2- 3- mm2 AWG TW THWN THHN 3-w 4-w 5-w 4-w 6-w CB rating Wire w w w 2 14 15 15 25 20 20 20 20 15 15 15 15 15 2 3.5 12 20 20 30 20 20 20 25 15 15 15 20 20 3.5 5.5 10 30 30 40 20 20 25 25 15 15 15 20 30 5.5 8 8 40 45 50 25 25 32 32 20 20 25 25 8 40 5.5 14 6 55 65 70 25 32 32 40 20 25 25 32 14 60 5.5 22 4 70 85 90 25 32 40 40 25 25 32 32 14 100 8 30 2 90 110 115 32 40 40 50 25 32 32 40 14 200 14 38 1 100 125 130 32 40 40 50 32 32 40 50 14 300 22 50 1/0 120 145 150 40 40 50 50 32 40 50 50 14 400 30 60 2/0 135 160 170 40 50 50 63 40 40 50 50 22 600 38 80 3/0 160 195 205 40 50 63 63 40 50 50 65 22 800 50 100 4/0 185 220 225 50 63 63 75 50 50 65 65 30 1000 60 125 250 210 255 285 50 63 75 75 50 65 65 80 30 1200 80 150 300 240 280 295 63 75 75 90 50 65 80 80 30 1600 100 200 400 280 330 355 63 75 90 90 65 80 80 90 30 2000 125 250 500 315 375 400 75 90 90 110 80 80 90 100 50 2500 200 325 600 370 435 470 75 90 110 110 80 80 90 100 50 3000 200 400 750 405 485 515 90 110 110 160 80 90 100 115 60 4000 250 500 1000 445 540 580 60 5000 400 6000 b) MCM – Thousand “M” Circular Mils. Circular mils are artificial measurement used to represent the diameter of the conductor. It begins with 500 mils. 500 mils (M) = 0.5 inches diameter (D) “MCM” M = 1000 CM = D2 Therefore , MCM = CM = D2 1000 1000 For 500 mils, MCM = 5002 = 250000 =250 1000 1000 500 mils is called 250 MCM Metal is generally use as conductors for electrical system components. Electrical conductors are the means by which the current is conducted through the electrical system. Usual method of specifying a wire or cable is by: 1) no. and size of conductor 2) insulation 3) voltage class Factors which influence resistance of conductors: a) composition b) length c) cross sectional area d) temperature c) Characteristics of Insulated Conductors Operating Trade Name Type Application Temp. D & W Location – for not well ventilated 1. Moisture and Heat Resistant Rubber RHW 750C temp 400c D & W Location – for not well ventilated 2. Thermoplastic T 600C temp 400c 3. Moisture Resistant Thermoplastic TW 600C D&W 4. Heat Resistant Thermoplastic THHN 900C D & W – Boiler 450C 5. Moisture and Heat Resistant Thermoplastic THW 750C D&W 6. Moisture and Heat Resistant Thermoplastic THWN 750C D&W 7. Moisture and Heat Resistant Thermoplastic XHHW 900C D&W Polyethylene 8. Silicon Asbestos SA 750C D 9. Asbestos and Varnish Cambric AVA 1100C Dry Location – Direct sunlight d) Wire Conversion Factors Circular mil = d2 Sq. mil = Circular mil x 0.7854 Sq. mil = 3,1416 x v2 Millimeter = Inches x 25.4 Sq. inch = Sq. mil x.000001 Sq. mil = Circular mil x 1.0005067 Sq. mil = Sq. inch x 1,000,000 e) Good Electric Conductors silver aluminum brass platinum lead copper nickel zinc iron tin C) Electrical Conductor Insulation The conductor acts as guide for the conduction of electrical power from one point to another point to another point and must be insulated to prevent the escape or leakage of the current. The types of insulation used are: a) Moisture and heat resistant rubber b) Heat-resistant rubber c) Silicone Rubber d) Thermoplastic and asbestos e) Thermoplastic f) Flame resistant, moisture-and heat-resistant thermoplastic g) Moisture-resistant h) Perflouroalkoxy Good Electric Insulators rubber glass thermoplastic dry-air porcelain mica paper varnish latex oil slate asbestos wax D) Wiring System There are two types of applications in electrical wiring systems: 1) Wiring to provide power to operate for lighting, outlets and equipments. 2) Control wiring to operate equipment. Wiring Systems may be: 1) Exposed wiring , where wire feeders are installed on the surface of walls, ceilings etc. 2) Concealed wiring, where wires or feeders are concealed inside the walls, ceiling etc. Wiring System Color Code: 1) Phase A or (1) black 2) Phase B or (2) red 3) Phase C or (3) blue 4) Neutral white or gray 5) Ground green or bare Standard wire colours for flexible cable Region Live Neutral Protective earth EU, Australia & South brown blue green & yellow Africa (IEC 60446) UK, Ireland & Australia red black green before 1969 United States and Canada black white green (green) (screw colour) (brass) (silver) Standard wire colours for fixed cable Region Live Neutral Protective earth EU (IEC 60446) including brown or blue green & yellow UK from 31 March 2004 