Solution and Answer Guide Electrical Wiring Commercial 18th Edition by Phil Simmons, Ray C. Mullin,

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 1: COMMERCIAL BUILDING PLANS AND SPECIFICATIONS

TABLE OF CONTENTS Review ..................................................................................................................................1

Note to instructor: It is recommended that students be required to respond, where appropriate, with answers that are complete sentences.

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

1.

What section of a commercial building’s specification contains a list of contract documents?

Answer: A list of the contract documents is contained in General Clauses and Conditions. A listing of the Commercial Building contract documents is presented in this chapter under the heading “Commercial Building Plans.” The instructor may wish to have the students check over this listing and compare it with the plans provided.

2. The requirement for temporary light and power at the job site will be found in what portion of a commercial building’s specification?

Answer: The Supplementary General Conditions specifies the job site requirements for temporary light and power. In some contracts, this electrical system becomes the responsibility of the general contractor; in other contracts, it is the electrical contractor’s responsibility to install and maintain the temporary electrical system. The instructor may wish to refer the student to NEC Article 590 and discuss the requirements in detail.

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Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

3. The electrician uses the Schedule of Working Drawings for what purpose?

Answer: The electrician uses the Schedule of Working Drawings to determine whether all of the drawings are at hand. The information on “the other sheets” may be very important, especially in coordinating with other contractors.

4. Complete the following items by indicating the letter(s) designating the correct source(s) of information: No.

Answer

Item

Information

4.

Sections

Ceiling height

Sections, Sheet A6

5.

Electrical symbol schedule

Electrical receptacle style

Electrical symbol schedule, Chapter 2, Figure 2–6

6.

Electrical layout drawings

Electrical outlet location

Electrical layout drawings, Sheets El, E2, and E3

7.

Elevations

Exterior wall finishes

Elevations, Sheets A4 and A5

8.

Site plan

Grading elevations

Site plan, Sheet A4

9.

Electrical layout drawings

Panelboard schedules

Electrical layout drawings, Sheet E4

10.

Architectural floor plan

Room width

Architectural floor plan, Sheets Al, A2, and A3

11.

Architectural floor plan

Swing of door

Architectural floor plan, Sheets Al, A2, and A3

12.

Sections

View of interior wall

Sections, Sheet A6

Match the items on the left with those on the right by writing the letter designation of the appropriate organization from the list on the right.

13.

NEC

Electrical Code

National Electrical Code (NEC)

14.

IAEI

Electrical inspectors

International Association of Electrical Inspectors (IAEI)

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

15.

NFPA

Fire codes

National Fire Protection Association (NFPA)

16.

IESNA

Lighting information

Illuminating Engineering Society of North America (IESNA)

17.

UL

Listing service

Underwriters Laboratories, Inc. (UL)

18.

NEMA

Manufacturers’ standards

National Electrical Manufacturers Association (NEMA)

19.

PE

Seal

Professional Engineer (PE)

Match the items on the left with those on the right by writing the letter designation of the proper level of NEC interpretation from the list on the right.

20.

with special permission

Allowed by the Code

Shall be permitted, or Shall not be required, NEC

21.

with special permission

May be done

Shall be permitted, or Shall not be required, NEC

22.

shall

Must be done

Shall, National Electrical Code

23.

shall

Required by the Code

Shall, National Electrical Code

24.

never

Up to the electrician

Shall be permitted, or Shall not be required, NEC

25. Find NEC 250.52(A)(5) and record the first four words.

Answer: The first four words of NEC 250.52(A)(5) are Rod and pipe electrodes.

Show required conversion calculations for problem 26 and problem 27.

26. Luminaire style F is four feet long. The length in SI units, as specified by the NEC, is Answer: The length in SI units is 1.22 m; 4 ft × 0.3048 m/ft = 1.2192 m. As will be discussed later, this luminaire is now called a 4 by 2 or the equivalent 1200 by 600 in metric terms. This question assumes that the luminaire is exactly 4 ft long.

27. The gross area of the drugstore basement is 1395 square feet. The area in square meters is Answer: The area in SI units is 129.7 sq. m; 1395 sq. ft × 0.093 sq. m/sq. ft = 129.7 sq. m.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

To answer Questions 28–31, refer to the Plans included with this book. Determine the Following dimensions. Write the dimensions using unit names, not symbols (for example, 1 foot, not 1’), and indicate the source of the information.

28. What is the inside clear distance of the interior stairway to the drugstore basement?

Answer: The inside clear distance of the interior stairway to the Drugstore basement is 4 ft 0 in. (1.22 m), as scaled from Sheet A2.

29. What is the gross square footage of each floor of the building?

Answer: The gross area of each floor of the building is 60 ft × 43 ft = 2580 sq. ft (18.82 m × 13.1 m = 246.5 sq. m), as taken from Sheets Al, A2, and A3.

30. What is the distance in the drugstore from the exterior block wall to the block wall separating the drugstore from the bakery?

Answer: The distance from the exterior block wall in the Drugstore to the block wall separating the Drugstore from the Bakery is 21 ft 7 in. (6.58 m), as shown on Sheet A2.

31. What is the finished floor to finished ceiling height on the second floor?

Answer: The finished floor to finished ceiling height on the second floor is 8 ft 6 in.

(2.59 m), as available from East and West Elevations A41–2, and Sheet A6, Cross Sections A–A and B–B. For problems 32–34, cite the NEC source. We will show the method of using the NEC Index for the first two questions in Chapter 1 and will provide this same method of locating requirements in other chapters of this book.

32. The standard ampere ratings for fuses and fixed trip circuit breakers.

Answer: The standard ampere rating for fuses and fixed trip circuit breakers is given in NEC Table 240.6(A).

To find this information in the Index of the NEC, locate “Circuit breakers, Article 240, and locate Rating and under that locate Fixed-Trip circuit breakers, 240.6(A)…” This will provide the Section number for the ratings.

33. The minimum bending radius for metal-clad cable with a smooth sheath with an external diameter of 1 in.

Answer: The minimum bending radius for metal clad cable with a smooth sheath with an external diameter of 1 in. (size 1) is given in NEC 330.24(A)(2) as 12 times the diameter.

To find this information in the Index of the NEC, locate “Metal-clad Cable, Article 330, and under that locate “Bends, 330.24.” 330.24(A)(2).

34. The permission to use splices in busbars as grounding electrode conductors.

Answer: The permission to use splices in busbars as a grounding electrode conductor is given in NEC 250.64(C)(2).

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Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

35. a) Where is the sump pump in the Commercial Building located? __________________ b) To what branch circuit is the sump pump connected? _________________________ Answer: a. The sump pump is located in the Owner’s space in the floor of the basement. b. The sump pump is connected to circuit 11 in the Owner’s panelboard.

36. Write a letter to one of the organizations listed in this unit requesting information about the organization and the services it provides.

Answer: Write a letter to one of the organizations listed in Chapter 1, requesting information about the organization and the services it provides.

It is suggested that the instructor assign each student an organization to contact to provide the class with information about several organizations. Students should be encouraged to investigate the proper form of a business letter. They should be alerted that a poorly written letter is unlikely to get a response. If possible, the letter should be on business letterhead stationery. One alternative is for the students to make arrangements with employers to send the letters on company stationery.

37. The temperatures from an arc flash can reach approximately ________________°F. Answer: The temperatures from an arc flash can reach approximately 35,000°F. 38. The Occupational Safety and Health Act (OSHA) Code of Federal Regulations (CFR) Number 29, Subpart S, in paragraph ____________________ discusses the training needed for those who face the risk of electrical injury.

Answer: The Occupational Safety and Health Act (OSHA) Code of Federal Regulations (CFR) Number 29, Subpart S, in paragraph 1910.332, discusses the training needed for those who face the risk of electrical injury.

39. The NEC defines a qualified person as ________________________________________ Answer: The NEC defines a Qualified Person as One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved, Article 100.* 40. According to NFPA 70E Article 110, an electrician is qualified to do any and all electrical wiring tasks. True _____ False _____ Answer: According to NFPA 70E Article 110, an electrician is qualified to do any and all electrical wiring tasks. False.

41. Live parts to which an employee may be exposed are required to be de-energized before the employee works on or near them unless _________________.

Answer: Live parts to which an employee may be exposed are required to be deenergized before the employee works on or near them, unless the employer can demonstrate that de-energizing introduces additional or increased hazards.

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Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 1: Commercial Building Plans and Specifications

42. The OSHA regulations provide rules regarding _____________ to make sure that the electrical equipment being worked on will not inadvertently be turned on while someone is working on the supposedly dead equipment.

Answer: The OSHA regulations provide rules regarding lockout and tagout (LOTO) to make sure that the electrical equipment being worked on will not inadvertently be turned on while someone is working on the supposedly dead equipment.

43. Nearly _____ % of the electrocutions each year are from 120-volt systems.

Answer: Nearly 50% of the electrocutions each year are from 120-volt systems.

44. NEC 590.6(A) and (B) require that ground-fault, circuit-interrupter protection for personnel be provided for all 125-volt, single-phase, ________________-ampere receptacle outlets used for temporary wiring.

Answer: NEC 590.6(A) and (B) require that ground-fault circuit-interrupter protection for personnel be provided for all 125-V, single-phase, 15-, 20- and 30-A receptacle outlets used for temporary wiring.

45. Section _______ of the NEC contains important rules on the arrangement of the NEC. Answer: Section 90.3 of the NEC contains important rules on the arrangement of the NEC. 46. The National Electrical Code is updated on a ________ -year cycle. At the first meeting of the revision cycle, the Code Panel considers the ________ ________ that were submitted. At the second meeting, ________ ________ are considered.

Answer: 3, Public, Inputs, Public, Comments *Source NFPA 70-2023 .

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 2: Reading Electrical Working Drawings—Entry Level

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 2: READING ELECTRICAL WORKING DRAWINGS—ENTRY LEVEL

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Answer problems 1–7 by identifying the symbol and the type of installation (wall, floor, or ceiling) for the boxes. ________________________________________ Answer: Duplex receptacle 15- or 20-A: wall installation: see Figure 2–6 and Specifications. ________________________________________ Answer: Duplex receptacle on emergency/standby circuit: wall installation: see Figure 2–6 and Specifications. ________________________________________ Answer: Single-pole, key-operated switch with pilot light; wall installation; see Figure 2–7. ________________________________________ Answer:

Surface-mounted luminaire (fixture); ceiling installation; see Figure 2–5.

________________________________________

Answer:

Telephone outlet ; wall installation; see Figure G–6 in Appendix G.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 2: Reading Electrical Working Drawings—Entry Level

________________________________________ Answer: Figure 2–8.

Disconnect switch; unfused type, size as indicated on drawings, see

________________________________________ Answer:

Lighting outlet; wall installation; see Figure 2–5.

How many duplex receptacle outlets are to be installed in the Drugstore basement storage area? ______________________________________________________________ Answer: Eight duplex receptacles are to be installed in the Drugstore basement storage area; this information is found on drawing El. The duplex receptacle outlets in the Drugstore basement storage area are supplied from which panelboard? ____________________________________________________ Answer: The duplex receptacle outlets in the Drugstore basement storage area are to be supplied from the Drugstore panelboard located on the first floor. This information is found on drawing El, in the worksheet for the Drugstore included in the Specifications in Appendix A, and in the panelboard schedule shown on drawing E4.

The duplex receptacle outlets in the Drugstore basement storage area are to be connected to which branch circuit(s)? __________________________________________ Answer: The duplex receptacle outlets in the basement storage area for the Drugstore are to be connected to branch circuit 9. This information is found on drawing El, in the worksheet for the Drugstore included in the specifications in Appendix A, and in the panelboard schedule shown on drawing E4.

How many lighting outlets are to be installed in the Drugstore basement storage area? _______________________________________________________________________________ Answer: Nine lighting outlets are to be installed in the Drugstore basement storage area. This information is found on drawing El. What style(s) of luminaires is/are to be installed in the Drugstore basement storage area? _________________________________________________________________________ Answer: Style B and B-EM luminaires are to be installed in the Drugstore basement.

This information is found on drawing El and in the luminaire schedule included in Appendix A. How may the luminaires for the Drugstore basement storage area be installed?

Answer: The style B and B-EM luminaires may be either surface mounted or chainhung. This information is found in the Luminaire/Lamp/Ballast Schedule in Table A-11 in Appendix A.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 2: Reading Electrical Working Drawings—Entry Level

List the luminaires required for the Drugstore including the basement storage area.

Give the style, count, and mounting method for each style.

Answer: Information for responses to Question 14 can be located on drawing E2, and in the Luminaire/Lamp/Ballast Schedule in Table A-11 in Appendix A. Style B

Count 5

Mounting method Surface or chain hung

Style B-EME

Count 4

Mounting method Surface or chain hung

Style E

Count 2

Mounting method Recessed

Style E-EM

Count 1

Mounting method Recessed

Style E2

Count 3

Mounting method Recessed

Exit

Count 2

Mounting method Ceiling, wall, or comer end mounting

Style G

Count 7

Mounting method Recessed troffer for grid ceiling

Style G-EM

Count 2

Mounting method Recessed troffer for grid ceiling

Style I

Count 27

Mounting method Recessed strip light

Style N

Count 2

Mounting method Surface

Style Q

Count 2

Mounting method Recessed

From the information you have studied about the various electrical symbols, identify the following symbols, some of which are not shown in the symbol schedule.

Answer: One wall-mounted exit sign with directional arrow and one ceiling-mounted exit sign with directional arrow. See Figure 2–4.

Multioutlet assembly, devices as indicated. See Figure 2–6.

Telephone/data outlet floor type, flush mount. See Figure G-6 in Appendix G Fire-alarm horn and strobe. See Figure G–4 in Annex G.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 2: Reading Electrical Working Drawings—Entry Level

What is the source of supply and circuit numbers for the air-conditioner compressor unit for the Drugstore?

Answer: Shown as circuits 14-16-18 from the Drugstore panelboard on drawing E2, on the worksheet in Appendix A, and on the panelboard schedule on drawing E4.

In the spaces, draw in the symbol for each of the following: a. Wall-mounted exit luminaire ______________________ b. Bollard-type site luminaire ______________________ c. A double duplex receptacle ______________________ d. A key-operated switch ______________________ e. Enclosed circuit breaker with a 400 A frame size and 350 A trip ____________________ f.

A fluorescent dimmer switch ______________________

g.

A 3-HP motor ______________________

h. A surface-mounted panelboard ______________________ i.

A flush panelboard on normal and generator feeder ___________

j.

A capacitor ______________________

k. One-line diagram symbol for a corner-grounded delta transformer ______________________ l.

One-line diagram symbol for a system- or equipment-grounding connection ______________________

m. One-line diagram symbol for a start push button and a stop push button ______________________

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 2: Reading Electrical Working Drawings—Entry Level

Answer: In the spaces, draw in by hand the symbol for each of the following:

The load calculation for the Bakery and the panelboard schedule are located in ____________________________________________________________________ Answer: Appendix A

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 3: General Requirements for Conductors

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 3: GENERAL REQUIREMENTS FOR CONDUCTORS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

1.

The proper size and type of conductor must be installed to comply with the manufacturer’s installation instructions. (True) (False) (Circle the correct answer.)

Answer: True

2. The definition of ampacity is “The __________________ current, in amperes, that a conductor can carry __________________ under the __________________ of use without exceeding its __________________ rating.” (Fill in the blanks with the appropriate words.)

Answer: maximum, continuously, conditions, temperature 3. Ampacities of NEC Table 310.16 is based on not more than __________________ currentcarrying conductors in a raceway, cable, or earth based on an ambient temperature of __________________ degrees F. (Fill in the blanks with the appropriate words.)

Answer: 3, 86 4. Conductors with a -2 insulation designation have a (higher) (lower) ampacity in a wet location than do conductors without the designation. (Circle the correct answer.)

Answer: higher 5. For the same size of conductor, aluminum conductors have a (higher) (lower) ampacity then do copper conductors. (Circle the correct answer.)

Answer: lower 6. Describe what the following conductor designation means when it is printed on the insulation; RHH/RHW/USE ______________________________________________________. _______________________________________________________________________________ _______________________________________________________________________________

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 3: General Requirements for Conductors

Answer: These are considered as triple-rated conductors and can be used at any of the locations designated by the Type of insulation. Type RHH is permitted to be used in dry and damp locations with a 90°C ampacity. Type RHW is permitted to be used in dry, damp, or wet locations at 75°C ampacity. Type USE is permitted to be used as underground service-entrance cable – single conductor at 75°C ampacity. See NEC Table 310.4(A).

7. Which one of the following two insulation types is more likely to soften when heated?

THWN XHHW (Circle the correct answer.)

Answer: THWN 8. The ampacity of 400 kcmil copper conductors is as follows: (Fill in the blanks with the correct value.)

With 60°C insulation ______________________________ With 75°C insulation ______________________________ With 90°C insulation ______________________________ Answer: 280,335,380 9. The correction factor for a conductor with 75°C insulation that is installed in a 104°F ambient temperature is ______________________. (Fill in the blank with the correct value.)

Answer: 0.88 Table 310.15(B)(1)(1) 10. The corrected ampacity of a 250 kcmil copper conductor that has Type THWN insulation that is installed in an ambient temperature of 96°F is ______________________ amperes.

Answer: 255 amperes × 0.88 = 224 amperes 11. If nine current-carrying conductors are installed in one raceway for a length greater than 24 in., the ampacity must be reduced to ______________________ percent.

Answer: 70%, Table 310.15(C)(1) 12. If nine current-carrying conductors are installed in a raceway that is installed in an ambient temperature of 104°F the following adjustment and correction factors must be applied: (Fill in the blanks with the correct number.) (a) ______________________ percent for the number of current-carrying conductors (b) ______________________ percent for the elevated ambient temperature Answer: (a) 0.70, (b) 0.88 13. If raceways or cables are installed on or within ¾ in. of a rooftop with sunlight exposure, the following temperature must be added to the ambient temperature for the application of the correction factor: ______________________ °F (Insert the correct number.)

Answer: 60°, 310.15(B)(2) In Chapter 3, change Question 13 to read as follows: If raceways conduits or cables are installed less than ¾ in. of a rooftop….

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 3: General Requirements for Conductors

14. Indicate whether the following conductor insulations that are installed in raceways or cables within ¾ in. of a rooftop having sunlight exposure are required to have the correction factor applied: (Circle the correct answer/answers.) a. THW

(Yes)

(No)

b. THWN

(Yes)

(No)

c. THWN-2

(Yes)

(No)

d. USE-2

(Yes)

(No)

e. XHHW

(Yes)

(No)

f.

(Yes)

(No)

XHHW-2

Answer: a. Yes, b. Yes, c. Yes, d. Yes, e. Yes, f. No In Chapter 3, change Question 14 to read as follows : Indicate whether the following conductor insulations that are installed in raceways conduits or cables less than ¾ in. of a rooftop….

15. If a conductor is installed so that not more than 50% is in a cooler area and 50% is in a hotter ambient temperature, the ampacity determined in the cooler area can be used for the entire run. (True) (False) (Circle the correct answer.)

Answer: False, 310.14(A)(2) Exception 16. Conductors with dual ratings, such as THHN/THWN-2 are rated for __________________ °C in both ______________________ and ______________________ locations.

Answer: 90, Wet and Dry 17. Where the same conductor encounters two different temperature environments, the portion of the conductor with the higher ampacity (lower temperature) is permitted to be used where the portion with the lower ampacity (higher temperature) is not more than ______________________ and not more than ______________________ of the total circuit length.

Answer: 10 ft., 10% 18. If eight two-wire Type MC cables that have 12 AWG conductors are installed for a length greater than 24 in. without maintaining spacing, the ampacity must be reduced by ______________________ percent. (Insert the correct number) Answer: 0 percent, 310.15(C)(1)(d) 19. Spare conductors installed in a raceway are required to be counted. (Circle your answer or answers.) a. For conductor fill b. For the number of current-carrying conductors c. Neither of these For questions 20 through 23, assume that nonlinear loads are not a major portion of the load on the branch circuit: Answer: a. and b. Table 310.15(C)(1)

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 3: General Requirements for Conductors

20. The neutral conductor of a 2-wire circuit from a 3-phase, the 4-wire system is required to be counted as a current-carrying conductor in a raceway or cable. (True) (False) (Circle your answer.)

Answer: True, Both conductors of a 2-wire circuit carry the same current 21. The neutral conductor of a 3-wire circuit from a 3-phase, 4-wire system is required to be counted as a current-carrying conductor in a raceway or cable. (True) (False) (Circle your answer.)

Answer: True, 310.15(E)(2) 22. The neutral conductor of a 2-wire circuit from a 1-phase, 3-wire system is required to be counted as a current-carrying conductor in a raceway or cable. (True) (False) (Circle your answer.)

Answer: True, Both conductors of a 2-wire circuit carry the same current 23. The neutral conductor of a 3-wire circuit from a 1-phase, 3-wire system is required to be counted as a current-carrying conductor in a raceway or cable. (True) (False) (Circle your answer.)

Answer: False, 310.15(E)(1) 24. Terminations for circuits 100 amperes or less with the conductor marked 60°C will be sized ________________ through ________________ and terminations for circuits over 100 amperes with conductors marked 75°C will be sized ________________ and larger.

Answer: 14 AWG, 1 AWG, 1/0 AWG 25. Unless marked otherwise, the temperature rating of the terminal(s) for the following conductors or overcurrent device is: (Circle your answers and assume a dry location.) a. 12 AWG conductors with THWN insulation

(60°C)

(75°C)

(90°C)

b. 12 AWG conductors with XHHW insulation

(60°C)

(75°C)

(90°C)

c. 3/0 AWG conductors with THWN insulation

(60°C)

(75°C)

(90°C)

d. 3/0 AWG conductors with XHHW insulation

(60°C)

(75°C)

(90°C)

e. A 40-ampere circuit-breaker

(60°C)

(75°C)

(90°C)

f.

(60°C)

(75°C)

(90°C)

A 200-ampere circuit-breaker

Answer: a. 60°C, b. 60°C, c. 75°C, d. 75°C, e. 60°C, f. 75°C 26. A continuous load is defined as a load that is likely to continue for 8 hours or more.

(True) (False) (Circle your answer.)

Answer: False, 3-hours, NEC Article 100 27. A (100) (125) percent load factor must be applied for continuous loads. (Circle your answer.)

