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EN5140 B





Subcourse EN 5140
United State (US) Army Engineer School

Fort Leonard Wood, Missouri 65473
2 Credit Hours
Edition Date: September 1999

This subcourse is designed to teach the student the identification of electrical symbols, the use of electrical materials, and the skills necessary to extract information from a electrical print and legend.
There are no prerequisites for this subcourse.
This subcourse reflects the doctrine which was current at the time this subcourse was prepared. In your own work, always refer to the latest official publications.
Unless otherwise stated, the masculine gender of singular pronouns is used to refer to both men and women.
ACTION: You will learn to identify electrical symbols; extract information from an electrical print and legend; and list electrical materials by type, size, and amount.
CONDITION: You will be given this subcourse and an Army Correspondence Course Program (ACCP) examination response sheet.
STANDARD: To demonstrate competency of this task, you must achieve a minimum score of 70 percent on the subcourse examination.

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Section Page
Subcourse Overview i
Administrative Instructions iii
Grading and Certification Instructions iii
Lesson: Prepare an Electrical-Materials Takeoff List., 1
Part A: Electrical-Symbol Identification 2
Part B: Print Verification 6
Part C: Print Legends 8
Part D: List of Electrical Materials 14
Part E: Service-Entrance Requirements 15
Practice Exercise 17
Answer Key and Feedback 22
Appendix A: List of Common Acronyms A-1
Appendix B: Recommended Reading List B-1
Appendix C: Metric Conversation Chart C-1
Student Inquiry Sheets

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Examination: This subcourse contains a multiple-choice examination covering the material in the lesson. After studying the lesson and working through the practice exercise, complete the examination. Mark your answers in the subcourse booklet, 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 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 two credit hours for successful completion of this examination.

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Critical Task: 051-246-1101

In this lesson, you will learn to identify electrical symbols, interpret electrical prints, use print legends, and prepare an electrical-materials takeoff list (MTOL).
ACTION: You will learn to identify and extract information from an electrical print and legend and prepare an electrical MTOL.
CONDITION: You will be given the material contained in this lesson. You will work at your own pace and in your own selected environment with no supervision.
STANDARD: You will correctly answer questions on the practice exercise at the end of the lesson.
REFERENCES: The material contained in this lesson was derived from FM 5-424, STP 5-51R12-SM-TG, TM 5-303, and TM 5-704.
Before beginning an electrical job, materials must be ordered. Materials are ordered on a bill of materials (BOM). The BOM is based on the MTOL. In order to prepare an electrical MTOL, you must know how to identify electrical symbols and extract information from an electrical print and legend.

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1. Electrical symbols are divided into four areas: panels and circuits, switches, convenience outlets, and general outlet.
a. Figure 1 shows electrical symbols used in panel and circuit outlets; Figure 2, page 3, shows their common equipment use.

Figure 1. Electrical symbols in panel and circuit outlets

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Figure 2. Equipment with panel and circuit outlets
b. There are about 20 different switch symbols. Switches are generally characterized by the letter "S" and then further identified by an additional letter or number. The symbols used in this subcourse are those most applicable to military use. Figure 3, page 4, shows electrical symbols in switch outlets; Figure 4, page 4 shows their common equipment use.
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Figure 3. Electrical symbols in switch outlets

Figure 4. Equipment with switch outlets
c. Figure 5 shows electrical symbols in convenience outlets; Figure 6 shows their common equipment use.
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Figure 5. Convenience outlet symbols

Figure 6. Equipment with convenience outlets
d. General outlets have the widest variety of symbols. In some cases, the same symbol may have more than one meaning. Figure 7 shows symbols in general outlets; Figure 8, page 6, shows their common equipment use.

Figure 7. Electrical symbols in general outlets
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Figure 8. Equipment with general outlets
2. Electricians must be able to read and understand an electrical print in order to verify its completeness and correctness. Each print has areas known as the legend and the diagram. The legend contains detailed and general information as well as the scale of the print. The diagram contains electrical symbols ad indicates where each device is to be installed.
a. Figure 9 is an incomplete print of an electrical-wiring diagram. In the upper left corner of circuit D15, one switch is shown. Several switches are needed for this circuit. This could have several meanings, either one switch controls all the lights on the circuit, one switch controls all the lights in one room, or one switch controls all the lights in both rooms. Any questions or problems with prints should be addressed immediately to avoid project delays.
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Figure 9. Incomplete print of an electrical-wiring diagram

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b. One method of performing a complete check of a print is to isolate an individual circuit or run. Once isolated, follow the entire circuit, checking for errors. Continue this process until all circuits are checked.
c. Refer to Figure 10. Begin with circuit A1, indicated by the small home-run arrow, and follow the line in the opposite direction to the end of the circuit. Circuit A1 is missing switches for the six lights in the large room and the light in the small room. It is also missing a junction box where circuits A1 and A2 join. The electrician should resolve any questions or misunderstandings about the prints before ordering the materials or beginning the work.

Figure 10. Isolated circuit
3. General information is found in the legend. The legend is located in the lower, right corner of the electrical print. The schedule of drawings, as shown in Table 1, is the part of the legend that identifies all the drawings by number, gives the description of each, and lists the number of sheets per drawing. The general notes also provide additional information, but normally this information pertains to the overall electrical project rather than individual circuits.

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Table 1. Print legend

4. The print scale can be either graphic or ratio (Figure 11). Each segment of line in the graphic scale equals 1 foot of actual space; on a ratio scale, 1/8 inch equals 1 foot of actual space.

