1. Wiring Circuits
Lesson Plan PSTS: C6-7

2. Anticipated Problems
What are some proper safety practices that should be observed when working with electricity?
What are the NEC requirements on wire splices and connections?
What are the NEC requirements regarding the size and use of electrical boxes?
What are the NEC requirements regarding wiring circuits safely?
What are the steps to complete an electricity project?

3. Terms double-pole double-throw (DPDT) switches
duplex convenience outlet (DCO)
duplex receptacle
equipment grounding conductor
grounded conductor
individual branch circuit
multipurpose tool
National Electrical Code (NEC)
pole

4. Terms single-pole double-throw (SPDT) switches
single-pole single-throw (SPST) switch
solderless connectors
switch-controlled split-duplex receptacle
switch loop
throw
ungrounded conductor
wire splice

5. Safety First Electricity is a safe and economical source of power.
Injuries and loss of life can occur quickly when electricity is improperly used.
Property can be destroyed by electrical failures and fires.

6. Electrical Safety Tips
Avoid damp working areas.
Protect each circuit.
Ground each circuit properly.
Use ground-fault circuit interrupters (GFCIs).
Ground electrical equipment.
Disconnect the main switch.

7. Electrical Safety Tips
Correct the source of trouble.
Purchase safe equipment.
Review and follow local electrical codes.
Seek professional help.
Avoid plumbing hazards.
Inspect and repair cords periodically.

8. Electrical Safety Tips
Open circuits with switches.
Never make temporary repairs.
Use electrical cords safely.
Do not overload circuits.
Unplug electrical tools when they are not in use.

9. Wire Splicing A wire splice is one wire connected to another wire.
The purpose of the splice is to conduct electricity through the conjunction.
According to the NEC, connectors and splices must be enclosed in a junction box.

10. Solderless Connectors
Solderless connectors, sometimes called wire nuts, are devices used to splice smaller conductors (e.g., those in typical wiring applications).
Most have an insulated cover that twists onto a spliced wire. It holds and insulates the splice.
The proper size depends on the conductor size and the number of conductors being used.

11. Steps to Splice Wires
To splice wires, first strip about ½ to ¾ inch of insulation from the ends of the wires to be spliced.
Use a multipurpose tool - a device used for cutting wire, stripping conductors, and attaching terminals to conductors.

12. Steps to Splice Wires
Choose the correct size wire nut by following the instructions on the label.

13. Steps to Splice Wires
Hold all the wires to be spliced in one hand so the ends of the wires are even.
While holding the wires firmly, push the wires into the wire nut while twisting it.
Continue until the wire nut is tight.

14. Steps to Splice Wires
Test the splice by holding the wire nut in one hand while pulling firmly on the wires one at a time.
If the splice is complete, none of the wires will be pulled out.
Check to make sure no uninsulated wire is exposed at the splice.

15. Electrical Boxes
Boxes and fittings are used to keep cable and conduit in place and to prevent damage to it.

16. Electrical Boxes
Boxes must secure the cable or conduit connected to the box for prevention of mechanical strain on the wiring connections.
They attach to the building structure and provide support for switches, receptacle outlets, and fixtures.
They enclose all wiring connections to provide protection and prevent accidental contact with uninsulated components.

17. Fitting Types
Various fitting types are used to secure the conduit or cable to the box.
The type of fitting to use will depend on the type of connection needed and the location of the connection (e.g., in a dry or in a damp area).

18. Selecting the Box
It is important to select the correct box size for the application. A box must have adequate volume for all of the conductors and devices that will be in the box.
The correct box size depends on the size of the conductor and the number of equivalent conductors to be used in the box.

19. Selecting the Box
A person may refer to the National Electrical Code (NEC) for the appropriate table in sizing a box.
General rules to follow in determining the number of equivalent conductors in a box are to follow.

20. Selecting the Box
Each conductor passing through a box without being spliced or connected to a device is counted as one conductor.

21. Selecting the Box
Each conductor connecting to a splice or a device is counted as one conductor.
However, if a conductor is contained completely within the box (e.g., a pigtail splice), it is not counted.

22. Selecting the Box
All grounding conductors in a box are counted as only one conductor.
A switch or receptacle counts as two conductors.

23. Selecting the Box
Each of the following types of fittings is counted as one conductor: cable clamps, fixture studs, hickeys, and straps.
Each type of fitting is only counted once, even if two or more of the same fittings are present.

