Electrical Principles and Wiring Materials.ppt
- 1. Electrical Principles and Electrical Principles and Wiring Materials Wiring Materials
- 2. Principles of Electricity Principles of Electricity Electricity is a form of energy that can Electricity is a form of energy that can produce light, heat, magnetism, chemical produce light, heat, magnetism, chemical changes changes Resistance: tendency of a material to Resistance: tendency of a material to prevent electrical flow prevent electrical flow Conductor: if electricity flows easily Conductor: if electricity flows easily Insulator: material that provides great Insulator: material that provides great resistance resistance
- 3. Amps, Volts, Watts Amps, Volts, Watts Amperes: measure of the rate of flow of Amperes: measure of the rate of flow of electricity in a conductor electricity in a conductor Volts: measure of electrical pressure Volts: measure of electrical pressure Watts: measure of the amount of energy Watts: measure of the amount of energy or work that can be done or work that can be done Ohms: measure of electrical resistance Ohms: measure of electrical resistance to flow to flow
- 4. Ohm’s Law Ohm’s Law Ohm = R Ohm = R Volts = E Volts = E Amps = I Amps = I Ohm’s Law: E = IR Ohm’s Law: E = IR I=E/R I=E/R R=E/I R=E/I
- 5. Electrical Safety Electrical Safety Shock and Fire Shock and Fire Never disconnect any safety device Never disconnect any safety device Don’t touch electrical items with wet hands or Don’t touch electrical items with wet hands or feet feet Don’t remove ground plug prong Don’t remove ground plug prong Use GFI in wet areas Use GFI in wet areas GFI- Ground Fault Interrupter GFI- Ground Fault Interrupter Designed to protect from electrical shock by Designed to protect from electrical shock by interrupting household circuit when there is interrupting household circuit when there is difference in currents in “hot” and neutral wires. difference in currents in “hot” and neutral wires.
- 7. Electrical Safety Electrical Safety Discontinue use of extension cord that feels Discontinue use of extension cord that feels warm warm Don’t put extension cords under carpet Don’t put extension cords under carpet Install wiring according to NEC Install wiring according to NEC Blown fuse or breaker, determine cause Blown fuse or breaker, determine cause Don’t replace fuse with larger fuse Don’t replace fuse with larger fuse Don’t leave heat producing appliances Don’t leave heat producing appliances unattended unattended Heaters & lamps away from combustibles Heaters & lamps away from combustibles
- 8. Electrical Safety Electrical Safety Don’t remove back of TV (30,000v when Don’t remove back of TV (30,000v when off) off) Electric motors lubricated, free of grease Electric motors lubricated, free of grease etc. etc. Keep appliances dry Keep appliances dry Don’t use damaged switches, outlets, Don’t use damaged switches, outlets, fixtures, extension cords fixtures, extension cords Follow manufacturer’s instructions for Follow manufacturer’s instructions for installation and use of electrical equipment installation and use of electrical equipment
- 9. Service Entrance Service Entrance Power from power company Power from power company Transformer: drops volts from 25,000 volts Transformer: drops volts from 25,000 volts to 240 volts to 240 volts Service drop: wires etc from transformer to Service drop: wires etc from transformer to house house Entrance head: weather-proof at house Entrance head: weather-proof at house Meter: $$$ Meter: $$$ Service Entrance Panel (SEP): box with Service Entrance Panel (SEP): box with fuses or breakers fuses or breakers
- 10. Service Cable Entrance Service Cable Entrance The service cable runs down The service cable runs down the outside of the wall to the the outside of the wall to the level of the breaker box level of the breaker box Weatherhead = conduit Weatherhead = conduit entrance cap entrance cap
- 11. Electric Meter Electric Meter Kilowatthours: how electricity is sold Kilowatthours: how electricity is sold Kilo = 1000 Kilo = 1000 Watthour = use of 1 watt for one hour Watthour = use of 1 watt for one hour 100 watt light bulb for 1 hour - 100 100 watt light bulb for 1 hour - 100 watthours watthours Kilowatthour = 1000 watts for one hour Kilowatthour = 1000 watts for one hour
- 12. Branch Circuits Branch Circuits usually begin at SEP usually begin at SEP branch out into a variety of places branch out into a variety of places only 1 motor or; only 1 motor or; series of outlets or; series of outlets or; series of lights series of lights use correct size wire and fuse or use correct size wire and fuse or breaker breaker
- 13. Types of Cable Types of Cable Nonmetallic sheathed cable: copper or Nonmetallic sheathed cable: copper or alluminum wire covered with paper, alluminum wire covered with paper, rubber, or vinyl for insulation rubber, or vinyl for insulation Armored cable: flexible metal sheath with Armored cable: flexible metal sheath with individual wires inside. Wires are individual wires inside. Wires are insulated insulated Conduit: tubing with individually insulated Conduit: tubing with individually insulated wires wires
- 14. Conduit Conduit Flexible Metal Conduit Flexible Metal Conduit Steel Conduit Steel Conduit Polyflex Polyflex
- 15. Wire Type and Size Wire Type and Size copper copper No 14 (14 gauge) = 15 amp circuits No 14 (14 gauge) = 15 amp circuits No 12 = 20 amps No 12 = 20 amps No 10 = 30 amps No 10 = 30 amps aluminum use one size larger aluminum use one size larger lower gauge number = larger wire lower gauge number = larger wire No 8 and larger use bundles of wires No 8 and larger use bundles of wires current travels on outer surface of wire, so a current travels on outer surface of wire, so a bundle of smaller wires can carry more bundle of smaller wires can carry more
- 16. Voltage Drop Voltage Drop loss of voltage as it travels along a wire loss of voltage as it travels along a wire lights dim, motors overheat lights dim, motors overheat larger wires have less voltage drop for a larger wires have less voltage drop for a given amount of current given amount of current longer wire = greater problem longer wire = greater problem must increase wire size as distance must increase wire size as distance increases increases
- 17. Wire Identification Wire Identification Type of outer covering, individual wire Type of outer covering, individual wire covering, cable construction, number of covering, cable construction, number of wires wires Wire type stamped on outer surface Wire type stamped on outer surface
- 18. Wire Types Wire Types Type T - dry locations Type T - dry locations Type TW - dry or wet Type TW - dry or wet THHN - dry, high temps THHN - dry, high temps THW and THWN - wet, high temps THW and THWN - wet, high temps XHHW - high moisture & heat resistance XHHW - high moisture & heat resistance UF - direct burial in soil but not concrete UF - direct burial in soil but not concrete
- 19. Wire Identification Wire Identification Color coded: black, red, & blue = Color coded: black, red, & blue = positive or hot wires which carry current positive or hot wires which carry current to appliances to appliances White = neutral wires carry current from White = neutral wires carry current from appliance back to source appliance back to source Green or Bare = ground all metal boxes Green or Bare = ground all metal boxes and appliances and appliances
- 20. Wire Identification Wire Identification Wire Size: 12-2 has two strands of No. Wire Size: 12-2 has two strands of No. 12 wire (black & white) 12 wire (black & white) 12-2 w/g same, with one green or bare 12-2 w/g same, with one green or bare 12-3 has three strands of No. 12 (black, 12-3 has three strands of No. 12 (black, red, white) red, white) 12-3 w/g same, with green or bare 12-3 w/g same, with green or bare
- 21. 12-2 w/g 12-2 w/g 12-2 12-2 12-3 w/g 12-3 w/g 12-3 12-3