Figure 11. Print scale
5. Additional instructions are found on the schedule of equipment, electrical notes, electrical legend, and panelboard schedule.
a. The schedule of equipment (Table 2, page 10) lists the equipment needed to complete a project. Numbers are used to represent each piece of equipment. These numbers are then placed on the print where the equipment is to be used. The schedule of equipment also lists the horsepower of motors, phase, and quantity of each equipment type, depending on the size of the structure.
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NOTE: To allow for easier reading, some item numbers shown in Table 2 have been removed from Figure 9, page 7.
Table 2. Schedule of equipment

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b. Electrical notes (Table 3) list specific instructions on special wiring requirements and equipment use.
Table 3. Electrical notes

c. The electrical legend (Figure 12) lists the interpretations for various electrical systems on the print. Since some electrical symbols have more than one meaning, the electrician can refer to the legend ad determine what device to install.

Figure 12. Electrical symbols in the legend
d. The panelboard schedule (Table 4, page 12) contains information such a wire size, circuit number, breaker size, load per circuit, and service entrance (SE) requirements, including demand and connected load.

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Table 4. Panelboard schedule

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e. The wiring diagram (Figure 13) uses symbols to show the location of fixtures and devices in the electrical system.

Figure 13. Wiring diagram
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6. The first task in an electrical job is to prepare an electrical MTOL. To do this, you must know how to extract information from the wiring diagram and legend. To determine installation needs for branch circuits, look for items such as switch types, receptacles, lighting fixtures, cable, conductors, and conduit.
7. The wiring diagram and legend are necessary to correctly identify symbols and understand wiring requirements. Using the wiring diagram (Figure 13, page 13), electrical notes (Table 3, page 11), and the panelboard schedule (Table 4, page 12), compile an MTOL as shown in Table 5. Begin this task by identifying the wires needed for branch circuits.
a. The size and type of conductors are not always shown in the wiring diagram. This information may also be found in the electrical notes or the panelboard schedule. Item 3 on the electrical notes states that branch circuit conductors should be No. 12. This means that all wiring should be 12/2 or 12/3 nonmetallic (NM), nonmetallic corrosive (NMC)(corrosion-resistant), or underground feeder (UF) cable unless otherwise indicated; however, the panelboard schedule shows that circuits E4, ES, and E7 require 10-gauge conductors. When preparing an MTOL, look at each circuit individually and determine what is needed to install each. In this example, circuit E7 requires 10-gauge, three-wire conductors to complete. Item 2 in the electrical notes states that if a conductor is size No. 2 or smaller, NM, NMC, or UF cable will be used. Begin the MTOL as shown in step 1.
b. A special-purpose outlet is needed on circuit E7. Add to the MTOL as shown at step 2. The panelboard schedule shows that circuit E7 requires a 30-amp, three-pole circuit breaker. Add this information to the MTOL as shown at step 3.
c. Locate circuit E8 on Figure 13, page 13. The wire gauge is not listed on the print, so you must look at the panelboard schedule. The panelboard schedule shows that circuit E8 requires 12-gauge conductors. Add this information to the MTOL as shown in step 4.
d. Follow the line representing circuit E8. There are 4 fluorescent and 11 incandescent lighting fixtures listed in this circuit. Add this information to the MTOL as shown in steps 5 and 6.
e. Two three-way switches are shown in circuit E8. Add them to the MTOL as shown in step 7.
f. Three-wire conductors are shown in circuit E8. Remember from the electrical notes (Table 3, page 11) that NM, NMC, or UF cable is used on two- or three-cable branch circuits. Add this entry to the MTOL as shown in step 8.
g. Make sure that you check the entire circuit. Circuit E8 continues on the right side of Figure 13. Twelve-gauge thermal/heat/water (TEW) conductors and 1/2-inch conduit are required. Add these items to the MTOL as shown in step 9.
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NOTE: If you feel that there is a better way to run a circuit than that listed on the diagram, discuss alternatives with your supervisor.
h. Refer to the panelboard schedule for the type of breaker required in circuit E8. The panelboard schedule shows a three-pole, 20-amp breaker. Add this entry to the MTOL as shown in step 10.
i. To complete the MTOL, repeat the procedures shown for circuits E7 and E8 on all remaining circuits.
NOTE: Do not list supply items on the MTOL. Items such as staples, straps, boxes, and wire nuts will be calculated and ordered on the BOM.
Table 5. Electrical MTOL

8. Continue to refer to the wiring diagram (Figure 13, page 13), electrical notes (Table 3, page 11), and panelboard schedule (Table 4, page 12) to add the SE requirements to the MTOL (Table 5, page 15).
a. Item 1 on the electrical notes status that the SE conductors should be type THW single-conductor copper cables, in heavy, wall, galvanized-steel conduit. Panelboard E shows that we need phase 3, four-wire conductors, run in 1 1/2-inch conduit. Add both of these entries to the MTOL as shown at step 11.
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b. Panelboard E also requires a 100-amp main breaker and room for at least 10 branch circuit breakers. Add this item to the MTOL as shown at step 12.
9. Grounding requirements, which vary from state to state and county to county, are not listed on the MTOL. Electricians should be familiar with local codes for grounding and take the codes into consideration before ordering grounding materials and equipment. Order grounding materials when preparing the BOM.

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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 key that follows. If you answer any item incorrectly, study again that part which contains the portion involved.
1. Match the symbols with the correct definition by placing the correct number in the blank provided.

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2. Refer to Figure 14. What materials are needed to install circuit A6?

Figure 14. Sample wiring diagram No. 1
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3. Refer to Figure 15. Identify one major error in circuits A1 and A2.

Figure 15. Sample wiring diagram No. 2
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4. Refer to Figure 16. What type of lighting fixture is called for in circuit D15?
A. Weathertight

B. Incandescent

C. Fluorescent

D. Explosion proof

Figure 1. Sample wiring diagram No. 3
5. Refer to Figure 16. List the types of switches, outlets, and conductors needed in circuit D15.

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