Practice Exam 2026 | 100 Questions &
Answers with Detailed Rationales |
Complete Exam Prep & Study Guide
1. During an inspection, an inspector finds a 120/240-volt single-phase
dwelling service with a grounded conductor that is bonded to the service
disconnect enclosure. At a downstream panelboard, the grounded
conductor is also bonded to the enclosure. What is the primary concern?
A. The grounded conductor is too small
B. The service disconnect is improperly bonded
C. The downstream neutral-to-ground bond can create objectionable current on
equipment grounding paths
D. The grounding electrode conductor must be isolated at the service
Answer: The downstream neutral-to-ground bond can create objectionable
current on equipment grounding paths
Rationale: The grounded conductor-to-enclosure connection belongs at the
service disconnecting means or other permitted service bonding point.
Downstream equipment generally requires isolated grounded and equipment
grounding conductors.
, 2. A 200-ampere dwelling service has a calculated load of 156 amperes. The
service conductors are rated 2/0 copper THHN. What should the inspector
verify before approving the installation?
A. Only the conductor insulation temperature rating
B. The service conductor ampacity, termination ratings, and applicable dwelling-
service provisions
C. Only the grounding electrode resistance
D. Only the meter socket rating
Answer: The service conductor ampacity, termination ratings, and applicable
dwelling-service provisions
Rationale: An inspector must evaluate the complete service installation,
including calculated load, conductor ampacity, terminal limitations, and
applicable NEC allowances.
3. A panelboard contains a circuit breaker identified for use with 75°C
conductors. The installed conductor insulation is marked THHN. Which
temperature limitation is generally applicable when sizing the conductor?
A. 60°C only
B. 75°C where permitted by the equipment and applicable ampacity rules
C. 90°C only for final ampacity
D. 100°C
Answer: 75°C where permitted by the equipment and applicable ampacity rules
Rationale: THHN is commonly rated 90°C dry, but the 90°C value is often used
only for adjustment/correction. The final conductor ampacity must comply with
terminal limitations and applicable NEC requirements.
4. An inspector discovers four current-carrying conductors in a raceway. Two
are ungrounded conductors of a 120/240-volt single-phase circuit and two
are the neutral conductors of separate circuits. What should be determined
before applying adjustment factors?
,A. Whether the conductors are all copper
B. Which conductors are actually current carrying under the applicable rules
C. The conductor insulation color
D. The raceway manufacturer
Answer: Which conductors are actually current carrying under the applicable
rules
Rationale: Adjustment-factor calculations depend on the number of current-
carrying conductors. Certain grounded conductors carrying only the imbalance
of a multiwire circuit are treated differently from grounded conductors carrying
significant nonlinear-load current.
5. A 20-ampere branch circuit supplies a continuous load of 16 amperes. What
minimum branch-circuit ampacity is generally required?
A. 16 amperes
B. 18 amperes
C. 20 amperes
D. 25 amperes
Answer: 20 amperes
Rationale: A continuous load is generally calculated at 125% of its value. Sixteen
amperes × 125% = 20 amperes.
6. An inspector finds a 20-ampere branch circuit protected by a 20-ampere
breaker supplying receptacles. The calculated continuous load is 18
amperes. What is the minimum circuit ampacity required?
A. 18 amperes
B. 20 amperes
C. 22.5 amperes
D. 25 amperes
Answer: 22.5 amperes
, Rationale: The continuous load is 18 × 125% = 22.5 amperes. The inspector must
then verify that the selected conductor and overcurrent protection comply with
the applicable NEC rules.
7. A conductor is installed in a raceway with several other current-carrying
conductors. Its 90°C ampacity is sufficient after adjustment, but its 75°C
ampacity is lower than the required final ampacity. Is the installation
automatically acceptable?
A. Yes, because 90°C ampacity always controls
B. Yes, if the breaker is 90°C rated
C. No, because the final ampacity cannot exceed the applicable terminal
limitation
D. No, because THHN cannot be used in raceways
Answer: No, because the final ampacity cannot exceed the applicable terminal
limitation
Rationale: The 90°C column can often be used for adjustment and correction,
but the final ampacity is constrained by terminal temperature ratings and other
applicable provisions.
8. An inspector observes a disconnecting means installed several feet from
electrical equipment. What is the inspector primarily concerned with?
A. Paint color
B. Whether the disconnect is readily accessible and properly located as required
C. Whether the enclosure is stainless steel
D. Whether the disconnect has a neutral conductor
Answer: Whether the disconnect is readily accessible and properly located as
required
Rationale: Disconnecting means must be located and installed so that
equipment can be safely disconnected for operation and servicing.