black green & yellow (core is usually bare UK before 1 April 2006 & red black and should be sleeved at Australia terminations) United States and Canada black or white green or bare (green) (screw colour) red (brass) (silver) Note: the colours in this table represent the most common and preferred standard colours however others may be in use, especially in older installations. E) Cables System Several Types of cable systems are used in wiring in building: 1) Nonmetallic sheathed cable –Commonly known as romex. Romex cable type NM are manufactured in two or three wires with conductors varying in sizes. Uncoated copper conductors with PVC insulation are color-  coded with bare ground wire. The jacket is made up of rubber, plastic or fiber. It can be concealed or exposed depending on the need. Code may restrict its use to residential not exceeding three stories. 2) Flexible armored cable – Commonly known as BX cable. It is manufactured in two-,three- and four-wire assemblies with insulated wires wrapped with spiral-wound interlocking steel jacket. There are two types of BX cable: a) BX cable type AC – for dry locations only b) BX cable type MC – cable has additional PVC jacket, can be use for wet locations 3) Underground feeder cable – Known as UF, it can be use for direct burial. When it is used above ground and exposed to the sun, the jacket must be sun resistant. 4) Service entrance cable – For service entrance cable, type SE may be used. It must be installed according to Philippine Electrical Code. This cable can be use for interior wiring system if cable id insulated with thermoplastic. 5) Mineral Insulated metal-sheathed cable – This cable id type MI. It is manufactured with one or more conductors. It is insulated with compressed mineral insulation, and enclosed n a gas-tight and liquid tight continuous copper sheath. Can be use for a service feeder or circuit branch. It can also be use for dry or wet, indoors or outdoors. It can also be use in hazardous areas. F) Raceway and Wireways Any channels, pipes, or conduits and ducts which are designed especially to house wires or cables are called raceways. They may be classified into: 1) Underground raceways – have resistance to corrosion because it is directly buried. They are normally installed in place first, and wires and cables are placed inside the raceway later. a) Insulated impregnated fiber b) Insulated cement-asbestos 2) Exposed and concealed raceways – an entire classification of raceways, covers those which are generally non circular in cross section & may only be utilized by attaching it to the surface. There are several types of raceways these are: a) Pipe or conduit –Most common type of raceways are pipes and conduits. b) Wireway – they are metal channels with a removable cover which permits easy access to conductors and allows addition to or replacement of a wiring system. They are used only for exposed applications and in dry locations. c) Ceiling raceways – Type of wiring system is less costly and more practical than floor raceways. It consists of a network of steel aluminum channels with removable cover located above the tile ceiling. The power and communication wiring system are supplied to work areas below the movable floor-to-ceiling poles called power poles. Powers poles are unpleasant in appearance. d) Floor raceways 1) Under-floor raceways – The distribution ducts are used under-floor to provide wiring system for spaces above the floor. 2) Cellular Floor Raceways – A metal or pre-cast concrete cellular flooring system used as floor structure. Each cell serves as raceway carrying power and communication wiring service above the floor. The header ducts for feeding the wiring system in the cells run perpendicular to the cells. G) Pipe or Conduit Raceways There are four types of pipe/conduit raceways: 1) Metallic Conduit – All rigid metallic conduits and their fittings are required to be corrosion resistant. Steel conduits are manufactured as follows: a) Hot-dip galvanized b) Enameled c) Sheranized (coated with zinc) d) Plastic-covered Classifications according to wall thickness a) Heavy-wall steel conduit – known as Rigid Steel Conduit “RS”, has wall thickness of 0.113 inch.Trade sizes ½ “ 3/4”, 1”, 1 ½”, 2”, 2 ½”, 3”, 3 ½”, 4, 5, 6. Standard length 10 ft which include one coupling per length. Direct contact with earth needs hot deep G. I. & coated with asphalt.If earth is very wet , conduit should be coated with asphalt compound. It should be supported within 3 ft interval. Long straight pulls maximum distance of 200 ft. All splices, connections & taps shall be made within connection boxes. NEC states that no wire shall be spliced , connected or tapped and then drawn into conduit so itself.  