Electrical Wiring Residential

Unit 5Switch Control

Receptacle BondingConductor Identification

Unit 5 2

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.

Conductor Identification

Unit 5 3

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.

Grounded (Neutral) Conductor

Unit 5 4

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

Grounded (Neutral) Conductor

Unit 5 5

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)

Color Coding (Cable Wiring)

Unit 5 6

• Three-wire:

One black (“hot” Phase conductor)

One white (grounded “identified” conductor)

One red (“hot” Phase conductor)

One bare (equipment grounding conductor)

Color Coding (Cable Wiring)

Unit 5 7

Color Coding (Cable Wiring)

Unit 5 8

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.

Changing Colors When Conductors Are in a Raceway

Unit 5 9

Typical Colors for Residential Wiring

Unit 5 10

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

Push-in Terminations

Unit 5 11

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.

Push-in Terminations

Unit 5 12

Exploded Receptacle

Diagram

Unit 5 13

Always pigtail for

more than 2 conductors

Unit 5 14

Receptacle Configurations

15A125V

20A125V

15A250V

20A250V

Unit 5 15

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.

Conductor Color Coding For Switch Connections

Unit 5 16

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

Conductor Color Coding For Switch Connections

Unit 5 17

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.

Connecting Switches, Receptacles, and Lighting Outlets.

Unit 5 18

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.

Connecting Switches, Receptacles, and Lighting Outlets.

Unit 5 19

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”

Connecting Switches, Receptacles, and Lighting Outlets.

Unit 5 20

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.

Connecting Switches, Receptacles, and Lighting Outlets.

Unit 5 21

Proper Use of

Conductors in Romex Cabling

Unit 5 22

Conductors in

Trenches

Unit 5 23

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.

Grounded Conductors at Switch Locations

Unit 5 24

Grounded Conductors at Switch Locations

Unit 5 25

Using a2-Wire as a

Switch Loop

Unit 5 26

Using a 3-Wire To Send a Feed Through a Light

Unit 5 27

3-Way Switch Line

Diagram and Graphic

Unit 5 28

3-Way Fed at Light,

Dead Ended at Both Ends

Unit 5 29

4-Way Switch Line Diagram & Drawing

Unit 5 30

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.

Bonding and Grounding at Receptacles and Switches

Unit 5 31

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.

Bonding and Grounding at Receptacles and Switches

Unit 5 32

Bonding and Grounding at Receptacles and Switches

Unit 5 33

Bonding and Grounding at Receptacles and Switches

Unit 5 34

Various Listed

Means of Grounding

and Bonding

Unit 5 35

A “G-Clip” is a Great

Way to Attach a

Ground To an Existing Metal Box

Unit 5 36

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 37

Intermatic Timer

Unit 5 38

Photocells

Unit 5 39

This Concludes Unit #5