24. Electrical Circuits
When installing electrical equipment and materials, it is of extreme importance to follow approved guidelines and to use approved devices and materials.
The National Electrical Code (NEC) is a set of guidelines for electrical wiring established to ensure the safe use of electricity.

25. Electrical Circuits
To determine the wire size and the circuit breaker or fuse size, a person needs to know what electrical devices or appliances might be operated on a given circuit.

26. Electrical Circuits
The voltage source is known from the electric company. The wattage rating can be found on the nameplate of each appliance or device being used.
From this, it can determine how many amps of current would flow through the circuit using the power equation.

27. Electrical Circuits

28. Electrical Circuits
A table in the National Electric Code can be used for allowable current-carrying capacities of insulated conductors, or a wire-size calculator

29. Electrical Circuits
Three basic conductors are used in electric wiring.
A grounded conductor
An equipment grounding conductor
An ungrounded conductor

30. Grounded Conductor
A grounded conductor is a conductor intentionally connected to ground. It is connected to the neutral bar in the service entrance panel (SEP) and is often referred to as a neutral conductor.
In a 120-volt circuit, the grounded conductor is a normal current carrying conductor.
According to the NEC, an ungrounded conductor AWG #6 or smaller must have white or natural gray insulation.

31. Grounded Conductor
An equipment grounding conductor is a conductor that bonds conductive materials that enclose electrical conductors or equipment back to the system grounding electrode.
It protects people and property from damage or injury in case of a ground-fault.
During normal operation, this conductor carries no current. It is usually uninsulated or bare. If it is insulated, the conductor must be green or green with one or more yellow stripes.

32. Ungrounded Conductor
An ungrounded conductor is a conductor that originates at the circuit breaker or fuse.
It is usually black or red.

33. Choosing the Conductor
Choosing the right type and size of conductor is important. Considerations include:
The load in amps required
The type of wire used
The length of travel the wire must go from the SEP to the load

34. Cable and Conduit
The NEC requires single wires to be protected from physical damage.
When wiring branch circuits, a person generally does this with cable or conduit.

35. Receptacle Outlets
Receptacle outlets provide a convenient means of connecting electrical equipment to the wiring system.
Most outlets are the duplex convenience outlet or the special purpose outlet.

36. Receptacle Outlets
A duplex convenience outlet (DCO) is a general purpose outlet with two receptacles built into one device.
Another name is a duplex receptacle.
A DCO is available in 15 and 20 ampere, 120-volt ratings.

37. Receptacle Outlets
The two halves of a DCO are connected by a removable tab between the two brass-colored ungrounded (hot) terminal screws and by a second removable tab between the two silver-colored grounded (neutral) terminal screws.
Grounding-type DCOs have a green grounding screw where the branch circuit equipment grounding conductor is attached.

38. Receptacle Outlets
When wiring a single DCO, the ungrounded (black) conductor attaches to one of the brass-colored terminal screws on the DCO.
The grounded (white) conductor attaches to one of the silver-colored terminal screws on the DCO.
The equipment grounding conductor (bare or green) attaches to the green grounding screw on the DCO.

39. Wiring connections for two or more unswitched DCOs.
When two or more 120-volt DCOs are on the same branch circuit and no switch is used, the DCOs are always hot, unless shut off at the SEP. To wire, the first receptacle is connected to the circuit using short pigtail wires. These wires must have the same color insulation as the circuit conductors to which they are spliced. Insulated wire nuts are used to make the splices. At the last receptacle, the circuit conductors attach directly to the appropriate terminals, and no pigtails are required.

40. Switch-Controlled Split-Duplex Receptacle
Sometimes a DCO may be used so a table lamp may be plugged into half of the DCO and turned on and off with a wall switch.
A switch-controlled split-duplex receptacle is a device that has power whether the switch is on or off. So a clock or television, for example, may be plugged into the other half of the DCO.

41. Switch-Controlled Split-Duplex Receptacle
Typically, 12-2 with ground cable is used between the source and the switch; 12-3 with ground is used between the switch and the receptacle.
At the switch box, the two grounded wires are spliced together using a wire nut. (Never attach grounded or neutral wires to a single-pole switch.)
The incoming ungrounded (black) wire is spliced to a short pigtail wire and to the black wire of the outgoing cable.

