Download US ARMY ENGINEER SCHOOL

SUBCOURSE
EN5145
EDITION
B
US ARMY ENGINEER SCHOOL
INSTALL CONVENIENCE DEVICES
INSTALL CONVENIENCE DEVICES
Subcourse Number EN 5145
EDITION B
United States Army Engineer School
Fort Leonard Wood, Missouri 65473
3 Credit Hours
Edition Date: October 1999
SUBCOURSE OVERVIEW
This subcourse is designed to teach the knowledge necessary to describe the types and installation
procedures of switches, receptacles, and incandescent and fluorescent lighting fixtures. This subcourse
contains three lessons, each corresponding to a terminal learning objective as indicated below.
There are no prerequisites for this subcourse.
This subcourse reflects the doctrine which was current at the time it was prepared. In your own work
situation, always refer to the latest official publications.
Appendix A contains a metric conversion chart.
Unless otherwise stated, the masculine gender of singular pronouns is used to refer to both men and
women.
TERMINAL LEARNING OBJECTIVE
ACTION:
You will learn to describe the types of switches, receptacles, and incandescent and
fluorescent lighting fixtures and their installation procedures.
CONDITION:
You will be given the material in this subcourse, and an Army Correspondence
Course Program (ACCP) examination response sheet.
STANDARD:
To demonstrate competency of this task, you must achieve a minimum of 70 percent
on the subcourse examination.
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TABLE OF CONTENTS
Section
Page
Subcourse Overview ...............................................................................................................................i
Administrative Instructions ..................................................................................................................iv
Grading and Certification Instructions .................................................................................................iv
Lesson 1: Switches............................................................................................................................. 1-1
Part A: Basic Switches .......................................................................................................... 1-2
Part B: Installing Basic Switches ........................................................................................... 1-4
Part C: Types of Switches ...................................................................................................... 1-7
Practice Exercise .................................................................................................................. 1-17
Answer Key and Feedback................................................................................................... 1-19
Lesson 2: Receptacles ........................................................................................................................ 2-1
Part A: Basic Receptacles ..................................................................................................... 2-2
Part B: Special-Use Outlets.................................................................................................... 2-6
Part C: Power Outlets............................................................................................................. 2-8
Part D: Miscellaneous Receptacles...................................................................................... 2-11
Practice Exercise .................................................................................................................. 2-13
Answer Key and Feedback .................................................................................................. 2-14
Lesson 3: Lighting Fixtures ............................................................................................................... 3-1
Part A: Basic Incandescent Light Fixtures ............................................................................ 3-2
Part B: Basic Fluorescent Light Fixtures ............................................................................... 3-9
Practice Exercise .................................................................................................................. 3-20
Answer Key and Feedback .................................................................................................. 3-21
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ii
Appendix A: Metric Conversion Chart ............................................................................................ A-1
Appendix B: List of Common Acronyms ..........................................................................................B-1
Appendix C: Recommended Reading List ....................................................................................... C-1
Student Inquiry Sheets
Important: Electronic Examination Information
This paper subcourse does not contain the examination. The examination response sheet is included
only as a mailing label. You must go to the following web site to complete the examination and submit
it for grading.
http://www.aimsrdl.atsc.army.mil/accp/accp_top.htm
Registered students (those with ACCP userids and passwords) should key in the userid and password to
LOGON, then click on the EXAM button to access the examination.
Students who have not yet registered should click on the REGISTER button on the lower right corner of
the screen. Follow directions to create a userid and password. Then click on the EXAM button to
access the examination.
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EN5145
ADMINISTRATIVE INSTRUCTIONS
1.
Number of lessons in this subcourse: Three.
2.
Materials you need in addition to this booklet are a number (No.) 2 pencil and the ACCP
examination response sheet and the preaddressed envelope you received with this subcourse.
3.
Supervisory requirements: None.
4.
References: The following publications provide additional information about the material in this
subcourse. You do not need these materials to complete this subcourse.
•
FM 5-424. Theater of Operations Electrical Systems. 25 June 1997.
•
Soldier Training Publication (STP) 5-51R12-SM-TG. Soldier's Manual and Trainer's Guide,
MOS 51R, Interior Electrician, Skill Levels 1/2. 27 October 1988.
