SOLUTION AND ANSWER GUIDE
ELECTRICAL WIRING RESIDENTIAL
21ST EDITION
CHAPTER 1: GENERAL INFORMATION FOR ELECTRICAL
INSTALLATIONS
REVIEW QUESTION & ANSWERS
Refer to the NEC or the plans in the back of this text where necessary.
1. What code sets the standard for electrical installation work in the United States?
Answer: The NEC is the basic standard; local and state codes are to be considered also.
2. What entity enforces the requirements set by the NEC? Answer: The local electrical inspection authority or
Authority Having Jurisdiction(AHJ)
3. Does the NEC provide minimum or maximum standards?
Answer: Minimum
4. What do the letters “UL” signify?
Answer: When shown on an electrical product or in a certification mark, it means the product is Listed by
Underwriters Laboratories. It also means that the product met applicable safety standards when it left the
manufacturer’s plant.
5. What section of the NEC states that all listed or labeled equipment shall be installed or used in accordance
with any instructions included in the listing or labeling?
Answer: NEC 110.3(B)
6. When the word “shall” appears in an NEC reference, it means that it (must)(may) be done. (Select the
correct word.)
, Answer: Must
7. What is the purpose of the NEC? What section can this statement be found in?
Answer: The NEC states in 90.2(A) that “The purpose of this Code is the practical safeguarding of persons
and property from hazards arising from the use of electricity.”*
8. Does compliance with the NEC always result in an electrical installation that is adequate, safe, and
efficient? Why?
Answer: No. The NEC states in 90.2(B) that “This Code contains provisions that are considered necessary
for safety. Compliance therewith and proper maintenance results in an installation that is essentially free
from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of
electrical use.”*
Informational Note: Hazards often occur because of overloading of wiring systems by methods or usage not
in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of
electricity. An initial adequate installation and reasonable provisions for system changes will provide for
future increases in the use of electricity.
9. Name two nationally recognized testing laboratories. Answer: Underwriters Laboratories (UL) and Intertek
Testing Services (ETL listing mark). There are other testing laboratories such as Canadian Standards
Association (CSA), Factory Mutual (FM), and others the student might refer to that may be acceptable to
the authority enforcing the Code.
10. a. Do Underwriters Laboratories and the other recognized testing laboratories “approve” products?
b. What do these testing laboratories do?
Answer: a. No. Approval is up to the Authority Having Jurisdiction. See NEC 90.4 and 110.2.
b. They test the products for conformance to applicable product safety standards. When the
product passes these tests, the manufacturer of the product is then permitted to affix a
“label” (often referred to as a “listing mark”) that indicates the product complied with the
applicable safety standard when it left their factory.
11. a. Has the NEC been officially adopted by the community in which you live?
, b. By the state in which you live?
c. If your answer is YES to (a) or (b), are there amendments to the NEC?
d. If your answer is YES to (c), list some of the more important amendments.
Answer: Student answers will vary, depending on where this course is taught. The questions refer to local
issues.
12. Does the NEC make suggestions about how to wire a house that will be occupied by handicapped persons?
Answer: Informative Annex J includes information that is intended to assist the users of the Code in
properly considering the various electrical design constraints of other building systems and are part of the
2010 ADA Standards for Accessible Design. The Informative Annex is not enforceable. The basic NEC
rules still apply. Local communities, counties, states, and/or other govern-mental bodies might have
requirements. Check with your local inspection authority. Ask them if there are any requirements or
suggestions that you might need to follow.
13. A junction box on a piece of European equipment is marked 344 cm3. Convert this to cubic inches. (Hint: Is
there a table that lists standard box sizes?) Answer: 200 0.06102 = 12.204 cubic in.
14. Convert 4500 watts to Btu/hour. Answer: 4500 3.4129 = 15.358 Btu/hour
15. You will learn in Chapter 3 that residential lighting loads are based on 3 volt-amperes per ft.2 (33 volt-
amperes per m2). Determine the minimum lighting load required for an area of 186 m2. Do calculations for
both feet squared and meters squared so you can see the difference in answers. To convert meters squared
to feet squared, refer to Table 1-8.