42. Switch-Controlled Split-Duplex Receptacle
The pigtail wire is attached to one of the switch’s brass-colored terminal screws.
The red wire (second ungrounded conductor) from the outgoing cable is connected to the other brass-colored terminal screw at the switch.
At the receptacle outlet, the grounded conductor attaches to the silver- colored terminal screw

43. Special Purpose Outlet
A special purpose outlet (SPO) is a device installed to serve a specific machine or appliance.
An SPO is usually installed on an individual branch circuit, which is a circuit with just one load on it.

44. Switches
Switches control one or more electrical loads by opening and closing the circuit serving the load(s).
Switches may be installed in the ungrounded or hot conductor(s) of a circuit.

45. Switches
Switches are rated for a specific maximum voltage and amperage. If designed to control motors, they may be rated for a maximum horsepower.

46. Switches
Grounding-type switches provide grounding protection for the normally noncurrent carrying metal components of the switch and have a green grounding screw terminal.

47. Switches
A switch often is described based on its number of poles and throws.
A pole is a movable contact within a switch.
A throw is the number of paths provided for current to flow through the switch.

48. Single-Throw Switch
Flush-mounted toggle switches often are called snap switches. When mounted in a box with a cover plate, only the insulated switch handle is exposed.
A single-pole single-throw (SPST) switch is a device used to control load(s) in a circuit from a single location.

49. Single-Throw Switch
A single-pole single-throw (SPST) switch has two brass-colored screw terminals where the incoming and outgoing ungrounded conductors are attached.
The “on” and “off” positions are marked and should be installed so the toggle is up when “on” and down when “off.”

50. Three-Way Switch: End of Run
When using an SPST switch to control a light at the end of a run, only the ungrounded conductors from the incoming and outgoing cables attach to the brass-colored switch terminals.
The grounded conductors from the two cables are spliced together at the switch box.

51. Three-Way Switch: End of Run
At the lighting fixture, the ungrounded conductor connects to the brass-colored terminal screw and the grounded conductor connects to the silver-colored terminal screw.
The equipment grounding conductor is connected to the metal fixture box with a grounding clip.

52. Three-Way Switch: Middle of Run
When using an SPST switch to control a light in the middle of a run, the grounded conductor from the source is connected directly to the silver-colored terminal of the lighting fixture.
When using an SPST switch to control a light in the middle of a run, the grounded conductor from the source is connected directly to the silver-colored terminal of the lighting fixture.

53. Three-Way Switch: Middle of Run
A switch loop is the wires from the lighting fixture to the switch.
When cable is used to wire a circuit containing a switch loop, a white wire must be used as an ungrounded conductor and connected to the switch.
According to the NEC, the white wire must supply the switch, and the black wire must return to the load.

54. Single-Pole Double Throw Switch
Single-pole double-throw (SPDT) switches, commonly called three-way switches, are devices used in pairs to control lights from two locations.
They have three terminal screws: one common terminal and two traveler terminals.
The common terminal is normally darker or marked as such.
They are not marked “on” or “off” and are commonly used when rooms have two entrances, in long hallways, in stairwells, and in other similar locations.

55. Three-Way Switches
Four points should be kept in mind in wiring three- way switches:
The grounded wire from the electrical supply connects directly to the silver-colored terminal of the load and is never switched or interrupted.
The ungrounded wire from the electrical supply connects to the common terminal of the first three- way switch.

56. Three-Way Switches
Four points should be kept in mind in wiring three- way switches:
The ungrounded black wire from the brass terminal of the load connects to the common terminal of the second three-way switch.
To complete the circuit, the traveler terminals of the two three-way switches are connected together using three-wire cable (or individual wires in conduit).

57. Double-Pole Double Throw Switch
Double-pole double-throw (SPDT) switches, commonly called four-way switches, are devices used in a circuit with a pair of three-way switches.
They are used to control lighting fixtures from three or more locations.
They have four terminals, which are all traveler terminals

59. Three-Way & Four-Way
Four points should be kept in mind in wiring three- way and four-way switch circuits:
The grounded conductor from the electrical supply is connected to the silver terminal of the load.
The ungrounded conductor from the electrical supply is connected to the common terminal of one three-way switch.

60. Three-Way & Four-Way
Four points should be kept in mind in wiring three- way and four-way switch circuits:
The traveler terminals of both three-way switches are connected to the traveler terminals of the four- way switch.
The ungrounded black wire from the brass terminal of the load connects to the common terminal of the other three-way switch.

61. Planning a Project

62. Review
Give three safety tips to follow while working with electricity.
What is the purpose of a wire splice?
What are the general rules to follow in determining the number of equivalent conductors in a box?
What does NEC stand for?
List the five steps to completing an electrical project.