•
1999 National Electrical Code® (NEC®), available from the-National Fire Protection Association
1 Batterymarch Park
Quincy, Massachusetts 02269-9101
GRADING AND CERTIFICATION INSTRUCTIONS
Examination: This subcourse contains a multiple-choice examination covering the material in the three
lessons. After studying the lessons and working through the practice exercises, complete the
examination. Mark your answers in the subcourse booklet, and then transfer them to the ACCP
examination response sheet. Completely black out the lettered oval which corresponds to your selection
(A, B, C, or D). Use a No. 2 lead pencil to mark your responses. When you complete the ACCP
examination response sheet, mail it in the preaddressed envelope you received with this subcourse. You
will receive an examination score in the mail. You will receive three credit hours for successful
completion of this examination.
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iv
LESSON 1
SWITCHES
Critical Task: 051-246-1112
OVERVIEW
LESSON DESCRIPTION:
In this lesson, you will learn to describe the types of switches and their installation procedures.
TERMINAL LEARNING OBJECTIVE:
ACTION:
You will learn to describe the types of switches and their installation procedures.
CONDITION:
You will be given the material contained in this lesson.
STANDARD:
You will correctly answer practice exercise questions at the end of this lesson.
REFERENCES: The material contained in this lesson was derived from STP 5-51R12-SM-TG, FM 5424, and the National Electrical Code (NEC).
INTRODUCTION
This lesson, part of the military occupational specialty (MOS) 51R Skill Levels 1 and 2 course, provides
the knowledge necessary to identify and install the various types of electrical switches.
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PART A: BASIC SWITCHES
The electrical device itself (color, shape, and printed words) provides important installation information
(Figure 1-1).
Figure 1-1. Electrical switches
The UL stamp (Figure 1-2) means that the Underwriters' Laboratories, Inc. (UL) has tested the device
and found it safe for use.
Figure 1-2. Safety tested stamp
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1-2
Switches are now manufactured with green grounding screws attached. This will allow for the circuit
and the switch to be grounded without using a metal box (Figure 1-3).
Figure 1-3. Green ground screw found on most new switches
Devices may have the initials "CU/AL" imprinted on them (Figure 1-4). This means the device is
approved for copper and aluminum conductors. However, due to a change in the NEC, aluminum
conductors cannot be used for interior branch circuits. They are only approved for service-entrance
installations.
Figure 1-4. Approved conductors
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The proper wiring of a circuit is one of the most important factors for installing a device. The NEC
color code must be followed. Single-pole switches are not color-coded; both screws will be the same
color.
PART B: INSTALLING BASIC SWITCHES
Plaster ears on a device keep it even with the mounted surface. They help keep the switch flat against
the wall, even if the box is crooked. The ears can be broken off when not needed (Figure 1-5).
Figure 1-5. Plaster ears
The elongated slot in the device's mounting bracket is designed to align the switch vertically. This will
allow you to make the switch straight even when the box is not straight (Figure 1-6).
Figure 1-6. Elongated slot
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1-4
Switches come with mounting screws already attached. They are held in place with fiber washers
(Figure 1-7).
Figure 1-7. Mounting screws
Many devices have wiring holes to speed up the installation of conductors. This procedure is called
back feeding or back wiring. When troubleshooting, examine the wiring holes for loose or poor
connections. Wiring holes are used with solid wire only; good connections are not made with stranded
wires. The electrical equipment being installed determines the size of the wire/conductor that can be
back fed. Regardless of what the equipment recommends, never force a conductor into a device (Figure
1-8).
Figure 1-8. Wiring holes
The strip gauge is an installation guide found on the back of some devices. It shows how much
insulation should be removed from the conductors. The strip gauge is normally between 1/2 and 3/4
inch long. The length depends on the type of device and the manufacturer.
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When back feeding, remember to check the length of the strip gauge. Make sure that you remove the
proper amount of insulation from the conductor to make a good connection with the device (Figure 1-9).
