AZ L-74 HVAC Contractor Exam Questions and
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. What is the primary function of a thermostat in a forced-air HVAC
system?
a. Increase refrigerant pressure
b. Control blower speed continuously
c. Sense space temperature and initiate heating or cooling operation
d. Remove moisture from the refrigerant
Rationale: A thermostat monitors the temperature of the conditioned
space and signals the HVAC equipment when heating or cooling is
required. It does not directly control refrigerant pressure or remove
moisture.
2. Which component of a vapor-compression refrigeration system
removes heat from the conditioned space?
a. Condenser
b. Compressor
,c. Expansion device
d. Evaporator
Rationale: The evaporator absorbs heat from the air or space being
conditioned as refrigerant changes from a low-pressure liquid-vapor
mixture into vapor. The condenser rejects that absorbed heat to the
surrounding environment.
3. What is the primary purpose of the compressor in a refrigeration
system?
a. Reduce refrigerant temperature without changing pressure
b. Raise the pressure and temperature of refrigerant vapor
c. Convert liquid refrigerant directly into ice
d. Remove air from the conditioned space
Rationale: The compressor receives low-pressure refrigerant vapor
from the evaporator and compresses it into a high-pressure, high-
temperature vapor. This allows the refrigerant to reject heat in the
condenser.
4. Which component separates the high-pressure side from the low-
pressure side of many refrigeration systems?
a. Filter-drier
b. Accumulator
,c. Metering device
d. Condenser fan
Rationale: The metering device creates a pressure drop between the
high side and low side of the refrigeration circuit. It controls
refrigerant flow into the evaporator while maintaining the desired
operating conditions.
5. What is superheat?
a. The temperature of saturated liquid above its boiling point
b. The temperature of a vapor above its saturation temperature at a
given pressure
c. The temperature difference between outdoor air and indoor air
d. The amount of subcooled liquid in a condenser
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the measured pressure. Measuring superheat helps
technicians determine whether the evaporator is receiving an
appropriate amount of refrigerant.
6. What does subcooling describe?
a. Vapor temperature below saturation temperature
b. Refrigerant pressure below atmospheric pressure
c. Liquid temperature below its saturation temperature at a given
, pressure
d. Air temperature below the thermostat setting
Rationale: Subcooling occurs when liquid refrigerant is cooled below
its saturation temperature at a particular pressure. It is commonly
measured at the condenser outlet or liquid line to evaluate system
charging and condenser performance.
7. A dirty air filter in a forced-air cooling system can commonly
cause:
a. Increased airflow
b. Higher indoor humidity removal under all conditions
c. Reduced airflow across the evaporator
d. Increased evaporator pressure
Rationale: A restricted filter reduces the volume of air moving across
the evaporator coil. Reduced airflow can decrease cooling
performance and may cause the evaporator coil to become excessively
cold and potentially freeze.
8. What is the primary purpose of an evaporator blower?
a. Compress refrigerant
b. Reject refrigerant heat outdoors
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. What is the primary function of a thermostat in a forced-air HVAC
system?
a. Increase refrigerant pressure
b. Control blower speed continuously
c. Sense space temperature and initiate heating or cooling operation
d. Remove moisture from the refrigerant
Rationale: A thermostat monitors the temperature of the conditioned
space and signals the HVAC equipment when heating or cooling is
required. It does not directly control refrigerant pressure or remove
moisture.
2. Which component of a vapor-compression refrigeration system
removes heat from the conditioned space?
a. Condenser
b. Compressor
,c. Expansion device
d. Evaporator
Rationale: The evaporator absorbs heat from the air or space being
conditioned as refrigerant changes from a low-pressure liquid-vapor
mixture into vapor. The condenser rejects that absorbed heat to the
surrounding environment.
3. What is the primary purpose of the compressor in a refrigeration
system?
a. Reduce refrigerant temperature without changing pressure
b. Raise the pressure and temperature of refrigerant vapor
c. Convert liquid refrigerant directly into ice
d. Remove air from the conditioned space
Rationale: The compressor receives low-pressure refrigerant vapor
from the evaporator and compresses it into a high-pressure, high-
temperature vapor. This allows the refrigerant to reject heat in the
condenser.
4. Which component separates the high-pressure side from the low-
pressure side of many refrigeration systems?
a. Filter-drier
b. Accumulator
,c. Metering device
d. Condenser fan
Rationale: The metering device creates a pressure drop between the
high side and low side of the refrigeration circuit. It controls
refrigerant flow into the evaporator while maintaining the desired
operating conditions.
5. What is superheat?
a. The temperature of saturated liquid above its boiling point
b. The temperature of a vapor above its saturation temperature at a
given pressure
c. The temperature difference between outdoor air and indoor air
d. The amount of subcooled liquid in a condenser
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the measured pressure. Measuring superheat helps
technicians determine whether the evaporator is receiving an
appropriate amount of refrigerant.
6. What does subcooling describe?
a. Vapor temperature below saturation temperature
b. Refrigerant pressure below atmospheric pressure
c. Liquid temperature below its saturation temperature at a given
, pressure
d. Air temperature below the thermostat setting
Rationale: Subcooling occurs when liquid refrigerant is cooled below
its saturation temperature at a particular pressure. It is commonly
measured at the condenser outlet or liquid line to evaluate system
charging and condenser performance.
7. A dirty air filter in a forced-air cooling system can commonly
cause:
a. Increased airflow
b. Higher indoor humidity removal under all conditions
c. Reduced airflow across the evaporator
d. Increased evaporator pressure
Rationale: A restricted filter reduces the volume of air moving across
the evaporator coil. Reduced airflow can decrease cooling
performance and may cause the evaporator coil to become excessively
cold and potentially freeze.
8. What is the primary purpose of an evaporator blower?
a. Compress refrigerant
b. Reject refrigerant heat outdoors
