NEVADA C-21B AIR CONDITIONING
CONTRACTOR EXAM PRACTICE
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2026/2027 Q&A | INSTANT DOWNLOAD PDF.
Core Domains
1. Refrigeration Cycle and Thermodynamics
2. Electrical Components and Theory (NEC Article 440)
3. Heating and Ventilation Systems
4. Load Calculations and Duct Design (Manual J, D, S)
5. Refrigerants and EPA Section 608 Compliance
6. Nevada Mechanical Codes (UMC/IMC) and Contractor Law
7. Safety Standards (OSHA, NFPA)
8. System Troubleshooting and Diagnostics
Introduction
This comprehensive examination assesses the knowledge and skills
required for the Nevada C-21B Air Conditioning Contractor license. It
evaluates understanding of refrigeration theory, electrical components,
heating and ventilation systems, load calculations, refrigerant handling,
mechanical codes, and Nevada contractor law. The examination employs
multiple-choice and scenario-based questions that mirror the actual PSI-
administered C-21B exam format. Emphasis is placed on critical
thinking, code compliance, and practical HVAC troubleshooting.
Success on this examination demonstrates readiness for Nevada HVAC
,contractor licensure and confirms mastery of essential mechanical
systems competencies.
SECTION ONE: QUESTIONS 1–100
1. What is the primary function of a refrigerant in an air
conditioning system?
A. To provide electrical power to the compressor
B. To absorb heat from the indoor air and release it outdoors
C. To lubricate the moving parts of the compressor
D. To prevent moisture from entering the system
Correct answer B. To absorb heat from the indoor air and release it
outdoors
RATIONALE: The refrigerant circulates through the system,
absorbing heat from indoor air at the evaporator coil and releasing it to
outdoor air at the condenser coil. This heat transfer process is the
fundamental principle of air conditioning .
2. 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
Correct answer B. To de-energize the unit for safe servicing
, RATIONALE: The NEC requires a disconnect within sight of the
appliance to allow service personnel to safely lock out the power
source .
3. A capacitor labeled "35/5 μF 440V" is typically a:
A. Start Capacitor
B. Run Capacitor
C. Dual Run Capacitor
D. Ceramic Capacitor
Correct answer C. Dual Run Capacitor
RATIONALE: The dual rating (35μF and 5μF) indicates it serves
two functions, typically for the compressor (35μF) and the condenser fan
motor (5μF) .
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
Correct answer B. Good
RATIONALE: 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
Correct answer B. The current draw when the rotor is unable to turn
RATIONALE: 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
Correct answer B. Remove the start capacitor from the circuit once
the motor reaches about 75% of its rated speed
RATIONALE: 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
CONTRACTOR EXAM PRACTICE
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2026/2027 Q&A | INSTANT DOWNLOAD PDF.
Core Domains
1. Refrigeration Cycle and Thermodynamics
2. Electrical Components and Theory (NEC Article 440)
3. Heating and Ventilation Systems
4. Load Calculations and Duct Design (Manual J, D, S)
5. Refrigerants and EPA Section 608 Compliance
6. Nevada Mechanical Codes (UMC/IMC) and Contractor Law
7. Safety Standards (OSHA, NFPA)
8. System Troubleshooting and Diagnostics
Introduction
This comprehensive examination assesses the knowledge and skills
required for the Nevada C-21B Air Conditioning Contractor license. It
evaluates understanding of refrigeration theory, electrical components,
heating and ventilation systems, load calculations, refrigerant handling,
mechanical codes, and Nevada contractor law. The examination employs
multiple-choice and scenario-based questions that mirror the actual PSI-
administered C-21B exam format. Emphasis is placed on critical
thinking, code compliance, and practical HVAC troubleshooting.
Success on this examination demonstrates readiness for Nevada HVAC
,contractor licensure and confirms mastery of essential mechanical
systems competencies.
SECTION ONE: QUESTIONS 1–100
1. What is the primary function of a refrigerant in an air
conditioning system?
A. To provide electrical power to the compressor
B. To absorb heat from the indoor air and release it outdoors
C. To lubricate the moving parts of the compressor
D. To prevent moisture from entering the system
Correct answer B. To absorb heat from the indoor air and release it
outdoors
RATIONALE: The refrigerant circulates through the system,
absorbing heat from indoor air at the evaporator coil and releasing it to
outdoor air at the condenser coil. This heat transfer process is the
fundamental principle of air conditioning .
2. 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
Correct answer B. To de-energize the unit for safe servicing
, RATIONALE: The NEC requires a disconnect within sight of the
appliance to allow service personnel to safely lock out the power
source .
3. A capacitor labeled "35/5 μF 440V" is typically a:
A. Start Capacitor
B. Run Capacitor
C. Dual Run Capacitor
D. Ceramic Capacitor
Correct answer C. Dual Run Capacitor
RATIONALE: The dual rating (35μF and 5μF) indicates it serves
two functions, typically for the compressor (35μF) and the condenser fan
motor (5μF) .
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
Correct answer B. Good
RATIONALE: 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
Correct answer B. The current draw when the rotor is unable to turn
RATIONALE: 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
Correct answer B. Remove the start capacitor from the circuit once
the motor reaches about 75% of its rated speed
RATIONALE: 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