Figure 1-9. Strip gauge
If back feeding cannot be accomplished, screw loops must be used. To make screw loops, remove
approximately 5/8 inch of insulation from the conductor. Grip the end of the conductor with needlenose pliers, and bend the conductor to form a loop. When the conductor is placed around a screw, it
must wrap in the direction the screw turns to tighten. This will cause the screw to pull the conductor in
tight when the screw is tightened (Figure 1-10).
Figure 1-10. Screw loops
All electrical devices are marked with voltage and amperage ratings. Wattage, amperage, and voltage
are all in direct relation to each other. To determine the wattage, use the formula voltage x amperage =
wattage. Thus, to figure voltage, use the formula wattage divided by amperage = voltage. An easy way
to remember this is to use the chart shown in Figure 1-11.
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1-6
To use this chart, insert the values you know and perform the mathematic calculation that is depicted.
Example: A light uses 60 watts at 120 volts. How many amperes (amps) is it using? Insert the amounts
for watts and volts. To get amps, you divide 60 by 120 and the answer is 0.5.
Figure 1-11. Pie chart
PART C: TYPES OF SWITCHES
Switches are made in assorted sizes and shapes and are rated at different voltages and amperages. A
single-pole switch is the most commonly used type of switch. Single-pole switches are used to control
devices, such as lights or receptacles, from one location (Figure 1-12).
Figure 1-12. Single-pole switch
There are simple rules of thumb, that when followed, make wiring circuits very easy. Here are the rules
of thumb for a single-pole switch:
Rule 1: The hot conductor (wire) is the only conductor that is switched. The incoming hot
conductor from the power source goes to either terminal on the switch.
Rule 2: The conductor going from the other terminal of the switch goes to the device. This
conductor must be black.
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Rule 3: The neutral conductor goes to the current-using device (such as a receptacle or a light
fixture), and it must be white or neutral gray.
There are two wiring methods that the electrician must know. The first is an "in line," and the
second is a "switch loop." If the conductors from the panel box go to the switch then to the light, it is an
in-line circuit. Follow the rules of thumb and compare them with Figure 1-13 below.
Figure 1-13. In-line circuit
A switch loop occurs when the conductors go to the light then to the switch. In Figure 1-14 notice that
the same rules of thumb were used for both wiring methods.
Figure 1-14. Switch-loop circuit
In the switch loop (Figure 1-14), the incoming black (hot) conductor is spliced to a white conductor
(making it a hot conductor) at the light to complete the run to the switch.
When a white conductor is used to carry current to a switch, as in a switch loop, the white conductor
must be permanently marked to indicate it is not neutral but is now a hot conductor. This is usually
done with black electrician's tape. Place a piece of tape at both ends of the white conductor that is being
used as a hot conductor everywhere it is exposed in every box. Do not tape a white conductor that is
being used as a neutral conductor.
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1-8
When an electrical device requires control from two different locations (for example, the top and bottom
of stairs), three-way switches are used. Three-way switches must be used in pairs. Three-way switches
have three terminals or screws on them and no ON or OFF markings on the handle (Figure 1-15).
Figure 1-15. Three-way switch
A three-way switch has three terminals, one common in brass or black and two travelers in silver, white,
or a light-colored metal. If all terminals are the same in appearance, there may be a letter beside the
common terminal (Figure 1-16).
Figure 1-16. Three-way switch with three terminals
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A three-way switch shift's the electrical path from the common terminal to one of the traveler terminals
(Figure 1-17).
NOTE: The terminal with a "C" beside it will be the common in this lesson; however, it may or
may not be marked with a "C" on an actual switch.
Figure 1-17. Three-way switch shifting the electrical path
When installing three-way switches, the silver screws on one three-way switch are wired together with
the silver screws on the other three-way switch, using conductors called travelers (Figure 1-18).
Figure 1-18. Traveler conductors
NOTE: As seen in Figure 1-18 a three-conductor cable is installed between three-way switches. A
three-conductor cable has a black, a white, and a red conductor in a protective outer sheathing.
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1-10
There are four simple rules of thumb for wiring three-way switches. They are -Rule 1: The incoming hot conductor goes to the common terminal on the nearest three-way
switch.