Purpose of Metal Conduit 1. Protect wiring from mechanical injury & corrosion 2. Provide a grounded metal enclosure to avoid shock hazard. 3. Protect surrounding against fire hazard as a result of over heating. 4. Support the conductors. 5. Provide good ground path for wiring system. Rules to be observed for conduit work in concrete slab 1. Conduit O. D. (overall diameter) must be no greater than 1/3 of slab thickness 2. Parallel conduit run must be spaced not less than 3 X OD of the longest conduit center to center. 3. Conduit shall not run above beams 4. Conduit crossing shall be 900 5. Minimum thickness of concrete cover must be ¾”. b) Intermediate Metal Conduit “IMC” , has wall thickness of 0.071 inch. c) Electric Metallic Tubing “EMT” , has wall thickness of 0.05 inch. Also known as thin-wall conduit. Similar to use & application of RSC. May not be used in hazardous areas & must be approved for embedding in concrete. 2) Aluminum Conduit- can be used in placed of steel conduits in all locations. Major drawback is its deleterious effect on many types of concrete. Not to be used underground because of corrosion. Advantages of aluminum conduits: a) Lighter than steel conduits b) Less costly than steel conduits c) Less labor cost than steel conduits d) Better corrosion resistant e) Lower voltage drop f) Do not need painting g) Non sparkling and non magnetic. 3) Flexible Metallic Conduit- A flexible metal conduit is a halo spirally wound interlocked armor or raceway called Greenfield. Manufactured with galvanized steel or aluminum. Usually used in wiring connections of electrical equipment where vibration is present (motors, transformers etc.) and where it is difficult to install rigid conduit. May not be used for wet locations, hoist way, battery rooms, hazardous areas or in atmosphere injurious to rubber insulated conductors. When it is covered with liquid-tight plastic jacket called sealtite, it can be used outside or inside the structure in moist and wet areas. 4) Nonmetallic Conduit – can be use without restrictions in any non-hazardous structures and both inside and outside the building. Separate ground wire must be provided for nonmetallic conduits. Classification: a) Rigid polyvinyl chloride “PVC” b) High-density polyethylene “HPDE” c) Asbestos-cement Required characteristics: a) For indoor use flame proof, heat resistant, strong b) For underground use same as above c) For outdoor use same as above, plus cold-resistant, sunlight proof H) Switches and Outlets Devices used in wiring systems can be classified into: 1) Switches –device used for opening or closing or changing the connection of circuit Switches Classification: a) Number of poles(P) and number of throws - Available in 1,2,3,4,5P and single-throw, double throw, or triple throw. b) Current rating - amount of current a switch can carry continuously ( 15, 20, 30 Amp at 120 V, 240 v etc) c) Voltage Class – rated 250 V, 600 v , 6 kV etc d) Horsepower (HP) switches for motors are rated in HP e) Heavy Duty (HD) switches used for constant interruption  f) Fusible – those that contain fuses(s) g) Enclosure – all separately enclosed switches are installed in metal cabinets. Switches’ Operating Handles: a) Toggle types –small noise b) AC quite and mercury types – noiseless c) Key, rocker, rotary, push, torch and tap-plate types Type of Switches a) Toggle switch – for 15, 20 and 30 amp b) Contact switch - for 15 and 20 amp. They are double throw center off. c) Top-plate switch – for 15 and 20 amp d) Dimmer switch for 5 amp incandescent lamp e) Press switch – for 15 and 20 amp, lighted button in off position. f) Timer switch – for 20 amp. They spring-wound up to 60 minutes. g) Key switch – for 15 and 20 amp, operates with a key h) Tumbler-lock controlled switch – these are used for high-security areas. i) Programmable switch - 15 amp, used to control the circuit by