CO HVAC Contractor Exam Questions and
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
Pdf
1. What is the primary purpose of a refrigeration compressor in an
HVAC system?
A. To absorb heat from the conditioned space
B. To reduce refrigerant pressure before expansion
C. To circulate refrigerant and raise its pressure and temperature
D. To remove moisture from the evaporator
Answer: C. To circulate refrigerant and raise its pressure and
temperature
Rationale: The compressor is the driving force of a vapor-compression
refrigeration cycle. It draws low-pressure refrigerant vapor from the
evaporator and compresses it into a high-pressure, high-temperature
vapor that can reject heat in the condenser.
, 2. Which component removes heat from indoor air during the
cooling cycle?
A. Condenser
B. Evaporator
C. Compressor
D. Receiver
Answer: B. Evaporator
Rationale: The evaporator contains low-pressure refrigerant that
absorbs heat from the indoor air as the refrigerant changes state from
liquid to vapor. This heat-transfer process produces the cooling effect.
3. What is the main function of the condenser?
A. Absorb heat from the building
B. Lower refrigerant pressure
C. Reject heat from the refrigerant to the surrounding medium
D. Meter refrigerant into the compressor
Answer: C. Reject heat from the refrigerant to the surrounding
medium
Rationale: In cooling mode, the condenser receives high-pressure, high-
temperature refrigerant vapor from the compressor. It removes heat
from the refrigerant and condenses it into a liquid.
, 4. Which device meters refrigerant into an evaporator?
A. Accumulator
B. Expansion device
C. Filter-drier
D. Compressor
Answer: B. Expansion device
Rationale: An expansion valve, metering device, or similar component
controls the amount of refrigerant entering the evaporator and creates
the pressure drop needed for evaporation.
5. What happens to refrigerant pressure as it passes through a
typical thermostatic expansion valve?
A. It increases substantially
B. It remains constant
C. It decreases substantially
D. It becomes atmospheric
Answer: C. It decreases substantially
Rationale: The expansion device creates a restriction between the high-
pressure liquid side and low-pressure evaporator side. The resulting
pressure drop allows part of the refrigerant to flash into vapor and
lowers its saturation temperature.
, 6. What is superheat?
A. The temperature of liquid below its saturation temperature
B. The temperature of vapor above its saturation temperature
C. The difference between condensing and evaporating pressures
D. The temperature difference between indoor and outdoor air
Answer: B. The temperature of vapor above its saturation
temperature
Rationale: Superheat is the number of degrees a vapor is heated above
its saturation temperature at a given pressure. Measuring superheat
helps technicians determine whether refrigerant is properly feeding and
leaving an evaporator.
7. What is subcooling?
A. Cooling vapor below its saturation temperature
B. Heating liquid above its saturation temperature
C. Cooling a liquid below its saturation temperature
D. Reducing compressor discharge temperature
Answer: C. Cooling a liquid below its saturation temperature
Rationale: Subcooling occurs when liquid refrigerant is cooled below its
saturation temperature at the measured pressure. Proper subcooling
can help ensure that solid liquid refrigerant reaches the metering
device.
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
1. What is the primary purpose of a refrigeration compressor in an
HVAC system?
A. To absorb heat from the conditioned space
B. To reduce refrigerant pressure before expansion
C. To circulate refrigerant and raise its pressure and temperature
D. To remove moisture from the evaporator
Answer: C. To circulate refrigerant and raise its pressure and
temperature
Rationale: The compressor is the driving force of a vapor-compression
refrigeration cycle. It draws low-pressure refrigerant vapor from the
evaporator and compresses it into a high-pressure, high-temperature
vapor that can reject heat in the condenser.
, 2. Which component removes heat from indoor air during the
cooling cycle?
A. Condenser
B. Evaporator
C. Compressor
D. Receiver
Answer: B. Evaporator
Rationale: The evaporator contains low-pressure refrigerant that
absorbs heat from the indoor air as the refrigerant changes state from
liquid to vapor. This heat-transfer process produces the cooling effect.
3. What is the main function of the condenser?
A. Absorb heat from the building
B. Lower refrigerant pressure
C. Reject heat from the refrigerant to the surrounding medium
D. Meter refrigerant into the compressor
Answer: C. Reject heat from the refrigerant to the surrounding
medium
Rationale: In cooling mode, the condenser receives high-pressure, high-
temperature refrigerant vapor from the compressor. It removes heat
from the refrigerant and condenses it into a liquid.
, 4. Which device meters refrigerant into an evaporator?
A. Accumulator
B. Expansion device
C. Filter-drier
D. Compressor
Answer: B. Expansion device
Rationale: An expansion valve, metering device, or similar component
controls the amount of refrigerant entering the evaporator and creates
the pressure drop needed for evaporation.
5. What happens to refrigerant pressure as it passes through a
typical thermostatic expansion valve?
A. It increases substantially
B. It remains constant
C. It decreases substantially
D. It becomes atmospheric
Answer: C. It decreases substantially
Rationale: The expansion device creates a restriction between the high-
pressure liquid side and low-pressure evaporator side. The resulting
pressure drop allows part of the refrigerant to flash into vapor and
lowers its saturation temperature.
, 6. What is superheat?
A. The temperature of liquid below its saturation temperature
B. The temperature of vapor above its saturation temperature
C. The difference between condensing and evaporating pressures
D. The temperature difference between indoor and outdoor air
Answer: B. The temperature of vapor above its saturation
temperature
Rationale: Superheat is the number of degrees a vapor is heated above
its saturation temperature at a given pressure. Measuring superheat
helps technicians determine whether refrigerant is properly feeding and
leaving an evaporator.
7. What is subcooling?
A. Cooling vapor below its saturation temperature
B. Heating liquid above its saturation temperature
C. Cooling a liquid below its saturation temperature
D. Reducing compressor discharge temperature
Answer: C. Cooling a liquid below its saturation temperature
Rationale: Subcooling occurs when liquid refrigerant is cooled below its
saturation temperature at the measured pressure. Proper subcooling
can help ensure that solid liquid refrigerant reaches the metering
device.