Answer: 125%

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Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 3: General Requirements for Conductors

28. Lighting loads in a store building (are) (are not) are usually considered as continuous loads. (Circle your answer.)

Answer: are 29. Compensation for voltage drop (is) (is not) generally required in the NEC. (Circle your answer.)

Answer: is not 30. The acronym “cmil” that is used while exploring voltage drop means what: ________________ Answer: circular mil area 31. The letter K when used to represent the resistivity of a conductor in voltage drop calculations for copper is ________________ and ________________ for aluminum conductors.

Answer: 12.9, 21.2

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 4: Branch Circuits

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 4: BRANCH CIRCUITS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Complete the following table using the following circuits: 1.

Eleven 120-volt duplex receptacles for general use. Receptacle loads are considered to be noncontinuous and are not subject to the 80% load limitation as applied for continuous loads.

2. Ten 120-volt fluorescent luminaires, rated at 150 volt-amperes each.

3. Eight 120-volt incandescent luminaires, rated at 200 watts or VA each.

4. One 240-volt exhaust fan, rated at 5000 watts or VA. 5. One 120/240-volt single-phase, 3-wire feeder, 40-kVA continuous load, originating in a room with an ambient temperature of 100°F (38°C).

Answer: Circuit 1 = eleven 120-V, duplex receptacles for general use. Receptacle loads are considered to be noncontinuous and are not subject to the 80% load limitation as applied for continuous loads.

Circuit 2 = ten 120-volt fluorescent luminaires, rated at 150 volt-amperes each Circuit 3 = eight 120-volt incandescent luminaires, rated at 200 watts each Circuit 4 = one 240-V exhaust fan, rated at 5000 W Circuit 5 = one 120/240-volt single-phase, 3-wire feeder, 40-kVA continuous load, originating in a room with ambient temperature of 100°F (38°C)

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 4: Branch Circuits

Row

Circuit Number

1

2

3

4

5

1.

Calculated Load in Volt-Amperes

1980

1500

1600

5000

40,000

2.

Calculated Load in Amperes

16.5

12.5

13.3

20.8

167

3.

Load Type

R

C

C

M

C

4.

Load Modifier

1.0

1.25

1.25

1.25

1.25

5.

OCPD Selection Amperes

16.5

16

16.6

26

208

6.

OCPD Ampere Rating

20

20

20

30

225

7.

Minimum Conductor Ampacity

20

16

17

26

208

8.

Minimum Conductor Size Type THHN/THWN

12 AWG 12 AWG 12 AWG 10 AWG

9.

Ambient Temperature

86°F

86°F

86°F

86°F

100°F

10.

Temperature Correction Factor

1.0

1.0

1.0

1.0

0.91

11.

Number of Branch Circuits Required

1

1

1

1

1

12.

Number of Current-Carrying Conductors

2

2

2

2

2

13.

Raceway Fill Adjustment Factor

1.0

1.0

1.0

1.0

1.0

14.

Conductor Ampacity Before Correcting/Adjusting

25

25

25

35

230

15.

Conductor Ampacity After Correcting/Adjusting

25

25

25

35

236

4/0 AWG

Factors: •

Circuits 1, 2, 3, and 4 are installed in the same raceway for a distance of 10 ft in an environment where the maximum ambient temperature will be 86°F (30°C).

•

Type THHN/THWN conductors shall be used for all circuits.

•

Minimum conductor size 12 AWG.

Row 1: Calculated load in volt-amperes from problem statements.

Row 2: Calculated load in amperes divided by voltage factor.

Row 3: Load type: C = continuous; N = noncontinuous; M = motor; R = receptacle.

Row 4: Load modifier, 1.25 for C and M load types, 1.0 for R and N load types.

Row 5: Calculated load amperes (Row 2) multiplied by load modifier (Row 4).

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 4: Branch Circuits

Row 6: OCPD rating is equal to or next higher standard ampere rating than OCPD selection amperes (Row 5).

Row 7: Ampacity of conductor equal to or greater than the calculated load amperes (Row 2).

Row 8: Conductor size with ampacity equal to or greater than calculated load amperes (Row 2). Select from Table 310.16 using the appropriate 60°C for circuits rated 100 amperes or less, and the 75°C column for loads over 100 amperes.

Row 9: From problem statements.

Row 10: From NEC Table 310.15(B)(1)(1).

Row 11: From load calculation.

Row 12: From problem statements.

Row 13: From NEC Table 310.15(C)(1).

Row 14: From NEC 310.16 for conductor type specified in the problem statement: (THHN/THWN).

Row 15: Value from Row 13 multiplied by correction and/or adjustment factors. This value must be equal to or greater than the minimum conductor ampacity value in Row 7.

Answer: Circuits 1,2,3, and 4 are installed in the same raceway for a distance of 10 ft in an environment where the maximum ambient temperature will be 86°F (30°C). Type THHN/THWN conductors shall be used for all circuits. The minimum conductor size is 12 AWG. Row 1: Calculated load in volt-amperes from problem statements.

Row 2: Calculated load in amperes divided by voltage factor.

Row 3: Load type: C = continuous; N = noncontinuous; M = motor; R = receptacle.

Row 4: Load modifier: 1.25 for C and M load types, 1.0 for R and N load types.

Row 5: Calculated load amperes (Row 2) multiplied by load modifier (Row 4).

Row 6: OCPD rating equal to or next higher standard ampere rating than OCPD selection amperes (Row 5).

Row 7: Ampacity of conductor equal to or greater than calculated load amperes (Row 2). Note that for the receptacle load in Column 1, 240.4(B) does not permit rounding up to the next standard-rated overcurrent device. Thus the minimum ampacity of the branch circuit conductor for the receptacles in Column 1 is 20 A. Row 8: Conductor size with ampacity equal to or greater than the calculated load amperes (Row 2). Select from the 75°C Column of Table 310.16 as we are assuming that all terminals are rated 75°C. The student should be cautioned to use the 60°C Column of Table 310.16 for circuits rated 100 amperes or lower if the temperature rating of the terminals is unknown.

Row 9: From problem statements.

Row 10: From NEC Table 310.15(B)(1)(1).

Row 11: From load calculation.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 4: Branch Circuits

Row 12: From problem statements. Neutral conductor for the feeder is not counted as current carrying, NEC 310.15(E)(1).

Row 13: From NEC Table 310.15(C)(1).

Row 14: From NEC Table 310.16 for conductor type specified in problem statement: (THHN/THWN). Assume 75°C terminals for all connections. Note: The values shown are the conductors’ ampacity from the 75°C column of Table 310.16 without any limitation imposed by 240.4(D)for small conductors.

Row 15: Value from Row 13 multiplied by correction and/or adjustment factors if applicable.

90°C ampacity permitted for derating purposes in dry location by 110.14(C). This value must be equal to or greater than the minimum conductor ampacity value in Row 7.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 5: SWITCHES AND RECEPTACLES

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the NEC or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Indicate which of the following switches may be used to control the loads listed in problems 1–7. a. Ac/dc

10 A–125-V/5 A–250 V

b. Ac only

10 A–120 V

c. Ac only

15 A–120/277 V

d. Ac/dc

20 A–125-V –T/10 A–250-V–T

________ A 120-volt incandescent lamp load (tungsten filament) consisting of ten 150-watt lamps Answer: A 120-V incandescent lamp load (tungsten filament) consisting of ten 150-W lamps may be controlled by either a (c) AC only 15 A–120/277 V switch or a (d) AC/DC 20 A–125 V–T/10 A–250 V–T switch. ________ A 120-volt fluorescent lamp load (inductive) of 1500 volt-amperes Answer: A 120-V fluorescent lamp load (inductive) of 1500 VA may be controlled by a (c) AC only 15 A–120/277 V switch. ________ A 277-volt fluorescent lamp load of 625 volt-amperes Answer: A 277–V fluorescent lamp load of 625 VA may be controlled by a (c) AC only 15 A–120/277 V switch. ________ A 120-volt motor with a current of 10 amperes Answer: A 120-V motor drawing 10 amperes may be controlled by either a (c) AC only 15 A–120/277 V switch or a (d) AC/DC 20 A–125 V–T/10 A–250 V–T switch provided they are horsepower rated.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

________ A 120-volt resistive load of 1250 watts Answer: A 120-V resistive load of 1250 W maybe controlled by either a (c) AC only 15 A–120/277 V switch or a (d) AC/DC 20 A–125 V–T/10 A–250 V–T switch. ________ A 120-volt incandescent lamp load of 2000 watts Answer: A 120-V incandescent lamp load of 2000 W may be controlled by a (d) AC/DC 20 A–125 V–T/10 A–250 V–T switch. ________ A 230-volt motor with a current of 2.5 amperes Answer: A 230-V motor rated at 2.5 A may be controlled by an (a) AC/DC 10 A–l 25 V/5 A–250 V switch, a (c) AC only 15 A–120/277 V switch, or a (d) AC/DC 20 A–125 V–T/10 A–250 V–T switch.

Using the information in Tables 5-3 and 5-4, select by number the correct receptacle for the conditions described in problems 8–11.

A 20-ampere, 120/208-volt, single-phase load __________________ Answer: A 20-ampere, 120/208 volt, single-phase load will require a NEMA 14-20R receptacle.

A 50-ampere, 230-volt, 3-phase load __________________ Answer: A 50-ampere, 230-volt, 3-phase load will require a NEMA 11-50R receptacle if there is no grounding requirement, or a NEMA 15-50R if grounding is required. See NEC 250.138.

A 30-ampere, 208-volt, single-phase load __________________ Answer: A 30-ampere, 208-volt, single-phase load will require a NEMA 6-30R receptacle if grounding is required. See NEC 250.138.

A 20-ampere, hospital-grade, 120-volt, single-phase __________________ Answer: A 20-ampere, hospital grade, 120-volt, single-phase load will require a NEMA 5-20R HG receptacle.

The metal yoke of an isolated grounding-type receptacle (is) (is not) connected to the green equipment grounding terminal of the receptacle. (Circle the correct answer.)

Answer: The metal yoke of an isolated grounding-type receptacle is not connected to the green equipment grounding terminal of the receptacle. See NEC 250.146(D).

For problems 13-15, check the correct statement. □ The recommended method for grounding computer/data-processing equipment is to use the metal raceway as the equipment grounding conductor. □ The recommended method for grounding computer/data-processing equipment is to install a separate insulated equipment grounding conductor in the same raceway in which the branch-circuit conductors are installed.

Answer: The recommended method for grounding computer/data processing equipment is to install a separate insulated equipment grounding conductor in the same raceway in which the branch-circuit conductors are installed.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

□ When a separate insulated equipment grounding conductor is installed to minimize line disturbances on the circuit supplying an isolated grounding-type receptacle, it □ shall terminate in the panelboard where the branch circuit originates. □ may run through the panelboard where the branch circuit originates, back to the main disconnect (the source) for the building.

Answer: When a separate insulated equipment grounding conductor is installed to minimize line disturbances on the circuit supplying an isolated grounding-type receptacle, it may run through the panelboard where the branch circuit originates, back to the main disconnect (the source) for the building. □ To eliminate the overheated neutral problem associated with branch-circuit wiring that supplies computer/data-processing equipment, □ install a separate neutral conductor for each phase conductor. □ install a common neutral conductor on multiwire branch circuits.

Answer: To eliminate the overheated neutral problem associated with branch-circuit wiring that supplies computer/data processing equipment, install a separate neutral for each phase conductor. (Installing a single neutral of increased size is an option.)

Note to instructor for Questions 16–24: As discussed in the text, the color coding of conductors is left up to the electrician, other than for identified conductors (white, gray, or a colored conductor with three white or gray stripes) and equipment grounding conductors (green, green with yellow stripes or bare).

In most instances, electricians will decide on certain colors to be used for switch returns and travelers. Consistency of color coding for all of the branch-circuit wiring, switch returns (switch legs), and travelers in a particular installation simplifies the installation and makes troubleshooting at a later date much easier. Confusion is minimized. The Code does not dictate the colors for switch returns and travelers, nor does it dictate the colors to be used for the actual branch-circuit and feeder conductors other than for the identified conductor. The text discusses this in detail.

When installing cable, it is often necessary to reidentify a white conductor if it is to be used as a “hot” conductor. It is apparent that cable wiring can be more confusing than raceway wiring so far as conductor color coding is concerned. See NEC 200.7(C) for details.

NEC, 404.2(C) requires that a grounded circuit conductor be run to all switches that control lighting and has been extensively revised for recent editions of the NEC. See NEC 404.2(C).

This requirement is a result of electronic control devices, such as occupancy sensors and electronic timers, that require operation for sending even with the switch in the “off” poisiton. There were too many cases where “electricians” were using the equipment grounding conductor as a substitute for the grounded circuit conductor. Not a good idea— not to mention, an NEC violation!

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

For simplicity, the wiring diagrams shown do not include a separate equipment grounding conductor. Grounding is a separate issue. Metal raceways, the metal armor of Type AC and MC cable, and the equipment grounding conductor in nonmetallicsheathed cable and nonmetallic conduit provide the required grounding. See NEC 250.118(A) for aceptable equipment grounding means. Don’t ask students to include an EGC when they complete the wiring diagrams—but it might make sense to talk about it.

For the following problems, wiring has been installed for 3-way control of a light. The power source is available at one of the 3-way switches; the load is located between the 3-way switches. Be sure to study the requirements of 404.2(C).

Draw a wiring diagram illustrating the connection of the conductors.

Answer:

Draw the conductors in the raceway diagram that follows. Draw the connections to the switches and the luminaire. Label the conductors for color and function.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Answer:

Following is the same arrangement but using nonmetallic sheathed cable, Type AC or Type MC cable. Draw connections to the switches and the luminaire. Label the conductors for color and function. A 2-wire cable would contain black and white conductors; a 3-wire cable would contain red, black, and white conductors. A 4-wire cable has black-, white-, red-, and blue-colored insulations.

Answer:

Note: White grounded circuit conductor run to switches, where required by NEC 404.2(C).

Note: NEC 200.7(C)(1) states a conductor with white insulation is not permitted as the return traveler from a switch. re = reidentification with colored tape, heat shrink tubing, permanent marking pen, or other acceptable means.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

This diagram consists of two lamps and two 3-way switches. Draw a wiring diagram of the connections. Bring the circuit in from the left.

Answer:

Following is a diagram showing the installation of a metallic raceway system connecting two lamps and two 3-way switches. Draw the necessary conductors and show their connections.

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Answer:

Following is a diagram showing the installation of a nonmetallic sheathed cable system connecting two lamps and two 3-way switches. Draw the necessary conductors and show their connections.

Answer: This diagram indicates the need to use a 4-wire cable between the two switches. If 4wire cable is not readily available, it would be necessary to redesign the cable layout by connecting the second lamp (in the diagram, the one to the right) with a 2-wire cable to the lamp on the left. Thus, a 3-wire cable would be needed between the two switches.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

This diagram consists of one lamp, two 3-way switches, and one 4-way switch. Draw a wiring diagram of the connections. Bring the circuit in from the top (lamp location first).

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8

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Answer:

Following is a diagram showing the installation of a metallic raceway system connecting a lamp outlet to a 4-way switch system. Draw the necessary conductors and show their connections.

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9

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Answer:

Following is a diagram showing the installation of a nonmetallic sheathed cable system connecting a lamp and a 4-way switch system. Draw the necessary conductors and show their connections.

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10

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 5: Switches and Receptacles

Answer:

Note: White grounded circuit conductor run to all switches, where required by NEC 404.2(C).

Note: NEC 200.7(C)(1) states a conductor with white insulation is not permitted as the return traveler from a switch. re = reidentification with colored tape, heat shrink tubing, permanent marking pen, or other acceptable means.

An occupancy sensor (is) (is not) required in every habitable room, as defined in the applicable building code.

Answer: is not A grounded conductor (is) (is not) required at every switch for general-purpose lighting branch circuits. (Choose the correct answer.)

Answer: is not

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11

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E © 2024, 9780357767115; CHAPTER 6: WIRING METHODS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. If applicable, responses should be written in complete sentences.

For problems 1–4, select from the following list of raceway types. Check the letter(s) representing the correct response(s): a. electrical metallic tubing b. electrical nonmetallic tubing c. flexible metallic tubing d. rigid metal conduit e. intermediate metal conduit f.

rigid nonmetallic conduit

Note to instructor: Be sure to take into consideration the diameters of the bushings, and lugs in the case of grounding and bonding bushings. This comment applies to Questions 11–16 and 21–27.

Which raceway(s) may be used where cinder fill is present? □a.

□b.

□c.

□d.

□e.

□f.

Answer: (d) Rigid metal conduit, (e) intermediate metal conduit, and (f) rigid nonmetallic conduit (PVC) may be used where cinder fill is present.

Which raceway(s) may be used in hazardous locations? □a.

□b.

□c.

□d.

□e.

□f.

Answer: Unless otherwise provided for a limited application, (d) rigid metal conduit or (e) intermediate metal conduit are permitted to be used in hazardous locations.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Which raceway(s) may be used in wet locations? □a.

□b.

□c.

□d.

□e.

□f.

Answer: (a) Electrical metallic tubing, (b) electrical nonmetallic tubing where not prohibited in exposed locations, (d) rigid metal conduit, (e) intermediate metal conduit, and (f) rigid nonmetallic conduit (PVC) may be used in wet locations.

Which raceway(s) may be used for service entrances? □a.

□b.

□c.

□d.

□e.

□f.

Answer: (a) Electrical metallic tubing, (b) electrical nonmetallic tubing where not prohibited in exposed locations, (d) rigid metal conduit, (e) intermediate metal conduit, and (f) rigid nonmetallic conduit (PVC) may be used for service entrances. See NEC 230.43.

Give the raceway size required for each of the following conductor combinations: Five, 10 AWG, Type THW in Schedule 80 PVC ______________________ Answer: Five, 10 AWG, Type THW conductors in Schedule 80 PVC would require a trade size ¾ raceway.

Three, 1 0 AWG, Type THHN in EMT ______________________ Answer: Three, 1 0 AWG, Type THHN conductors in EMT would require a trade size 1¼ raceway.

Three, 1 0 AWG and one, 1 AWG, Type THW in EMT ______________________ Answer: The area of a 1 0 AWG Type THW conductor is 0.2223 sq. in. (143.4 sq. mm) as

found in NEC Table 5 of Chapter 9.

The area of a 1 AWG Type THW conductor is 0.1901 sq. in. (122.6 sq. mm) as found in NEC Table 5 of Chapter 9.

The total area for three 1 0 AWG and one 1 AWG Type THW = (3 × 0.223) + 0.1901 =

0.8591 sq. in., or (3 × 143.4) + 122.6 = 552.8 sq. mm. A maximum 40% fill is permitted for over 2 wires in EMT. A trade size 1½ EMT has an internal area of 0.814 sq. in. (525 sq. mm) and is too small.

A trade size 2 EMT has an internal area of 1.342 sq. in. (866 sq. mm).

A trade size 2 is the minimum size EMT for three 1 0 AWG and one 1 AWG Type THW

conductors.

For problems 8 and 9, determine the correct box size for each of the following conditions:

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Two nonmetallic sheathed cables with two 12 AWG conductors, an equipment grounding conductor, and a switch in a metal box without a plaster ring.

Answer: Two nonmetallic sheathed cables with two 12 AWG conductors, a grounding conductor, and a switch in a metal box. The wire count is as follows: Circuit conductors

4

Equipment grounding conductor

1

Cable clamp(s)

1

Switch

2

TOTAL

8 conductors

From NEC Table 314.16(A), the minimum-size device box is 3 × 2 × 3½ (75 × 50 × 90 mm).

A raceway run serving a series of luminaires, connected to a total of three circuits. The luminaires are supplied by 120 volts from a 3-phase, 4-wire system. Each box will contain two circuits running through the box and a third circuit connected to a luminaire, which is supported by a luminaire stud in the box. Use 12 AWG Type THHN conductors.

Answer: A conduit run is serving a series of luminaires connected to a total of three circuits. The luminaires are supplied by 120 V from a 3-phase, 4-wire system. Each box will contain two circuits running through the box and a third circuit connected to a luminaire, which is hung from a luminaire stud. Use 12 AWG Type THHN conductors.

The wire count is as follows: Conductors running through 2 Conductors running through

2

Conductors splicing in box

4

Fixture wires

2

Fixture stud

1

TOTAL

9 conductors

From NEC Table 314.16(A), the minimum size octagonal box is a 4 × 2⅛ (100 × 54 mm).

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

What is the minimum cubic in. volume that is permissible for the following outlet box?

Show your calculations.

Answer: The outlet box shown contains the following items: Two 12 AWG conductors @ 2.25 cu. in.

= 4.50 cu. in.

Three 14 AWG conductors @ 2.00 cu. in.

= 6.00 cu. in.

One cable clamp @ 2.25 cu. in. (based on size of largest conductor in box)

= 2.25 cu. in.

One equipment grounding conductor @ 2.25 cu. in. (based on size of largest equipment grounding conductor)

= 2.25 cu. in.

One duplex receptacle @ 2 × 2.25 cu. in. (based on size of connecting conductors)

= 4.50 cu. in.

One switch/pilot light @ 2 × 2.00 cu. in. (based on size of connecting conductors)

= 4.00 cu. in,

The minimum box volume

= 23.50 cu. in.

Two trade size 3 raceways enter a pull box directly across from each other. No other raceways enter the box. What are the minimum dimensions of the box?

Length ______________________ Answer: Length: The minimum length distance between the raceways for a pull box with two trade size 3 raceways entering opposite each other would be 3 × 8 = 24 in., or 78 × 8 = 624 mm. See NEC 314.28(A)(1).

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Width ______________________ Answer: Width: The minimum width would be raceway diameter plus room to install locknuts and bushings as required; in this case, 6 in., or 150 mm.

Depth ______________________ Answer: Depth:

The minimum depth would be the same as the width.

Two trade size 3 raceways enter a pull box at right angles to each other. No other raceways enter the box. What are the minimum dimensions of the box?

Length ______________________ Answer: Length: The minimum length for a pull box where two trade size 3 raceways enter at right angles to each other would be 3 × 6 = 18 in., or 3 × 78 = 624 mm; and the raceway must be located where the separation distance is no less than 3 × 6 = 18 in., or 3 × 78 = 624 mm. See NEC 314.28(A)(2).

