North Carolina Electrical Inspector – Level II
Commercial Code Enforcement Practice Bank Original
Questions with Detailed Rationales
Section 1: Branch Circuits, Feeders & Service Calculations
(Questions 1–12)
Question 1
An electrical inspector is evaluating a 480Y/277V, 3-phase, 4-wire
commercial service feeders supplying non-linear electronic lighting
loads. How must the neutral conductor be sized in relation to the
ungrounded phase conductors when non-linear loads account for
more than 50% of the total load?
• A. Sized at 50% of the ungrounded conductor capacity
• B. Reduced by applying a 70% demand factor per NEC 220.61(B)
• C. Sized at 100% of the ungrounded conductor ampacity without
reduction, considering the neutral a current-carrying conductor for
ampacity derating
• D. Sized two AWG sizes larger than the ungrounded conductors in
all circumstances
Correct Answer: C
Detailed Rationale: Per NEC 220.61(C) and NEC 310.15(E)(3),
neutral conductors supplying 3-phase, 4-wire systems where over 50%
of the load consists of non-linear loads (such as fluorescent/LED ballasts
or electronic equipment) carry significant triplen harmonic currents.
Therefore, the neutral cannot be reduced and must be counted as a
current-carrying conductor when applying adjustment factors.
Question 2
,During an inspection of a commercial office building, a 20-ampere,
120-volt branch circuit supplies multiwire branch circuits. Which
code requirement applies to the circuit breakers disconnecting these
multiwire branch circuits at the panelboard?
• A. Circuit breakers must have handle ties or be multi-pole breakers
to simultaneously disconnect all ungrounded conductors at the
point of origin.
• B. Breakers must be GFCI-protected regardless of location.
• C. Neutral conductors must be tied together across different
multiwire circuits.
• D. Individual single-pole breakers without handle ties are
permitted if labeled in red.
Correct Answer: A
Detailed Rationale: NEC 210.4(B) explicitly requires each multiwire
branch circuit to be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where the branch
circuit originates (e.g., approved handle ties or a multi-pole circuit
breaker) to ensure safety during maintenance.
Question 3
A commercial service is being installed with three parallel 500 kcmil
THHN copper ungrounded conductors per phase in separate
raceways. What is the minimum size required for the aluminum
equipment grounding conductor (EGC) installed in each parallel
raceway if the overcurrent protective device is rated at 1200
amperes?
• A. 3/0 AWG Aluminum
• B. 4/0 AWG Aluminum
• C. 250 kcmil Aluminum
• D. 350 kcmil Aluminum
,Correct Answer: C
Detailed Rationale: According to NEC 250.122(F) and Table 250.122,
when conductors are installed in parallel in separate raceways, the
equipment grounding conductor in each raceway must be sized based on
the rating of the overcurrent device protecting the circuit. For a 1200-
ampere overcurrent device, Table 250.122 specifies a minimum size of
250 kcmil Aluminum (or 3/0 AWG Copper).
Question 4
What is the minimum clearance required in front of a 480Y/277V
commercial switchboard where exposed live parts are on one side
and grounded building structural steel is directly opposite
(Condition 2)?
• A. 3.0 feet (900 mm)
• B. 3.5 feet (1.07 m)
• C. 4.0 feet (1.2 m)
• D. 5.0 feet (1.52 m)
Correct Answer: B
Detailed Rationale: Per NEC 110.26(A)(1) and Table 110.26(A)(1),
for nominal voltages to ground between 151V and 600V:
• Condition 1 (Exposed live parts on one side, non-grounded on the
other): 3.0 ft
• Condition 2 (Exposed live parts on one side, grounded structural
parts/concrete/steel on the other): 3.5 ft
• Condition 3 (Exposed live parts on both sides): 4.0 ft
Question 5
In a commercial kitchen, which of the following 120-volt to 250-volt
receptacles requires Ground-Fault Circuit-Interrupter (GFCI)
protection?
, • A. Only 15-ampere and 20-ampere 120V single-phase receptacles
• B. All single-phase receptacles rated 50 amperes or less and three-
phase receptacles rated 100 amperes or less
• C. Only receptacles installed within 6 feet of the sink edge
• D. Receptacles dedicated exclusively to fixed refrigeration
equipment
Correct Answer: B
Detailed Rationale: Under NEC 210.8(B)(2), all single-phase
receptacles rated 50 amperes or less and three-phase receptacles rated
100 amperes or less installed in commercial kitchens require GFCI
protection, regardless of distance from sinks or equipment served.
Question 6
An inspector evaluates a feeders supplying a continuous commercial
lighting load calculated at 80 amperes. If the panelboard terminals
are rated for 75∘ C, what is the minimum required ampacity rating
for the feeder conductors prior to applying ambient temperature
correction factors?
• A. 80 amperes
• B. 92 amperes
• C. 100 amperes
• D. 125 amperes
Correct Answer: C
Detailed Rationale: Per NEC 215.2(A)(1) and NEC 230.42(A), feeder
and service conductors supplying continuous loads must have an
ampacity not less than 100% of non-continuous loads plus 125% of
continuous loads.