Rule 2: The conductor from the common terminal on the other three-way switch goes to the
device (light, receptacle). This conductor must be black.
gray.
Rule 3: The neutral conductor goes to the device. The neutral conductor must be white or neutral
Rule 4: The traveler terminals on one three-way switch go to the traveler terminals on the other
three-way switch.
Wiring a three-way lighting circuit follows the simple rules previously stated. To complete the circuit,
one of the switches is operated as shown in Figure 1-19a. In Figure 1-19a, the circuit is open and the
light will not burn. In Figure 1-19b, the circuit is complete and the light burns.
Figure 1-19a. Wiring a three-way lighting circuit
Figure 1-19b. Wiring a three-way lighting circuit
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Look at Figure 1-20 and follow the rules to wire a three-way switch system.
Figure 1-20. Wiring a three-way switch system
A four-way switch is similar to a three-way switch. Neither switch has ON and OFF markings. The
four-way switch has four terminal screws and no special markings. A four-way switch is used with two
three-way switches to control electrical equipment from three or more locations. Each additional fourway switch will give one additional control point (Figure 1-21).
Figure 1-21. Four-way switch
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1-12
A four-way switch controls the two traveler conductors by switching the electrical flow through one
terminal or the other (Figure 1-22).
Figure 1-22. Wiring a four-way switch
Follow the current flow in Figures 1-22, positions 1 and 2. You will notice that the circuit is complete in
both and the light is on. Simply changing the switch position of any of the three switches will cause the
light to go off. Change any switch position a second time, and it will turn the light back on.
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A double-thrown switch is used when two conductors must be open at the same time. Double-thrown
switches are used primarily in 240-volt lines; however, they are occasionally used when the hot and
neutral conductors must be disconnected from the device. Double-thrown switches look just like fourway switches, but they have ON and OFF markings (Figure 1-23).
Figure 1-23. Double-thrown switch controlling a duplex receptacle
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1-14
Duplex switches have two switches mounted on a single frame. Duplex switches are used to control two
separate electrical devices from a single location (Figure 1-24).
Figure 1-24. Duplex switch
A switch can also be used to control a receptacle. It is common to wire a duplex receptacle where half
the receptacle is controlled by a switch and the other half has power all the time. This type of circuit is
called "split wired." Split-wired receptacles are covered in Lesson 2.
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A switch-receptacle combination may be wired two ways: the switch controls the outlet, or the switch
controls a light and the outlet is always hot (Figure 1-25).
Figure 1-25. Switch-receptacle combination
General-use snap switches rated for alternating current (AC) only can be used for control of resistive and
inductive loads. Check the load rating of the switch. Do not overload it. A switch will not carry more
than its rated voltage.
Motors require additional amperage until the rotation speed is achieved. For this reason, motor loads
should not exceed 80 percent of the ampere (amp) rating of the switch at its rated voltage. For example,
a switch rated at 120 volts and 20 amps can only carry a 16-amp motor load.
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1-16
LESSON 1
PRACTICE EXERCISE
The following items will test your grasp of the material covered in this lesson. There is only one correct
answer for each item. When you complete the exercise, check your answer with the answer key that
follows. If you answer any item incorrectly, study again that part of the lesson which contains the
portion involved.
1.
What do the letters UL mean when printed on a switch?
A.
B.
C.
D.
2.
When installing a three-way switch, what color screw generally indicates the common terminal?
A.
B.
C.
D.
3.
1
2
3
4
How many three-way switches are needed when controlling lights from three locations?
A.
B.
C.
D.
5.
White
Black
Green
Silver
When using three-way switches, from how many locations can you control a light?
A.
B.
C.
D.
4.
Designed for uniform load
Used with aluminum conductors
Made in a union shop
Tested for safety
1
2
3
4
When installing a switch, what is the function of the strip gauge?
A.
B.
C.
D.
Removes the insulation from conductors
Holds the conductors when removing insulation
Determines the amount of insulation to be removed from conductors
Strips the insulatio n as the conductor is pushed into the switch
1-17
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6.
When installing switches, the green grounding screw allows the __________ and the
__________ to be grounded.
A.
B.
C.
D.