Width ______________________ Answer: Width:

The minimum width would be the same as the length.

Depth ______________________ Answer: Depth: The minimum depth would be 6 in. (150 mm), which is the raceway diameter plus room to install locknuts and bushings as required.

If you had a choice, what type of raceway would you select for installation under the sidewalks and driveways of the Commercial Building? Support your selection by stating the section of the NEC permitting this installation. _______________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: Rigid nonmetallic conduit (PVC) would be an appropriate type of raceway for installation under sidewalks and driveways of a commercial building. The following reasons come to mind: It is lighter in weight and would be easier to handle and install; it not only meets the requirements for installation but is also impervious to cinder fill; it is easier to install, as the joints do not need to be screwed together, so one person could install it; it is less costly than the other two options. Also look in Table 300.5 for minimum burial depth, especially under driveways.

Determine the required EMT size for the following combination of conductors: Four 8 AWG Type THW and four 12 AWG Type THW: Answer: From NEC Chapter 9, Table 5: The 8 AWG type THW has an area of 0.0437 sq. in. (28.16 sq. mm) and the 12 AWG Type THW has an area of 0.0181 sq. in. (11.68 sq. mm).

The total conductor area is (4 × 0.0437) + (4 × 0.0181) = 0.1748 + 0.0724 = 0.2472 sq. in., or (4 × 11.68) + (4 × 28.16) = 46.72 + 112.64 = 159.36 sq. mm.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

From NEC Chapter 9, Table 4: For over two conductors, a trade size ¾ will allow 0.213 sq. in. of conductor, or 137 sq. mm of conductor; a trade size 1 will allow 0.346 sq. in., or 223 sq. mm, of conductor.

A trade size 1 is the minimum trade size EMT that is permitted to contain four 8 AWG and four 12 AWG Type THW conductors.

Three 350 kcmil and one 250 kcmil Type XHHW conductors and a 4 AWG bare conductor: Answer: From NEC Chapter 9, Tables 4, 5, and 8: Insulation Area in.2 Total Area Area mm2 in.2

Total Area mm2

Quantity

Size

3

350

XHHW

0.5166

1.5498

333.3

999.90

1

250

XHHW

0.3904

0.3904

251.9

251.90

1

4

Bare

0.042

0.0420

27.19

27.19

1.9822

1278.99

From NEC Chapter 9, Table 4: For over two wires, a trade size 2 1 2 EMT will allow 2.343

sq. in., or 1513 sq. mm, of conductor.

A trade size 2½ EMT is the minimum size that is permitted to contain three 350-kcmil and one 250-kcmil conductors with Type XHHW insulation and a 4 AWG bare conductor.

In a nonmetallic-sheathed (Type NM) cable installation, a 10 3 with equipment grounding conductor is installed in a metal octagonal box to supply two 12 2 with equipment grounding conductor branch-circuit cables. What is the minimum size box?

The box contains internal cable clamps. _______________________________ Answer: In a nonmetallic sheathed cable installation, a 10 3 with ground is installed in a metal octagonal box to supply two 12 2 with ground branch-circuit cables.

Three 10 AWG @ 2.5 cu. in. per conductor

= 7.5 cu. in.

Four 12 AWG @ 2.25 cu. in. per conductor

= 9.0 cu. in.

Equipment grounding conductor @ 2.5 cu. in.

= 2.5 cu. in.

Cable clamp @ 2.5 cu. in.

= 2.5 cu. in.

TOTAL

= 21.5 cu. in.

A 4 × 2⅛ (100 × 54) octagonal box has a volume of 30.3 cu. in.

For Questions 21–23, two 3 in, raceways enter a box, one through a side and the other in the back. Four 500 kcmil type THHN conductors will be installed in the raceway. No other raceways enter the box. What are the minimum dimensions?

For Questions 21, 22, and 23, two 3-in. raceways enter a pull box, one through a side and the other in the back. Four 500 kcmil, type THHN conductors will be installed in the raceway. No other raceways enter the box. What are the minimum dimensions of the pull box?

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Length ________________ Answer: Length: The minimum length would be (3 × 6) + 6 = 24 in., or (75 × 6) + 150 = 660 mm. The distance between the raceway entries must be 6 times the diameter.

Because this is measured from the near edge of the raceway, the diameter of the raceway plus room to install required locknuts and bushings must be added.

Width ________________ Answer: Width: The minimum width would be 6 in. (150 mm). This is diameter of the raceway plus room to install required locknuts and bushings.

Depth ________________ For Questions 24, 25, 26, and 27, determine the answers using the information shown in the drawing.

Answer: Depth: The minimum depth would be 6 in. (150 mm). From NEC Table 312.6(A), the minimum bending space for one 500 kcmil is 6 in., or 150 mm.

For Questions 24–27, using information from this drawing, the answers are as follows:

Dimension a must be at least ________________ inches.

Answer: Dimension a must be at least 24 in., or 600 mm, to satisfy 314.28(A)(1). Two conditions must be tested to determine distance a. Because the trade size 3 raceways constitute a straight pull, the required distance is 3 × 8 = 24 in., or 78 × 8 = 624 mm.

There are also angle pulls, and these require a minimum of (3 × 6) + 2 + 2 = 22 in., or (78 × 6) + 53 + 53 = 730 mm. The greater distance of 24 in. for the straight pull is chosen. Allow an additional 1 in. for the bushing.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Dimension b must be at least ________________ inches (the raceways contain the same conductors).

Answer: Because the conductors from the trade size 2 conduit on the left transition to the trade size 2 conduit at the top right of the pull box, dimension b must be at least 2 × 6 = 12 in., or 53 × 6 = 318 mm. See 314.28(A)(2). It is anticipated that the same 12 in., or 300 mm, spacing is required between the bottom trade size 2 conduit and the conduit at the top left of the pull box.

Dimension c must be at least ________________ inches.

Answer: Dimension c is based upon the distance from the top to the bottom of the pull box and is determined by the size and number of conduit entries at the top. It must be at least (2 × 6) + 2 = 14 in., or (53 × 6) + 53 = 371 mm. Allow an additional 1 in. for the bushing.

Do you foresee any difficulties in installing the conductors in these raceways? Explain. ________________________________________________________________________________ ________________________________________________________________________________ Answer: The arrangement of the raceways poses some difficulties. The conductors from the trade size 3 raceway will pass directly in front of the raceways leading out of the top. All the conductors from the trade size 2 raceways must pass over or under the other conductors. It would be wise to use a deeper box if conditions permit.

The minimum size raceway for the following conductors is: a. Three, 250 kcmil conductors with XHHW insulation ________________ b. One, 3 0 AWG conductor with XHHW insulation ____________________ c. One, 4 AWG conductor with XHHW insulation _____________________ Answer: Informative Annex Table C.1 gives the following trade size EMT as the smallest size. You may want to have your students check these answers with IMC as it has the largest internal area in trade size ½ through trade size 2. For EMT, it has the largest internal area in trade size 2½ through trade size 6. a) 2 b) 1¼ c) ½ The minimum size raceway for the following conductors is: a. Twelve, 6 AWG conductors with THHN insulation _____________________ b. Nine, 8 AWG conductors with THHN insulation _______________________ c. Eighteen, 10 AWG conductor with THHN insulation ____________________ d. One, 10 AWG equipment grounding conductor with THHN insulation _____________

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8

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 6: Wiring Methods

Answer: Informative Annex Table C.1 gives the following trade size EMT as the smallest size. a) 1¼ b) 1 c) 1¼ d) ½ The minimum size wireway for the following with parallel conductors is: a. Two sets of three, 250 kcmil conductors with XHHW insulation _________________ b. Two, 3 0 AWG conductors with XHHW insulation _________________ c. 1, 4 AWG conductor with XHHW insulation _________________ d. The conductors terminate on three power distribution blocks. Each one has a dimension of 4 in. wide and 3 in. high. _________________ Answer: The minimum size wireway for the following feeder with parallel conductors is: a. Two sets of three, 250 kcmil conductors with XHHW insulation Six 250 kcmil XHHW are 0.3904 in2 times 6 conductors = 2.3424 in2 b. Two 3 0 AWG conductor with XHHW insulation Two 3 0 AWG are 0.2642 in2 times 2 = 0.5284 in2 c. One 4 AWG conductor with XHHW insulation One 4 AWG is 0.0814 in2 = 0.0814 in2 d. The conductors terminate on three power distribution blocks. Each one has a dimension of 4 in. wide and 3 in. high.

4 in. times 3 in. =12 in2 times three = 36 in2 2.3424 in2 plus 0.5284 in2 plus 0.0814 in2 plus 36.00 in2 = 38.9522 in2 area divided by 80% to get 20% fill = 48.69 in2 Using a 16-inch by 16-inch wire way = 256 in2 and using a 20% fill maximum = 51.2 in2 See 376.22 for proper sizing of wireways.

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9

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 7: MOTOR AND APPLIANCE CIRCUITS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the NEC or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Cite the appropriate NEC Article, Section, or Table for each of the following: Where does the NEC refer specifically to air-conditioning equipment? ________________________________________________________________________________ Answer: NEC Article 440 refers directly to air-conditioning equipment.

Where does the NEC refer specifically to appliances? _______________________________ Answer: NEC Article 422 refers specifically to appliances.

Where does the NEC refer specifically to disconnecting means for a motor? __________ ________________________________________________________________________________ Answer: NEC Article 430, Part IX, refers specifically to disconnecting means for a motor.

Where does the NEC refer specifically to grounding exposed noncurrent-carrying metal parts of motor circuits? ________________________________________________________________________________ Answer: NEC Article 430, Part XIII, refers specifically to grounding exposed noncurrentcarrying metal parts of motor circuits.

The following three problems refer to cord-and-plug-connected appliances.

In your own words, define an appliance and give examples. ________________________________________________________________________________ ________________________________________________________________________________ Answer: An appliance is an item of utilization equipment, generally other than industrial as defined in NEC Article 100. Also see the definition of “Utilization Equipment” in NEC Article 100.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

A 20-ampere branch circuit is not permitted to serve a single appliance with a rating greater than ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: A 20-ampere branch circuit shall not serve a single appliance with a rating greater than 16 A; see NEC 210.23(B)(1) .

An appliance is fastened in place and other cord-and-plug-connected appliances are connected to a 20-ampere branch circuit. What is the maximum allowable load for the appliance that is fastened in place? ______________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: An appliance is fastened in place and other cord-and-plug-connected appliances are connected to a 20-ampere branch circuit. The maximum allowable load for the appliance that is fastened is 10 A (50% of 20); see NEC 210.23(B)(2).

The following six problems refer to motors and motor circuits.

Where is the disconnect means for a 208-volt, 3-phase motor controller required to be located? _______________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: The disconnecting means for a 208-V, 3-phase motor controller shall be located within sight of the controller; see NEC 430.102(A).

Where is the disconnect means for a motor required to be located? _________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: The disconnecting means for a motor is required to be located (1) within sight of the motor location and driven machinery location or (2) the disconnecting means for the controller in accordance with 430.102(A) is located in sight from the motor and driven machine location; see NEC 430.102(B). Note the Exception.

When selecting conductors, from where is the motor full-load ampere rating to be taken? _________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

Answer: When selecting conductors, the motor full-load current (FLC) rating is to be taken from NEC Tables 430.247, 430.248, 430.249, or 430.250. Also see Notes to these Tables and 430.6(A).

When selecting motor overload protective devices, from where is the full-load ampere rating taken? ________________________________________________________________________________ ________________________________________________________________________________ Answer: When selecting motor overload protective devices, the full-load ampere (FLA) rating is taken from the motor nameplate; see NEC 430.6(A)(2) and Article 430, Part III. A motor with a service factor of 1.25 is required to be protected by an overload device set to trip at not more than __________________________ of the motor FLA rating.

Answer: A motor with a service factor of 1.25 shall be protected by an overload device set to trip at not more than 125% of the motor full-load current rating; see NEC 430.32(A)(1).

The full-load current (FLC) rating of a 5-horsepower, 208-volt, 3-phase motor is 16.7 amperes. The minimum ampacity of the branch-circuit conductors supplying this motor would be not less than. _____________________________________ Answer: The full-load current (FLC) rating of a 5-hp, 208-V, 3-phase motor is 16.7 A. The minimum ampacity of the branch-circuit conductors supplying this motor shall be not less than 16.7 Amps × 1.25 = 20.9 or 21 A; see NEC 430.22.

Problems 14, 15, and 16 are for a 5-horsepower, 3-phase motor that has a nameplate current rating of 16 amperes. Dual-element, time-delay fuses are to be used for the motor’s branch-circuit short-circuit and ground-fault protection. Show your calculations.

The preferred rating of dual-element, time delay fuses (125% of motor full-load amperes) is _____________________________________ amperes. ________________________________________________________________________________ Answer: The preferred rating of the time-delay fuses is 1.25 × 16 Amps = 20 A in a 30A fusible switch.

If dual-element, time delay fuses with the preferred rating will not permit the starting of the motor, the dual-element, time delay fuse rating may be increased to a maximum (175% of motor full-load amperes) of ____________________ amperes.

Answer: If the time-delay fuse with the preferred rating will not permit starting of the motor, the fuse rating may be increased to 1.75 × 16 Amps = 28 A or 30 A; NEC 430.52(C)(1)(a) , permits the use of the next higher standard-rated fuse if the calculated size will (1) not carry the load or (2) not allow the motor to start. Therefore, a 30-A, dual-element, time-delay fuse is permitted. Because a dual-element, timedelay fuse is capable of carrying 5 times its ampere rating for at least 10 seconds, a 25-A, dual-element, time-delay fuse could also be used. Both the 25- and 30-A fuses are in conformance with the NEC and both fit into a 30-A disconnect switch.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

If the motor is to be started and stopped repeatedly, possibly resulting in nuisance opening of the circuit, the dual-element, time delay fuse rating may be increased to an absolute maximum (225% of motor full-load amperes) of ____________________ amperes.

Answer: If the motor is to be started and stopped repeatedly, possibly resulting in nuisance opening of the circuit, the time-delay fuse rating may be increased to 2.25 × 16 Amps = 36 Amps in a 60-A fusible switch. This is the absolute maximum ampere rating. Because 36-A fuses are not available, it is necessary to “round down” to 35-A fuses. The standard rating of fuses is listed in NEC Table 240.6(A).

The following problems apply to alternating-current motors: Define in sight as it applies to a motor and its disconnect switch. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: For a motor and its disconnect switch to be “in sight,” the disconnecting means must be visible from the motor location and not more than 50 ft (15 m) from the motor location, NEC Article 100.

A motor has a full-load current (FLC) rating of 74.8 amperes. What is the minimum ampacity of the branch-circuit conductors? ________________________________________________________________________________ ________________________________________________________________________________ Answer: A motor has a full-load current rating of 74.8 A. It requires branch-circuit conductors with a minimum ampacity of 74.8 Amps × 1.25 = 93.5 A; see NEC 430.22.

A motor has a full-load current (FLC) rating of 74.8 amperes and the terminations are rated for 75°C. What is the minimum conductor size and type? ________________________________________________________________________________ ________________________________________________________________________________ Answer: A motor has a full-load current rating of 74.8 A and terminations that are rated for 75°C. The minimum ampacity is 74.8 Amps × 1.25 = 93.5 Amps; see NEC 430.22. From NEC Table 310.16, the smallest conductor with an ampacity equal to or greater than 93.5 amperes is a 3 AWG 75°C THWN or XHHW conductor.

Three 3-phase motors are supplied by a single set of conductors. The motors are rated 208 volts and 5, 10, and 15 horsepower. The minimum ampacity of the feeder conductors is ______________ amperes.

Answer: Three 208-V, 3-phase motors are supplied by a single set of feeder conductors. The motors are 5, 10, and 15 hp. The minimum ampacity of the feeder conductors is 105.3 A.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

From NEC Table 430.250, the full-load currents are 16.7 Amps, 30.8 Amps, and 46.2 Amps. The conductor ampacity must not be less than 16.7 Amps + 30.8 Amps + (46.2 Amps × 1.25) = 105.3 Amps; see NEC 430.24.

A 1 2 -horsepower, 115-volt motor (service factor 1.15) is to be installed, and a Type S

fuseholder and switch are provided to control and protect the motor. The proper size fuse will have a rating of _____________ amperes.

Answer: A 1 2 -hp, 115-V motor (service factor 1.15) is to be installed, and a Type S

fuseholder and switch are provided to control and provide overload protection for the motor.

From NEC Table 430.248, the full-load current rating is 9.8 A. From Table 7–7A, the correct rating fuse would be 12 A, Calculation: 9.8 × 1.25 = 12.25 A. Round down to 12 A, which is the next standard lower fuse size.

For a 25-horsepower, 480-volt, Code letter G motor, the minimum starting current will be ____________amperes, and the maximum starting current will be __________ amperes.

Answer: The starting current for a 25-hp, 480-V, 3-phase motor marked with a Code letter G would not be less than 168 A or greater than 189 A; see NEC Table 430.7(B).

25 hp × 5.6 kVA/hp = 140 kVA

140,000 VA/(480 V × √3) = 168 A

25 hp× 6.29 kVA/hp = 157 kVA

157,000 VA/(480 V × √3) = 189 A

Type 1 and Type 2 Protection are terms that might be found on the nameplate of a motor controller. Explain in your own words what these terms mean. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: Type 1 and Type 2 Protection (coordination) are terms that might be found stamped on the nameplate of a motor controller. Both types require that under shortcircuit conditions, no hazard shall present itself that might injure a person working on or near the equipment. Type 1 protection allows a certain amount of damage to the controller, such as welding of the controller contacts. Type 2 protection does not allow any damage to the controller.

NEMA-rated general-purpose motors can operate on voltages ±10% of their rated nameplate voltage. An unbalanced voltage situation is extremely damaging to a motor.

Calculate the expected heat rise in a motor subjected to an unbalanced voltage situation where the voltages between phases AB = 465 volts, BC = 487 volts, and CA = 473 volts.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

Add these voltages: __________________ __________________ __________________ __________________ Total __________________ Find the average voltage: __________________ volts Subtract the average voltage from the voltage reading that results in the greatest difference: ___________ – ____________ = __________ volts

100 × Greatest voltage difference = Average voltage

% voltage unbalance

Temperature rise in the winding with highest current = 2 × (percent voltage unbalance)2 ___________ = ____________ % temperature rise in the winding with highest current Answer: NEMA-rated general-purpose motors can operate on voltages ±10% of their rated nameplate voltage. An unbalanced voltage situation can be extremely damaging to a motor. Calculate the expected heat rise in a motor subjected to an unbalanced voltage situation where the voltages between phases AB = 465 V, BC = 487 V, and CA = 473 V. Add these voltages:

465 487 473

Total

1425

Find the average voltage: Total ÷ 3 voltages = 1425 total voltage ÷ 3 = 475 V (average) Subtract the average voltage from the voltage reading that results in the greatest difference.

487 highest voltage – 475 average voltage = 12 Volt difference The 100 in the formula below is 100% for converting to a percentage

100 × greatest voltage difference 100 × 12 = = 2.52% voltage unbalance average voltage 476 Temperature rise in the winding with highest current = 2 × (percent voltage unbalance)2 2 × 2.52 × 2.52 = 12.7% temperature rise in the winding with the highest current.

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 7: Motor and Appliance Circuits

Generally, the disconnecting means for an appliance is required to be located _____________ of the appliance.

Answer: Generally, the disconnecting means for an appliance is required to be located within sight from of the appliance. Article 422 Part III An appliance is supplied by a branch circuit that is rated 60 amperes. What is the minimum size for a wire-type equipment grounding conductor? ________ AWG Answer: An appliance is supplied by a branch circuit that is rated 60 amperes. What is the minimum size for a wire type equipment grounding conductor? _10 AWG 250.122 and Table 250.122.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL , 18E, © 2024, 9780357767115; CHAPTER 8: FEEDER LOAD CALCULATION AND INSTALLATION

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

For problems 1–4, indicate the general lighting unit load that would be included in the branch-circuit calculations as required in NEC Table 220.42(A).

A restaurant

__________________

Answer: A restaurant is allocated a unit load of 1.5 VA/sq. ft, as stipulated in NEC Table 220.42(A).

A schoolroom __________________ Answer: A schoolroom is allocated a unit load of 1.5 VA/sq. ft, as stipulated in NEC Table 220.42(A).

A corridor in a school __________________ Answer: A corridor in a school is allocated a unit load of 1.5 VA/sq. ft, as stipulated in NEC Table 220.42(A).

A hallway in a dwelling __________________ Answer: A hallway in a dwelling is allocated a unit load of 3 VA/sq. ft, as stipulated in NEC 220.41 .

The load to be included for general-purpose convenience receptacles is __________________ VA. Answer: The load to be included for general-purpose receptacles is 180 VA. NEC 220.14(J).

The load to be included for an outlet for a specific appliance or load is. ________________________________________________________________________ Answer: The load to be included for an outlet for a specific appliance or load is the ampere rating of the appliance or load served. NEC 220.14(A).

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

For problems 7–9, indicate the effect, if any, a change in loads can have on the feeder serving the panelboard for a given area.

An increase in the calculated load ________________________________________________________________________ Answer: An increase in the calculated load can result in the need for a larger-size feeder.

An increase in the balanced load ________________________________________________________________________ Answer: An increase in the balanced load can result in a reduction in the size of the neutral.

An increase in the nonlinear load ________________________________________________________________________ Answer: An increase in the nonlinear load can result in an increase in the neutral size.

Answer problems 10, 11, and 12 using the following information: An addition is being planned to a school building. You have been asked to determine the load that will be added to the panelboard that will serve this addition.

The addition will be a building 80 ft × 50 ft. It will consist of four classrooms, every 40 ft × 20 ft and a corridor that is 10-ft wide.

The following loads will be installed: Each classroom: 12 fluorescent luminaires, 2 ft × 4 ft @ 85 VA each 20 duplex receptacles AC unit, 208-volt, 1-phase @ 5000 VA Corridor: 5 fluorescent luminaires, 1 ft × 8 ft @ 85 VA each 8 duplex receptacles Exterior: 4 wall-mounted luminaires @ 125 VA each 4 duplex receptacles Note to instructor: The student is to determine the NEC calculated load for a panelboard that will serve an 80 ft × 50 ft school addition consisting of four classrooms. The items to be installed and the load calculations are given in the following table.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Load

Count

VA/Unit

Classrooms 3200 ft2 @ 1.5 VA Ft2

1.5

Connected 48 Load. luminaires Luminaires w/12 per classroom times 4 classrooms (The number of branch circuits are required for only the connected load.

