Electrical Wiring Residential - PowerPoint by X8ee493

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									Electrical Wiring Residential

             Unit 5
         Switch Control
       Receptacle Bonding
     Conductor Identification
         Conductor Identification

1) For alternating-current circuits, The NEC®
   requires that the grounded (identified)
   conductor have an outer finish that is either
   continuous white or gray.
2) The grounded conductor is also called the
   neutral conductor.
3) 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.
                        Unit 5                     2
     Grounded (Neutral) Conductor

1) 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.




                         Unit 5                   3
    Grounded (Neutral) Conductor
2) 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

                        Unit 5                   4
      Color Coding (Cable Wiring)

1) 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)




                       Unit 5                   5
      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)




                       Unit 5                   6
Color Coding (Cable Wiring)




            Unit 5            7
  Changing Colors When Conductors
         Are in a Raceway

1) 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.
2) 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.


                        Unit 5                  8
Typical Colors for Residential Wiring




                 Unit 5           9
           Push-in Terminations


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




                        Unit 5                10
           Push-in Terminations

2) 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.
3) Push-in terminals for 12 AWG solid copper
   conductors are still permitted on snap switches.


                        Unit 5                 11
 Exploded
Receptacle
 Diagram




             Unit 5   12
  Always
 pigtail for
more than 2
conductors




               Unit 5   13
Receptacle Configurations


      15A         15A
      125V        250V




      20A         20A
      125V        250V


             Unit 5         14
  Conductor Color Coding For Switch
            Connections

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




                         Unit 5                 15
  Conductor Color Coding For Switch
            Connections
3) 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.
4) Never use a green colored insulation for a
   grounded or ungrounded conductor. Green is
   reserved for equipment grounding conductors



                         Unit 5                 16
  Connecting Switches, Receptacles,
        and Lighting Outlets.
1) A conductor carrying an alternating current
   produces a magnetic field (flux) around the
   conductor.
2) The greater the current, the stronger the
   magnetic field.




                        Unit 5                   17
 Connecting Switches, Receptacles,
       and Lighting Outlets.
3) In alternating current @ 60Hz., the current and
   magnetic field reverses direction 120 times
   each second.


4) 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.



                        Unit 5                 18
  Connecting Switches, Receptacles,
        and Lighting Outlets.
5) 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.

6) 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”
                        Unit 5                 19
 Connecting Switches, Receptacles,
       and Lighting Outlets.

7) 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”.

8) Switch loops do not require a grounded
   conductor.




                        Unit 5                 20
Proper Use
     of
Conductors
 in Romex
  Cabling




             Unit 5   21
Conductors
    in
 Trenches




             Unit 5   22
      Grounded Conductors at Switch
                Locations
1) 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.         Unit 5                23
 Grounded
Conductors
 at Switch
 Locations




             Unit 5   24
Using a
2-Wire
 as a
Switch
 Loop




          Unit 5   25
Using a 3-Wire To Send a Feed
       Through a Light




             Unit 5         26
  3-Way
Switch Line
 Diagram
and Graphic




              Unit 5   27
3-Way Fed
 at Light,
  Dead
 Ended at
Both Ends




             Unit 5   28
4-Way Switch Line Diagram &
         Drawing




            Unit 5            29
Bonding and Grounding at Receptacles
           and Switches
1) 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.

2) Grounding and bonding of the equipment
   grounding conductor to a metal box, switch, or
   receptacle is important.

3) Most metal boxes have a No. 10-32 tapped hole
   for securing a green hexagon shaped equipment
   grounding screw.
                       Unit 5                 30
Bonding and Grounding at Receptacles
           and Switches
4) 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.”

5) Splices shall not depend on solder!

6) 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.
                        Unit 5               31
Bonding and Grounding at Receptacles
           and Switches




                Unit 5          32
Bonding and Grounding at Receptacles
           and Switches




                Unit 5          33
 Various
  Listed
Means of
Grounding
   and
 Bonding




            Unit 5   34
A “G-Clip”
 is a Great
   Way to
  Attach a
Ground To
an Existing
Metal Box


              Unit 5   35
                     Timers
1) Timers a unique on that they provide automatic
   control of electrical loads.

2) Timers are used where a load is to be controlled
   for specific “ON/OFF” times of the day or night.

3) Timers come in a wide variety of styles. Some
   fit in switch-boxes, some have weatherproof
   cases.

4) Timers can also be used with photocells to
   provide even more flexibility for exterior
   lighting.
                        Unit 5                  36
Intermatic Timer




      Unit 5       37
Photocells




   Unit 5    38
This Concludes Unit #5




         Unit 5          39

								
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