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switch, panel
circuit, switch
light, switch
grounding rod, grounding wire
1-18
LESSON 1
PRACTICE EXERCISE
ANSWER KEY AND FEEDBACK
Item
Correct Answer and Feedback
1.
D. Tested for safety...(page 1-2, para 2)
2.
B. A three-way switch has three...(page 1-9, para 2)
3.
B. When an electrical device requires...(page 1-9, para 1)
4.
B. A four-way switch is used with two three-way...(page 1-12, para 2)
5.
C. It shows how much insulation should be removed from conductors. (page 1-5, para 3)
6.
B. circuit, switch - switches are now manufactured...(page 1-3, para 1)
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THIS PAGE IS INTENTIONALLY LEFT BLANK.
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1-20
LESSON 2
RECEPTACLES
Critical Task: 051-246-1112
OVERVIEW
LESSON DESCRIPTION:
In this lesson, you will learn to describe the types of receptacles and their installation procedures.
TERMINAL LEARNING OBJECTIVE:
ACTION:
You will learn to describe the types of receptacles and their installation procedures.
CONDITION:
You will be given the material contained in this lesson.
STANDARD:
You will correctly answer practice exercise questions at the end of this lesson.
REFERENCES: The material contained in this lesson was derived from STP 5-51R12-SM-TG, FM 5424, and the NEC.
INTRODUCTION
This lesson, part of the MOS 51R Skill Levels 1 and 2 course, is designed to teach the knowledge
necessary to identify and install the various types of electrical receptacles.
2-1
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PART A: BASIC RECEPTACLES
Items and markings that are found on switches are also found on outlets (Figure 2-1).
Figure 2-1. Basic receptacles
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2-2
A grounded electrical system, where all components and devices are grounded, offers maximum
protection from electrical shock and equipment damage. The electrical layout in Figure 2-2 is a very
simple branch circuit, but all circuits work basically the same. Notice in the figure that the grounding
wire, which is either green or bare, is attached to the green hexagonal terminal.
Figure 2-2. Electrical layout
2-3
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The grounding blade on appliances and extension cords is designed so that plugs will be grounded
before current is applied to the blade of the male plug. As you can see in Figure 2-3, the grounding
blade is longer than the current-carrying blade.
Figure 2-3. Grounding blade
The grounding blade and the green grounding screw are tied together along with the mounting bracket.
As you can see in Figure 2-4, the grounding blade hits the grounding terminal first. This helps to
prevent electrical shook by allowing current to flow to ground in case of a fault.
Figure 2-4. Grounding terminal
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2-4
When a switch circuit with a split wired duplex receptacle is needed, the most common setup has a split
hot or ungrounded terminal and a common neutral or grounded bar. The top of the outlet is always hot.
The bottom outlet is controlled by a switch. This is useful, for example, in the kitchen. The garbage
disposal and the dishwasher are plugged into the same receptacle, the garbage disposal is controlled by
the switch and the dishwasher has constant power but the two devices share a common neutral (Figure
2-5).
Figure 2-5. Split hot terminal and common neutral bar
2-5
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PART B: SPECIAL-USE OUTLETS
A clock outlet is shown in Figure 2-6. By using a clock outlet, the entire cord is hidden from sight.
Figure 2-6. Clock outlet
Waterproof covers may be installed over standard switches and receptacles (Figure 2-7).
Figure 2-7. Waterproof covers
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2-6
A combination 250/125-volt receptacle is used when two voltages are required in a single outlet. This
type of outlet is handy when an air conditioner and a lamp are needed at the same time. This type outlet
would be powered by two different circuits (Figure 2-8).
Figure 2-8. Combination 250/125-volt receptacle
Figure 2-9 shows single-outlet receptacles. Keep the different terminal shapes in mind before trying to
plug in equipment.
NOTE: The shape and position of the terminal holes are indicators of the voltage and amperage
rating of the device.
Figure 2-9. Single-outlet receptacles
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Locking plugs and outlets are used in heavy-duty equipment installations. The curved prongs are
inserted into the curved terminals, and the plug is twisted to lock (Figure 2-10).