210.11(B).)

85

Corridor @ 1.5 VA FT2

1.5

800 ft2

NEC Load

Connected Calculated Load

4800 VA 4080 VA

1200 VA 425 VA

Exterior

125 VA

500 VA

16,560

Circuits

Neutral Load

4080 VA × 1.25  120 V = 42.5 A = Three 20-A

4080 VA

1200 VA

85 VA

Receptacles: 92 180 VA First 10 kVA receptacles @ 100% remainder @ 50%

Branch

4800 VA

Connected 5 Load. (The luminaires number of branch circuits are required for only the connected load.

210.11(B).)

4 luminaires

Load

Minimum

425 VA × 425 VA 1.25  120 V = 4.4 A = One 15-A

625 VA

500 VA × 500 VA 1.25  120 V = 5.2 A = One 15-A

13,280 VA  120 = 111 A = 6,560 VA ÷ Six 20-A 2 = 3,280 VA 10,000 VA

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10,000 VA 3,280 VA

3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Motors—AC Units

4

5000 VA

Total Volt-Amperes

20,000 VA 5000 VA × 1.25 = 6250 VA + 15,000 VA = 21250

Four 30- 0 A: 5000 VA × 1.25 = 6250 VA  208 = 30-A

25,005

41155

18,285

Q. 11

Q. 10

Q. 12

Notes: Continuous loads are calculated at 125% for the feeder conductors. See Table 220.42(A) and the Note at the bottom of the table, 215.2(A)(1) One of the AC units is considered the largest motor and 25% is added. 430.24 The neutral for a feeder is not required to be calculated at 125% for continuous loads since it does not connect to an overcurrent device. 215.2(A)(1) Exception No. 3.

180 VA per receptacle for determining the number of branch circuits. 220.14(I).

The calculated load is ______________________ VA. Answer: The calculated load is 41,155 VA. The connected load is ______________________ VA. Answer: The connected load is 25,005 VA. The neutral load is ______________________ VA. Answer: The neutral load is 18,285 VA. Why does the NEC require the overcurrent device to be rated not less than 125% of continuous loads? __________________________________________________________ ____________________________________________________________________________ Answer: The NEC requires the overcurrent device to be rated not less than 125% of continuous loads to prevent overheating conductors and terminals within panelboards and similar equipment, such as circuit breakers and connections for fusible switches.

Explain the concept of noncoincident loads for load calculations. _________________ ____________________________________________________________________________ Answer: If two different loads will not operate at the same time, such as heating and cooling equipment, the smaller loads can be omitted.

Determine the conductor sizes for a feeder to a panelboard. It is a 120/240-volt, single-phase system. The OCPD has a rating of 100 amperes. The calculated load is 15,600 VA. All the loads are 120 volts.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Answer: A 120/240 panelboard has a main OCPD rated at 100 A and serves a load of 15,600 VA. All the circuits are single-phase 120 V. The load in amperes is 15,600 VA/240 V = 65 A. As the rating of the panelboard is 100 A, unless otherwise known, it must be assumed that the terminations are rated at 60°C. The smallest conductor with a 60°C insulation with an ampacity equal to or greater than 100 A is a 1 AWG. This conductor allows the use of a 100-A OCPD and qualifies to carry the load. It thus becomes the smallest conductor that may be installed.

If it is assured that terminations are rated for 75°C, a 3 AWG copper conductor with 75°C insulation is acceptable.

Calculate the neutral current in a 120/240-volt, single-phase system when the current in phase A is 20 amperes and the current in phase B is 40 amperes. The load is resistive.

Answer: In a 120/240-V single-phase system when the current in Phase A is 20 A and the current in Phase B is 40 A, the neutral current would be 40 Amps − 20 Amps = 20 Amps.

Calculate the neutral current in a 208Y/120-volt, 3-phase, 4-wire system when the current in phase A is 0, in phase B is 40, and in phase C is 60 amperes. The load is resistive.

Answer: In a 208Y/120-V, 3-phase, 4-wire system if the current in Phase A is 0, in Phase B is 40 A, and in Phase C is 60 A, the current in the neutral would be

N = A 2 + B2 + C2 - AB-BC- AC = (0 × 0) + (40 × 40) + (60 × 60)-(0 × 40)-(40 × 60)-(0 × 60) = 0 + 1600 + 3600-0-2400-0 = 2800 = 52.9A Calculate the neutral current in a 208Y/120-volt, 3-phase, 4-wire system when the current in phase A is 20, in phase B is 40, and in phase C is 60 amperes. The load is resistive.

Answer: In a 208Y/120, 3-phase, 4-wire system when the current in Phase A is 20 A, in Phase B is 40 A, and in Phase C is 60 A, the neutral current would be

N = (20 × 20) + (40 × 40) + (60 × 60)-(20 × 40)-(40 × 60)-(20 × 60) = (400 + 1600 + 3600 - 800 - 2400 - 1200) = 1200 = 35 A A balanced electronic ballast load connected to a 3-phase, 4-wire multiwire branch circuit (look at the definition in NEC Article 100) can result in a neutral current of (zero times) (half) (two times) that of the current in the phase conductors. (Circle the correct answer.)

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Answer: A balanced electronic ballast load connected to a 3-phase, 4-wire branch circuit can result in a neutral current two times that of the current in the phase conductors. This is particularly true for computer loads.

Harmonic currents associated with electronic equipment (add together) (cancel out) a shared common neutral on multiwire branch circuits and feeders. (Circle the correct answer.)

Answer: Harmonic currents associated with electronic equipment are additive on a common neutral.

Check the correct statement: For circuits that supply computer/data-processing equipment, it is recommended that a separate neutral be installed for each hot-phase branch-circuit conductor. a common neutral be installed for each multiwire branch circuit.

Answer: For circuits that supply computer/data-processing equipment, it is recommended that a separate neutral be installed for each hot-phase branch-circuit conductor, A 1200-ampere service was installed, consisting of three sets of 600 kcmil THHN/ THWN copper conductors per phase. The electrical contractor was careful to cut the conductors the same length. When the utility crew made up the connections at the service heads, they cut the conductors to different lengths to make their connections simpler.

The actual lengths of the service-entrance conductors in a given phase ended up being 20 ft (6.1 m), 22 ft (6.7 m), and 24 ft (7.3 m). The maximum ampacity of a 600-kcmil THHN/THWN copper conductor is 420 amperes using the 75°C column of Table 310.16. This is more than adequate for the calculated 1200 amperes when three conductors are run in parallel.

Determine how the load of 1200 amperes would divide in each of the three paralleled conductors in a phase.

Answer: Step 1: Add the conductor lengths together: 20 ft + 22 ft + 24 ft = 66 ft Step 2: Make the calculation for each conductor:

Conductor A :

20 × 1200 = 364 A 66

Conductor B :

22 × 1200 = 400 A 66

Conductor C :

24 × 1200 = 436 A 66

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Because current flow is inversely proportional to resistance (the higher the resistance, the lower the current), list the conductors in reverse order to show that the shortest conductor having the lowest resistance will share the highest amount of current. The longest conductor having the highest resistance will share the smallest amount of current. In the preceding example: Conductor A will carry 436 A. Conductor B will carry 400 A. Conductor C will carry 364 A. It is apparent that Conductor A is in trouble. The current value of 436 A exceeds its ampacity of 420 A. This does not “Meet Code,” and is a violation of NEC 310.10(G). It also does not meet the requirement of NEC 310.14(A)(3) that sets the temperature limitations for conductors. The NEC in numerous places states that conductors shall have sufficient ampacity to carry the load.

An alternative solution to the dilemma is to simply install 1000-A or 1100-A fuses or circuit breaker.

Note to instructor: Here are two additional optional (extra-credit) problems that you might want students to do. Solving these extra calculations makes it very clear that different lengths result in different currents in the paralleled conductors. The dilemma is whether to enforce NEC 310.10(G) or to take a more practical approach by making a calculation to prove that the conductors will not be subjected to more current than their ampacity or to lower the ampere rating of the overcurrent protection ahead of the parallel conductors.

The letter of the law is all conductors shall be of the same length. The intent of the NEC is to not exceed a conductor’s ampacity so as not to overheat the conductor.

There are many places in the NEC that state that conductors shall have sufficient ampacity to carry the load.

An alternative solution to the dilemma is to install 1000-A or 1100-A fuses.

Encourage class discussion.

Optional Problem 9A: Make a calculation for three paralleled 600-kcmil THHN/THWN copper conductors per phase with conductor lengths of 20 ft, 21 ft, and 22 ft.

Answer: Step 1: Add the conductor lengths together: 20 ft + 21 ft + 22 ft = 63 ft Step 2: Make the calculation for each conductor:

Conductor A :

20 × 1200 = 381 A 63

Conductor B :

21 × 1200 = 400 A 63

Conductor C :

22 × 1200 = 419 A 63

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

Because current flow is inversely proportional to resistance (the higher the resistance, the lower the current), merely list the conductors in reverse order to show that the shortest conductor (the lowest resistance) will share the highest amount of current.

The longest conductor (the highest resistance) will share the smallest amount of current. In the preceding example, Conductor A will carry 419 A. Conductor B will carry 400 A. Conductor C will carry 381 A. Under the conditions stated, none of the conductors’ ampacity of 420 amperes is exceeded. Although the installation does not “Meet Code” in the strict sense of the wording in NEC 310.10(G) for parallel conductors, the calculation does show the intent of NEC 310.14(A)(3) regarding conductor temperature limitations is met. There are also many places in the NEC that state that conductors shall have sufficient ampacity to carry the load.

An alternative solution to the dilemma is to install 1000-A or 1100-A fuses or circuit breakers.

Optional Problem 9B: Make a calculation for three paralleled 600-kcmil THHN/ THWN copper conductors per phase with conductor lengths of 50 ft, 51 ft, and 52 ft.

Answer: Step 1: Add the conductor lengths together: 50 ft + 51 ft + 52 ft = 153 ft Step 2: Make the calculation for each conductor:

Conductor A :

50 × 1200 = 392 A 153

Conductor B :

51 × 1200 = 400 A 153

Conductor C :

52 × 1200 = 408 A 153

Because current flow is inversely proportional to resistance (the higher the resistance, the lower the current), merely list the conductors in reverse order to show that the shortest conductor (the lowest resistance) will share the highest amount of current.

The longest conductor (the highest resistance) will share the smallest amount of current, hi the preceding example: Conductor A will carry 408 A. Conductor B will carry 400 A. Conductor C will carry 381 A. Under the conditions stated, none of the conductors’ ampacity of 420 A is exceeded.

Although the installation does not “Meet Code” in the strict sense of the wording in NEC 310.10(G) for parallel conductors, the calculation does show the intent of NEC 310.14(A)(3) regarding conductor temperature limitations is satisfied. There are also

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8

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 8: Feeder Load Calculation and Installation

many places in the NEC that state that conductors shall have sufficient ampacity to carry the load.

An alternative solution to the dilemma is to install 1000-A or 1100-A fuses or circuit breakers.

The load shown in Table 8-6 for the AC Indoor Unit is ____________________ VA. Answer: The load shown in the Table 8-5 for the AC Indoor Unit is 15,156 VA The concept of including only the largest of the heating or cooling load in Table 8-6 is known as ____________________.

Answer: The concept of including only the largest of the heating or cooling load in Table 8-5 is known as noncoincident load The load for the electric sign in Table 8-6 is shown as a (continuous) (noncontinuous) load. (Circle the correct answer.)

Answer: The load for the electric sign in Table 8-5 is shown as a continuous load.

A tap conductor that complies with appropriate Code requirements has an ampacity of 30 amperes and is 9 ft (2.74 m) long. This is a field installation in which the tap conductor leaves the enclosure where the tap is made (a large junction box). The maximum allowable overcurrent protection for the feeder conductor would be ____________________ amperes.

Answer: A tap conductor that complies with appropriate Code requirements has an ampacity of 30 amperes and is 9 ft (2.74 m) long. This is a field installation in which the tap conductor leaves the enclosure where the tap is made (a large junction box).

The maximum allowable overcurrent protection for the feeder conductor would be _300_amperes since the 10 ft tap rule in 240.21(B)(1) would only permit a maximum of 10% of the 300 ampere overcurrent protective device.

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9

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 9: Special Systems

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 9: SPECIAL SYSTEMS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

The responses to problems 1–3 are to cite the applicable NEC references.

Surface raceways may be extended through dry partitions if ________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: Surface raceways may be extended through dry partitions if they are unbroken; see NEC 386.10(4).

Where power and communications circuits are to be installed in a combination raceway, the different types of circuits must be installed in ________________________________________________________________________________ ________________________________________________________________________________ Answer: Where power and communications circuits are to be installed in a combination raceway, the different types of circuits must be installed in separate compartments; see NEC 386.70.

If it is necessary to make splices in a multioutlet assembly, the conductors plus the splices shall not fill more than _____________________ % of the cross-sectional area at the point where the splices are made. _________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: If it is necessary to make splices in a multioutlet assembly, the conductors plus the splices shall not fill more than 75% of the cross-sectional area at the point where the splices are made; see NEC 386.56.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 9: Special Systems

Respond to problems 4 and 5 by showing the required calculations and citing NEC Sections.

Using a maximum conductor fill of 40% for a surface metal raceway that measures ½ in. × ¾ in., the maximum allowable cross-sectional area fill is sq. _________________ in.

Answer: This question asks for a calculation based on a maximum conductor fill of 40% for a surface metal raceway that measures 1 2 in. × ¾ in.

In the question, there is a 3 rather than an X. Make that change in the text of the question.

Step 1: Calculate the cross-sectional area of the raceway: 0.5 in × 0.75 in = 0.375 sq. in.

Step 2: Calculate the 40% fill: 0.375 in2 × 0.40 = 0.15 sq. in.

Therefore, the total conductor fill for this surface metal raceway shall not exceed 0.15 sq. in. Question 5 provides further details on exactly how conductor fill calculations are made.

Each compartment of the multioutlet assembly installed in the Insurance Office has a cross-sectional area of 3.7 sq. in. (2390 sq. mm). The maximum number of 10 AWG, Type THWN conductors that may be installed in a compartment of the multioutlet assembly is ___________________________________________________________________ ________________________________________________________________________________ Answer: Conductor fill for surface metal raceways and surface nonmetallic raceways varies from 20% to 40%, depending upon the size and type of the conductors. Fittings may also cause additional variance to the fill capacity. NEC 386.22 states that The number of conductors or cables installed in surface metal raceway shall not be greater than the number for which the raceway is designed.* Per UL Standards 5 (surface metal raceway) and 5A (surface nonmetallic raceway), the number, types, and size of conductors that may be installed in the listed surface metal and nonmetallic raceways are marked on the raceway, on the instructions, or on the package in which the raceway is shipped.

Checking a manufacturer’s catalog, students will find rather detailed conductor fill restrictions.

For this question, students should use the 40% fill limitation for their calculation. If they have a manufacturer’s catalog, they should feel free to answer this question using the manufacturer’s conductor fill restrictions.

From NEC Chapter 9, Table 5, the cross-sectional area of a 10 AWG Type THWN is 0.0211 sq. in. From the problem statement, the area of the raceway is 3.7 sq. in. Using the 40% fill limitation: 3.7 in2 × 0.4 = 1.48 in2 1.48 in2/0.0211 in2 = 70 size 10 AWG Type THWN conductors

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 9: Special Systems

NEC 386.22 limits the number of conductors permitted in a surface raceway. The adjustment factors of NEC 310.15(C)(1) do not apply to conductors installed in surface metal raceways where all of the following conditions are met: (1) The cross-sectional area of the raceway exceeds 2500 mm2 (4 in.2).

(2) The current-carrying conductors do not exceed 30.

(3) The sum of the cross-sectional areas of all contained conductors does not exceed 20% of the interior cross-sectional area of the surface metal raceway.* Several computer circuits are to be installed in a building where nonmetallic cables and metal boxes are being used. Specify the number of conductors required for a cable serving a computer outlet similar to those in the Insurance Office. Note any special actions that must be taken to use that cable and cite the NEC references. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: When using nonmetallic cable, install a cable that contains one black and one white conductor, plus a green insulated equipment grounding conductor that will serve as the isolated ground, plus a bare equipment grounding conductor that will serve as the grounding means for the metal box.

When using a metal raceway wiring method, such as EMT, install one black conductor, one white conductor, plus a green insulated equipment grounding conductor that will serve as the isolated ground.

To reduce “electromagnetic interference” on branch circuits that supply computer loads, do not share neutrals. such as would be the case in multiwire branch circuits.

Typical fire-alarm cable is marked with the letters ________________________________.

Answer: Typical power-limited fire alarm cable is marked with an “F” in addition to other markings to indicate its suitability for specific locations such as “PLFA,” PLFAP, or PLFAR. Underfloor raceway systems are covered in Article ________________ of the NEC. Answer: Underfloor raceway systems are covered in Article 390 of the NEC. * Source NFPA 70-2020.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 10: Working Drawings—Upper Level

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 10: WORKING DRAWINGS —UPPER LEVEL

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Problems 1–3 refer to the water heater circuit to be installed in the Beauty Salon.

Is it permissible to install a receptacle for the water heater in the Salon? What section of the Code permits or prohibits this installation? ________________________________________________________________________________ ________________________________________________________________________________ Answer: The following questions refer to the water-heater circuit to be installed in the Beauty Salon.

A receptacle connection for an appliance (the water heater) that is not identified or designed for connection by flexible cord is not permitted. See NEC 400.10(A)(8), 422.16, and 422.31. Figure 10–2 illustrates an acceptable installation.

The water heater has nine elements. Under what conditions are these elements heating? ________________________________________________________________________________ ________________________________________________________________________________ Answer: The electric water heater has nine heating elements controlled by nine thermostat/high-limit controls. The thermostats are set so the lower elements maintain the desired normal-use water temperature. Should there be a huge demand for hot water, the middle set of thermo- stat/high-limit controls will energize the middle heating elements. Now, both the lower and middle heating elements are energized.

With a further demand for hot water, the upper set of thermostat/high limit controls will energize the upper heating elements. Now, the lower, middle, and upper heating elements are all energized.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 10: Working Drawings—Upper Level

Proper settings of the thermostat/high limit controls as recommended by the water heater manufacturer provide fast recovery when needed, as is typical in a beauty salon; see Figure 10–2.

If the water heater is not marked with the maximum overcurrent protective device rating, the maximum overcurrent protection is to be sized not to exceed ______________________ % of the water heater’s ampere rating; see NEC 422.11(E).

Answer: If the water heater is not marked with the maximum overcurrent protective device rating, the maximum overcurrent protection is to be sized not to exceed 150% of the water heater’s ampere rating; see NEC 422.11(E).

The following problems refer to the branch-circuit panelboard in the Real Estate Office. The panelboard schedule is shown in drawing E4 and the panelboard summary in Appendix A. How many single-pole branch circuits can be added to the panelboard? ________________________________________________________________________________ ________________________________________________________________________________ Answer: According to the Panelboard Summary on drawing E4, 16 spaces are available for future use.

How many general-purpose branch circuits are to be installed? ________________________________________________________________________________ ________________________________________________________________________________ Answer: A total of six branch circuits are to be installed; one is for the heating and cooling equipment, the outlet for the water heater is classified as an individual branch circuit. The remaining four branch circuits meet the definition of Branch Circuit, General-Purpose in NEC Article 100.

If an appliance that will operate for long periods is marked with the rating of the overcurrent device, is it permissible to install a device with the next higher rating? ________________________________________________________________________________ ________________________________________________________________________________ Answer: The overcurrent device shall not exceed the rating marked on the appliance.

Explain why 3-phase systems operate the same load at a lower current than a 1-phase system. ________________________________________________________________________ ________________________________________________________________________________ Answer: Explain why 3-phase systems operate the same load at a lower current than a 1-phase system. _______________________________________________________________ There are three conductors working rather than two.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 10: Working Drawings—Upper Level

Refer to the working drawings for the Insurance Office for problem 7.

Tabulate the following materials: Luminaires installed in the ceiling of the Insurance Office Room No. 1?

Style/count ________________________________________________________ ___________________________________________________________________ Manufacturers’ catalog number(s) ____________________________________ Luminaires installed in the ceiling of the Insurance Office Reception Room?

Style/count ________________________________________________________ ___________________________________________________________________ Manufacturers’ catalog number(s) ____________________________________ c. Luminaires installed in the ceiling of the Insurance Office Room No. 2?

Style/count ________________________________________________________ ___________________________________________________________________ Manufacturers’ catalog number(s) ____________________________________ d. Receptacles in the Insurance Office Room No. 1, Insurance Office Room No. 2, and Reception Room?

Type/count ________________________________________________________ ___________________________________________________________________ Ampere/voltage rating ______________________________________________ e. Wall switches in the Insurance Office Room No. 1, Insurance Office Room No. 2, and Reception Room?

Type/count ________________________________________________________ ___________________________________________________________________ Ampere/voltage rating ______________________________________________ f.

There are nine receptacles along one wall of the Insurance Office Room No. 2 (Computer Room). Explain what type these receptacles are. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 10: Working Drawings—Upper Level

Answer: Refer to the working drawings for the Insurance Office for problem 7. (Note that this answer actually refers to question 8.) a. Luminaire tabulation, Insurance Office room 1: Style G = 12, 2GR8-232A-UNV-EL4-EB81 Style Q = 1 b. Luminaire tabulation, Insurance Office reception room Style E luminaire

= 6—14 W, ML709835ICAT120D-494P06

Style E-EM luminaire = 2—14 W, ML709835ICAT120D-EM-494P06 c. Luminaire tabulation, Insurance Office room 2 Style G luminaire

= 2—80 W, 2GR8-332A-UNV-EB82

Style G-EM luminaire = 1—80 W, 2GR8-332A-UNV-EL4-EB82 d. Receptacles Multioutlet assembly 42—NEMA 5-15R Computer room

18—NEMA 5-20R with isolated grounding and surge suppression (Option is to use nine quad receptacles.)

Coffee outlet

1—NEMA 5-20R

Floor in Room 1

3—NEMA 5-20R

Miscellaneous

6—NEMA 5-15R

e. Switches f.