Answer: Step 1: Convert square meters to square feet
186 10.764 = 2002 sq. ft
Step 2: 2002 3 = 6006 volts-amperes
Working in metrics, the answer is
186 33 = 6138 volt-amperes
, Note: This is an excellent example of what happens when converting inch-pound units to metrics, or vice
versa. You can see that the NEC decided to “round-off”
3 volt-amperes per sq. ft to 33 volt-amperes per square meter. The result is different answers. Not a big
difference, but different nevertheless. Converting a rounded-off inch-pound number to metrics always
results in a fractional metric value. Converting a rounded-off metric number to inch-pound units always
results in a fractional
inch-pound value.
There is no easy way to resolve this issue. Just follow the values as found in the NEC. No doubt inch-
pound measurements will be used in this country for quite a while, so use the inch-pound values until such
time that more information becomes available as on how to handle conversions in the NEC.
See Tables 1-6, 1-7 and 1-8 in Electrical Wiring Residential.
There is also a comprehensive inch-pound/metric conversion table in Appendix D of Electrical Wiring
Residential. Refer to it often.
16. What federal organization dictates requirements for work-related safety issues? (Select the correct answer.)
a. NEC
b. OSHA
c. IAEI
Answer: b. OSHA
17. What can you do to reduce or eliminate the possibility of receiving an electric shock when working on
electrical circuits? (Select the correct answer.)
a. Turn off the power on the circuit you are working on.
b. Turn off the power on the circuit you are working on, tag it, and lock the disconnect in the OFF
position, and verify the absence of voltage on the circuit.
c. Turn off the power on the circuit you are working on, then tell everyone else working with you not to
turn the power back on.
Answer: b. Turn off the power on the circuit you are working on, tag it, and lock the disconnect in
the OFF position.
ELECTRICAL WIRING RESIDENTIAL
21ST EDITION
CHAPTER 1: GENERAL INFORMATION FOR ELECTRICAL
INSTALLATIONS
REVIEW QUESTION & ANSWERS
Refer to the NEC or the plans in the back of this text where necessary.
1. What code sets the standard for electrical installation work in the United States?
Answer: The NEC is the basic standard; local and state codes are to be considered also.
2. What entity enforces the requirements set by the NEC? Answer: The local electrical inspection authority or
Authority Having Jurisdiction(AHJ)
3. Does the NEC provide minimum or maximum standards?
Answer: Minimum
4. What do the letters “UL” signify?
Answer: When shown on an electrical product or in a certification mark, it means the product is Listed by
Underwriters Laboratories. It also means that the product met applicable safety standards when it left the
manufacturer’s plant.
5. What section of the NEC states that all listed or labeled equipment shall be installed or used in accordance
with any instructions included in the listing or labeling?
Answer: NEC 110.3(B)
6. When the word “shall” appears in an NEC reference, it means that it (must)(may) be done. (Select the
correct word.)
, Answer: Must
7. What is the purpose of the NEC? What section can this statement be found in?
Answer: The NEC states in 90.2(A) that “The purpose of this Code is the practical safeguarding of persons
and property from hazards arising from the use of electricity.”*
8. Does compliance with the NEC always result in an electrical installation that is adequate, safe, and
efficient? Why?
Answer: No. The NEC states in 90.2(B) that “This Code contains provisions that are considered necessary
for safety. Compliance therewith and proper maintenance results in an installation that is essentially free
from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of
electrical use.”*
Informational Note: Hazards often occur because of overloading of wiring systems by methods or usage not
in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of
electricity. An initial adequate installation and reasonable provisions for system changes will provide for
future increases in the use of electricity.