Required Ampacity = 80 A × 1.25 = 100 amperes
Required Ampacity = 80 A × 1.25 = 100 amperes
Commercial Code Enforcement Practice Bank Original
Questions with Detailed Rationales
Section 1: Branch Circuits, Feeders & Service Calculations
(Questions 1–12)
Question 1
An electrical inspector is evaluating a 480Y/277V, 3-phase, 4-wire
commercial service feeders supplying non-linear electronic lighting
loads. How must the neutral conductor be sized in relation to the
ungrounded phase conductors when non-linear loads account for
more than 50% of the total load?
• A. Sized at 50% of the ungrounded conductor capacity
• B. Reduced by applying a 70% demand factor per NEC 220.61(B)
• C. Sized at 100% of the ungrounded conductor ampacity without
reduction, considering the neutral a current-carrying conductor for
ampacity derating
• D. Sized two AWG sizes larger than the ungrounded conductors in
all circumstances
Correct Answer: C
Detailed Rationale: Per NEC 220.61(C) and NEC 310.15(E)(3),
neutral conductors supplying 3-phase, 4-wire systems where over 50%
of the load consists of non-linear loads (such as fluorescent/LED ballasts
or electronic equipment) carry significant triplen harmonic currents.
Therefore, the neutral cannot be reduced and must be counted as a
current-carrying conductor when applying adjustment factors.
Question 2
,During an inspection of a commercial office building, a 20-ampere,
120-volt branch circuit supplies multiwire branch circuits. Which
code requirement applies to the circuit breakers disconnecting these
multiwire branch circuits at the panelboard?
• A. Circuit breakers must have handle ties or be multi-pole breakers
to simultaneously disconnect all ungrounded conductors at the
point of origin.
• B. Breakers must be GFCI-protected regardless of location.
• C. Neutral conductors must be tied together across different
multiwire circuits.
• D. Individual single-pole breakers without handle ties are
permitted if labeled in red.
Correct Answer: A
Detailed Rationale: NEC 210.4(B) explicitly requires each multiwire
branch circuit to be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where the branch
circuit originates (e.g., approved handle ties or a multi-pole circuit
breaker) to ensure safety during maintenance.
Question 3
A commercial service is being installed with three parallel 500 kcmil
THHN copper ungrounded conductors per phase in separate
raceways. What is the minimum size required for the aluminum
equipment grounding conductor (EGC) installed in each parallel
raceway if the overcurrent protective device is rated at 1200
amperes?
• A. 3/0 AWG Aluminum
• B. 4/0 AWG Aluminum
• C. 250 kcmil Aluminum
• D. 350 kcmil Aluminum
,Correct Answer: C
Detailed Rationale: According to NEC 250.122(F) and Table 250.122,
when conductors are installed in parallel in separate raceways, the
equipment grounding conductor in each raceway must be sized based on
the rating of the overcurrent device protecting the circuit. For a 1200-
ampere overcurrent device, Table 250.122 specifies a minimum size of
250 kcmil Aluminum (or 3/0 AWG Copper).
Question 4
What is the minimum clearance required in front of a 480Y/277V
commercial switchboard where exposed live parts are on one side
and grounded building structural steel is directly opposite
(Condition 2)?
• A. 3.0 feet (900 mm)
• B. 3.5 feet (1.07 m)
• C. 4.0 feet (1.2 m)
• D. 5.0 feet (1.52 m)
Correct Answer: B
Detailed Rationale: Per NEC 110.26(A)(1) and Table 110.26(A)(1),
for nominal voltages to ground between 151V and 600V:
• Condition 1 (Exposed live parts on one side, non-grounded on the
other): 3.0 ft
• Condition 2 (Exposed live parts on one side, grounded structural
parts/concrete/steel on the other): 3.5 ft
• Condition 3 (Exposed live parts on both sides): 4.0 ft
Question 5
In a commercial kitchen, which of the following 120-volt to 250-volt
receptacles requires Ground-Fault Circuit-Interrupter (GFCI)
protection?
, • A. Only 15-ampere and 20-ampere 120V single-phase receptacles
• B. All single-phase receptacles rated 50 amperes or less and three-
phase receptacles rated 100 amperes or less
• C. Only receptacles installed within 6 feet of the sink edge
• D. Receptacles dedicated exclusively to fixed refrigeration
equipment
Correct Answer: B
Detailed Rationale: Under NEC 210.8(B)(2), all single-phase
receptacles rated 50 amperes or less and three-phase receptacles rated
100 amperes or less installed in commercial kitchens require GFCI
protection, regardless of distance from sinks or equipment served.
Question 6
An inspector evaluates a feeders supplying a continuous commercial
lighting load calculated at 80 amperes. If the panelboard terminals
are rated for 75∘ C, what is the minimum required ampacity rating
for the feeder conductors prior to applying ambient temperature
correction factors?
• A. 80 amperes
• B. 92 amperes
• C. 100 amperes
• D. 125 amperes
Correct Answer: C
Detailed Rationale: Per NEC 215.2(A)(1) and NEC 230.42(A), feeder
and service conductors supplying continuous loads must have an
ampacity not less than 100% of non-continuous loads plus 125% of
continuous loads.
Required Ampacity = 80 A × 1.25 = 100 amperes
Required Ampacity = 80 A × 1.25 = 100 amperes