7—single-pole 20A, 125-volt

The nine quad receptacles are isolated ground receptacles with surge protection for computers and related equipment, such as printers, scanners, and fax machines.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 11: SPECIAL CIRCUITS (OWNER’S CIRCUITS)

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

The first four problems refer to the installation of the electrical supply to the boiler.

What is the proper name of the electrical supply to the boiler? ________________________________________________________________________________ ________________________________________________________________________________ Answer: Chapter 11 discussed the electrical requirements for an optional electric boiler for the Commercial Building. Here are a few questions relating to electric boilers: The electrical supply to a boiler is properly called a branch circuit. The circuit supplies supplementary overcurrent protective devices, according to NEC 424.72(D), is a branch circuit.

Describe, in detail, the electrical supply to the boiler, indicating options available and any special precautions. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: The electrical supply to the boiler consists of two trade size 3 raceways.

•

The raceways could be electrical metallic tubing, rigid metal conduit, or Schedule 80 rigid nonmetallic conduit. See specifications.

•

A flexible connection is to be installed at the place of connection to the boiler.

See NEC Article 348. See NEC 348.60 for the requirement of equipment grounding and bonding.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

•

Parallel conductors are to be installed and all must be cut the exact same length. See NEC 310.10(G).

•

The phase conductors are to be copper 500-kcmil THHN/THWN. and the equipment grounding conductor a 1/0 AWG. See NEC Table 250.122.

•

The equipment grounding conductors may be insulated or bare. See NEC 250.118(A)(1).

Show the calculations to determine the minimum size Type THHN conductors and the rating of the overcurrent protective device (fuses) for the circuit supplying the boiler.

Use two conductors per phase in two raceways. Also, determine the size of the equipment grounding conductors to be installed in each raceway. The expected maximum temperature in the room where the boiler is located is 100°F (37.8°C). The boiler electrical panel and the distribution panel are rated 75°C. All conductors are copper. ________________________________________________________________________________ ________________________________________________________________________________ Answer: This is a rather complex question because it involves many parts to solve the problem. Let’s discuss the calculations in detail. The first step is to determine the fullload current of the boiler.

I = kW × 1000/E × 1.732 I = 200 × 1000/208 × 1.732 I = 556 A To begin calculating all of the components of the boiler’s branch circuit, it is important to note that NEC 424.4(B) states that the branch circuit for fixed electric space heating is required to be rated not less than 125% of the load. This is true even though the load is no longer considered to be a continuous load. We note that 220.51 permits fixed electrical space heating load to be calculated at 100 percent of the total connected load for feeders.

Overcurrent Protection: 556 Amps × 1.25 = 695 Amps The next standard size overcurrent device as permitted by NEC 240.4(B) is 800 A per NEC Table 240.6(A). However, because 700-A Class L fuses are readily available and are the same physical size as 800-A Class L fuses, it would be acceptable to install 700-A Class L fuses in an 800-A switch. It would also be acceptable to install an adjustable-trip circuit breaker or circuit breaker with a 700-A rating plug.

Conductors: We multiply the boiler’s load current by a factor of 1.25.

556 Amps × 1.25 = 695 Amps

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

Because we are paralleling two conductors per phase, each conductor in the parallel set must have a minimum ampacity of 695 Amps ÷ 2 = 348 Amps. Because these conductors are installed in two raceways, there is no need to derate their ampacity as would be required when more than three current-carrying conductors are installed in a single raceway.

The expected room temperature of 100°F (37.8°C) means that we must adjust (reduce) the conductors’ ampacity according to the Correction Factors found in NEC Table 310.15(B)(1)(1). The Correction Factor to be applied is 0.91 since we are using THHN/THWN in a dry location.

In NEC Table 310.16 we find in the 90°C column that a 500-kcmil THHN/THWN copper conductor has an ampacity of 430 Amps.

In NEC 110.14(C), we find that it is permissible to use the conductors’ 90°C ampacity as the starting point for applying Adjustment Factors and Correction Factors.

After applying the Ambient Temperature Correction Factor, we find that the reduced ampacity of a 500-kcmil Type THHN/THWN copper conductor is 430 Amps × 0.91 = 391 Amps This is more than adequate for the required 348 Amps needed for each of the paralleled conductors. To prevent overheating the terminals, this conductor satisfies the ampacity in the 75°C column of 380 A. For curiosity, we could do a sample trial-and-error calculation for another type of conductor, such as a 500-kcmil THW copper conductor that has an insulation rating of 75°C. The result of this calculation is 380 Amps × 0.88 = 334 Amps This is not adequate to serve the 348 A needed for each of the paralleled conductors.

Thus, the branch-circuit conductors for the boiler will be two 500-kcmil Type THHN/THWN copper conductors per phase connected in parallel. There will be three of these conductors plus one equipment grounding conductor in each of the two raceways. This selection meets the needs for both the current-carrying capacity and the high ambient temperature requirements for the conductors.

Equipment Grounding Conductors (EGC): NEC 250.122(F)(1)(b) states that where conductors are run in parallel in multiple raceways as permitted in NEC 310.10(G), each parallel equipment grounding conductor shall be sized on the basis of the ampere rating of the overcurrent device protecting the circuit. In our example, the OCD is rated either 700 or 800 A. In NEC Table 250.122, we find that for a circuit having an OCD rated 601 through 800 A, the EGC size is 1/0 copper. Therefore, a 1/0 copper EGC will be installed in each of the two raceways. The EGC is permitted to be insulated or bare, NEC 250.118(A)(1).

We find in NEC 310.15(F)(1)(b) that an EGC is not considered to be a current-carrying conductor. Therefore, no adjustment factor from NEC Table 310.15(C)(1) is applied even though there are four conductors in each raceway (three 500-kcmil Type THHN/THWN and one 1/0 EGC).

See Figure 11-9 for a drawing of the boiler electrical connections.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

The following three problems refer to the installation of various items of equipment in the equipment room.

What is the proper rating of the overload protection to be installed for the sump pump? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: Checking the Owner Panelboard Worksheet, Table A–9 in Appendix A, we find that the sump pump has a rating of 1127 volt-amperes. Most sump pumps have builtin overload protection. If the electrician wishes to install additional backup overload protection, it would be sized at 115% of the motor’s rating according to NEC 430.32(A)(1).

Step 1: 1127 VA ÷ 120 V = 9.4 Amps Step 2: 9.4 Amps × 1.15 = 10.8 Amps Detail the installation of the outside heat sensor. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: The outside heat sensor should be installed out of direct sunlight and separated from the wall so the latent heat in the wall will not affect its operation.

Note No. 1 to instructor: Question 6 encourages students to think about how they would layout the wiring for the outdoor lighting and front entry lighting of the Commercial Building. Obviously, there is more than one way to accomplish this.

Students should think about the easiest path to run the raceways or Type MC cable.

They should study the Plans and Specifications (found in Appendix A of the text). This question also provides students with an opportunity to show their skills in sketching out a wiring layout, hopefully neatly.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

The Specifications for the Commercial Building call for the electrician to furnish, install, and connect a timer to control all outdoor Wal-Pak® luminaires and the two ceiling luminaires in the front entry. Refer to the Specifications in Appendix A at the back of this book for specific requirements.

There are many different ways that the wiring of these luminaires can be accomplished. It is up to the electrician to decide how to run the branch circuit to the luminaires.

Sketch how you would lay out the wiring of the Wal-Pak luminaires and the two ceiling luminaires in the front entry. Use separate 8 1 2 × 11 paper for your drawing(s) if needed.

Answer: Students make a sketch of the location of the timer—next to the Owner’s panelboard—and the raceway or cable layout to the luminaires.

Remind students that these types of outdoor luminaires are quite heavy. They require anchors. They are not to be supported by the electrical outlet box.

Checking the Elevations for the Commercial Building, students should note that the outdoor Wal-Pak luminaires are positioned at approximately the same level as the space between the first and second floor. The raceways or cables run to connect the luminaires can be easily run in this joist space.

A suggestion for approaching this question is to have students first make a sketch of the building’s outside walls. Next, they sketch in the location of the eight outdoor WalPak luminaires and the two recessed front entrance luminaires, and then the raceway or cable runs between all of the eight luminaires. Next, they must decide where to run the home-run raceway or cable from one of the luminaires to the timer that is located next to the Owner’s panelboard.

The timer is mounted adjacent to the Owner’s panelboard, which is located in the Owner’s Storage Room in the basement. The raceway or cable coming out of the top of the timer runs to the outlet box located where one of the outdoor luminaires is to be mounted. From that box, raceways are run to the other luminaire outlet boxes. The specified Wal-Pak luminaires are quite heavy. They are not to be supported by the outlet box, and they require anchors to be installed into the brick wall. The manufacturer provides a template showing where to set the anchors in relation to the outlet box.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

Note to Instructor #2: In Question 6, the student is encouraged to think about how he would go about wiring the outdoor lighting wall-paks.

Another excellent topic for discussion is how they would do the wiring for the Second Floor Women’s and Men’s Toilet Room electric point-of-use electric water heaters and electric space heaters. There are a number of options. Get them to think and to contribute their ideas. A discussion of this sort will surely surface a lot of opinions.

The Electrical Plans clearly show a symbol where a certain piece of equipment is to be installed. However, the Electrical Plans do not show how to run the circuits. This is where training and experience prevails.

While thinking about time, material, and how best to run the circuits for these appliances, the installation must be in conformance to the requirements in the National Electrical Code. As trained and experienced persons say: “Let the Code Decide.” We discuss some of the options of how to run the circuits in Chapter 11.

Now is an excellent opportunity to have your students discuss these options. What are the pros and cons?

Ask the student: •

Is adjusting the ampacity of the conductor a problem?

•

What is the adjusted ampacity of a 12 AWG THHN/THWN copper conductor?

30-Amps × 0.8 = 24 amperes

•

Is the adjusted ampacity of the conductor still properly protected by the 20 ampere circuit breaker?

•

What the student believes about how to keep the branch circuits from getting mixed up or improperly connected?

Do the students believe this is a problem?

•

The 208-volt electric space heater must be connected to opposite phases in the panelboard. How is this accomplished?

•

What NEC table provides the maximum number of 12 AWG THHN/THWN conductors? Informational Annex C Table C.l

•

If you install EMT, how many 12 AWG THHN/THWN conductors are permitted in a 1 2 inch EMT?

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 11: Special Circuits (Owner’s Circuits)

•

Any other suggestions of how to connect the point-of-use water heaters and space heaters?

The three documents that are used to determine the branch circuit layout, panelboard circuit layout, and the calculated load are: _________________, _________________, and _________________.

Answer: The three documents that are used to determine the branch circuit layout, panelboard circuit layout, and the calculated load are: panelboard worksheet, panelboard schedule, and load calculation.

The branch circuits for water heaters (are) (are not) considered to be a continuous load.

Answer: The branch circuits for water heaters are not considered to be a continuous load.

The installation requirements for electric elevators are covered in NEC Article _________________.

Answer: The installation requirements for electric elevators are covered in NEC Article 620.

The disconnecting means for elevators is required to be an _______________ _______________, externally operable _______________ motor-circuit switch or ______________________________ that is capable of being locked in the open position.

Answer: The disconnecting means for elevators is required to be an enclosed _________, externally operable fused motor circuit switch or circuit breaker that is capable of being locked in the open position.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 12: Panelboard Selection and Installation

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 12: PANELBOARD SELECTION AND INSTALLATION

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

The NEC refers to switchboards and panelboards. For problems 1 and 2, write the distinguishing characteristics of each. By observing these characteristics, a person would know which type of equipment was being viewed.

Switchboard: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: ►Switchboard: A large single-panel, frame, or assembly of panels on which are mounted on the face or back, or both, switches, overcurrent and other protective devices, buses, and usually instruments. *◄ ►Informational Note These assemblies can be accessible from the rear or side as well as from the front and are not intended to be installed in cabinets.*◄ Switchboards are large—usually standing on the floor.

Panelboard: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: ►Panelboard: A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet, enclosure, or cutout box placed in or against a wall, partition, or other support and accessible only from the front.*◄ Panelboards are accessible only from the front and are typically much smaller in size than a typical switchboard. © 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 12: Panelboard Selection and Installation

Past editions of the NEC had a definition for a lighting and appliance panelboard. The 2008 edition of the NEC deleted this equipment and definition.

Refer to the Drugstore panelboard directory (Table 12-1) and the Drugstore load calculation form in Appendix A for the information necessary to answer problems 3–7.

The panelboard must be rated for at least ___________________________ ampere(s).

Answer: The Drugstore feeder OCPD (fuses) have a rating of 150-A; thus the panelboard load is limited to this value. The panelboard could have a higher rating, but the load is still limited by the 150-A OCPD. Panelboards of the type used in the Commercial Building typically have a main bus rating of 150, 175, 200, or 225 A. The panelboard has a total of ___________________________ poles.

Answer: The Drugstore panelboard has 30 active poles. There are 12 single-pole circuit breakers, four 3-pole circuit breakers, six spare single-pole circuit breakers, and 12 single-pole spaces. The panelboard has the capability of handling a total of 42 poles.

There is space for the addition of ___________________________ 3-pole breaker(s).

Answer: The panelboard presently has four 3-pole circuit breakers installed. Six additional 3-pole circuit breakers could be added.

There is space for the addition of ___________________________ 2-pole breaker(s).

Answer: The panelboard presently has no 2-pole circuit breakers installed. Leaving the four single-pole circuit breakers in, six 2-pole circuit breakers could be added.

There is space for the addition of ___________________________ single-pole breaker(s).

Answer: Fourteen additional single-pole breakers could be added.

How much working space must be provided in front of a 480/277-volt dead front switchboard according to Table 110.26(A)(1)? The switchboard faces a concrete block wall.

3 ft (914 mm) 3½ ft (1.0 m) 4 ft (1.2 m) (Circle the correct answer.)

Answer: The voltage to ground on a 480/277-V, wye-connected system from any of the three “hot” phase conductors is 277 V. The description indicates that it is a Condition 2 installation. The minimum working space is 3½ ft (1.0 m). See NEC Table 110.26(A)(1).

A wall-mounted panelboard has several electrical raceways installed from the top and bottom of the cabinet. A sheet metal worker started to run a cold-air return duct through the wall approximately 8 ft (2.5 m) directly above the panel. The electrician stated that this is not permitted and that this space is only to be used for electrical equipment. He cited _________________ Section of the National Electrical Code to support his argument. Is the electrician correct? (Yes) (No). (Circle your answer.)

Answer: NEC 110.26(E)(1) prohibits installing nonelectrical equipment in the space above electrical equipment. This space is to be dedicated for electrical raceways. Yes, the electrician is correct.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 12: Panelboard Selection and Installation

For the service equipment located outside the Commercial Building, what rule describes the installation relative to working space? Refer to NEC 110.26 ________________.

Answer: NEC 110.26(E)(2) refers to dedicated equipment space located outdoors.

However, this section includes a requirement: The working clearance space shall include the zone described in 110.26(A).* NEC 408.4 is quite demanding in how to prepare the directories in panelboards. On the jobs you work on, do you (Circle your choice.) use a pencil to mark in the circuit directory? have the circuit directory typed up to be neat and easy to read?

Answer: Note to instructor: This is a question of neatness and compliance with the following: ►408.4(B) Source of Supply. All switchboards, switchgear, and panelboards supplied by a feeder(s) in other than one- or two-family dwellings shall be permanently marked in accordance with the following: (1) With the identification and physical location of where the power originates (2) With a label that is permanently affixed and of sufficient durability to withstand the environment involved (3) Using a method that is not handwritten.*◄H the directory typed to be neat, clear, permanent, and easy to read is the best choice and a hand written label is not permitted. As an instructor, you might want to discuss this with your students. Get their opinions.

Panelboard manufacturers provide directories on the inside cover of the panelboard, generally protected by a clear plastic cover. Some directories have space to add information such as voltage, date, name of contractor, phone number, and power source location as required by NEC 408.4(A); maximum available fault current as required by NEC 110.24; series-rating if applicable as required by NEC 110.22, and similar information.

You are filling out the directory in a panelboard. (Circle the best way to indicate one of the circuits that supply a computer room.)

Computer room Receptacles in computer room Receptacle for computer room no. 3.

Receptacles in middle of north wall.

Tom Jones’s office Answer: Note to instructor: Tenants and electricians need to know precisely what a circuit supplies. It is a matter of safety when working on the system. Here are the author’s opinions, not necessarily the only opinions. Get your students to discuss this. a. Computer room This might be too vague because there will be many very specific circuits to supply a computer room. b. Receptacles in computer vague

A little better than choice “a”., but still a little too

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 12: Panelboard Selection and Installation

c. Receptacle for computer This pinpoints the circuit to a specific computer.

But if any of the 3 computers are relocated, the words “Computer Room No. 3” might be wrong. d. “Receptacles in middle of north wall” might be the best choice because the receptacles in middle of north wall probably remain, no matter what equipment is plugged into it. e. Tom Jones’s office Not a good choice because Tom Jones might move out. If no one changes the circuit directory for the new tenant, the directory would be confusing. In fact, this is a violation of NEC 408.4(A)(5).

Match up the NEC section with the requirement by placing the letter from column 2 in the appropriate space.

110.26(A)(1) ________________

a. Clear Spaces

110.26(A)(2) ________________

b. Depth of Working Space

110.26(A)(3) ________________

c. Height of Working Space

110.26(B) ________________

d. Illumination

110.26(C)(1) ________________

e. Indoor Dedicated Equipment Space

110.26(C)(2)(a) ________________

f.

Large Equipment

110.26(C)(2)(b) ________________

g.

Minimum Entrance to and Egress from Working Space

110.26(C)(3) ________________ 110.26(D) ________________ 110.26(E)(1) ________________ 110.26(E)(2) ________________

h. Outdoor Dedicated Equipment Space i.

Personnel Doors

j.

Width of Working Space

k. Working Space

Answer: Match up the NEC section with the requirement by placing the letter from column 2 in the appropriate space.

110.26(A)(1)

b.

Depth of Working Space

110.26(A)(2)

j.

Width of Working Space

110.26(A)(3)

c.

Height of Working Space

110.26(B)

a.

Clear Spaces

110.26(C)(1)

g.

Minimum Entrance to and Egress from Working Space

110.26(C)(2)

f.

Large Equipment

110.26(C)(3)

i.

Personnel Doors

110.26(D)

d.

Illumination

110.26(E)(1)

e.

Indoor Dedicated Equipment Space

110.26(E)(2)

h.

Outdoor Dedicated Equipment Space

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 12: Panelboard Selection and Installation

A panelboard is rated at 150 amperes. The calculated load is 78 amperes. Which of the following rating of overcurrent protection is acceptable? (Mark all that are correct.)

70 amperes 80 amperes 90 amperes 100 amperes 125 amperes 150 amperes 175 amperes 200 amperes 225 amperes Answer: A panelboard is rated at 150 amperes. The calculated load is 78 amperes.

Which of the following rating of overcurrent protection is acceptable? (Mark all that are correct) b. 80 amperes c. 90 amperes d. 100 amperes e. 125 amperes f. 150 amperes a. No The minimum size of access to working space for equipment that is located above a lay-in suspended ceiling is ________________.

Answer: The minimum size of access to working space for equipment that is located above a lay-in suspended ceiling is 22 in. x 22 in. * Source NFPA 70-2023.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 13: THE ELECTRIC SERVICE AND GROUNDING

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

A 300-kVA (kilovolt-ampere) transformer bank consisting of three 100-kVA (kilovoltampere) transformers has a 3-phase, 480-volt delta primary and a 120/240-volt, 3-phase, 4-wire delta-connected secondary.

For problems 1 through 5 show calculations and/or sources of information.

What is the full-load current in the primary? ______________________________________ ________________________________________________________________________________ Answer: A 300-kVA transformer bank consisting of three 100-kVA transformers has a 3-phase, 480-V delta primary and a 120/240-volt, 3-phase, 4-wire delta-connected secondary.

The full-load current in the primary of the specified transformer bank is 300,000 VA ÷ (480-V × √3 or 1.732) = 361 Amps.

What is the full-load current in the secondary?

Answer: The full-load current in the secondary of the specified transformer bank is 300,000 VA ÷ (240-V × √3 or 1.732) = 722 Amps.

What is the proper rating of the fuses to install for overcurrent protection of the secondary?

Answer: The permitted rating of the fuses to install in the secondary is 722 Amps × 1.25 = 903-Amps; the next higher rating of 1000 amperes is permitted. See NEC 450.3(B) and Table 240.6(A).

Overcurrent protection requirements for transformers rated 1000 V or less are found in NEC 450.3(B) and Table 450.3(B). The table shows two conditions: (1) primary protection only and (2) primary and secondary protection. Assuming that the transformer has primary overcurrent protection not exceeding 250% of the primary rated current, then overcurrent protection on the secondary is not permitted to exceed 125% of the secondary rated current but can be rounded up to the next standard size fuse or circuit breaker. © 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

Note 1 to Table 450.3(B) permits using the next higher standard rating for transformers rated 1000 volts and below. In this question, the secondary overcurrent protection calculation indicates a current value of 903 amperes. Note 1 permits the secondary overcurrent device to be rated 1000 A, which is the next higher standard rating of overcurrent devices as listed in NEC Table 240.6(A).

Installing a fuse or adjustable trip circuit breaker that is closer to the full-load current of 722 amperes will offer improved protection. However, the overcurrent device should be sized to allow for the inrush current of the transformer which can be as much as 10 times the full-load current for a brief period of time.

Students should be aware that all of the above relates to sizing overcurrent protection for a transformer. Overcurrent protection for the secondary conductors must be determined as a separate issue and is covered in 240.21(C).

What is the kilovolt-ampere of the bank if one of the transformers is removed?

Answer: If one of the three transformers is removed, the capacity would be reduced to 300 VA × 0.577 = 173 kVA. Another way to make the calculation is: two transformers totaling 200 VA × 0.866 = 173 kVA, or 100 VA × √3 or 1.732) = 173 kVA. Sketch the secondary connections and indicate where a 120-volt load could be connected.

Answer: Assuming the transformer is delta connected as stated before Question No. 1, a 120-V load can be connected between Phase A and the neutral, or Phase C and the neutral, See the following figure.

The two broad types of supply of the electrical system are _________________________ and _____________________________.

