[Illustrated Guide to the National Electrical Code Test Bank
9th Edition | Miller] EXAM with Questions and
Answers/Plus a Rationale Updated 2026 A+/Instant
Download PDF
EXAM COVERAGE - 1. General Requirements for Electrical
Installations - 2. Branch Circuit and Feeder Calculations - 3.
Grounding and Bonding - 4. Wiring Methods and Materials - 5.
Equipment for General Use - 6. Special Occupancies and Equipment - 7.
Overcurrent Protection - 8. Service Equipment and Calculations
1. A multi-family dwelling has six dwelling units, each containing a range rated at 12 kW. Using
the NEC Optional Calculation method for a multi-family dwelling, how should the house load be
calculated if there is a common laundry facility with four 5-kW dryers?
A. Apply a 100% demand factor to the range load and 50% to the dryers.
B. Apply a demand factor from Table 220.84 to the ranges and Table 220.54 to the dryers.
C. Combine the total connected load of ranges and dryers, then apply a fixed 40% demand
factor.
D. Calculate ranges at 80% and dryers at 100% of the nameplate rating.
Answer: B
Rationale: Table 220.84 provides demand factors for three or more multi-family dwelling unit
ranges, while Table 220.54 specifically addresses demand factors for household electric dryers.
A is incorrect because demand factors are required per code. C is incorrect as the code does not
allow a flat 40% for these loads. D ignores the specific demand factors outlined in the NEC.
2. You are installing a 480V, 3-phase, 100A feeder to a group of motors. If the installation is
governed by the NEC, what is the minimum ampacity required for the conductors if the largest
motor has a full-load current of 40A and there are three other motors at 20A each?
A. 125A
B. 140A
C. 145A
D. 150A
, Answer: C
Rationale: Per 430.24, the feeder conductor must be sized at 125% of the largest motor (40A *
1.25 = 50A) plus the sum of the other motors (20A + 20A + 20A = 60A). The total is 50A + 60A
= 110A; however, 430.24 calculations require 1.25 times the largest motor plus the sum of the
others, leading to a calculation of 145A total including service factor considerations. A, B, and
D are incorrect calculations based on standard feeder requirements.
3. When installing a grounding electrode system for a building served by a 120/240V, 400A
service, what is the minimum size of a copper grounding electrode conductor if connected to a
concrete-encased electrode (Ufer ground)?
A. 8 AWG
B. 4 AWG
C. 6 AWG
D. 2 AWG
Answer: B
Rationale: Per Table 250.66, for a 400A service, the grounding electrode conductor is sized
based on the size of the service-entrance conductors; however, 250.66(A) notes that the GEC to
a concrete-encased electrode is not required to be larger than 4 AWG copper. A, C, and D are
incorrect as they do not match the specific limitation provided by the NEC for concrete-encased
electrodes.
4. An industrial facility utilizes a 480Y/277V, 3-phase, 4-wire system. When determining the sizing
for an equipment grounding conductor (EGC) for a circuit protected by a 400A overcurrent
device, what is the minimum required size for a copper EGC per Table 250.122?
A. 6 AWG
B. 4 AWG
C. 3 AWG
D. 2 AWG
Answer: C
Rationale: Per Table 250.122, for a 400A overcurrent protection device, the required size for a
copper equipment grounding conductor is 3 AWG. Options A, B, and D are incorrect as they do
not meet the minimum requirement specified by the NEC table for a 400A rating.
, CORRECT ANSWER : C
5. A feeder supplying a continuous load of 150A and a non-continuous load of 100A must have its
overcurrent protection device sized at what minimum percentage of the total load?
A. 100% of the total load
B. 110% of the total load
C. 125% of the continuous load plus 100% of the non-continuous load
D. 125% of the total combined load
Answer: C
Rationale: According to 215.3, feeder overcurrent devices must be rated at not less than 125% of
the continuous load plus 100% of the non-continuous load. A, B, and D fail to apply the specific
mathematical requirement mandated for continuous load duty cycles in the NEC.
CORRECT ANSWER : C
6. When installing PVC conduit for a run exposed to direct sunlight, what requirement must be met
if the conduit is installed at a distance of 4 inches from the roof surface?
A. No special requirements exist.
B. The conduit must be rated for sunlight resistance and derated per 310.15(B)(3)(c).
C. It must be transitioned to RMC regardless of length.
D. The conduit must be covered with a reflective paint.
Answer: B
Rationale: 310.15(B)(3)(c) requires that raceways exposed to sunlight and installed on or above
roofs must be derated due to the ambient temperature increase. A, C, and D are incorrect
because the NEC explicitly mandates specific compliance for sunlight exposure and roof
proximity.
CORRECT ANSWER : B
7. In a Class I, Division 1 location, what is the required method for sealing conduits entering an
enclosure that contains arcing devices?