Figure 2-10. Locking plug and outlet
PART C: POWER OUTLETS
Usually, power outlets for ranges, welders, electrical furnaces, and clothes dryers have 220 volts or
more.
Figure 2-11. Power outlet
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2-8
Figure 2-12 shows a flush-mounted outlet. The grounding conductor is hooked to the back of the box
with the green screw. This screw can have no other purpose than to ground the device.
Figure 2-12. Flush-mounted outlet
Figure 2-13 shows a surface-mounted power receptacle. The cable used for this installation is threeconductor cable with a ground. The grounding conductor is hooked only to the outlet's steel frame.
Figure 2-13. Surface-mounted power receptacle
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Figure 2-14 shows a power plug. Notice that there are blade connections for only three conductors (two
hot and one neutral). There is no connection point for a grounding conductor.
Figure 2-14. Power plug
On ranges, dryers, ovens, and surface cooking units, the neutral terminal is also the grounding terminal.
A jumper is applied to the appliance's metal frame and to the neutral terminal to ground the appliance
(Figure 2-15).
Figure 2-15. Terminal block on appliance frame
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2-10
PART D: MISCELLANEOUS RECEPTACLES
Grounding adapter plugs are useful in older electrical systems where a grounding conductor was not
installed. Do not depend on this ground to save your life unless you check to see if the box is grounded
first (Figure 2-16).
NOTE: The NEC now requires all new installments to be grounded.
Figure 2-16. Grounding adapter plug
Use a voltmeter or a neon tester to determine whether or not a box is grounded. To accomplish the test,
touch one leg of the tester to the hot side of the receptacle and the other leg of the tester to the outlet
box. To do this, you may need to remove the cover from the receptacle. Another way to accomplish the
test is to touch the second leg of the tester to the screw holding the cover. If the tester lights, the box is
grounded (Figure 2-17).
Figure 2-17. Test for grounding
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Lightning-surge arresters provide a high-voltage surge with an easy path to the ground. The arrester is
installed on the power panel. The black conductors are hooked to the panel's hot leads. The white lead
is hooked to the ground (Figure 2-18).
Figure 2-18. Lightning-surge arrester
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2-12
LESSON 2
PRACTICE EXERCISE
The following items will test your grasp of the material covered in this lesson. There is only one correct
answer for each item. When you complete the exercise, check your answer with the answer key that
follows. If you answer any item incorrectly, study again that part of the lesson which contains the
portion involved.
1.
When using a male plug, which is the first blade to make contact with the receptacle?
A.
B.
C.
2.
What is the purpose of installing a combination duplex receptacle?
A.
B.
C.
D.
3.
To control it from two different positions
To allow for two different voltages
To provide a common neutral
To have a common bonding strip
Which conductor is attached to the green screw on a receptacle?
A.
B.
C.
4.
Hot
Neutral
Ground
Hot
Neutral
Ground
A duplex receptacle can have one outlet with constant power and the other controlled by a
switch.
A.
B.
True
False
2-13
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LESSON 2
PRACTICE EXERCISE
ANSWER KEY AND FEEDBACK
Item
Correct Answer and Feedback
1.
C. ...grounding blade is longer...(page 2-4, para 1)
2.
B. when two voltages are required...(page 2-7, para 1)
3.
C. Grounding. (page 2-3, figure 2-2)
4.
A. True. (page 2-5)
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2-14
LESSON 3
LIGHTING FIXTURES
Critical Task: 051-246-1112
OVERVIEW
LESSON DESCRIPTION:
In this lesson, you will learn to describe the types of incandescent and fluorescent lighting fixtures and
their installation procedures.
TERMINAL LEARNING OBJECTIVE:
ACTION:
You will learn to describe incandescent and fluorescent lighting fixtures and their
installation procedures.
CONDITION:
You will be given the material covered in this lesson.
STANDARD:
You will correctly answer practice exercise questions at the end of this lesson.
REFERENCES: The material contained in this lesson was derived from STP 5-51R12-SM-TG, FM 5424, and the NEC.
INTRODUCTION
This lesson, part of the MOS 51R Skill Levels 1 and 2 course, is designed to teach the knowledge
necessary to identity and install incandescent and fluorescent lighting fixtures.
