Nevada (NV) C-21B Air Conditioning Contractor
Practice Exam 2025 || VERIFIED QUESTIONS &
ANSWERS || LATEST UPDATE
Description: This practice exam for the Nevada C-21B Air Conditioning Contractor license
includes the most recent verified questions and accurate answers for 2025. Covers HVAC
installation, service procedures, safety standards, and Nevada state regulations. Ideal for
contractors preparing for state licensing exams.
Keywords: Nevada C-21B exam air conditioning contractor HVAC license Nevada contractor
practice test state licensing exam HVAC installation HVAC service procedures Nevada contractor
test mechanical systems construction licensing
Nevada C-21B Air Conditioning Contractor Practice Exam 2025
Instructions: Read each question carefully and select the best possible answer. The correct
answer is marked with a . Review the explanations to understand the reasoning, which is
crucial for both the exam and your professional practice.
Category 1: Electrical Knowledge & Components (Questions 1-25)
1. What is the primary purpose of a disconnect switch within sight of an air conditioning unit?
A. To act as a regular operating control.
B. To de-energize the unit for safe servicing.
C. To protect the compressor from low voltage.
D. To reset the circuit breaker remotely.
Answer: B. To de-energize the unit for safe servicing.
Explanation: The NEC requires a disconnect within sight of the appliance to allow service
personnel to safely lock out the power source.
2. A capacitor labeled "35/5 µF 440V" is typically a:
A. Start Capacitor
B. Run Capacitor
C. Dual Run Capacitor
D. Ceramic Capacitor
Answer: C. Dual Run Capacitor
,Explanation: The dual rating (35µF and 5µF) indicates it serves two functions, typically for the
compressor (35µF) and the condenser fan motor (5µF).
3. The locking, rotary compressor used in most modern residential AC systems is powered by:
A. Single-Phase AC Current
B. Three-Phase AC Current
C. Direct Current (DC)
D. Split-Phase DC Current
Answer: A. Single-Phase AC Current
Explanation: Residential power is almost exclusively single-phase. Three-phase is more common
in large commercial applications.
4. If a technician measures 0 ohms across a fuse with the power OFF, it indicates the fuse is:
A. Blown
B. Good
C. Requires more testing
D. The wrong type
Answer: B. Good
Explanation: 0 ohms indicates continuity, meaning the circuit inside the fuse is complete and
unbroken.
5. The LRA (Locked Rotor Amps) of a compressor motor represents:
A. The normal running current.
B. The current draw when the rotor is unable to turn.
C. The current at the moment of start.
D. The maximum continuous current.
Answer: B. The current draw when the rotor is unable to turn.
*Explanation: LRA is the very high current drawn when the motor is energized but not rotating,
which can be 5-7 times higher than the RLA.*
6. A potential relay is used to:
A. Protect the compressor from high pressure.
B. Remove the start capacitor from the circuit once the motor reaches about 75% of its rated
speed.
C. Control the low-voltage thermostat circuit.
D. Sense low refrigerant charge.
Answer: B. Remove the start capacitor from the circuit once the motor reaches about 75% of
its rated speed.
Explanation: Potential relays use back EMF (electromotive force) generated by the motor itself
to open the circuit to the start capacitor.
, 7. The minimum working clearance in front of a 240V electrical panel, as per NEC, is:
A. 2 feet
B. 3 feet
C. 4 feet
D. 5 feet
Answer: B. 3 feet
Explanation: NEC 110.26 requires a clear working space of 3 feet in depth for equipment up to
250V to ground.
8. What device protects a motor from overheating due to overload?
A. Contactor
B. Run Capacitor
C. Thermal Overload
D. Transformer
Answer: C. Thermal Overload
Explanation: Thermal overloads, often inherent in the motor, open the circuit if the motor draws
excessive current for a prolonged period.
9. The purpose of a transformer in a low-voltage HVAC control circuit is to:
A. Step up 24V to 240V.
B. Step down line voltage (e.g., 120V/240V) to a safer control voltage (e.g., 24V).
C. Convert AC to DC.
D. Increase the amperage for the control circuit.
Answer: B. Step down line voltage to a safer control voltage.
Explanation: This allows for safer wiring and the use of low-voltage thermostats and controls.
10. A "floating" contact in a pressure switch means:
A. The contacts are welded shut.
B. The switch is in a normally open state.
C. The switch is in a normally closed state.
D. The switch is neither making nor breaking the circuit as the system is in a stable state.
Answer: D. The switch is in a stable state, neither making nor breaking.
Explanation: This term is often used with anti-short cycle timers, where the contacts are open for
a set time after the system cycles off.
