Nevada (NV) C-21B Air-Conditioning
Contractor Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Exam Prep &
Study Guide
1. What is the primary function of an air-conditioning system?
A. Increase indoor humidity only
B. Control indoor temperature and related air conditions
C. Produce domestic hot water
D. Increase electrical voltage
Answer: B. Control indoor temperature and related air conditions
Rationale: An air-conditioning system removes or adds heat as needed to
control indoor temperature. Depending on the equipment, it may also control
humidity, air movement, and filtration.
2. Which component removes heat from indoor air in a typical split-system air
conditioner?
A. Condenser coil
B. Compressor
,C. Evaporator coil
D. Receiver
Answer: C. Evaporator coil
Rationale: The evaporator absorbs heat from the indoor air as refrigerant
evaporates inside the coil.
3. What is the primary function of the compressor?
A. Remove moisture from the air
B. Circulate refrigerant and raise its pressure
C. Reduce refrigerant pressure
D. Filter indoor air
Answer: B. Circulate refrigerant and raise its pressure
Rationale: The compressor draws low-pressure refrigerant vapor from the
evaporator and compresses it into a high-pressure, high-temperature vapor.
4. What happens to refrigerant in the condenser?
A. It absorbs heat from the building
B. It evaporates completely
C. It rejects heat and changes from vapor toward liquid
D. It loses all pressure
Answer: C. It rejects heat and changes from vapor toward liquid
Rationale: The condenser rejects heat to the outdoor environment, causing high-
pressure refrigerant vapor to condense into liquid.
5. What is the purpose of the metering device?
,A. Increase refrigerant pressure
B. Reduce refrigerant pressure and regulate flow
C. Increase compressor speed
D. Remove oil from the compressor
Answer: B. Reduce refrigerant pressure and regulate flow
Rationale: The metering device creates a pressure drop between the high side
and low side while controlling the amount of refrigerant entering the
evaporator.
6. Which device is commonly used as a refrigerant metering device?
A. Thermostatic expansion valve
B. Contactor
C. Pressure switch
D. Transformer
Answer: A. Thermostatic expansion valve
Rationale: A TXV regulates refrigerant flow into the evaporator based largely on
evaporator outlet conditions and superheat.
7. What does superheat describe?
A. Liquid temperature below saturation temperature
B. Vapor temperature above its saturation temperature
C. Condenser pressure below atmospheric pressure
D. Compressor temperature below room temperature
Answer: B. Vapor temperature above its saturation temperature
Rationale: Superheat is the amount by which a vapor's actual temperature
exceeds its saturation temperature at a given pressure.
, 8. What does subcooling describe?
A. Liquid temperature below its saturation temperature
B. Vapor temperature above saturation
C. Compressor temperature above discharge temperature
D. Air temperature below freezing
Answer: A. Liquid temperature below its saturation temperature
Rationale: Subcooling indicates how much a liquid refrigerant has been cooled
below its saturation temperature at the measured pressure.
9. What is the purpose of a filter-drier in a refrigeration circuit?
A. Increase airflow
B. Remove moisture and contaminants from refrigerant
C. Increase compressor horsepower
D. Reduce blower noise
Answer: B. Remove moisture and contaminants from refrigerant
Rationale: A filter-drier helps trap contaminants and absorb moisture that could
damage system components or contribute to corrosion and acid formation.
10. Why is moisture in a refrigeration system undesirable?
A. It increases airflow
B. It can freeze, corrode components, and contribute to acid formation
C. It improves compressor lubrication
D. It increases system capacity
Answer: B. It can freeze, corrode components, and contribute to acid formation
Contractor Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Exam Prep &
Study Guide
1. What is the primary function of an air-conditioning system?
A. Increase indoor humidity only
B. Control indoor temperature and related air conditions
C. Produce domestic hot water
D. Increase electrical voltage
Answer: B. Control indoor temperature and related air conditions
Rationale: An air-conditioning system removes or adds heat as needed to
control indoor temperature. Depending on the equipment, it may also control
humidity, air movement, and filtration.
2. Which component removes heat from indoor air in a typical split-system air
conditioner?
A. Condenser coil
B. Compressor
,C. Evaporator coil
D. Receiver
Answer: C. Evaporator coil
Rationale: The evaporator absorbs heat from the indoor air as refrigerant
evaporates inside the coil.
3. What is the primary function of the compressor?
A. Remove moisture from the air
B. Circulate refrigerant and raise its pressure
C. Reduce refrigerant pressure
D. Filter indoor air
Answer: B. Circulate refrigerant and raise its pressure
Rationale: The compressor draws low-pressure refrigerant vapor from the
evaporator and compresses it into a high-pressure, high-temperature vapor.
4. What happens to refrigerant in the condenser?
A. It absorbs heat from the building
B. It evaporates completely
C. It rejects heat and changes from vapor toward liquid
D. It loses all pressure
Answer: C. It rejects heat and changes from vapor toward liquid
Rationale: The condenser rejects heat to the outdoor environment, causing high-
pressure refrigerant vapor to condense into liquid.
5. What is the purpose of the metering device?
,A. Increase refrigerant pressure
B. Reduce refrigerant pressure and regulate flow
C. Increase compressor speed
D. Remove oil from the compressor
Answer: B. Reduce refrigerant pressure and regulate flow
Rationale: The metering device creates a pressure drop between the high side
and low side while controlling the amount of refrigerant entering the
evaporator.
6. Which device is commonly used as a refrigerant metering device?
A. Thermostatic expansion valve
B. Contactor
C. Pressure switch
D. Transformer
Answer: A. Thermostatic expansion valve
Rationale: A TXV regulates refrigerant flow into the evaporator based largely on
evaporator outlet conditions and superheat.
7. What does superheat describe?
A. Liquid temperature below saturation temperature
B. Vapor temperature above its saturation temperature
C. Condenser pressure below atmospheric pressure
D. Compressor temperature below room temperature
Answer: B. Vapor temperature above its saturation temperature
Rationale: Superheat is the amount by which a vapor's actual temperature
exceeds its saturation temperature at a given pressure.
, 8. What does subcooling describe?
A. Liquid temperature below its saturation temperature
B. Vapor temperature above saturation
C. Compressor temperature above discharge temperature
D. Air temperature below freezing
Answer: A. Liquid temperature below its saturation temperature
Rationale: Subcooling indicates how much a liquid refrigerant has been cooled
below its saturation temperature at the measured pressure.
9. What is the purpose of a filter-drier in a refrigeration circuit?
A. Increase airflow
B. Remove moisture and contaminants from refrigerant
C. Increase compressor horsepower
D. Reduce blower noise
Answer: B. Remove moisture and contaminants from refrigerant
Rationale: A filter-drier helps trap contaminants and absorb moisture that could
damage system components or contribute to corrosion and acid formation.
10. Why is moisture in a refrigeration system undesirable?
A. It increases airflow
B. It can freeze, corrode components, and contribute to acid formation
C. It improves compressor lubrication
D. It increases system capacity
Answer: B. It can freeze, corrode components, and contribute to acid formation
