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EET Survey of Electronics

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Presentation on theme: "EET Survey of Electronics"— Presentation transcript:

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)


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


10 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


12 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

13 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 volt lines)

14 Service entry wiring


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

17 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

18 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

19 Other circuits General purpose circuit Small appliance
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

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

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

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

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

24 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

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

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

27 Receptacles Connections Lamp holders Screw terminals
push in (solderless) Ganged outlets Lamp holders ceramic …

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

29 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

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

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