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