command. Multi-way switching 2) Outlets (sockets) – used in wiring system at which electric current id diverted to supply an electric load to devices, appliances, and equipment. Outlet classification: a) Duplex outlets – two outlet in one box b) Single outlets – used for appliances and equipments to prevent additional plug ins c) Ground fault interrupter (GFI) outlets – used for moist and wet areas d) Waterproof outlets – duplex outlets placed in water proof box generally used outside the building. e) Floor outlets – used in floor with protective cover. f) Safety outlets – generally covered with plastic cap when they are not in use. g) Switch-controlled outlets – used in bedrooms, living rooms where table lamps are used and operated by switches. h) Split-duplex outlets – same as switch controlled outlets, except the one outlet is controlled by switch. Types of plug and sockets Electrical plugs and their sockets differ by country in shape, size, and type of connectors. The type used in each country is set by national standards legislation. In this article each type is designated by a letter, plus a short comment in parentheses giving its country of origin and number of contacts. Subsections then detail the subtypes of each type as used in different parts of the world. a) Type A (North American/Japanese 2-pin) b) Type B (American 3-pin) c) Type C (European 2-pin) CEE 7/16 (Europlug 2.5 A/250 V unearthed) CEE 7/16 plug and socket CEE 7/17 plug CEE 7/17 (German/French 16 A/250 V unearthed) BS 4573 socket BS 4573 (UK shaver) d) Type D (Old British 3-pin) BS 546 (Indian 5 A/250 V earthed) BS 546 (South African 15 A/250 V earthed) e) Type E (French 2-pin, female earth) French type E f) Type F (German 2-pin, side clip earth) CEE 7/4 (German "Schuko" 16 A/250 V earthed) g) Type E and F hybrid CEE 7/7 (French/German 16 A/250 V earthed) BS 1363 (British 13 A/250 V earthed and fused) h) Type H (Israeli 3-pin)  i) Type I (Australian/Chinese 2/3-pin) AS 3112 (Australian 10 A/250 V) CPCS-CCC (Chinese 10 A/250 V) CCC Mark j) Type J (Swiss 3-pin) SEV 1011 (Swiss 10 A/250 V) IEC 60906-1 (Brazilian 16 A/250 V) k) Type K (Danish 3-pin) 107-2-D1 DS Afsnit 107-2-D1 (Danish 10 A/250 V) 23-16/VII with socket 23-16/VII rewirable l) Type L (Italian 3-pin) (no picture) m) Type M (see D) BS 546 (South African 15 A/250 V) I) Boxes & Cabinets a) those included pull boxes, connection boxes & outlet boxes b) used to provide access to conduits for installing necessary wires c) usually rectangular, octagonal or round with knock out holes to fit conduit d) holes for knock out available are ½, ¾ & 1” e) outlet boxes for lighting & receptacles outlets & junction of wire in branch & feeder circuit f) pull boxes – pulling of wires & cable g) cabinets – boxes with hinged doors & contain equipment other than wiring J) Electric Meter The electric meters are installed and controlled by the utility company (MERALCO)in order to measure the electric power used in buildings. Electric meter is usually located outside the exterior wall of the building inside the property line visible to a meter reader. A meter is located between the service line and the main switch or panel boards with main breaker. The typical induction type AC kilowatt-hour meter c onsist of two types of coils: a) Current coils – located below the rotating disk b) Voltage coils – located above the rotating disk Three-phase electromechanical induction meter, metering 100 A 230/400 V supply. Horizontal aluminium rotor disc is visible in centre of meter. The coils are connected to the electric power entering from the service lines and electric load being used in the circuit branches within and outside the building. The induction created when electric power is used caused the disk to rotate. The speed of the rotating disk is proportional to the power being used. The number of rotation is counted in dials, which are calibrated in kilowatt-hours. K) Main Switch and Panel Boards Main switch are also known as service switch, service disconnect, main disconnect and main breaker. The purpose of the main switch is to bridge, break, or disconnect the flow of all electricity to the building(s), except emergency equipment in the event of fire and emergency or major repairs in electrical system. Main switch is usually located between meter