9. Name two nationally recognized testing laboratories. Answer: Underwriters Laboratories (UL) and Intertek
Testing Services (ETL listing mark). There are other testing laboratories such as Canadian Standards
Association (CSA), Factory Mutual (FM), and others the student might refer to that may be acceptable to
the authority enforcing the Code.
10. a. Do Underwriters Laboratories and the other recognized testing laboratories “approve” products?
b. What do these testing laboratories do?
Answer: a. No. Approval is up to the Authority Having Jurisdiction. See NEC 90.4 and 110.2.
b. They test the products for conformance to applicable product safety standards. When the
product passes these tests, the manufacturer of the product is then permitted to affix a
“label” (often referred to as a “listing mark”) that indicates the product complied with the
applicable safety standard when it left their factory.
11. a. Has the NEC been officially adopted by the community in which you live?
, b. By the state in which you live?
c. If your answer is YES to (a) or (b), are there amendments to the NEC?
d. If your answer is YES to (c), list some of the more important amendments.
Answer: Student answers will vary, depending on where this course is taught. The questions refer to local
issues.
12. Does the NEC make suggestions about how to wire a house that will be occupied by handicapped persons?
Answer: Informative Annex J includes information that is intended to assist the users of the Code in
properly considering the various electrical design constraints of other building systems and are part of the
2010 ADA Standards for Accessible Design. The Informative Annex is not enforceable. The basic NEC
rules still apply. Local communities, counties, states, and/or other govern-mental bodies might have
requirements. Check with your local inspection authority. Ask them if there are any requirements or
suggestions that you might need to follow.
13. A junction box on a piece of European equipment is marked 344 cm3. Convert this to cubic inches. (Hint: Is
there a table that lists standard box sizes?) Answer: 200 0.06102 = 12.204 cubic in.
14. Convert 4500 watts to Btu/hour. Answer: 4500 3.4129 = 15.358 Btu/hour
15. You will learn in Chapter 3 that residential lighting loads are based on 3 volt-amperes per ft.2 (33 volt-
amperes per m2). Determine the minimum lighting load required for an area of 186 m2. Do calculations for
both feet squared and meters squared so you can see the difference in answers. To convert meters squared
to feet squared, refer to Table 1-8.
Answer: Step 1: Convert square meters to square feet
186 10.764 = 2002 sq. ft
Step 2: 2002 3 = 6006 volts-amperes
Working in metrics, the answer is
186 33 = 6138 volt-amperes
, Note: This is an excellent example of what happens when converting inch-pound units to metrics, or vice
versa. You can see that the NEC decided to “round-off”
3 volt-amperes per sq. ft to 33 volt-amperes per square meter. The result is different answers. Not a big
difference, but different nevertheless. Converting a rounded-off inch-pound number to metrics always
results in a fractional metric value. Converting a rounded-off metric number to inch-pound units always
results in a fractional
inch-pound value.
There is no easy way to resolve this issue. Just follow the values as found in the NEC. No doubt inch-
pound measurements will be used in this country for quite a while, so use the inch-pound values until such
time that more information becomes available as on how to handle conversions in the NEC.
See Tables 1-6, 1-7 and 1-8 in Electrical Wiring Residential.
There is also a comprehensive inch-pound/metric conversion table in Appendix D of Electrical Wiring
Residential. Refer to it often.
16. What federal organization dictates requirements for work-related safety issues? (Select the correct answer.)
a. NEC
b. OSHA
c. IAEI
Answer: b. OSHA
17. What can you do to reduce or eliminate the possibility of receiving an electric shock when working on
electrical circuits? (Select the correct answer.)
a. Turn off the power on the circuit you are working on.
b. Turn off the power on the circuit you are working on, tag it, and lock the disconnect in the OFF
position, and verify the absence of voltage on the circuit.
c. Turn off the power on the circuit you are working on, then tell everyone else working with you not to
turn the power back on.
Answer: b. Turn off the power on the circuit you are working on, tag it, and lock the disconnect in
the OFF position.