11. The RLA (Rated Load Amps) on a compressor nameplate is:
A. The current you should always measure during operation.
B. The maximum current the compressor should draw under standard operating conditions.
C. The current draw when the compressor starts.
Practice Exam 2025 || VERIFIED QUESTIONS &
ANSWERS || LATEST UPDATE
Description: This practice exam for the Nevada C-21B Air Conditioning Contractor license
includes the most recent verified questions and accurate answers for 2025. Covers HVAC
installation, service procedures, safety standards, and Nevada state regulations. Ideal for
contractors preparing for state licensing exams.
Keywords: Nevada C-21B exam air conditioning contractor HVAC license Nevada contractor
practice test state licensing exam HVAC installation HVAC service procedures Nevada contractor
test mechanical systems construction licensing
Nevada C-21B Air Conditioning Contractor Practice Exam 2025
Instructions: Read each question carefully and select the best possible answer. The correct
answer is marked with a . Review the explanations to understand the reasoning, which is
crucial for both the exam and your professional practice.
Category 1: Electrical Knowledge & Components (Questions 1-25)
1. What is the primary purpose of a disconnect switch within sight of an air conditioning unit?
A. To act as a regular operating control.
B. To de-energize the unit for safe servicing.
C. To protect the compressor from low voltage.
D. To reset the circuit breaker remotely.
Answer: B. To de-energize the unit for safe servicing.
Explanation: The NEC requires a disconnect within sight of the appliance to allow service
personnel to safely lock out the power source.
2. A capacitor labeled "35/5 µF 440V" is typically a:
A. Start Capacitor
B. Run Capacitor
C. Dual Run Capacitor
D. Ceramic Capacitor
Answer: C. Dual Run Capacitor
,Explanation: The dual rating (35µF and 5µF) indicates it serves two functions, typically for the
compressor (35µF) and the condenser fan motor (5µF).
3. The locking, rotary compressor used in most modern residential AC systems is powered by:
A. Single-Phase AC Current
B. Three-Phase AC Current
C. Direct Current (DC)
D. Split-Phase DC Current
Answer: A. Single-Phase AC Current
Explanation: Residential power is almost exclusively single-phase. Three-phase is more common
in large commercial applications.
4. If a technician measures 0 ohms across a fuse with the power OFF, it indicates the fuse is:
A. Blown
B. Good
C. Requires more testing
D. The wrong type
Answer: B. Good
Explanation: 0 ohms indicates continuity, meaning the circuit inside the fuse is complete and
unbroken.
5. The LRA (Locked Rotor Amps) of a compressor motor represents:
A. The normal running current.
B. The current draw when the rotor is unable to turn.
C. The current at the moment of start.
D. The maximum continuous current.
Answer: B. The current draw when the rotor is unable to turn.
*Explanation: LRA is the very high current drawn when the motor is energized but not rotating,
which can be 5-7 times higher than the RLA.*
6. A potential relay is used to:
A. Protect the compressor from high pressure.
B. Remove the start capacitor from the circuit once the motor reaches about 75% of its rated
speed.
C. Control the low-voltage thermostat circuit.
D. Sense low refrigerant charge.
Answer: B. Remove the start capacitor from the circuit once the motor reaches about 75% of
its rated speed.
Explanation: Potential relays use back EMF (electromotive force) generated by the motor itself
to open the circuit to the start capacitor.
, 7. The minimum working clearance in front of a 240V electrical panel, as per NEC, is:
A. 2 feet
B. 3 feet
C. 4 feet
D. 5 feet
Answer: B. 3 feet
Explanation: NEC 110.26 requires a clear working space of 3 feet in depth for equipment up to
250V to ground.
8. What device protects a motor from overheating due to overload?
A. Contactor
B. Run Capacitor
C. Thermal Overload
D. Transformer
Answer: C. Thermal Overload
Explanation: Thermal overloads, often inherent in the motor, open the circuit if the motor draws
excessive current for a prolonged period.
9. The purpose of a transformer in a low-voltage HVAC control circuit is to:
A. Step up 24V to 240V.
B. Step down line voltage (e.g., 120V/240V) to a safer control voltage (e.g., 24V).
C. Convert AC to DC.
D. Increase the amperage for the control circuit.
Answer: B. Step down line voltage to a safer control voltage.
Explanation: This allows for safer wiring and the use of low-voltage thermostats and controls.
10. A "floating" contact in a pressure switch means:
A. The contacts are welded shut.
B. The switch is in a normally open state.
C. The switch is in a normally closed state.
D. The switch is neither making nor breaking the circuit as the system is in a stable state.
Answer: D. The switch is in a stable state, neither making nor breaking.
Explanation: This term is often used with anti-short cycle timers, where the contacts are open for
a set time after the system cycles off.
11. The RLA (Rated Load Amps) on a compressor nameplate is:
A. The current you should always measure during operation.
B. The maximum current the compressor should draw under standard operating conditions.
C. The current draw when the compressor starts.