and circuit breaker. It is usually rated by current, voltage, number of poles and throw. Two different ways of installation: a) Main switch located within the panel board – usually found in residential and small buildings b) Main switch installed as a separate device – usually used in medium size and large buildings. Panel boards are know as electric panels, load centers, and distribution boards. It consists of metal cabinet containing overcurrent protection and other devices. A panelboard is a distribution center for receiving electrical power and feeding the branch circuits. Panel boards are classified into two mounting types: a) Flush mounting – recessed with the finish-wall surface b) Surface mounting – surface-mounted usually in columns or solid walls. Panel boards are classified into two categories: a) Circuit Breaker b) Fuse Panelboards contain a main breaker(main switch) and main fuses to receive circuit protective device such as circuit breakers or fuses which serves as branch circuits containing electrical devices (lighting outlets, appliances, motors etc.) L) Circuit Breakers and Fuses Circuit breaker is the most widely used device for overcurrent protective device. All conductors are designed to carry specific amount of current which is called ampacity. When the conductor exceeds the designed ampacity by overloading or short circuit or grounding, the circuit opens automatically (trips) and stops the flow of the current in the branch circuit. After the problem has been corrected, the circuit breaker can be turned on. Fuses are the simplest circuit-protective device before circuit breakers where introduced. They are of different sizes, shapes and capacity. They have two terminals which are connected together with fusible metal. Fusible metal melts when the branch circuit exceeds the design ampacity. Fuse is a one-time device and has to be replaced with a new one each time the fusible metal melts. 1. Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the on position. This is sometimes referred to as "free trip" or "positive trip" operation. 2. Actuator mechanism - forces the contacts together or apart. 3. Contacts - Allow current to flow when touching and break the flow of current when moved apart. 4. Terminals 5. Bimetallic strip 6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly. 7. Solenoid 8. Arc divider / extinguisher M) Grounding and Ground Fault Protection Grounding and ground fault protection in all wiring systems are used to safeguard from electric shock the people who are using electrically operated devices and equipment. All building grounding is provided at the panel ground bus. Grounding connects the electrical systems neutral wire to the moist or wet ground. Grounding can be done by: a) Connect ground wire to cold water piping in the building. b) Connect to ground rod or ground plate placed underground which is moist or wet. Ground fault protection is needed to avoid accidents of electric shock. Ground fault protection can be achieved by using ground fault interrupter (GFI) in all locations which have tendency to become moist or wets such as kitchen, bathrooms, basements, outdoors etc. GFI operate the same principle as any other receptacle and at the same time monitors the current. If outgoing current is less than the incoming current, current leakage is present. The current leakage is ground fault. When this happens GFI will open the circuit automatically to eliminate shock hazard from electricity. N) Switchgear and Switchboards A switch board is an insulated metal cabinet 1 ½ to 4 ½ ft. deep with a width and height depending on the number of circuits. It contains the following: a) Primary disconnect switches b) Secondary feeder switches c) Overcurrent protective devices, circuit breaker and fuses Switchgear is the term used to describe a switchboard when it is used of power which carries above 600 V service. It is usually located in a room called electrical switchgear room normally located in the basement. Natural ventilation system of 1 sq.in. per kVA of capacity should be provided only for this system. Bulacan State University College of Architectecture and Fine Arts BU 313 Utilities 2: Electrical and Mechanical Systems Module 4: ELECTRICAL WIRING AND SERVICE UTILIZATION A) ELECTRIC SERVICE Service Entrance – defined a portion of the supply conductors which extended from the street main, duct or transformer to the service switch or switchboard of the building supply. The NEC defines that the service entrance as “ conductor and equipment for delivering energy from the electric supply to the wiring system of the premises served.” Service entrance is either: a. Overhead service entrance –most common type. The conductors enter the building through weather head and exterior electrical power meter b. Underground Service Entrance – consist of raceway/conduit extending from the building through the property line tapped through the main using the underground e.g. soil/earth. Recommended cable is the USE type Electric Service Metering – a meter is normally located outside the building or at the property line wall or post for the ready access of meter reader. For multi service door apartments and commercial units, battery of meters are laid out in parallel with main service disconnect Feeder – “All circuit conductors between the service equipment or the generator switchboard of an isolated plant, and the final branch circuit over current protection device. Feeder is installed under the following considerations: a. On large installations, each floor is provided with one feeder. b. In small installations, 1 – 2 feeder is satisfactory. c. Feeder for electric motor must be independent and totally separated from the lights circuits. d. Feeders requiring more than 50mm (2”) diameter conduit pipe should not be used. e. Feeders should be subdivided if there are several bends or offset on the line. f. Feeders radiating from the distribution panel should be provided each with properly rated switch and circuit breaker. g. Feeders and main shall be installed inside the conduit pipe for protection. Main – is a feeder interior wiring extending from service switch, generator bus or converter bust to the main distribution line or electric service equipments. The service equipment should be centrally located. a) To shorten circuit homeruns. Voltage drop will be experience if circuit is more than 30 meters. b) It should be located near the load centers. residential, kitchen and laundry. B) GENERAL RULES FOR WIRING INSTALLATION a) Conductors of light & power system of 600 V or less may occupy the same enclosure. b) Conductors of signal or radio system shall not occupy the same enclosure of light and power system except specifically permitted for elevators, recording, remote control & communications. c) Conductors of emergency wiring system shall not occupy the same enclosure as any wiring except in transfer switches or exit & emergency fed from both normal & emergency sources.  d) All metal raceways, cable armor, metal enclosure shall be metallically joined either mechanically or by bonding jumper to provide effective electrical continuity. e) Conductors in vertical raceway shall be supported at intervals as specified in NEC by means of insulated wedges & other approved devices f) When insulated in ferrous enclosures, circuits all phase run together. When feeder are paralleled & run in more than one steel conduit, each conduit shall contain all phases & neutral to minimized induced body current heating effects. g) Generally, when necessary to run wiring through air handling ducts or plenum chambers, the wiring method shall be RSC or EMT. h) No bare conductors may be used for wiring of any temporary circuit. i) Electrical connections & dull boxes, raceways & under floor ducts, should never be located near very hot or cold pipes or ducts. j) All metal in wiring systems shall be suitable for the environment installation. Types of WiringConnections a) necessary in installation b) for joints, splices, branch circuit c) solderless connection, crimp connector, lug terminal (bolted) C) BRANCH CIRCUIT DESIGN AND GUIDELINES Branch Circuit – circuit conductors between the final over current protective device and outlet. a) Circuit Design Must be Based on: a) Flexibility b) Reliability – efficiency of service c) Safety – size of wire d) Economy e) Energy Consideration – energy law and code, budget, energy conservation technique. f) Space Allocation – sq. m , capacity of ventilation b) Types of Branch Circuit a) Gen. Purpose – branch circuit supplies lighting and appliances b) Appliance