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Comprehensive Guide to Residential Wiring Requirements and Devices

Learn about electrical service entry components, ground system requirements, overcurrent protection devices, and National Electrical Code rules for safe residential wiring. Understand different wiring methods, circuit connections, wire sizes, and installation practices.

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Comprehensive Guide to Residential Wiring Requirements and Devices

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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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