Electrical Wiring Residential

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Electrical Wiring Residential

• Unit 5
• Switch Control
• Receptacle Bonding
• Conductor Identification

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Conductor Identification

• For alternating-current circuits, The NEC
  requires that the grounded (identified) conductor
  have an outer finish that is either continuous
  white or gray.
• The grounded conductor is also called the neutral
  conductor.
• An ungrounded (hot) conductor must have an outer
  finish that is a color other than green, white,
  natural gray, or gray with three continuous white
  stripes.

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Grounded (Neutral) Conductor

• For residential wiring, the 120/240 volt
  electrical system is grounded by the electric
  utility at their transformer, and again by the
  electrician at the main service.

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Grounded (Neutral) Conductor

• By definition a neutral conductor is
• The conductor that carries only the unbalanced
  current from the other conductors, as in the case
  of a multi-wire circuit of three or more
  conductors.
• The conductor where the voltage from every other
  conductor to it is equal under normal operating
  conditions.
• By these definitions, the white conductor in a
  two-wire branch circuit is not truly a neutral
  conductor

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Color Coding (Cable Wiring)

• The conductors in nonmetallic-sheathed cable
  (Romex) are color coded as follows.
• Two-wire
• One black (hot Phase conductor)
• One white (grounded identified conductor)
• One bare (equipment grounding conductor)

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Color Coding (Cable Wiring)

• Three-wire
• One black (hot Phase conductor)
• One white (grounded identified conductor)
• One red (hot Phase conductor)
• One bare (equipment grounding conductor)

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Color Coding (Cable Wiring)
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Changing Colors When Conductors Are in a Raceway

• For cable wiring such as nonmetallic-sheathed
  cable or armored cable, 200.7(C)(1) and (2)
  permits the white conductor to be used for
  single-pole, three-way, or four-way switch loops.
• These code sections require that when used for a
  switch loop, the conductor that is white is to be
  used for the supply to the switch, and not as the
  return conductor from the switch, to the switched
  outlet.

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Typical Colors for Residential Wiring
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Push-in Terminations

• Screwless push-in terminals on receptacles are
  listed by Underwriters Laboratories (UL) for
  use only with solid 14 AWG copper conductors.

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Push-in Terminations

• They are not to be used with
• Aluminum or copper-clad aluminum conductors.
• Stranded conductors
• 12 AWG conductors By design, the holes are large
  enough to take only a 14 AWG solid conductor.
• Push-in terminals for 12 AWG solid copper
  conductors are still permitted on snap switches.

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Exploded Receptacle Diagram
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Always pigtail for more than 2 conductors
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Receptacle Configurations
15A 250V
15A 125V
20A 125V
20A 250V
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Conductor Color Coding For Switch Connections

• Always connect a white wire to the white (silver)
  terminal or to the white wire of a lampholder or
  receptacle.
• Always connect the black switch-leg conductor
  (red in some cases) to the black wire (or dark
  brassy terminal) of a lampholder or receptacle.

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Conductor Color Coding For Switch Connections

• In cables, always re-identify white conductors
  when they are used as ungrounded (hot)
  conductors.
• This re-identification must be done wherever the
  conductors are visible and accessible.
• Never use a green colored insulation for a
  grounded or ungrounded conductor. Green is
  reserved for equipment grounding conductors

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Connecting Switches, Receptacles, and Lighting
Outlets.

• A conductor carrying an alternating current
  produces a magnetic field (flux) around the
  conductor.
• The greater the current, the stronger the
  magnetic field.

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Connecting Switches, Receptacles, and Lighting
Outlets.

• In alternating current _at_ 60Hz., the current and
  magnetic field reverses direction 120 times each
  second.
• If the conductor is run through a steel raceway,
  steel jacketed cable, or a knockout in a steel
  box, the alternating magnetic field will induce
  heat into the steel.

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Connecting Switches, Receptacles, and Lighting
Outlets.

• When all the conductors of the same circuit are
  run through the same raceway, the magnetic fields
  around the conductors are equal and opposite,
  thereby canceling one another out.
• The NEC 300.3(B) requires that all conductors
  of the same circuit and, where used, the grounded
  conductor, all equipment grounding conductors and
  bonding conductors shall be contained within the
  same raceway, trench, cable, or cord, unless
  otherwise permitted

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Connecting Switches, Receptacles, and Lighting
Outlets.

• NEC 404.2(A) requires that three-way and
  four-way switches shall be so wired that all
  switching is done only in the ungrounded circuit
  conductor.
• Switch loops do not require a grounded conductor.

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Proper Use of Conductors in Romex Cabling
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Conductors in
Trenches
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Grounded Conductors at Switch Locations

• Are grounded (neutral) conductors needed at
  switching locations?
• In most cases, the answer is no.
• However, a grounded conductor is required when a
  true pilot light is connected at the switch
  location.
• In the event that electronic dimming and/or
  switching devices are to be used, a neutral may
  be required at one or more of the switch
  locations.

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Grounded Conductors at Switch Locations
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Using a
2-Wire as a Switch Loop
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Using a 3-Wire To Send a Feed Through a Light
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3-Way Switch Line Diagram and Graphic
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3-Way Fed at Light, Dead Ended at Both Ends
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4-Way Switch Line Diagram Drawing
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Bonding and Grounding at Receptacles and Switches

• A metal box is considered to be adequately
  grounded when the wiring method is armored cable,
  non-metallic sheathed cable with ground, or a
  metal raceway such as EMT.
• Grounding and bonding of the equipment grounding
  conductor to a metal box, switch, or receptacle
  is important.
• Most metal boxes have a No. 10-32 tapped hole for
  securing a green hexagon shaped equipment
  grounding screw.

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Bonding and Grounding at Receptacles and Switches

• To ensure the continuity of the equipment
  grounding conductor path, 250.148 requires that
  where more than one equipment grounding conductor
  enters a box, they shall be spliced with devices
  suitable for the use.
• Splices shall not depend on solder!
• In existing locations where there is no equipment
  grounding conductor in a switch box, and where
  within reach of a conductive floor (i.e.
  concrete, tile, etc), use non-metallic faceplates.

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Bonding and Grounding at Receptacles and Switches
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Bonding and Grounding at Receptacles and Switches
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Various Listed Means of Grounding and Bonding
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A G-Clip is a Great Way to Attach a Ground To
an Existing Metal Box
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Timers

• Timers a unique on that they provide automatic
  control of electrical loads.
• Timers are used where a load is to be controlled
  for specific ON/OFF times of the day or night.
• Timers come in a wide variety of styles. Some
  fit in switch-boxes, some have weatherproof
  cases.
• Timers can also be used with photocells to
  provide even more flexibility for exterior
  lighting.

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Intermatic Timer
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Photocells
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This Concludes Unit 5