Answer: The two types of supply of the electrical system are grounded and __________________________ ungrounded.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

Definitions related to various components of the service are located in NEC _____________________________.

Answer: Definitions related to various components of the service are located in NEC Article 100 _____________________________.

A cabinet with a panelboard, shown on the right in the following figure, is added to an existing panelboard installation. Two knockouts, one near the top of the panelboard and the other near the bottom, are cut in the adjoining sides of the cabinets. List any parts to be checked or added and indicate on the drawing the proper way of extending the phase and neutral conductors to the new panelboard.

Answer: It is assumed the line-side lugs are suitable for two conductors. All circuit conductors including ungrounded, neutral, and equipment grounding conductors, are required to be installed through the same knockout. See NEC 300.3(B). Refer to the following drawing:

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

The following problems refer to grounding requirements. Give the source of your responses.

What is the proper size copper grounding electrode conductor for a 100-ampere service that consists of 3/0 AWG ungrounded conductors?

Answer: The proper size copper grounding electrode conductor for a 100-A service that consists of 3/0 AWG phase conductors is 4 AWG. See NEC Table 250.66.

What is the minimum size copper grounding electrode conductor for a service with three sets of parallel 350 kcmil conductors (three conductors per phase)? ___________ ________________________________________________________________________________ Answer: The minimum size copper grounding electrode conductor for a service with three sets of parallel 350-kcmil conductors (three conductors per phase) is 2/0 AWG. The three 350 kcmil conductors are added together and treated as one 1050 kcmil conductor for use in Table 250.66. See NEC Table 250.66 and Notes following this table.

If present, what items are required to be bonded together to form a grounding electrode system? ______________________________________________________________ ________________________________________________________________________________ Answer: If present, the following items must be bonded together to form a grounding electrode system: metal underground water pipe, metal in-ground support structures, concrete-encased electrode, ground ring, rod and pipe electrodes, plate electrodes, and other listed grounding electrodes. See NEC 250.50 and 250.52(A); Article 250, Part III. and Article 250, Part V.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

The engineering calculations for an 800-ampere service entrance require two 500 kcmil copper conductors per phase connected in parallel. The neutral conductor calculations indicate that the neutral conductors need only be 3 AWG copper conductors. The riser diagram shows two rigid metal conduits, each containing three 500 kcmil phase conductors and one 1/0 AWG neutral conductor. Why is the neutral conductor sized as a 1/0 AWG, or is this a mistake? ________________________________________________________________________________ ________________________________________________________________________________ Answer: The neutral conductors are connected in parallel, and NEC 310.10/(G) prohibits conductors smaller than 1/0 AWG to be installed in this manner. See NEC ►250.24(D)(2) Conductors Connected in Parallel in Two or More Raceways or Cables. If the ungrounded service-entrance conductors are connected in parallel in two or more raceways or cables, the grounded conductors shall also be installed in each raceway or cable and shall be connected in parallel. The size of each grounded conductor(s) in each raceway or cable shall not be smaller than 1/0 AWG and shall be sized in accordance with 250.24(D)(2)(a) or (D)(2)(b) in accordance with 250.24(D)(1). (a) Shall be based on the largest ungrounded conductor in each raceway or cable. (b) Shall be based on the sum of the circular mil areas of the largest ungrounded conductors from each set connected in parallel in each raceway or cable.*◄. This ensures that the grounding path will be capable of safely earning any fault current, ensuring the proper operation of the overcurrent devices. Overload protection for the service-entrance conductors is provided by the overcurrent devices (fuses or circuit breakers) in the main service disconnecting means. Short-circuit protection for the service-entrance conductors is provided by the primary fuses of the utility company transformer supplying the service. Bear in mind that the serving electric utility sizes its transformer primary protection overcurrent protection to protect the transformer per the National Electrical Safety Code (NESC), not the NEC. Electric utility installations and equipment under the exclusive control of the utility do not have to conform to the National Electrical Code. However, electric utilities do have to conform to the ______________________________________________________________.

Answer: Electric utilities make electrical installations in conformance with the National Electrical Safety Code, except that the wiring that is not directly associated with and under the exclusive control of the utility must conform to the National Electrical Code. See NEC 90.2(C)(4).

The electrician typically (does) (does not) do the wiring of current transformers for CT metering.

Answer: The electrician typically does not do the wiring of current-transformers for CT metering.

Assume you are an electrical apprentice. The electrical supervisor on the job tells you to connect some equipment grounding conductors to the ground bus that runs along the front bottom of a dead-front switchboard. The system is 480Y/277-volt solidly grounded wye. The building is still under construction, and several other trades are working in the building. The switchboard has already been energized, and it is totally enclosed, except for two access covers near the front bottom where the grounding

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 13: The Electric Service and Grounding

bus runs. The grounding bus already has the proper number and size of lugs for the equipment grounding conductors. You ask permission to turn off the main power so that you can work on connecting the equipment grounding conductors to the grounding bus without having to worry about accidentally touching the phase buses with your hands or with a screwdriver or wrench. The electrical supervisor says, “No.” What would you do? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: The apprentice should make the point that working on energized electrical equipment is in violation of OSHA regulations, which are federal law. The apprentice does not become a qualified person because a supervisor tells the apprentice to be careful.

Note to instructor: This could be developed into a good discussion session to help the students appreciate the seriousness of the situation.

Electrical explosions, directly into the face of a person working on or near energized electrical equipment, can and will cause serious injury or death. OSHA laws and NFPA 70E have strict safety requirements for working on electrical equipment. The basic rules are to turn off the power before working on the equipment and to wear the proper type of arc-rated flame-resistant clothing. To further provide safety for the worker, the National Electrical Code has a requirement pertaining to arc-flash hazard warning. This requirement is found in ________________________ of the NEC. Answer: This requirement is found in 110.16(A) of the NEC.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 14: LAMPS AND BALLASTS FOR LIGHTING

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary.

What article in the NEC covers luminaires, lampholders, and lamps? Article ________________________________________________________________________________ Answer: NEC Article 410 covers luminaires, lampholders, and lamps. a. What does the term LED stand for? ___________________ b. What does the term CFL stand for? ___________________ Answer: a.

LED stands for light-emitting diode.

b. CLF stands for compact fluorescent lamp.

Complete the following sentences: ___________________.

A fluorescent lamp requires a ___________________.

An LED lamp requires a ___________________.

To assure that the luminaire is safe, always check its label to make sure it is ___________________.

An LED is a solid-state device. When connected to a dc source, the ___________________ in the LED ___________________ together, creating ___________________.

Answer: a. A fluorescent lamp requires a ballast. b. An LED lamp requires a driver. c. To assure that luminaire is safe, always check its label to make sure it is listed. d. An LED is a solid-state device. When connected to a dc source, the electrons in the LED, smash together, creating light.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

The NEC defines a fluorescent lamp as a (electric discharge lamp) (filament lamp) (resistive lamp). (Circle the correct answer.)

Answer: The NEC defines a fluorescent lamp as an electric discharge lamp, Light output of a lamp is measured in (lumens) (amperes) (volts). (Circle the correct answer.)

Answer: Light output of a lamp is measured in lumens.

The efficacy of a lamp is measured in (watts) (lumens per watt) (volt-amperes). (Circle the correct answer.)

Answer: The efficacy of a lamp is measured in lumens per watt.

Circle the lamp that has the highest lumens per watt. (incandescent)

(LED)

(fluorescent)

Answer: LED is the lamp that has the highest lumens per watt.

Circle the lamp that has the lowest lumens per watt. (incandescent)

(LED)

(fluorescent)

Answer: Incandescent lamps have the lowest lumens per watt.

All lamps have a Kelvin rating. The lower the K rating, the (warmer) (cooler) its color.

The higher the K rating, the (warmer) (cooler) its color. (Circle the correct answers.)

Answer: All lamps have a Kelvin rating. The lower the K rating, the warmer its color.

The higher the K rating, the cooler its color.

A halogen lamp provides a (whiter) (redder) color than a conventional tungsten filament lamp. (Circle the correct answer.)

Answer: A halogen lamp provides a whiter color than a conventional tungsten filament lamp.

Low-voltage lighting is trendy, but because the lamps operate at low voltage (typically 12 volts), the lamps draw significantly more current than a 120-volt lamp of the same wattage.

Calculate the amperes for a 300-watt 12-volt load and a 300-watt 120-volt load.

Answer: 300 W @ 120 V:= I

W 300 = = 2.5 A E 120

300 W @ 12 V:= I

W 300 = = 25 A E 12

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

What is the diameter of each of the following lamps?

A19 _______________________ T8 _______________________ T12 _______________________ R40 _______________________ Answer: a.

A19: 2.375 in. b. T8: 1 in. c. T12: 1.5 in. d.

R40: 5 in.

Is it permissible to discard old ballasts and lamps in the normal trash?

Answer: No. Ballasts and lamps contain mercury and other hazardous materials that must be disposed of properly.

What advantages are there to installing ballasts that have a rating of 120/277 volts? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: A ballast rated for 120/277 V may be connected to either voltage. This means less inventory needed, and reduces the errors and confusion when installing luminaires where 120-V lighting branch circuits and 277-V lighting branch circuits are present in a building.

The power factor of high-efficiency electronic ballasts is generally in the range of (50%) (80%) (98–99%). (Circle the correct answer.)

Answer: The power factor of high efficiency electronic ballasts is generally in the range of 98–99% Nonlinear loads have harmonic components that (increase) (decrease) the current of the neutral conductor. (Circle the correct answer.)

Answer: Nonlinear loads have harmonic components that increase current of the neutral conductor.

Most of the ballasts in the commercial building are (rapid start) (trigger start) (instant start) (series rated). (Circle the correct answers.)

Answer: Most of the ballasts in the commercial building are rapid start and instant start.

What is a Class P ballast? _______________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Answer: A Class P ballast has an internal thermal protective device that is sensitive to the ballast temperature. At a certain temperature, this device opens the circuit to the ballast, not allowing the ballast to overheat.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

A ballast is marked Sound Rating D. Another ballast is marked Sound Rating A. Which ballast is the quietest? ______________________________________________________ Answer: The quietest ballast is the one marked A. What do the letters HID stand for? _______________________________________________ Answer: HID stands for high-intensity discharge.

Does the NEC have requirements that mandate energy savings? ____________________ Answer: No, however, NEC 220.42(B) permits the use of the lighting loads that comply with local energy codes provided certain features are provided. NEC ►90.2(A) states: Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.*◄ Which ballast has the highest power factor? (magnetic) (electronic) (Circle the correct answer.)

Answer: Electronic ballasts have the highest power factor.

Give a brief explanation of the following terms: a. Efficacy ____________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ b. Footcandle _________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ c. Lumen _____________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: a. Efficacy: Lumens per watt is a measure of the effectiveness (efficacy’) of a light source in producing light from electrical energy. Checking lumens per watt enables the comparison of the energy effectiveness of various lamps. b. Footcandle: The footcandle is the unit of measurement of the quantity of light received by a surface. It is measured perpendicular to the surface. c. Lumen: The lumen is the quantity of light received by a source. Almost all lamps are marked (on the carton) with their lumen rating.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

What are the approximate lumens per watt for an incandescent lamp? ___________________ lumens per watt. fluorescent lamp? ___________________ lumens per watt.

LED lamp? ___________________ lumens per watt.

Answer: a. Incandescent lamp: 6–23 lumens per watt. b. Fluorescent lamp: 25–100 lumens per watt. c. LED lamp: 29 to >100 lumens per watt.

Note to instructor: These values were taken from one lamp manufacturer’s data sheet.

Obviously, values will differ among manufacturers.

To combat our country’s growing energy problem, the federal government established a building energy standard that stipulates, among other things, the amount of electricity allowed for various types of buildings. The types of lamps permitted and the lumens per watt are two of the items addressed in the standard. What is the name of the regulation? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The name of the regulation is the Energy Policy Act of 2005.

The Environmental Protection Agency (EPA) has a program that sets standards for the energy efficiency of appliances, lamps, and similar electrical equipment. This program is referred to as ____________________________________________________________________________ Answer: The program that sets standards for the energy efficiency of appliances, lamps, and similar electrical equipment is the Energy Star Program.

Let’s review our knowledge of where to find things in the National Electrical Code.

What Article in the National Electrical Code covers a. luminaires?

Article ________________

b. services?

Article ________________

c. grounding?

Article ________________

d. overcurrent protection? Article ________________ e. branch circuits?

Article ________________

f.

Article ________________

motors?

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 14: Lamps and Ballasts for Lighting

Answer: a.

Luminaires

Article 410

b.

Services

Article 230

c.

Grounding

Article 250

d.

Overcurrent protection

Article 240

e.

Branch circuits

Article 210

f.

Motors

Article 430

* Source NFPA 70-2023.

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 15: Luminaires

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 15: LUMINAIRES

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

For problems 1 and 2, six luminaires, similar to Style E used in the Commercial Building, are to be installed in a room that is 12 ft × 18 ft (~3.7 m × ~5.5 m) with a 9 ft (2.8 m) floor-to-ceiling height. The spacing ratio for the luminaire is 1:0.

The maximum distance that the luminaires can be separated and achieve uniform illuminance is ___________ ft (___________ m).

Answer: For Questions 1 and 2, six luminaires, similar to Style E used in the Commercial Building, are to be installed in a room that is 12 ft × 18 ft (~3.7 m × ~5.5 m) with a 9 ft (2.8 m) floor-to-ceiling height. The spacing ratio for the luminaire is 1:0.

The maximum distance that the luminaires can be separated and achieve uniform illuminance is 9 ft (2,74 m) [9 ÷ 1 = 9 ft (2.74 m)].

The spacing ratio is also referred to as the spacing criterion. This ratio is the maximum distance apart to the mounting height above the floor or work surface to obtain uniform lighting on the floor or work surface. Exceeding the spacing ratio will result in dark areas on the floor or work surface. There is no problem with spacing luminaires closer than the spacing ratio, but they should not be spaced farther apart than the spacing ratio.

Draw a sketch indicating center-to-center and center-to-wall distances of how the six luminaires are to be installed.

Answer: Draw a sketch indicating center-to-center and center-to-wall distances of how the six luminaires are to be installed.

12 ÷ 2 = 6 ft (1.83 m) 18 ÷ 3 = 6 ft (1.83 m)

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 15: Luminaires

For problems 3–6, two luminaires, 8 ft (2.5 m) and 4 ft (1.2 m) in length with dimensions as shown in Figure 15-7 are to be installed in tandem (end to end). The end of the long luminaire is to be 2 ft (600 mm) from the wall.

The center of the outlet box should be roughed in at ___________ ft (___________ m) from the wall.

Answer: The center of the outlet box should be roughed in at 2.67 ft (0.813 m) from the wall. 24 in. length of luminaire+ 8 in. (edge of luminaire to center of box) = 32 in.

2.67 ft (813 mm) The first support should be installed at ___________ ft (___________ m) from the wall.

Answer: The first support of the 8-ft luminaire should be installed at 3 ft (900 mm), from the wall.

24 in. + 4 in. + 8 in. = 36 in. (900 mm) The second support should be installed at ___________ ft (___________ m) from the wall.

Answer: The second support at the other end of the 8-ft luminaire should be installed at 9.3 ft (2.85 m) from the wall.

24 in. + 96¼ in. − 8 in. = 112¼ in. (2.85 m) (9.3 ft) The final support should be installed at ___________ ft (___________ m) from the wall.

Answer: The final support at the far end of the 4-ft luminaire should be installed at 13.4 ft (4.1 m) from the wall.

24 in. + 96½ in. + 48¼ in. − 8 in. = 160½ in. (4.1 m) (13.4 ft) Problems 7 and 8 concern the illumination in the Beauty Salon.

The minimum loading allowance required for the Beauty Salon illumination in accordance with NEC Table 220.42(A) is ___________ volt-amperes per square foot (___________ volt-amperes per square meter).

Answer: The minimum loading allowance for the Beauty Salon illumination, in accordance with NEC Table 220.42(A) , is 1.9 VA/sq. ft (20 VA/sq. m). There is approximately 514 ft2 in the Beauty Salon.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 15: Luminaires

Therefore, 514 ft2 × 1.9 VA per ft2 = 977 VA per Code for the feeder and serviceentrance calculations. The actual connected load is 490 VA. It is interesting to note how much less the actual connected load using energy efficient lighting is when compared to the minimum Code requirement.

Complete the information in the following table for the luminaires installed in the Beauty Salon. (Disregard those in the storage area.) Refer to the Luminaire/Lamp/ Ballast Schedules in this chapter and the Second Floor Electrical Plan E3.

LUMINAIRE STYLE

COUNT

WATTS/ LUMINAIRE (VA)

TOTAL WATTAGE (VA)

Total Answer: Complete the information in the following table for the luminaires installed in the Beauty Salon. Refer to the Luminaire/Lamp/Ballast Schedules in this chapter and the Second Floor Electrical Plan E3.

Luminaire Style

Count

Watts/Luminaire (VA)

Total Wattage (VA)

E F Q

15 4 1

14 64 24 TOTAL

210 256 24 490

A Style Q luminaire is installed in the ceiling of the Beauty Salon. Give a brief description of this luminaire. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: See second floor luminaire/lamp/ballast schedule for Style Q and Table A-11 for Style Q with Note 5. Style Q luminaire looks like a conventional ceiling panel and is hardly noticeable. It has an integral battery pack. Should the main power source fail, the doors on the luminaire drop open, the lamps come on, and they continue to operate on the battery for approximately 90 minutes. When power is restored, the lamps go off and the doors automatically close.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 15: Luminaires

The remaining problems pertain to the installation of luminaires in a clothes closet. Circle the correct answer (compliance or violation) and cite the NEC reference. In each case, the luminaire is located on the ceiling, with 10 in. (250 mm) clearance from the storage area.

A porcelain socket with a plug-in PL fluorescent lamp.

Compliance

Violation

A totally enclosed incandescent luminaire.

Compliance

Violation

A fluorescent strip luminaire (bare lamp).

Compliance

Violation

Answer: Questions 10–12 pertain to the installation of luminaires in a clothes closet.

Students are to circle the correct answer (compliance or violation) and cite the NEC reference. In each case, the luminaire is located on the ceiling with 10 in. (250 mm) clearance from the storage area. Also see Figures 15–35 and 15–36.

10. Violation. See NEC 410.16(B) and (C). This type of lamp is easily broken by storage boxes and other storable material.

11. Violation. If surface-mounted, a minimum 12 in. (300 mm) clearance is needed. See NEC 410.16(D)(1) .

Compliance. If recessed, a minimum 6 in, (150 mm) clearance is needed. See NEC 410.16(D)(3) .

12. Compliance. Minimum clearance for surface-mounted or recessed fluorescent luminaires is 6 in. (150 mm). See NEC 410.16(D)(2) and 410.16(D)(4).

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 16: Emergency, Legally Required Standby, and Optional Standby Power Systems

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 16: EMERGENCY, LEGALLY REQUIRED STANDBY, AND OPTIONAL STANDBY POWER SYSTEMS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

There are three options for providing standby electrical power to building systems.

The options are listed here. Discuss the advantages and disadvantages of each.

A local source of power such as a battery or a motor generator: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Note to instructor: The NEC defines three types of electrical systems used (one for emergency systems, one for legal required standby systems and one for optional standby systems. The small portable generator sets sold in hardware stores and home centers would normally be covered by NEC Article 702 [i]f connected to the building or structure electrical system.

ARTICLE 700: Emergency Systems See the Scope of NEC Article 700 in 700.1 and the definition of Emergency System in NEC Article 100 .

ARTICLE 701: Legally Required standby Systems See the Scope of NEC Article 701 in 701.1 and the definition of Legally Required Standby Systems in NEC Article 100.

ARTICLE 702: Optional standby Systems See the Scope of NEC Article 702 in 702.1 and the definition of Optional Standby System in NEC Article 100.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 16: Emergency, Legally Required Standby, and Optional Standby Power Systems

Answer: An option for emergency systems is to provide a local source of power such as a battery or motor-generator. For small loads, such as emergency illumination of corridors and stairways, unit equipment is often used as it has the lowest installation costs and there is no special wiring to be installed. Unit equipment does require periodic maintenance and occasional battery replacement. For larger loads, motorgenerators have a high reliability factor provided the generators are properly maintained, but require a space that is accessible and must be periodically checked.

The larger systems require separate wiring and are expensive to purchase, install, and maintain.

A separate service: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: An option for emergency systems is to install a separate service. The major question is, how far down the line is it necessary to go to be considered separate at the high voltage source? At the first substation? At the power plant? To separate power plants? The utility is certain to pass this cost on to the consumer. A completely separate wiring system is required—even a separate service.

A connection ahead of the service main: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: An option for legally required standby power is to make a connection ahead of the service main. A connection ahead of the main is not permitted for emergency systems. This has a lower reliability because there is no protection against failures outside the building, which is where most failures occur. A separate wiring system must be installed. There is minimum maintenance. See NEC 701.12(G).

For problems 4–7, perform the following calculations and cite NEC references.

The minimum starting kilovolt-amperes for a 7 1 2 -horsepower, 3-phase, 230-volt, Code letter F motor is ____________________________________________________.

Answer: The minimum starting kVA for a 7 1 2 -hp, 3-phase, 230-V, Code letter F motor is as follows: From NEC Table 430.7(B), the lowest locked rotor kVA per horsepower for a Code F motor is 5 kVA per hp; 7.5 hp × 5 kVA/hp = 37.5 kVA.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 16: Emergency, Legally Required Standby, and Optional Standby Power Systems

The maximum starting kilovolt-amperes for a 7 1 2 -horsepower, 3-phase, 230-volt, Code letter F motor is ____________________________________________________.

Answer: The maximum starting kVA for a 7 1 2 -hp, 3-phase, 230-V, Code letter F motor is as follows: From NEC Table 430.7(B), the highest locked rotor kVA per horsepower for a Code letter F motor is 5.59 kVA/hp; 7.5 hp × 5.59 kVA/hp = 41.9 kVA. The minimum kilovolt-amperes of a generator that will be required to start, simultaneously, two 7 1 2 -horsepower, 3-phase, 230-volt, Code letter F motors are ____________________________________________________________________________ Answer: If two 7 1 2 -hp, 3-phase, 230-V, Code letter F motors are to be started at the same time, the minimum kVA of a generator for this load would be two times the maximum starting kVA for each motor; 2 motors 41.9 kVA = 83.8 kVA.