Branch Circuit - supplies outlets intended for appliances c) Individual Branch Circuit – is designed to supply single specific item c) Outlet Receptacles and Other Wiring Devices Outlet – a term in wiring system at which current is therein to supply utilization. a) Convenience Outlet – a device which an insertion in a receptacle establishes connection of conductor. b) Lighting Outlet – intended for the connection of lamp holder. Lighting fixture or pendant cord. c) Receptacle Outlet – contact device installed for an outlet for connection of single attachment plug. Junction Box – box with blank cover for joining different runs of raceways; box for making taps.  Pull Box – box with blank cover inserted into raceways to facilitate pulling in of conductors. Switches – device that serves to open or close the circuit. Types: a. General Use Switches – intended for gen. distribution and branch circuit, which is rated in amperes. b. General Use Snap Switches – a form of gen. use switch installed in flush device boxes. c. Isolating Switch – intended for isolation an electrical circuit from power surge d) Maximum Voltage for Branch Circuit Circuit Breaker 120v 220v 15 A 1440w 2880w 20 A 1920w 3840w 30 A 2880w 5760w Gen. Purpose = 15 – 20 amp Appliance Branch Circuit = 20amp Individual Branch Circuit = 20amp and above f) Circuit Guidelines Based on NEC 1. Residential load use 30 watts /sq. m in buildings. Excluding porches, garages and basement. 2. Load should not exceed 80 % of the circuit breaker load 15 amp CB max 12 ampere load 20 amp CB max 16 ampere load 30 amp CB max 24 ampere load 3. Lighting Outlet/Branches 3.1 minimum wire size is 2.0 mm2 with 15 amp circuit breaker 3.2 Ampere rating 30, 40, 50 should not be used in fixed lighting in residences 3.3. Heavy duty lamp holders are - not less than 750 watts; 3.4 Separate branches for fence lighting outlets and building lighting outlets 3.5 Design switches according to use – timer switch; solar control switch etc. 4. General Purpose Branches - combination of lighting and small appliances 4.1 minimum wire size 3.5 mm2 with 20 amp circuit breaker 4.2 load of 15 ampere maximum load shall be 7.5 amp 4.3 20 ampere load – maximum load shall be 10 ampere. 5. Convenience Outlet 5.1 minimum wire size 3.5 mm2 with 20 amp circuit breaker 5.2 circuit must be computed 60% maximum capacity only 5.3 minimum of 20 amp for small appliance outlet , one outlet 180 watts – single, double or triple 5.4 receptacles for feeding portables and fixed appliance shall be limited to loads of 80% of their rating: 12 amp for 15 amp receptacles 16 amp for 20 amp receptacles 24 amp for 30 amp receptacles  5.6 number of outlet in circuit shall be limited to : 8 outlets on 20 amp circuit 6 outlets on 15 amp circuit 6. Individual Appliance Branches 6.1 minimum wire size 3.5 mm2 with 20 amp circuit breaker; 6.2 appliance outlet should have separate circuit such as water heater, air conditioner, water pumps, laundry etc. 6.3 wire size should be computed according to load. 6.4 bigger wattage requires bigger wires and higher ampere rating of circuit breaker. 6.5 provide grounding if necessary 6.6 single receptacles on individual branch shall have the rating not less than the circuit. 6.7 when loads are connected for long periods, actual load should not exceed 80% fuse rating. 6.8 continuous type load such as water pumps should be considered 125% of actual load in all load calculations. 7. Wiring for flux circuitry shall be RHW, T, THW, TW, THWN, XHHN should be inside the raceways or cables. e) Load Calculations Electrical Design Ampacity Equipment/Racewa Wire Size PVC Conduit Rigid Steel Conduit Grdng Elec y Grounding trode Conductor 60° 75° 90° Conductor 2- 3- 4- 5- 2- 3- 4- 6- mm2 AWG TW THWN THHN CB rating Wire w w w w w w w w 2 14 15 15 25 20 20 20 20 15 15 15 15 15 2 3.5 12 20 20 30 20 20 20 25 15 15 15 20 20 3.5 5.5 10 30 30 40 20 20 25 25 15 15 15 20 30 5.5 8 8 40 45 50 25 25 32 32 20 20 25 25 8 40 5.5 14 6 55 65 70 25 32 32 40 20 25 25 32 14 60 5.5 22 4 70 85 90 25 32 40 40 25 25 32 32 14 100 8 30 2 90 110 115 32 40 40 50 25 32 32 40 14 200 14 38 1 100 125 130 32 40 40 50 32 32 40 50 14 300 22 50 1/0 120 145 150 40 40 50 50 32 40 50 50 14 400 30 60 2/0 135 160 170 40 50 50 63 40 40 50 50 22 600 38 80 3/0 160 195 205 40 50 63 63 40 50 