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EET 110 - Survey of Electronics

EET 110 - Survey of Electronics. Chapter 23 - Residential Wiring Requirements and Devices. Residential Wiring Req & Dev. Objectives NEC Describe ‘electrical service entry’ components Understand the ground system required understand over current protection devices & requirements.

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EET 110 - Survey of Electronics

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  1. EET 110 - Survey of Electronics Chapter 23 - Residential Wiring Requirements and Devices

  2. Residential Wiring Req & Dev. • Objectives • NEC • Describe ‘electrical service entry’ components • Understand the ground system required • understand over current protection devices & requirements

  3. Approval of wiring • NEC - National Electrical Code • specifies ‘rules’ that must be followed to comply • intended to promote fire & electrical safety

  4. Approval of wiring • Approval of electrical installations • must be performed or approved by a licensed Master Electrician • inspected by state electrical inspector

  5. Electrical Service • May be run overhead or underground • OVERHEAD WIRES • 2 supply lines + neutral from the pole • connect to customers equipment at mast • neutral wire is used to support the others

  6. Electrical Service • Mast to meter head • Meter supplied by power company • Service conduit from meter head to entry panel • main panel to individual circuits • Main panel/ breaker box (fuse panel)

  7. Underground wiring • Same wires run to meter head • from service transformer to meter head • 2 ‘hot’ leads, one neutral

  8. Three wire power distribution • Single phase power • rated as 240 volts • 1 x 240 volts - 2 x 120 volts + ground • 2 hot leads - black or red • each is 120 volts to neutral • 240 volts between the two ‘hot’ leads

  9. neutral (not ground) white • only allowed to fuse or switch the ‘hot’ leads. • Never interrupt the neutral leads • neutral is grounded at the main box and at the meter head • may not be at ground (0 volt) potential elsewhere in the house

  10. General Wiring requirements • Service size requirements • 100 amp is common in older homes • 200 amp service is standard for installation in ‘new work’ or upgrades • High tension wire provides high voltage to local transformer • transformer provides 240 volts center tapped (gives 2 120 volt lines)

  11. Service entry wiring

  12. Main fuse / breaker with switch to disconnect entire house • Inside the neutral block is grounded.

  13. Circuit breaker protection • ‘opens’ if current is excessive • mechanical version of fuse • may be reset when metal cools • DOUBLE Pole for 240 volt circuits • SINGLE pole for 120 volt circuits

  14. Branch circuit connections • 240 volt from both hot leads through double pole breaker • note that both sides of the breaker are physically tied together • 120 volt from either hot lead through a single pole breaker • Wire Sizes depends on AMPACITY of wire • No. 2 gauge for 100 A service, 3/0 for 200A

  15. Other circuits • General purpose circuit • 14AWG through 15A breaker or 12 AWG/20A • one circuit is required for each 500 square feet • Small appliance • 12AWG/20A wiring • 2 for kitchen, breakfast room, dining room and pantry • no lighting is allowed on these circuits

  16. Individual circuits • for special equipment • runs from breaker to a single device • water heater, range

  17. Wiring • conduit • rigid • pvc or metal (steel/aluminum) • non-metallic sheathed cable wiring • ‘ROMEX’ • typical AWG with number of conductors • 12/2 with ground

  18. None - metallic wiring • NM - interior • NMC - interior but corrosive resistant sheathing • UF - rated for direct underground applications

  19. Armor cable • semi-flexible metal case • Knob and Tube wiring • antique wiring method - very common in older homes. (pre-1960’s)

  20. Installing romex type wiring • stapled w/in 12 inches of a box • also stapled or supported at least every 5 feet. • Clamped inside box • require 6 inches of free wiring inside the box • Sheathing must be removed carefully • do not nick insulation on wires

  21. Boxes • Boxes are required for lights, switches, receptacles, or splices • Steel or plastic are available • Octagon, square, outlet or exterior (all weather) boxes + ganged

  22. wires run through ‘knockouts’ • boxes must be physically secured to structure - mounted to be flush with wall

  23. Receptacles • Connections • Screw terminals • push in (solderless) • Ganged outlets • Lamp holders • ceramic …

  24. Switches / Dimmers • SPST - simple single circuit switching • DPST - 240 V • both ‘hot’ leads must be broken • SPDT - three way switches • four way switches

  25. Grounding system • safety - electrons take shortest path to ground • neutral wire carries electron flow from load • not a ground • never break neutral - ie. Switch • bare ground wire - to earth ground • Ground rod • sink to earth ground

  26. Water pipe as ground • Meter bonding jumper • Over current protection • fuse • circuit breaker • GFI - Ground Fault Interrupter

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