The minimum kilovolt-amperes of a generator that will be required to start two selectively controlled, 7 1 2 -horsepower, 3-phase, 230-volt, Code letter F motors is ____________________________________________________________________________ Answer: If two 7 1 2 -hp, 3-phase, 230-V, Code letter F motors are to be selectively

started, the minimum kVA of a generator would be the maximum starting kVA for one motor plus the running kVA for the other: 41.9 kVA + (230-V × 22 Amps × 1.732/1000) = 50.65 kVA. The number 22 is the full-load amperes from NEC Table 430.250; the 1.732 is the square root of 3 as this is a 3-phase motor; the 1000 converts from VA to kVA.

Branch circuits from a normal system are permitted to be installed in the same conduit as circuits from an emergency system. (True) (False) (Circle the correct answer.)

Answer: Branch circuits from a normal system are permitted to be installed in the same conduit with circuits from an emergency system. False. See NEC 700.10(B).

All generators connected to a building wiring system are considered “emergency systems.” (True) (False) (Circle the correct answer.)

Answer: All generators connected to a building wiring system are considered “emergency systems.” False. See NEC Definition of emergency systems in Article 100 and 700.1 with Informational Notes.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 16: Emergency, Legally Required Standby, and Optional Standby Power Systems

By placing a 1, 2, or 3 in the blank, identify the highest to the lowest level of the emergency and standby system.

Emergency system: ____________________________ Legally required standby: ____________________________ Optional standby: ____________________________ Answer: By placing a 1, 2, or 3 in the blank, identify the highest to the lowest level of standby system: Emergency system:

1

Legally required standby:

2

Optional standby:

3

The generator is required to be sized for all the loads that can be connected to it.

(True) (False) (Circle the correct answer.)

Answer: The generator is required to be sized for all the loads that can be connected to it. False. The generator for an Article 700, 701 or 702 system is required to be sized according to Article 220 or other approved method. See NEC 700.4(B), 701.4(B), 702.4(A)(1) and (2).

A tap ahead of the main is permitted as the source of power for emergency systems.

(True) (False) (Circle the correct answer.)

Answer: A tap ahead of the main is permitted as the source of power for emergency systems. False. See NEC 700.12.

When an automatic transfer switch is installed for an optional standby system, the owner is permitted to manually select the loads to be supplied. (True) (False) (Circle the correct answer.)

Answer: When an automatic transfer switch is installed for an optional standby system, the owner is permitted to manually select the loads to be supplied. False. See NEC 702.4(A)(2).

Where would the logical location be for running a portable generator? ____________________________________________________________________________ Answer: Where would the logical location be for running a portable generator?

Outdoors, clear of all openings to a building and away from any air intake ducts.

The technical NEC definition of a system in which the neutral conductor is not switched is referred to as: (Circle the correct answer.) a. a separately derived system. b. a nonseparately derived system.

Answer: The technical NEC definition of a system in which the neutral conductor is not switched is referred to as: b. a nonseparately derived system.

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 16: Emergency, Legally Required Standby, and Optional Standby Power Systems

NEC 590.6(A)(3) requires that all 125-volt and 125/250-volt, single-phase, 15-, 20-, and 30-ampere receptacle outlets used on a construction site that are a part of a portable generator have listed: (Circle the correct answer.) a. ground-fault circuit interrupter protection for personnel. b. grounding-type receptacles. c. locking-type receptacles.

Answer: NEC 590.6(A)(3) requires that all 125-volt and 125/250-volt, single-phase, 15-, 20-, and 30-ampere receptacle outlets used on a construction site that are a part of a portable generator have listed: a. ground-fault circuit interrupter protection for personnel.

What section of the NEC prohibits the use of series-connected, 3- and 4-way switches for the control of emergency system lighting? ____________________________________ _______________________________________________________________________________ Answer: NEC 700.20 prohibits the use of series-connected, 3-way, and 4-way switches for emergency lighting systems because multiple switch locations would give access to the control of the emergency lighting by other than authorized persons.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 17: OVERCURRENT PROTECTION: FUSES AND CIRCUIT BREAKERS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Why must overcurrent protection be provided? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: Overcurrent protection for conductors and equipment is provided to open the circuit if the current reaches a value that will cause an excessive or dangerous temperature in conductors or conductor insulation.* See NEC 240.1, Informational Note. It does not protect people except in the sense that it prevents fires, which could cause injury.

Several factors should be understood when selecting overcurrent protective devices. In your own words, define each of the following as they apply to overcurrent devices.

Voltage rating: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The voltage rating defines the voltage that may be applied to an electrical device or item of equipment. Examples are 120, 120/240, and 480Y/277. See NEC Article 100, 110.4, and 210.6.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Continuous current rating: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The continuous current rating of an overcurrent device is the current that the device will carry continuously without interrupting the circuit. See NEC 210.20, 215.3, and 230.42(A) for a few of the more common concerns about a continuous load.

Interrupting rating: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The interrupting rating of an overcurrent protection device is the highest current at rated voltage that a device is identified to interrupt under standard test conditions.* The interrupting ratings range from 5000 to 300,000 A. See NEC 110.9.

Speed of response: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The speed of response of an overcurrent protective device is the length of time, in seconds, that it takes for a protective device to open under overload or fault conditions. The speed is dependent on the magnitude of the current and the time/current characteristics of the overcurrent device. To indicate their relative speed of response, overcurrent devices are marked with such terms as dual-element, timedelay, fast-acting, and current-limiting. Manufacturers of fuses and circuit breakers provide time/current characteristic curves.

Current limitation: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Answer: Current limitation is when the speed of response of an overcurrent device is such that it will open a circuit before the current in the circuit reaches its maximum possible value. See Figures 17–27 and 19–4.

Peak let-through: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: Peak let-through refers to the maximum peak current that a current-limiting device will allow before it interrupts the circuit. See Figure 17–25.

NEC Table 430.52(C)(1) gives four options for selecting the maximum size motor branchcircuit, short-circuit, and ground-fault protective devices. These options are listed in problems 8, 9, 10, and 11. For each option, determine the correct rating or setting for a 25horsepower, 3-phase, 230-volt motor. The motor is marked “Design B.” Non-time-delay fuses: ____________________________________________________________________________ ____________________________________________________________________________ Answer: Referring to NEC Table 430.250, we find that a 25-hp, 3-phase, 230-V motor has a current rating of 68 A. From NEC Table 430.52(C)(1), for Design B motors the rating of a non-time-delay fuse may be 300% of the full load current (FLC), or 68 amps × 3.00 = 204 Amps.

If the rating of the fuses, as calculated by using the percentages in NEC Table 430.52(C)(1) results in a nonstandard rating, NEC 430.52(C)(1)(a), permits rounding up to the next higher standard rating. If the “next higher standard rating” will not allow the motor to start, higher maximum ampere rating percentages are given in NEC 430.52(C)(1)(b).

In the case above with the 25-hp, 3-phase, 230-V Design B motor, the use of 225-A non-time-delay fuses would be permitted if the motor will start. This would require the installation of a 400-A disconnect switch. It would be more reasonable and less costly to install a 200-A disconnect switch because the 4-A overage is insignificant, in which case 200-A non-time- delay fuses would be installed.

Never exceed the maximum size fuse specified by the manufacturer of the overload relays; NEC 430.52(C)(2). This information would be given on the label of the controller.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Dual-element, time-delay fuses: ____________________________________________________________________________ ____________________________________________________________________________ Answer: Referring to NEC Table 430.250, we find that a 25-hp, 3-phase, 230-V motor has a current rating of 68 A. From NEC Table 430.52(C)(1), for Design B motors the rating of a time-delay fuse may be 175% of the full load current (FLC), or 68 Amps × 1.75 = 119 Amps.

If the rating of the fuses as calculated by using the percentages in NEC Table 430.52(C)(1) results in a nonstandard rating, NEC 430.52(C)(1)(a) permits rounding up to the next higher standard rating. If the next higher standard rating will not allow the motor to start, higher maximum ampere rating percentages are given in NEC 430.52(C)(1)(b).

In the case above with the 25-hp, 3-phase, 230-V Design B motor, the use of 125-A. dual-element, time-delay fuses would be permitted, if the motor will start.

Never exceed the maximum size fuse specified by the manufacturer of the overload relays, NEC 430.52(C)(2). This information would be given on the label of the controller.

Instantaneous-trip breakers: ____________________________________________________________________________ ____________________________________________________________________________ Answer: Referring to NEC Table 430.250, we find that a 25-hp, 3-phase, 230-V motor has a current rating of 68 A. From NEC Table 430.52(C)(1), for an energy efficient Design B motors, the rating of an instantaneous trip breaker may be 1100% of the full-load current (FLC), or 68 Amps × 11 = 748 Amps (set at 800 A).

If the rating of the instantaneous trip breaker, as calculated by using the percentages in NEC Table 430.52(C)(1) results in a setting that will not allow the motor to start, NEC 430.52(C)(3)(b)(2)(b) permits increasing the setting to a maximum of 1300% for other than Design B motors and a maximum of 1700% for Design B motors. ►Where an engineering analysis determines the value is not sufficient for the starting current of the motor, it is not necessary to first apply the value specified in Table 430.52(C)(1).*◄ This means checking the starting characteristics of the motor, the load characteristic, and the time-current trip curve of the instantaneous trip breaker.

Instantaneous trip breakers are permitted only when part of a listed combination controller, NEC 430.52(C)(3)(a).

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Inverse time breakers: ____________________________________________________________________________ ____________________________________________________________________________ Answer: Referring to NEC Table 430.250, we find that a 25-hp, 3-phase, 230-V motor has a current rating of 68 A. From NEC Table 430.52(C)(1), for Design B motors the rating of an inverse-time circuit breaker may be 250% of the full load current (FLC), or 68 × 2.5 = 170 A. If the rating of the inverse-time circuit breaker as calculated by using the percentages in NEC Table 430.52(C)(1) results in a nonstandard rating or setting, NEC 430.52(C)(a), permits rounding up to the next higher standard rating or setting. The next higher standard rating is 175 A. If the next standard higher rating will not allow the motor to start, higher maximum ampere rating percentages are given in NEC 430.52(C)(1)(b).

Define the following terms: I2t ______________________________________________________________________ Ip ______________________________________________________________________ rms ____________________________________________________________________ Answer: a. I2t is used to represent the formula amperes × amperes × time in seconds. b. IP is used to represent peak amperes. c. RMS is used to represent root mean squared.

Class J fuses (will fit) (will not fit) into standard Class H fuse clips. (Circle the correct answer.)

Answer: Class J fuses will not fit into standard fuse clips.

Using the time-current curves from Figure 17-24, find the melting times for the following conditions: A 60-ampere fuse subjected to a 300-ampere overload will cause the fuse to melt in approximately _____________ seconds.

Answer: A 60-A fuse subjected to a 300-A overload will cause the fuse to melt in approximately 10 seconds.

A 60-ampere fuse subjected to a 600-ampere load will cause the fuse to melt in approximately _____________ seconds.

Answer: A 60-A fuse subjected to a 600-A load will cause the fuse to melt in approximately 0.02 seconds.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

A 200-ampere fuse subjected to a 1000-ampere overload will cause the fuse to melt in approximately _____________ seconds.

Answer: A 200-A fuse subjected to a 1000-A overload will cause the fuse to melt in approximately 10 seconds.

A 600-ampere fuse subjected to an 8000-ampere short circuit will cause the fuse to melt in approximately _____________ seconds.

Answer: A 600-A fuse subjected to an 8000Amp short circuit will cause the fuse to melt in approximately 0.01 second.

For problems 18 and 19, use the chart from Figure 17-27 to determine the approximate current values for a 60-ampere, 250-volt fuse when the prospective short-circuit current is 40,000 amperes.

The instantaneous peak let-through current is approximately _____________ amperes.

Answer: When using a 60-A, 250-V LPN fuse, the instantaneous peak let-through current will be approximately 7000 A when the short-circuit current is 40,000 A. The apparent rms current is approximately _____________ amperes.

Answer: When using a 60-A, 250-V LPN fuse, the apparent RMS current will be approximately 3000 A when the short-circuit current is 40,000 A. A section of the plug-in busway nameplate indicates that the busway is braced for 14,000 amperes. The available fault current is 30,000 amperes. Using Figure 17-27, determine whether a 200-ampere, 250-volt, dual-element fuse will limit the current sufficiently to protect the busway against a possible fault of 30,000 amperes. Explain. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The fuse will protect the busway in that the RMS let-through current is approximately 5500 A—well within the busway bracing of 14,000 A. In a thermal-magnetic circuit breaker, overloads are sensed by the _____________ element, and short circuits are sensed by the _____________ element.

Answer: In a thermal-magnetic circuit breaker, overloads are sensed by the thermal element, and short circuits are sensed by the magnetic element.

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Circle the correct answer. A cable limiter is a. a short-circuit device only.

True

False

b. not to be used for overload protection of conductors.

True

False

c. generally connected to both ends of large, paralleled conductors so that if a fault occurs on one of the conductors, that faulted cable is isolated from the system.

True

False

Answer: a. A cable limiter is a short-circuit device only. True b. A cable limiter is not to be used for overload protection of conductors. True c. A cable limiter is generally connected to both ends of large paralleled conductors so that if a fault occurs on one of the conductors, that faulted cable will be isolated from the system. True Listed series-rated equipment allows the branch-circuit breakers to have a lower interrupting rating than the main. What two sections of the National Electrical Code cover the marking of series-rated systems with the words CAUTION—SERIES RATED SYSTEM?____________________________________________________________________ ____________________________________________________________________________ Answer: The marking of series-rated systems is covered in NEC 110.22 and 240.86.

Using the chart in Figure 17-31 for problems 24, 25, 26, and 27, provide the unlatching time and interrupting time (also referred to as opening time) for a 50-ampere circuit breaker under the following stated conditions. Unlatching time and interrupting time are critical when designing a selectively coordinated electrical system.

For a load of 300 amperes, the minimum interrupting time is _______________________ seconds.

Answer: For a load of 300 A, the minimum interrupting time is 5 seconds for a 50-A molded-case circuit breaker. Note: A 300-A load is 600% of the 50-A circuit breaker rating.

For a load of 300 amperes, the maximum interrupting time is ___________________ seconds.

Answer: For a load of 300 A, the maximum interrupting time is 14 seconds for a 50-A molded-case circuit breaker.

For a 1000-ampere fault, the average unlatching time is ___________________ seconds.

Answer: For a 1000-A fault, the average unlatching time is 0.0080 second for a 50-A molded-case circuit breaker. One electrical cycle is 0.01666 second; thus, time is about one-half of a cycle.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

For a 5000-ampere fault, the average unlatching time is ___________________ seconds.

Answer: For a 5000-A fault, the average unlatching time is 0.0032 second for a 50-A molded-case circuit breaker. This is less than one-fifth of a cycle.

The ampere range of Class L fuses is from ___________________ to ___________________ amperes.

Answer: The ampere range of a Class L fuse is from 601 to 6000 A, The voltage rating of a plug fuse is ___________________ volts.

Answer: The voltage rating of a plug fuse is 125 V. The interrupting rating of a Class J fuse is ___________________ amperes.

Answer: The interrupting rating of a Class J fuse is 200.000 A, Some Class J fuses have an interrupting rating of 300,000 A. When the nameplate of HVAC equipment is marked “Maximum Size Fuse—50 Amperes,” is it permitted to connect the equipment to a 50-ampere circuit breaker with no 50-ampere fuse in the circuit? Explain. ____________________________________________________________________________ ____________________________________________________________________________ Answer: If the nameplate of HVAC equipment is marked “Maximum Size Fuse 50 Amperes,” it would be a violation of NEC 110.3(B) to install a 50-A circuit breaker.

Listed equipment has gone through exhaustive tests. NEC 110.3(B) tells us: ►Installation and Use. Equipment that is listed, labeled, or both or identified for a use shall be installed and used in accordance with any instructions included in the listing, labeling, or indentification.*◄

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8

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 17: Overcurrent Protection: Fuses and Circuit Breakers

Insert the correct response from Column B to correctly complete the statement in column A: a. b. c. d. e.

Column A Switches intended for isolating use only are marked Switches that are suitable for use as service equipment are marked Motor Circuit Switch Enclosed switches with horsepower ratings in addition to ampere ratings If a switch is marked with a dual horsepower rating

1.

Column B For use only in motor circuits.

2. The larger horsepower rating is applicable when using dualelement, time-delay fuses.

3. Suitable for use as service equipment.

4. For isolation use only—do not open under load.

5. Suitable for use in motor circuits as well as for general use.

Answer: Column A

Column B

a.

Switches intended for isolating use only are marked ___

4.

For isolation use only—do not open under load

b.

Switches that are suitable for use as service equipment are marked ___

3.

Suitable for use as service equipment.

c.

Motor Circuit Switch ___

1.

For use only in motor circuits.

d.

Enclosed switches with horsepower ratings, in addition to ampere ratings ___

5.

Suitable for use in motor circuits, as well as for general use.

e.

If a switch is marked with a dual horsepower rating ___

2.

The larger horsepower rating is applicable, when using dual element, time-delay fuses.

* Source NFPA 70-2023.

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9

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 18: SHORT-CIRCUIT CALCULATIONS AND COORDINATION OF OVERCURRENT PROTECTIVE DEVICES

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

For Questions 1, 2, and 3, a 300-kVA transformer with 2% impedance is installed.

Services for Commercial Buildings are required to be marked with (choose the best single answer): an arc-flash hazard warning the available short-circuit current both a and b.

Answer: Services for Commercial Buildings are required to be marked with (choose the best single answer): a. an arc-flash hazard warning b. the available short-circuit current c. both a. and b.

The short-circuit current on a 208-volt system at a distance of 50 ft, using 1 AWG conductors, will be __________________________ amperes.

Answer: The symmetrical short-circuit current on a 208-V system from a 300-kVA transformer with 2% impedance at a distance of 50 ft using 1 AWG conductors will be 11,740 Amps.

The short-circuit current on a 480-volt system at a distance of 100 ft, using 500 kcmil conductors, will be __________________________ amperes.

Answer: The symmetrical short-circuit current on a 480-V system from a 300-kVA transformer with 2% impedance at a distance of 100 ft using 500-kcmil conductors will be 14,810 Amps.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

In your own words, define and give a hypothetical example of a selectively coordinated system. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: Being selectively coordinated means that in case of a short circuit or ground fault, only the overcurrent device immediately upstream from the point of the short circuit or ground fault will interrupt the current. If a fault were to occur on a branchcircuit, only the breaker protecting the branch circuit would open.

Identify some common causes of nonselectivity. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: Non-selectivity is caused by the improper selection and/or setting of protective devices that provide upstream protection of circuits or feeders supplying other protective devices.

A panelboard is protected by a 225-ampere main circuit breaker and contains several 20-ampere breakers for branch-circuit protection. The breakers are all factory-set to unlatch at 10 times their rating. (Circle your response.)

For a 500-ampere short circuit or ground fault on the load side of a 20-ampere breaker, only the 20-ampere breaker will trip off. (True) (False) For a 3000-ampere short circuit or ground fault on the load side of the 20-ampere breaker, the 20-ampere breaker, and the 225-ampere breaker will trip off. (True) (False) Answer: a. For a 500-Amp short circuit or ground fault on the load side of a 20-Amp breaker, only the 20-Amp breaker will trip off. True. Both breakers’ magnetic trip settings are factory set at 10 times their current rating. The 20-Amp breaker will trip instantly at 20 amps × 10 = 200 A. It will trip off when a fault of 500 Amps occurs.

The 225-Amp breaker will trip instantly at 225 Amps × 10 = 2250 Amps. It will not trip off instantly when a fault of 500 Amps occurs but will be in a time-delay mode. The system is selective.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

b. For a 3000-Amp short circuit or ground fault on the load side of the 20-Amp breaker, the 20-Amp breaker and the 225-Amp breaker will trip off True. Both breakers’ magnetic trip settings are factory set at 10 times their current rating. The 20-Amp breaker will trip instantly at 20 Amps × 10 = 200 Amps. It will trip off without time delay when a fault of 3000 Amps occurs.

The 225-Amp breaker will trip instantly at 225 Amps × 10 = 2250 Amps. It will trip off without time delay when a fault of 3000 Amps occurs.

Because both breakers are in series, the current flowing through both breakers is the same. Both breakers will trip off for fault currents greater than 10 × 225 Amps = 2250 Amps. The system is nonselective.

Note to instructor: The values in the short-circuit calculation for Questions 7 and 8 have been determined using a pocket calculator. A greater level of accuracy is unnecessary because a degree of uncertainty always exists. For instance, the value of C is only approximate, for it will vary dependent on the temperature of the conductor and the value of the V3, which is usually rounded off to two places. Also, there may be a discrepancy in the actual length of the installed conductor. A person need not be overly sensitive to the actual values so long as the correct procedure has been followed. It is important to know how to perform the calculations to provide for adequate interrupting ratings of overcurrent devices in compliance with NEC requirements.

The following diagram is to be used for Questions 7 and 8.

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

Refer to the following drawing to make the requested calculations. Use the point-to-point method and show all calculations.

Calculate the short-circuit current at panelboard A. Answer: The short-circuit current at panelboard A is as follows: L = the distance from the transformer to the panelboard = 25 ft I = available short-circuit current at transformer = 20,000 A C = from table of C values for 3/0 AWG copper in steel conduit = 12,843 EL–L = line to line voltage = 208 ISCA = short-circuit current f = (√3 × L × I)/(C × EL–L) f = (1.73 × 25 ft × 20,000 A)/(12,843 × 208-V) f = 866,025/2,671,344 = 0.324 M = 1/(1 + f) = 1/1.324 = 0.755 ISCA = 20,000 × 0.755 = 15,100 A Calculate the short-circuit current at panelboard B. Answer: The short-circuit current at panelboard B is as follows: L = the distance from the panel A to panel B = 5 ft I = available short-circuit current at panel A = 15,100 A C = from table of C values for 2 AWG copper in steel conduit = 5906 EL–L = line-to-line voltage = 208-V ISCA = short-circuit current f = (√3 × L × I)/(C × EL–L) f = (1.73 × 5 ft × 15,100 A)/(5906 × 208 V) f = 130,769/1,228,448 = 0.10645 M = 1/(1 + f) = 1/1.10645 = 0.9038 ISCA = 15,100 × 0.9038 = 13,647 AMPS

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4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

Calculate the following fault-current values for a 3-phase L–L–L bolted short circuit that has been calculated to be 40,000 amperes.