50 65 22 800 50 100 4/0 185 220 225 50 63 63 75 50 50 65 65 30 1000 60 125 250 210 255 285 50 63 75 75 50 65 65 80 30 1200 80 150 300 240 280 295 63 75 75 90 50 65 80 80 30 1600 100 200 400 280 330 355 63 75 90 90 65 80 80 90 30 2000 125 11 10 250 500 315 375 400 75 90 90 80 80 90 50 2500 200 0 0 11 11 10 325 600 370 435 470 75 90 80 80 90 50 3000 200 0 0 0 11 11 16 10 11 400 750 405 485 515 90 80 90 60 4000 250 0 0 0 0 5 500 1000 445 540 580 60 5000 400 6000 1) Branch 1 (2...) Lighting Load 10 x 100w = 1,000 watts Compute current load  1,000 =4.35 amp 230v see table 5.3 (left side) to determine size of wire- use 2pcs, 2.0 mm2, THW copper wire 2) Branch 3 (4,5...) Convenience Outlet 6 x 180w = 1,080 watts Compute current load 1,080 =4.70 amp 230v see table 5.3 (left side) to determine size of wire use 2pcs, 3.5mm2, THHN copper wire 3) Branch 6 (7,8...) Appliance Outlet - Range = 8,000 watts Compute current load 8,000 =34.78 amp 230v see table 5.3 (left side) to determine size of wire use 2pcs, 8.0mm2, THHN copper wire D) LOAD TABULATION CRT Consumption L. C. Others Watts Voltage Amp/CRT Protection Size of wire Size of Conduit O. O. 1 Lighting outlet 10 1,000 230 V 4.35 15 Amp 2-2.0mm2 THW 15 mm  copper wire flexible conduit 2 Lighting outlet 10 1,000 230 V 4.35 15 Amp 2-2.0mm2 THW 15 mm  copper wire flexible conduit 3 Convenience 6 1,080 230 V 4.70 20 Amp 2-3.5mm2 THW 20 mm  outlet copper wire flexible conduit 4 Convenience 6 1,080 230 V 4.70 20 Amp 2-3.5mm2 THW 20 mm  outlet copper wire flexible conduit 5 Convenience 7 1,260 230 V 5.48 20 Amp 2-3.5mm2 THW 20 mm  outlet copper wire flexible conduit 6 Range 1 8,000 230 V 34.78 45 Amp 2-8.0mm2 THW 25 mm  copper wire flexible conduit 7 Refrigerator 1 5,000 230 V 21.74 30 Amp 2-5.5mm2 THW 25 mm  copper wire flexible conduit 8 Spare 2,000 230 V 8.69 20 Amp 2-3.5mm2 THW 20 mm  copper wire flexible conduit Total 19,16 88.79 4) Load Analysis It = [ It x 0.80 + 0.25(12.00)] = [88.79 x 0.80 + 3.0] It = 74.032 ampere see table 5.3 (left side) to determine size of wire for main feeder thus: MAIN FEEDER : use 2pcs- 22.0mm2 THHN copper wire 1 pc.-with22.0mm2 THHN for grounding with 80 AT 100 AF (meaning 80 ampere trip 100 ampere frame) Sample of General Notes and Specifications: 1. All electrical works and installation shall conform to the latest provision of the Phil. Electrical Code with the rules of the national and local authorities concerned in the enforcement of electrical law and regulation of the local power company. 2. All installations shall be done in work-manlike manner and shall include all necessary works that may not be clearly indicated in the plans or schematic but necessary to attain the purpose of the design. 3. The plan indicates the general layout of the system and the locations of the outlets are diagrammatic and may be adjusted as required by the architect before the installation. 4. All works shall be under the direct supervision of duly licensed electrical engineer or a registered master electrician. 5. All materials to be supplied and install shall be new, high quality and approved type and appropriate for both location and intended use. Materials shall be standard product of reputable manufacturers 6. Power service shall be 230 volts, single phase, 3 wire solid neutral 60 hertz. 7. Furnish and install the electrical panel boards as shown in plan, provided with effective grounding connection. 8. The installation shall be concealed view, wiring shall be concealed in flexible PVC except power conduit or (RCS) otherwise noted. 9. Unless other wire specified the min size in conduit wire shall be 2mm THW copper wire and 15 mm DIA, MOLDFLEX, flexible PVC electrical pipe. 10. Pull Boxes/ Junctions Box of appropriate size shall be provided even if not indicated in drawings to accommodate the number of splices of wire. 11. Conduit runs shall be continuous from outlet to outlet, from outlet to panel board, form pull box to pull box. 12. The mounting heights (above fin. wall ) flooring  Light controls switch – 1.20 m  Convenience outlet – 0.30 m  Panel Board – 1.35 m 13. No revision of the design shall be done without proper knowledge with the approval of the architect and the owner, any such revision done without the approval shall cause responsibility of the contractor to cease as a whole.