3-1
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PART A: BASIC INCANDESCENT LIGHTING FIXTURES
The fixture in Figure 3-1 is made of porcelain or plastic and is designed to help keep fingers off the hot
terminal.
Figure 3-1. Incandescent light fixture
The hot terminal will be located at the bottom of the fixture; it is the center strip at the bottom of the
fixture. The neutral is the threaded side of the fixture (Figure 3-2).
Figure 3-2. Hot/neutral terminal
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3-2
Some simple lamp fixtures have their own switch or pull chain. The pull chain is the simplest type
control for a light fixture (Figure 3-3).
Figure 3-3. Light fixture with pull chain
A brass-shell socket is one of the most widely used fixtures. This socket is used in lamps and can also
be found with a twist knob or push buttons (Figure 3-4).
Figure 3-4. Brass-shell socket
3-3
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There are several different ways to hang heavy or large light fixtures in boxes. Figure 3-5 shows a strap
and a nipple being used for support. Before heavy fixtures are installed, ensure that the outlet box is
adequately attached to the structure. Most ceiling finishes do not provide adequate support for heavy
fixtures. This setup is the most widely used with a standard fixture.
Figure 3-5. Standard fixture with strap-and-nipple support
Figure 3-6 shows a fixture stud being used for extra support. The stud-and-nipple combination is a good
way to hang heavy fixtures. In this situation, the stud is attached directly through the back of the outlet
box.
Figure 3-6. Fixture stud used for extra support
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3-4
The light fixture is hung by slipping it over the nipple and holding it in place with a cap nut. When
installed correctly, the fixture is electrically safe and will retard a fire for a short time (Figure 3-7).
Figure 3-7. Installing light fixture
When hanging fixtures, some basic procedures must be followed to ensure a safe installation (Figure 38).
Figure 3-8. Safe installation procedures
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Shades or reflectors are manufactured in various shapes of metal, glass, mirrored glass, prismatic glass,
and opaque materials (Figure 3-9).
Figure 3-9. Shades and reflectors
There are five types of reflectors which correspond to the five types of lighting areas: direct, semidirect,
general diffused, semi-indirect, and indirect. In direct lighting, the reflector allows practically all light
(90 to 100 percent) to be directed toward the work area. This type of reflector creates shadows, direct
glare, and reflected glare (Figure 3-10).
Figure 3-10. Direct lighting
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3-6
As shown in Figure 3-11, a glass reflector directs 60 to 90 percent of the light toward the work area, and
10 to 40 percent toward the sides and top of the globe. The globe is good for stairways, corridors, and
storage areas.
Figure 3-11. Semidirect lighting
Figure 3-12 shows general diffused lighting. Light is equally supplied in all directions. This type of
globe can be bad because of excessive brightness and glare (Figure 3-12).
Figure 3-12. General diffused lighting
In semi-indirect lighting, some of the lighting (10 to 40 percent) is directed to the work area, but most of
the light (60 to 90 percent) goes to the upper walls and ceilings. This fixture gives a good overall
lighting with low surface brightness and low glare (Figure 3-13).
Figure 3-13. Semi-indirect lighting
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In indirect lighting, most of the light (90 to 100 percent) is reflected onto the ceiling and the entire
ceiling becomes a light source, thus eliminating shadows and glares. Indirect lighting is good in an
office, a schoolroom, or in areas used for close work where eye strain may occur (Figure 3-14).
Figure 3-14. Indirect lighting
Incandescent light fixtures are manufactured in different designs, sizes, and shapes. They have basic
components and can be mounted on ceilings and walls (Figure 3-15).
Figure 3-15. Incandescent light fixtures
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3-8
PART B: BASIC FLUORESCENT LIGHT FIXTURES
Fluorescent lighting is highly efficient and gives two or three times as much light per watt as
incandescent lights. Fluorescent lights also produce less heat because they use less current (Figure 316).
Figure 3-16. Fluorescent light
The basic components of fluorescent lighting are-• The box or the channel casement (Figure 3-17). (The channel is made of sheet metal to help
prevent fire.)
•
The ballast and the lamp holder (Figure 3-18).
