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Electrical Principles and Wiring Materials

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OBJECTIVES 1. AM16.01 Define common electrical terms. 2. AM16.02 Compute electrical energy use and cost. 3. AM16.03 Investigate safe practices involving electricity.. 4. AM17.01 Describe materials used in electric wiring. 5. AM17.02 Explain the procedure for installing switches, making common splices, and doing other electrical wiring tasks.

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I. Principles of Electricity A. Electricity is a form of energy that can produce light, heat, magnetism, chemical changes B. Resistance: tendency of a material to prevent electrical flow C. Conductor: if electricity flows easily D. Insulator: material that provides great resistance

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II. TERMS A. Amperes: measure of the rate of flow of electricity in a conductor (gallons/min) B. Volts: measure of electrical pressure (PSI) C. Watts: measure of the amount of energy or work that can be done D. Ohms: measure of electrical resistance to flow

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III. Ohm’s Law A. Ohm = R (resistance) B. Volts = E (pressure) C. Amps = I (rate of flow) D. Ohm’s Law: E = IR or I=E/R or R=E/I

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IV. Electrical Safety A. Two most dangerous things about Electricity- Shock and Fire B. Never disconnect any safety device C. Don’t touch electrical items with wet hands or feet (sweat) D. Don’t remove ground plug prong E. Use GFI in wet areas-Ground Fault Interrupter F. Discontinue use of extension cord that feels warm G. Don’t put extension cords under carpet

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V. Electrical Safety A. Install wiring according to NEC- National Electrical Code B. Blown fuse or breaker, determine cause C. Don’t replace fuse with larger fuse D. Don’t leave heat producing appliances unattended E. Heaters & lamps away from combustibles F. Don’t remove back of TV (30,000v when off) G. Electric motors lubricated, free of grease etc.

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Electrical Safety H. Keep appliances dry I. Don’t use damaged switches, outlets, fixtures, extension cords J. Follow manufacturer’s instructions for installation and use of electrical equipment

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VI. Service Entrance A. Power from Electric company 1. Jones-Onslow 2. Progress Energy B. Transformer: drops volts from 25,000 volts to 240 volts C. Service drop: wires etc from transformer to house D. Entrance head: weather-proof at house E. Meter: $$$ F. Service Entrance Panel (SEP): box with fuses or breakers

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VII. Branch Circuits A. Usually begin at Service Entrance Panel (SEP) B. 1. Protection devices- stop current flow when max. amps are exceeded a. Fuses- metal strips 1). Cartridge 2). Screw in 2. Circuit breakers-reset B. Branch out all over house C. Size of circuit 1. Only 1 motor 2. Series of outlets 3. Series of lights D. Use correct size wire and fuse or breaker

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VIII. Types of Cable A. Nonmetallic sheathed cable- ROMEX: copper or aluminum wire covered with paper, rubber, or vinyl for insulation B. Armored cable: flexible metal sheath with individual wires inside. Wires are insulated C. Conduit: tubing with individually insulated wires

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IX. Wire Identification A. Type based on : 1. Outer cable (more than one wire) covering- underground 2. Individual wire covering a. Plastics 3. Size of wire- 1 st #=gauge 2 nd = # of conductors a. 12-2 has two strands of No. 12 wire (black & white) 1). 12-2 w / g same, with one green or bare 1). 12-2 w / g same, with one green or bare b. 12-3 has three strands of No. 12 (black, red, white) 1). 12-3 w/g same, with green or bare 1). 12-3 w/g same, with green or bare 4. Number of wires- 12-2 B. Wire type stamped on outer surface

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C. Wire Color codes 1. Black- load carrier a. Wire carries current to appliance 2. White- neutral a. Wires carry current from appliance back to source 3. Green- ground a. Ground all metal boxes and appliances 4. Red- load- traveler in 3-way switches

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X. Wire Type and Size A. Copper or aluminum 1. Aluminum use one size larger 2. Does not handle heat B. Sizes 1. Lower gauge number = larger wire 2. No 14 (14 gauge) = 15 amp circuits (125V) 3. No 12 = 20 amps (240 V) 4. No 10 = 30 amps 5. No 8 and larger use bundles of wires 6. Current travels on outer surface of wire, so a bundle of smaller wires can carry more

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C. Wire types (places in house ? ) 1. Type T - dry locations 2. Type TW - dry or wet 3. THHN - dry, high temps 4. THW and THWN - wet, high temps 5. XHHW - high moisture & heat resistance 6. UF - direct burial in soil but not concrete

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XI. Voltage Drop A. Loss of voltage as it travels along a wire 1. Lights dim, motors overheat B. Larger wires have less voltage drop for a given amount of current C. Longer wire = greater problem D. Must increase wire size as distance increases

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XII. Electric Meter-measures electricity used A. Watts: measure of the amount of energy or work that can be done B. Watt-hour = use of 1 watt for one hour 1. 100 watt light bulb for 1 hour - 100 watt-hours C. Kilowatt = 1000 watts 1. Kilowatt-hours: how electricity is sold 2. Kilowatt-hour = 1000 watts for one hour

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XIII. Calculating electrical use A. Watts=Volts x Amps 1. Problem=What is the watt rating of a 20 amp saw in a 220 V circuit ? 2. Solution= Watts = Volts x Amps Watts= 220 Volts x 20 Amps= 4400 B. Watt- hours = (V x A) x hours of use 1. Problem = How many watts will an electric motor that requires 7.5 amps of electricity, and is on a 120 V circuit for 10 hours? 2. Solution Watt- hours = V x A x hours of use Watt-hours= 120 V x 7.5 A x 10 Hrs= 9000

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C. Kilowatt- hours= watts/1000 x hours of use 1. Problem- An Ag. Shop has 5- 200 watt lights, a 600 watt saw and a 100 watt fan that were used for 5 Hrs. How many kilowatts were used. 2. Solution- Kilowatt-hours= watts/1000 x hrs used KWH= (5x200 watts) + 600 watts +100 watts x 5 = 8.5 1000 watts/Kilowatt D. Cost = KILOWATT-HOURS x Cost / kilowatt –hr. 1.. Problem = If the local rate for electricity is $.12 per KWH, how much should the electric bill be for 100 KWH ? a). Solution- Cost = KWH x Cost/KWH Cost = 100 KWH x $.12/KWH=$ 12.00

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