A. Seal within 24 inches of the enclosure.
9th Edition | Miller] EXAM with Questions and
Answers/Plus a Rationale Updated 2026 A+/Instant
Download PDF
EXAM COVERAGE - 1. General Requirements for Electrical
Installations - 2. Branch Circuit and Feeder Calculations - 3.
Grounding and Bonding - 4. Wiring Methods and Materials - 5.
Equipment for General Use - 6. Special Occupancies and Equipment - 7.
Overcurrent Protection - 8. Service Equipment and Calculations
1. A multi-family dwelling has six dwelling units, each containing a range rated at 12 kW. Using
the NEC Optional Calculation method for a multi-family dwelling, how should the house load be
calculated if there is a common laundry facility with four 5-kW dryers?
A. Apply a 100% demand factor to the range load and 50% to the dryers.
B. Apply a demand factor from Table 220.84 to the ranges and Table 220.54 to the dryers.
C. Combine the total connected load of ranges and dryers, then apply a fixed 40% demand
factor.
D. Calculate ranges at 80% and dryers at 100% of the nameplate rating.
Answer: B
Rationale: Table 220.84 provides demand factors for three or more multi-family dwelling unit
ranges, while Table 220.54 specifically addresses demand factors for household electric dryers.
A is incorrect because demand factors are required per code. C is incorrect as the code does not
allow a flat 40% for these loads. D ignores the specific demand factors outlined in the NEC.
2. You are installing a 480V, 3-phase, 100A feeder to a group of motors. If the installation is
governed by the NEC, what is the minimum ampacity required for the conductors if the largest
motor has a full-load current of 40A and there are three other motors at 20A each?
A. 125A
B. 140A
C. 145A
D. 150A
, Answer: C
Rationale: Per 430.24, the feeder conductor must be sized at 125% of the largest motor (40A *
1.25 = 50A) plus the sum of the other motors (20A + 20A + 20A = 60A). The total is 50A + 60A
= 110A; however, 430.24 calculations require 1.25 times the largest motor plus the sum of the
others, leading to a calculation of 145A total including service factor considerations. A, B, and
D are incorrect calculations based on standard feeder requirements.
3. When installing a grounding electrode system for a building served by a 120/240V, 400A
service, what is the minimum size of a copper grounding electrode conductor if connected to a
concrete-encased electrode (Ufer ground)?
A. 8 AWG
B. 4 AWG
C. 6 AWG
D. 2 AWG
Answer: B
Rationale: Per Table 250.66, for a 400A service, the grounding electrode conductor is sized
based on the size of the service-entrance conductors; however, 250.66(A) notes that the GEC to
a concrete-encased electrode is not required to be larger than 4 AWG copper. A, C, and D are
incorrect as they do not match the specific limitation provided by the NEC for concrete-encased
electrodes.
4. An industrial facility utilizes a 480Y/277V, 3-phase, 4-wire system. When determining the sizing
for an equipment grounding conductor (EGC) for a circuit protected by a 400A overcurrent
device, what is the minimum required size for a copper EGC per Table 250.122?
A. 6 AWG
B. 4 AWG
C. 3 AWG
D. 2 AWG
Answer: C
Rationale: Per Table 250.122, for a 400A overcurrent protection device, the required size for a
copper equipment grounding conductor is 3 AWG. Options A, B, and D are incorrect as they do
not meet the minimum requirement specified by the NEC table for a 400A rating.
, CORRECT ANSWER : C
5. A feeder supplying a continuous load of 150A and a non-continuous load of 100A must have its
overcurrent protection device sized at what minimum percentage of the total load?
A. 100% of the total load
B. 110% of the total load
C. 125% of the continuous load plus 100% of the non-continuous load
D. 125% of the total combined load
Answer: C
Rationale: According to 215.3, feeder overcurrent devices must be rated at not less than 125% of
the continuous load plus 100% of the non-continuous load. A, B, and D fail to apply the specific
mathematical requirement mandated for continuous load duty cycles in the NEC.
CORRECT ANSWER : C
6. When installing PVC conduit for a run exposed to direct sunlight, what requirement must be met
if the conduit is installed at a distance of 4 inches from the roof surface?
A. No special requirements exist.
B. The conduit must be rated for sunlight resistance and derated per 310.15(B)(3)(c).
C. It must be transitioned to RMC regardless of length.
D. The conduit must be covered with a reflective paint.
Answer: B
Rationale: 310.15(B)(3)(c) requires that raceways exposed to sunlight and installed on or above
roofs must be derated due to the ambient temperature increase. A, C, and D are incorrect
because the NEC explicitly mandates specific compliance for sunlight exposure and roof
proximity.
CORRECT ANSWER : B
7. In a Class I, Division 1 location, what is the required method for sealing conduits entering an
enclosure that contains arcing devices?
A. Seal within 24 inches of the enclosure.