The approximate value of a line-to-line fault will be ________________________ amperes.

Answer: The short-circuit current for a line-to-line (L–L; phase-to-phase) bolted fault on a 3-phase, 4-wire, wye-connected system is approximately 87% of a line-to-lineto-line (L–L–L; phase-to-phase-to-phase) bolted fault. Therefore, the RMS value is 40,000 Amps × 0.87 = 34.800 Amps.

The approximate value of a line-to-ground fault will be ________________________ amperes.

Answer: The short-circuit current for a line-to-ground (L–G; phase-to-ground) or lineto-neutral (LN; phase-to-neutral) bolted fault on a 3-phase, 4-wire, wye-connected system can theoretically vary from 25% to 125% of a 3-phase (L–L–L) bolted fault.

However, it is rare for a line-to-ground (L–G) or line-to-neutral (L–N) bolted fault to be more than 100% of the 3- phase (L–L–L) current. In fact, because of the relatively high impedance (opposition to current) of the return paths through metal raceways, locknuts, bushings, connectors, couplings, equipment grounding conductors, metal enclosures, and so on, the L–G or L–N bolted fault current will generally be less than the L–L–L bolted fault current. Therefore, it is common practice to consider a line-toground (L–G) or line-to-neutral (L–N) bolted fault to be 100% of the 3-phase (L–L–L) fault current. This has proved to be a conservative and safe assumption. Therefore, the RMS value is 40,000 × 1.00 = 40,000 A. Note to instructor: Some texts use the factor of 58%, which calculates out to 40,000 A × 58% = 23,200 A. The safe approach is to use the 100% factor.

The Bakery panelboard is marked as having a short-circuit rating of 10,000 amperes RMS symmetrical. The circuit breakers in the panelboard have an interrupting rating of 10,000 amperes.

Because the available fault current on the line side lugs of the Bakery panelboard is 21,417 amperes, explain in your own words how this installation can be made to comply with the NEC. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The Bakery panelboard is marked as having a short-circuit rating of 10,000 A RMS symmetrical. The circuit breakers in the panelboard have an interrupting rating of 10,000 A.

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5

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

Because the available fault current on the line side lugs of the Bakery panelboard is 21,942 A, explain in your own words how this installation can be made to be in compliance with the NEC. Answer: Note to instructor: Here are some things you might want to discuss with your students to further their understanding and appreciation of fault currents and equipment ratings.

The requirements that need to be complied with are found in NEC 110.3(B), 110.22(A), 110.22(B), 110.22(C), 240.86(A), and 240.86(B).

One solution is to install a fully rated system by selecting overcurrent devices that have an interrupting rating of 21,942 A or more. A few of the common interrupting ratings of circuit breakers are 10,000, 14,000, 22,000, and 42,000 A. Here again, it is necessary to check manufacturers’ technical literature.

Another solution is to install a series-rated system. A series-rated combination is basically a line-side (upstream) overcurrent device (fuse or circuit breaker) having an interrupting rating adequate for the available fault current, and a load-side (downstream) circuit breaker that does not have an interrupting rating adequate for the available fault current. Major manufacturers have submitted their series-rated equipment to be subjected to series-rated combination testing, listing, and marking requirements.

These tests verify that certain sizes and classes of fuses, and specific sizes and types of circuit breakers protecting specific circuit breakers do provide safe protection for the lower interrupting rated circuit breakers in the series-rated combination.

Series-rated combinations for use in specific panelboards, load centers, and switchboards can be found in the circuit-breaker manufacturers’ and fuse manufacturers’ literature.

Series-rated combinations can be circuit breaker/circuit breaker or fuse/circuit breaker.

Because the possibility exists in a series-rated system that the line-side device might open (trip off) under a fault condition, this presents another issue, that of selectivity. If selectivity is required, such as might be the case of critical electrical circuits, then a series-rated system might not be the best choice. Selectivity and non-selectivity are covered in detail in the text.

As the contacts of a circuit breaker begin to open, the arcing within the circuit breaker adds impedance to the circuit. This in turn results in lowering the available fault current at the point of application. There is no way to determine the impedance of the arc because it varies greatly. This is sometimes referred to as dynamic impedance, and it is why series-rated combinations require testing by a nationally recognized testing laboratory (NTRL).

Manufacturers show their series-rated combinations in their literature. It is easy to check out their technical information when considering a series-rated system.

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6

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 18: Short-Circuit Calculations and Coordination of Overcurrent Protective Devices

Important: The up-over-down method just described applies only to the currentlimiting effect of current-limiting overcurrent devices that protect equipment that do not begin to open (remains passive) during the time it takes the upstream currentlimiting device to open. Examples of this are old molded-case circuit breakers (often manufactured prior to 1987) that take about one cycle to open and power circuit breakers that take three or more cycles to open. Other examples would be protecting equipment, such as bus duct or busbars in switchboards. Bus duct and busbars have a “bus bracing” or “short-circuit” rating, not an interrupting rating.

The up-over-down method must not be applied to protect circuit breakers that open in 1 2 cycle or less (current limiting circuit breakers). That covers most circuit breakers manufactured in recent years.

Single phasing is caused by ___________________________________________________.

Answer: Single phasing is caused by one or more overcurrent devices opening on a multiphase (three phase) system.

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7

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 19: Equipment and Conductor Short-Circuit Protection

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 19: EQUIPMENT AND CONDUCTOR SHORT-CIRCUIT PROTECTION

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Explain what withstand rating means. _________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The withstand rating is a measure of the ability of conductors and equipment to remain intact for the length of time it takes for the overcurrent device to interrupt the current.

Explain what the term effective grounding path means. _________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The definition of an effective grounding path is found in NEC Article 100. An ►Effective Ground-Fault Current Path is An intentionally constructed, low-impedance electrically conductive path designed and intended to carry current during groundfault events from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors.*◄ Define I2t. __________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 19: Equipment and Conductor Short-Circuit Protection

Answer: I2t is read amperes squared seconds and is a measure of the quantity of energy that is generated as a result of and during a fault. “I” represents the RMS current in amperes and “t” represents the time in seconds.

Define a current-limiting overcurrent device. ___________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: A current-limiting overcurrent device is a protective device that will interrupt the current when a fault occurs before the current reaches its maximum magnitude. A device that, when interrupting currents in its current-limiting range, reduces the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance.* It limits the instantaneous peak-current to a value less than what the system could deliver under fault conditions; this current limitation occurs in less than a one-half cycle.

Define an equipment grounding conductor. ___________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: An equipment grounding conductor is used to provide a ground-fault current path, connect normally non-current-carrying parts of equipment together and to extend the connection to ground (earth). A conductive path(s) that is part of an effective ground-fault current path and connects normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.* NEC Article 100, Definitions. An equipment grounding conductor can be a wire, a busbar, a metallic raceway, or any of the other conductors as listed in NEC 250.118(A).

What table in the National Electrical Code shows the minimum size equipment grounding conductor? _______________________________________________________ Answer: NEC Table 250.122 gives the minimum size for an equipment grounding conductor.

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 19: Equipment and Conductor Short-Circuit Protection

For the following problems, show all required calculations.

What is the appropriate action if the label on a motor controller or the nameplate on other electrical equipment is marked “Maximum Fuse Size”? Cite the Code section that supports your proposed action. ____________________________________________________________________________ ____________________________________________________________________________ Answer: If the label of a motor is marked “Maximum Fuse Size” a fuse must be used to provide protection. See NEC 110.3(B).

What is the maximum current that a 12 AWG, 75°C conductor with thermoplastic insulation can safely carry for 5 seconds? ____________________________________________________________________________ ____________________________________________________________________________ Answer: The maximum current that a 12 AWG, 75°C conductor can safely carry for 5 seconds is 6530/42.25 = 155 Amps. The circular mil area of a 12 AWG conductor is 6530 circular mils, as given in NEC Table 8. The value 42.25 is a constant as given in this book.

What is the maximum current that an 8 AWG, 75°C conductor with thermoplastic insulation can safely carry for 1 second? ____________________________________________________________________________ ____________________________________________________________________________ Answer: The maximum current that an 8 AWG, 75°C thermoplastic insulated conductor can safely carry for 5 seconds is approximately 800 A. This value is taken from Figure 19–3 and is difficult to read to greater accuracy.

The cross-sectional area of an 8 AWG conductor is 16,510 cmil; see NEC Table 8. The constant 42.25 is given in the book; 16,510/42.25 = 391 A for 5 seconds. For 1 second the current is

391 × 391 ×5 = 764,405 = 874 A Note to instructor: If students would like to see or do more calculations similar to this, you may wish to create additional questions. The following rules will provide guidance in creating and solving those questions: •

The safe withstand rating for a 75°C thermoplastic insulated conductor is 1 A for 5 seconds for every 42.25 circular mils.

•

The safe withstand rating for a bare copper conductor or a bolted connection, based on a maximum temperature of 250°C, is 1 A for 5 seconds for every 29.1 circular mils.

•

The melting rating for copper conductors, based on a melting temperature of 1981°F (1083°C), is 1 A for 5 seconds for every 16.19 circular mils.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 19: Equipment and Conductor Short-Circuit Protection

What is the maximum current that a 12 AWG, 75°C conductor with thermoplastic insulation can safely carry for one-quarter cycle (0.004 seconds)? ____________________________________________________________________________ ____________________________________________________________________________ Answer: The maximum current that a 12 AWG 75°C thermoplastic insulated conductor can safely carry for a one-quarter cycle is 5480 Amps. The circular mil area of a 12 AWG conductor is 6530 cmil as given in NEC Table 8. The constant 42.25 is given in the text for a 75°C thermoplastic insulated conductor. A one-quarter cycle is equivalent to 0.004 second; 6532/42.25 = 155 A for 5 seconds; 155 A× 155 A× 5 seconds = 120,125; then

120, 125 / 0.004 = 5480 A for a one-quarter cycle.

Referring to Figure 19-3, if the available fault current is 10,000 amperes and the overcurrent device has a total clearing time of one cycle, the minimum permitted copper 75°C conductor that has thermoplastic insulation would be a ____________________ AWG. Answer: Referring to Figure 19–3, for a fault current of 10,000 A and a clearing time of one cycle, the minimum permitted copper 75°C thermoplastic insulated conductor would be a 6 AWG. Referring to Figure 19-2, if the available fault current is 40,000 amperes, a 200-ampere, 600-volt fuse of the type represented by the chart will have an instantaneous peak let-through current of approximately ____________________ amperes.

Answer: Referring to Figure 19–2, if the available fault current is 40,000 A, a 200-A fuse will have an instantaneous peak let-through current of approximately 14,000 A. Referring to Figure 19-2, if the available fault current is 40,000 amperes, a 200-ampere, 600-volt fuse of the type represented by the chart will have an apparent RMS let-through current of approximately ____________________ amperes.

Answer: Referring to Figure 19–2, if the available fault current is 40,000 A, a 200-A fuse will have an apparent RMS let-through current of approximately 6000 A.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 20: Low-Voltage Remote Control

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 20: LOW-VOLTAGE REMOTE CONTROL

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Refer to Figure 20-1 and respond to the following statements: One way of saving energy in a commercial building can be accomplished by installing luminaires that have _________________________________________________________ Answer: One way of saving energy in a commercial building can be accomplished by installing luminaires that have energy saving lamps and ballasts Describe the action of the low-voltage relay. ___________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The low-voltage relay is a split-coil relay that allows an instantaneous signal to the opposite coil to change the position of the contacts. It is basically a solenoid.

Describe the function of the red conductor. ___________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: In Figure 20–1, the red conductor connects from the ON terminal of the switch to the ON coil of the relay.

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1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 20: Low-Voltage Remote Control

Describe the function of the white conductor. __________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: In Figure 20–1, the white conductor supplies low voltage from the transformer to the common terminal of the switch.

Describe the function of the black conductor. __________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: In Figure 20–1, the black conductor connects the OFF terminal of the switch to the OFF coil of the relay.

Describe the function of the blue conductor. __________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The blue conductor supplies the low-voltage supply from the transformer to the common conductor of the relay.

Respond to the following statements.

The NEC article that governs the installation of the low-voltage remote-control system is _________________________________________________________________ Answer: NEC Article 725 governs the installation of the low-voltage remote-control system.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 20: Low-Voltage Remote Control

Complete the following diagram according to the switching schedule that is given at the bottom of the diagram. Indicate the color of the conductors.

Switching schedule Switch 1

Control relay A

1 2 3 4

A B C&D A&B

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3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 20: Low-Voltage Remote Control

Answer: Complete the diagram below according to the switching schedule that is given at the bottom of the diagram. Indicate the color of the conductors.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 21: The Cooling System

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 21: THE COOLING SYSTEM

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code® or the working drawings when necessary. Where applicable, responses should be written in complete sentences.

Complete the following sentences by writing a component used in a refrigeration system.

The _____________________________ raises the energy level of the refrigerant.

Answer: The compressor raises the energy level of the refrigerant.

The heat is removed from the refrigerant in the _____________________________.

Answer: The heat is removed from the refrigerant in the condenser.

The refrigerant absorbs heat energy in the ___________________________.

Answer: The refrigerant absorbs heat energy in the evaporator.

The _________________________ is a metering device.

Answer: The expansion valve is a metering device.

In the typical residential heating/cooling system, the evaporator would be located ____________________________________________________________________________.

Answer: In the typical residential heating/cooling system, the evaporator would be located in the air distribution duct.

In the typical residential heating/cooling system, the condenser would be located ____________________________________________________________________________.

Answer: In the typical residential heating/cooling system, the condenser would be located outside the residence.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 21: The Cooling System

Respond to the following statements.

Name three types of condensers. (1) _________________, (2) _________________, and (3) _________________.

Answer: Three types of condensers are water cooled, air cooled, and evaporative.

A 230-volt, single-phase, hermetic compressor with an FLA of 21 and an LRA of 250 requires a disconnect switch with a rating of _________________ horsepower.

Answer: A 230-V, single-phase, hermetic compressor with a FLA of 21 Amps and a LRA of 250 Amps requires a disconnect switch with a rating of 10 hp. See NEC Table 430.251(A).

A motor-compressor unit with a rating of 32 amperes is protected from overloads by a separate overload relay selected to trip at not more than _________________ ampere(s).

Answer: A motor-compressor unit with a rating of 32 Amps is protected from overloads by a separate overload relay selected to trip at not more than 32A × 1.4 = 44.8 A, See NEC 440.52(A)(1).

Which NEC section permits the disconnect switch for a large rooftop air conditioner to be mounted inside the unit? ____________________________________________________________________________ Answer: NEC 440.14 permits the disconnect switch for a large rooftop air conditioner to be mounted inside the unit.

The nameplate of an air-conditioning unit specifies 85 amperes as the minimum ampacity for the supply conductors. Select the conductor size and type. ____________________________________________________________________________ Answer: If the nameplate of an air-conditioning unit specifies 85 A as the minimum ampacity for the supply conductors, use this value when consulting NEC Table 310.16.

Because it is under 100 A, the value is selected from the 60°C column regardless of the type of conductor used; see NEC 110.14(C)(1)(a) and (b). The minimum size conductor is a 3 AWG in the 60°C column and may be any of the insulation types listed. A conductor is permitted to be selected from the 75°C column of Table 310.16 if all the terminations are rated at 75°C and the conductor has insulation rated 75°C or greater. A 4 AWG copper conductor with 75°C insulation would then be permitted.

Where the nameplate of an air-conditioning unit specifies the minimum ampacity required for the supply conductors, should the electrician multiply this ampacity by 1.25 to determine the correct size conductors? Explain. ____________________________________________________________________________ ____________________________________________________________________________

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2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 21: The Cooling System

Answer: No. Where the nameplate specifies the minimum ampacity requirements for the supply conductors, there is no need to increase this value by 25%, because the manufacturer of the unit has already applied the 1.25 factor as required by the UL Standards. Sometimes electricians do apply the 1.25 factor if the branch-circuit run is long and there is concern for voltage drop, in which case a larger size conductor might be desirable.

Which current rating of an air-conditioning unit is greater? Check the correct answer. ____________________ rated load current ____________________ branch-circuit selection current Answer: b. The branch-circuit selection current will be equal to or larger than the rated load current (rated load amperes), NEC Article 100. The larger current value must be used when determining branch-circuit conductor sizes, switches, and so on. See NEC Article 100.

In Figure 21-9, CR2 (Control Relay 2) is shown as normally ____________________.

CR1 (Control Relay 1) is shown as normally ____________________.

Answer: In Figure 21-9, CR2 (Control Relay 2) is shown as normally open.

CR1 (Control Relay 1) is shown as normally closed.

In the thermostat shown in Figure 21-9, the selector switch is shown in the (Cool), (Off), and (Heat) positions. (Circle your answer.)

Answer: In the thermostat shown in Figure 21-9, the selector switch is shown in the Cool position. (circle your answer) In Figure 21-9, the electrical supply system is shown as: (Mark the correct answer.) a. ____________________ 208-V, 3-Phase, 3-Wire b. ____________________ 120/240-V, 1-Phase, 3-Wire Answer: In Figure 21-9, the electrical supply system is shown as: a. 208-V, 3-Phase, 3-Wire

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 22: Commercial Utility-Interactive Photovoltaic Systems

Solution and Answer Guide

SIMMONS/ODE, ELECTRICAL WIRING COMMERCIAL, 18E, © 2024, 9780357767115; CHAPTER 22: COMMERCIAL UTILITY-INTERACTIVE PHOTOVOLTAIC SYSTEMS

TABLE OF CONTENTS Review ..................................................................................................................................1

REVIEW Refer to the National Electrical Code when necessary. Where applicable, responses should be written in complete sentences.

Is the electrical current produced by photovoltaic modules ac or dc?

Answer: The modules produce direct current (dc) To size module circuit (source) conductors and components, module string short circuit current (Isc) must be multiplied by _________________________.

Answer: To size module circuit (source circuit) conductors and components, module string short-circuit current (Isc) must be multiplied by 1.56. see NEC 690.8(A) and (B) As module temperature decreases, module open circuit voltage (Voc) _____________________.

Answer: As module temperature decreases, module open-circuit voltage (Voc) increases.

Photovoltaic modules must be grounded per _____________________ the instructions.

Answer: Photovoltaic modules must be grounded per the manufacturer’s instructions and UL Standards.

A group of modules that form a complete photovoltaic power source is known as a(n) _____________________.

Answer: A group of modules that form a complete photovoltaic generating unit is known as an array.

All conductors and components of array circuiting must be rated for _____________________.

Answer: All conductors and components of array circuiting must be rated for installation conditions and circuiting.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

1

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 22: Commercial Utility-Interactive Photovoltaic Systems

Which types of conductors are permitted to be installed as exposed array circuiting?

Answer: Single-conductor cable marked sunlight resistant, Type USE-2, Type RHW-2, or listed and identified Type PV wire or cable are permitted to be installed as exposed outdoor array circuiting within the PV array. See NEC 690.31(C)(1).

Part _____________________ of NEC Article 690 provides requirements for the installation of disconnects in a photovoltaic system.

Answer: Part III of NEC Article 690 provides requirements for installation of disconnecting means for a photovoltaic system.

How is the grounded dc conductor of a photovoltaic system required to be identified? ____________________________________________________________________________ ____________________________________________________________________________ Answer: NEC 210.5(C)(2(b) provides insulation color requirements for negative polarity as: (1) a continuous black outer finish. (2) a continuous black stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray or red. (3) Imprinted minus signs (–) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B). (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted minus signs (–) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red. * Describe the function of a combiner box. ____________________________________________________________________________ ____________________________________________________________________________ Answer: A combiner box connects multiple series strings of modules in parallel to a common output.

Describe the function of a utility-interactive inverter. ____________________________________________________________________________ ____________________________________________________________________________ Answer: A utility-interactive inverter converts the dc from the modules to ac that is synchronized with the utility power.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

2

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 22: Commercial Utility-Interactive Photovoltaic Systems

What are the two key requirements of UL 1741 for utility-interactive inverters? ____________________________________________________________________________ ____________________________________________________________________________ Answer: The two key requirements of UL 1741 for utility-interactive inverters are ground-fault protection and anti-islanding, List the four functions that the ground fault protection system for a utility-interactive inverter must perform. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ Answer: The ground fault protection system for dc PV arrays must: [In Question 13 in Chapter 22 Review, change “function” to “requirements” and delete “perform.”]

•

Detect ground fault in array dc current-carrying conductors and components

•

Be listed for providing PV ground-fault protection

•

Isolate faulted circuits by one of the following means: i.

The faulted current-carrying conductors are automatically disconnected

ii.

The inverter or charge controller fed by the faulted circuit must automatically cease to supply power to output circuits and isolate the PV system dc circuits from the ground reference in a functional grounded system.

Which NEC section provides the requirements for grounding electrode systems in a photovoltaic _____________________ installation?

Answer: NEC 690.47 provides the requirements for grounding electrode systems in a photovoltaic installation.

What are the two types of utility connections permitted by the NEC? ____________________________________________________________________________ ____________________________________________________________________________ Answer: The two types of utility connection permitted by the NEC are load side and supply side.

Which NEC section provides the utility connection requirements for utility-interactive photovoltaic systems? ___________________________ Answer: NEC 690.59 points to Parts I and II of Article 705 for connection requirements of PV systems to other sources.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

3

Solution and Answer Guide: Simmons/Ode, Electrical Wiring Commercial, 18E, © 2024, 9780357767115; Chapter 22: Commercial Utility-Interactive Photovoltaic Systems

The electrical schematic for a utility-interactive photovoltaic system is known as the _______________________________________________________________________________.

Answer: The electrical schematic for a utility-interactive photovoltaic system is known as the single-line diagram.

Which plan sheet will indicate the geographic locations of the photovoltaic system components?

Answer: The site or plot plan will indicate the geographic locations of the photovoltaic system components.

Which NEC section provides working space requirements? ________________________ Answer: NEC 110.26 provides working space requirements.

The process of initial start-up for a utility-interactive photovoltaic system is known as _______________________________________________________________________________.

Answer: The process of initial start-up for a utility-interactive photovoltaic system is known as commissioning. * Source NFPA 70-2023.

© 2024 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

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