California HVAC Contractor (C-20)
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary function of an evaporator in a vapor-
compression refrigeration system?
A. Reject heat to outdoor air
B. Increase refrigerant pressure
C. Absorb heat from the conditioned space
D. Store liquid refrigerant
Answer: C. Absorb heat from the conditioned space
Rationale: The evaporator is the heat-absorbing component of a
refrigeration cycle. Low-pressure refrigerant enters the evaporator and
absorbs heat from indoor air, water, or another medium as it changes
from liquid to vapor. The compressor then draws the resulting vapor
into the suction line.
2. Which component raises the pressure and temperature of
refrigerant vapor leaving the evaporator?
A. Compressor
B. Condenser
C. Expansion valve
D. Receiver
,Answer: A. Compressor
Answer: A. Compressor
Rationale: The compressor takes low-pressure, low-temperature
refrigerant vapor from the evaporator and compresses it into a high-
pressure, high-temperature vapor. This pressure increase allows the
refrigerant to reject heat effectively in the condenser.
3. In a conventional air-conditioning system, the condenser's
primary purpose is to:
A. Meter refrigerant
B. Remove moisture from indoor air
C. Lower compressor discharge pressure
D. Reject heat from the refrigerant to the surroundings
Answer: D. Reject heat from the refrigerant to the surroundings
Rationale: The condenser transfers heat from the hot refrigerant
vapor to outdoor air or another cooling medium. As heat is removed,
the refrigerant condenses from vapor to liquid. Proper condenser
airflow and heat transfer are essential for efficient system operation.
4. What does superheat describe in a refrigeration system?
A. Pressure above atmospheric pressure
B. Temperature of a vapor above its saturation temperature at a
given pressure
C. Temperature below freezing
D. Amount of liquid refrigerant in the receiver
,Answer: B. Temperature of a vapor above its saturation
temperature at a given pressure
Rationale: Superheat is the difference between the actual vapor
temperature and the saturation temperature corresponding to the
measured pressure. Measuring superheat helps technicians determine
whether refrigerant leaving an evaporator is completely vaporized and
can assist in diagnosing charging and metering problems.
5. What does subcooling indicate?
A. Liquid refrigerant temperature below its saturation temperature
at the measured pressure
B. Vapor temperature above saturation
C. Compressor motor temperature
D. Indoor-air temperature below setpoint
Answer: A. Liquid refrigerant temperature below its saturation
temperature at the measured pressure
Rationale: Subcooling is the difference between refrigerant saturation
temperature and actual liquid temperature. Adequate subcooling can
help ensure that solid liquid refrigerant reaches the metering device
rather than flashing prematurely in the liquid line.
6. Which device is commonly used to regulate refrigerant flow into
an evaporator according to evaporator load?
A. Sight glass
B. Accumulator
C. Thermostatic expansion valve
D. Liquid receiver
, Answer: C. Thermostatic expansion valve
Rationale: A thermostatic expansion valve, or TXV, regulates
refrigerant entering the evaporator based largely on evaporator outlet
superheat. It responds to load changes and helps maintain proper
evaporator utilization while protecting the compressor from liquid
refrigerant.
7. What is the purpose of an evaporator blower in a forced-air
HVAC system?
A. Compress refrigerant
B. Move air across the heat exchanger and through the duct system
C. Condense refrigerant
D. Meter fuel
Answer: B. Move air across the heat exchanger and through the
duct system
Rationale: The blower moves conditioned air through the evaporator
or furnace heat exchanger and distributes it throughout the building.
Insufficient airflow can cause poor comfort, reduced capacity, coil
icing, overheating, or other operating problems.
8. What is the main purpose of an air filter in an HVAC system?
A. Increase refrigerant pressure
B. Raise indoor humidity
C. Increase blower voltage
D. Remove airborne particles from circulating air
Answer: D. Remove airborne particles from circulating air
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary function of an evaporator in a vapor-
compression refrigeration system?
A. Reject heat to outdoor air
B. Increase refrigerant pressure
C. Absorb heat from the conditioned space
D. Store liquid refrigerant
Answer: C. Absorb heat from the conditioned space
Rationale: The evaporator is the heat-absorbing component of a
refrigeration cycle. Low-pressure refrigerant enters the evaporator and
absorbs heat from indoor air, water, or another medium as it changes
from liquid to vapor. The compressor then draws the resulting vapor
into the suction line.
2. Which component raises the pressure and temperature of
refrigerant vapor leaving the evaporator?
A. Compressor
B. Condenser
C. Expansion valve
D. Receiver
,Answer: A. Compressor
Answer: A. Compressor
Rationale: The compressor takes low-pressure, low-temperature
refrigerant vapor from the evaporator and compresses it into a high-
pressure, high-temperature vapor. This pressure increase allows the
refrigerant to reject heat effectively in the condenser.
3. In a conventional air-conditioning system, the condenser's
primary purpose is to:
A. Meter refrigerant
B. Remove moisture from indoor air
C. Lower compressor discharge pressure
D. Reject heat from the refrigerant to the surroundings
Answer: D. Reject heat from the refrigerant to the surroundings
Rationale: The condenser transfers heat from the hot refrigerant
vapor to outdoor air or another cooling medium. As heat is removed,
the refrigerant condenses from vapor to liquid. Proper condenser
airflow and heat transfer are essential for efficient system operation.
4. What does superheat describe in a refrigeration system?
A. Pressure above atmospheric pressure
B. Temperature of a vapor above its saturation temperature at a
given pressure
C. Temperature below freezing
D. Amount of liquid refrigerant in the receiver
,Answer: B. Temperature of a vapor above its saturation
temperature at a given pressure
Rationale: Superheat is the difference between the actual vapor
temperature and the saturation temperature corresponding to the
measured pressure. Measuring superheat helps technicians determine
whether refrigerant leaving an evaporator is completely vaporized and
can assist in diagnosing charging and metering problems.
5. What does subcooling indicate?
A. Liquid refrigerant temperature below its saturation temperature
at the measured pressure
B. Vapor temperature above saturation
C. Compressor motor temperature
D. Indoor-air temperature below setpoint
Answer: A. Liquid refrigerant temperature below its saturation
temperature at the measured pressure
Rationale: Subcooling is the difference between refrigerant saturation
temperature and actual liquid temperature. Adequate subcooling can
help ensure that solid liquid refrigerant reaches the metering device
rather than flashing prematurely in the liquid line.
6. Which device is commonly used to regulate refrigerant flow into
an evaporator according to evaporator load?
A. Sight glass
B. Accumulator
C. Thermostatic expansion valve
D. Liquid receiver
, Answer: C. Thermostatic expansion valve
Rationale: A thermostatic expansion valve, or TXV, regulates
refrigerant entering the evaporator based largely on evaporator outlet
superheat. It responds to load changes and helps maintain proper
evaporator utilization while protecting the compressor from liquid
refrigerant.
7. What is the purpose of an evaporator blower in a forced-air
HVAC system?
A. Compress refrigerant
B. Move air across the heat exchanger and through the duct system
C. Condense refrigerant
D. Meter fuel
Answer: B. Move air across the heat exchanger and through the
duct system
Rationale: The blower moves conditioned air through the evaporator
or furnace heat exchanger and distributes it throughout the building.
Insufficient airflow can cause poor comfort, reduced capacity, coil
icing, overheating, or other operating problems.
8. What is the main purpose of an air filter in an HVAC system?
A. Increase refrigerant pressure
B. Raise indoor humidity
C. Increase blower voltage
D. Remove airborne particles from circulating air
Answer: D. Remove airborne particles from circulating air