•
The lid (Figure 3-19).
•
The tube (Figure 3-20).
• External starters with the ballast (found in some older fluorescent preheated fixtures)(Figure 321). (Starters are rated by their wattage capacity. Make sure that you install the proper starter.)
Figure 3-17. Box or channel casement
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Figure 3-18. Ballast and lamp holder
Figure 3-19. Lid
Figure 3-20. Tube
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Figure 3-21. External starters
The schematic layouts for fluorescent fixtures are basically the same. The preheated system uses a
starter in conjunction with the ballast to get the tube glowing (Figure 3-22).
Figure 3-22. Schematic layout for fluorescent fixtures
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The instant-start fluorescent fixture does not have a starter. It has a special tube and a ballast which
produce 400 to 1,000 volts. This type of tube is called a single-contact pin type because it has a single
electrode pin on each end (Figure 3-23).
Figure 3-23. Instant-start fluorescent fixture
Rapid-start fluorescent fixtures have a ballast which works at lower voltages than other types. An
externally grounded metal plate helps the tube start up (Figure 3-24).
Figure 3-24. Rapid-start fluorescent fixture
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Different-size tubes can have from 4 to 245 watts and can be from 6 to 96 inches long. Tubes can be
straight, U-shaped, or round. Be careful when handling fluorescent tubes, since they are easily broken
(Figure 3-25).
Figure 3-25. Tubes
Fluorescent tubes come in different colors. The color variation is determined by the type of gas
contained in the tube. Table 3-1 explains this further.
Table 3-1. Fluorescent lighting colors and characteristics
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Ballasts supply the proper voltage and limit the current supplied to the tube (Figure 3-26).
Figure 3-26. Ballast
A single-tube fluorescent fixture is shown in Figure 3-27. This fixture will be a simple wiring job.
Figure 3-27. Single-tube fluorescent fixture
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Two-tube fluorescent fixtures are the most common and are used for both two-tube and four-tube
fixtures. To wire a four-tube fixture, 2 two-tube ballasts are used (Figure 3-28).
Figure 3-28. Two-tube fluorescent fixture
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Figure 3-29 shows a three-tube fluorescent fixture. Notice the difference in the amount of wires.
Figure 3-29. Three-tube fluorescent fixture
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Types of ballasts differ with each manufacturer. Check each ballast to be sure that it has a wiring
diagram on it (Figure 3-30).
Figure 3-30. Types of ballasts
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The pin arrangement should always be checked for adaptability (Figure 3-1).
Figure 3-31. Pin arrangement
Troubleshooting fluorescent faults is performed by using common sense, knowledge of fluorescent
fixtures, and a troubleshooting chart (Table 3-2).
Table 3-2. Troubleshooting chart for fluorescent lighting
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The average life of fluorescent ballasts and tubes is 12 years or about 60,000 hours. Most ballasts are
designed to operate at 90°C. A rise of 10°C can reduce a ballasts life by one half.
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LESSON 3
PRACTICE EXERCISE
The following items will test your grasp of the material covered in this lesson. There is only one correct
answer for each item. When you complete the exercise, check your answer with the answer key that
follows. If you answer any item incorrectly, study again that part of the lesson which contains the
portion involved.
1.
What is the weight, in pounds, of a fixture that must be supported independently of a box?
A.
B.
C.
D.
2.
What type of lighting reflector is required to direct 95 percent of the total light toward the
ceiling?
A.
B.
C.
D.
3.
Direct
Semidirect
Indirect
General diffused
What is the most commonly used pin type for instant-start fluorescent fixtures?
A.
B.
C.
D.
4.
40
30
20
10
Two pin
Recessed double contact
Single contact
Four pin
The type of gas contained in the tube determines the tube's color.
A.
B.
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True
False
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LESSON 3
PRACTICE EXERCISE
ANSWER KEY AND FEEDBACK
Item
Correct Answer and Feedback
1.
D. 10 pounds. (page 3-5, figure 3-8)
2.
C. Indirect. (page 3-8, para 1)
3.
C. Single contact. (page 3-12, para 1)
4.
A. True. (page 3-13, para 2)
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